Vipin Khetarpal, MD

• Fellow in Cardiology, Division of Cardiology, Department of Internal
• Medicine, Harper Hospital Wayne State University School of Medicine,
• Detroit, MI, USA

It is remarkable that so few cells with a particular specificity can accomplish the difficult task of combating various microbes; as discussed later gastritis symptoms livestrong 150 mg ranitidine purchase free shipping, the immune system has developed many mechanisms for optimizing reactions to microbial antigens gastritis weight gain purchase generic ranitidine. It is also remarkable that the system is capable of producing so many receptors gastritis unusual symptoms effective ranitidine 150 mg, far more than could be individually Adaptive Immunity the adaptive immune system consists of lymphocytes and their products gastritis diet soda cheap 300 mg ranitidine otc, including antibodies gastritis diet 21 discount ranitidine online visa. The lymphocytes of adaptive immunity use highly diverse receptors to recognize a vast array of foreign substances. In the remainder of this introductory section, we focus on lymphocytes and the reactions of the adaptive immune system. The mechanisms by which this happens are now well understood and have many interesting clinical implications. Antigen receptor diversity is generated by somatic recombination of the genes that encode antigen receptors. This creates many different genes that can be transcribed and translated into antigen receptors with diverse amino acid sequences, particularly in the regions of the receptors that recognize and bind antigen. Thus, assays that assess the clonality of antigen receptor gene rearrangements are useful in diagnosing lymphoid neoplasms (Chapter 13). T Lymphocytes There are three major populations of T cells, which serve distinct functions. Helper T lymphocytes stimulate B lymphocytes to make antibodies and activate other leukocytes. Mature T cells are found in the blood, where they constitute 60% to 70% of lymphocytes, and in T-cell zones of secondary lymphoid organs (described later). T cells tend to aggregate at epithelial surfaces, such as the skin and mucosa of the gastrointestinal and urogenital tracts, suggesting that these cells are sentinels that protect against microbes that try to enter through epithelia. Mature B cells constitute 10% to 20% of lymphocytes in the blood and are also present in peripheral lymphoid tissues such as lymph nodes, spleen, and mucosa-associated lymphoid tissues. After stimulation by antigen and other signals (described later), B cells develop into plasma cells, veritable protein factories for producing antibodies, as well as long-lived memory cells. It is estimated that a single plasma cell can secrete hundreds to thousands of antibody molecules per second, a remarkable measure of the power of the immune response for combating pathogens. These cells bear Fc receptors for IgG and receptors for C3b and can trap antigen bound to antibodies or complement proteins. They play a role in humoral immune responses by presenting antigens to B cells in the germinal center, part of a process through which only B cells that express antibodies with high affinity for antigen survive and go on to mature into plasma cells or memory cells. Here, their important functions in the induction and effector phases of adaptive immune responses are discussed. In this type of response, T cells activate macrophages and enhance their ability to kill ingested microbes (discussed later). Macrophages efficiently phagocytose and destroy microbes that are opsonized (coated) by IgG or C3b. B cells also express several other molecules that are essential for their responses. Tissues of the Immune System the tissues of the immune system consist of the primary (also called generative, or central) lymphoid organs, in which T and B lymphocytes mature and become competent to respond to antigens, and the secondary (or peripheral) lymphoid organs, in which adaptive immune responses to microbes are initiated. These cells have numerous fine cytoplasmic processes that resemble dendrites, from which they derive their name. First, these cells are located at the right place to capture antigens- under epithelia, the common site of entry of microbes and phoid organs are the thymus, where T cells develop, and the bone marrow, the site of production of all other blood cells, including naïve B cells. The secondary lymphoid organs-lymph nodes, spleen, and the mucosal and cutaneous lymphoid tissues-are the tissues where adaptive immune responses occur. Several features of these organs promote the generation of adaptive immunity-antigens are concentrated in these organs, naïve lymphocytes circulate through them searching for the antigens, and different the normal immune response lymphocyte populations (such as T and B cells) are brought together when they need to interact. As lymph slowly suffuses through lymph nodes, antigen-presenting cells are positioned to recognize antigens. Thus, the antigens of microbes that enter through epithelia or colonize tissues become concentrated in draining lymph nodes. Because most foreign antigens enter through epithelia or are produced in tissues, lymph nodes are the site of generation of the majority of adaptive immune responses. Blood-borne antigens are trapped in the spleen by these cells, which can then initiate adaptive immune responses to these antigens. Pharyngeal tonsils and Peyer patches of the intestine are two anatomically defined mucosal lymphoid tissues. In lymph nodes, the B cells are concentrated in discrete structures, called follicles, located around the periphery, or cortex, of each node. If the B cells in a follicle have recently responded to an antigen, this follicle may contain a central region called a germinal center. In the spleen, T lymphocytes are concentrated in periarteriolar lymphoid sheaths surrounding small arterioles, and B cells reside in follicles akin to those found in lymph nodes (the so-called splenic white pulp). This process of lymphocyte recirculation is most important for T cells, because naïve T cells have to circulate through the secondary lymphoid organs where antigens are concentrated and effector T cells have to migrate to sites of infection to eliminate microbes. Kathryn Pape and Jennifer Walter, University of Minnesota School of Medicine, Minneapolis, Minn. They are heterodimers consisting of a polymorphic, or heavy, chain (44-kD) linked noncovalently to a smaller (12-kD) nonpolymorphic protein called 2-microglobulin. The polymorphic amino acid residues line the sides and the base of the peptide-binding groove, explaining why different class I alleles bind different peptides. This, as we see subsequently, constitutes a formidable barrier in organ transplantation. The extracellular portions of the and chains both have two domains designated 1 and 2, and 1 and 2. It is believed that this degree of polymorphism evolved to ensure that at least some individuals in a species would be able to display any microbial peptide and thus provide protection against any infection. This is why siblings are screened first as potential donors for patients in need of a kidney or hematopoietic stem cell transplant. In contrast, an inherited capacity to bind a bacterial peptide may provide resistance to the infection by evoking a protective antibody response. These associations are discussed when the pathogenesis of autoimmune diseases is considered later in the chapter. Some of these interactions depend on cell-to-cell contact; however, many functions of leukocytes are stimulated and regulated by secreted proteins called cytokines. Molecularly defined cytokines are called interleukins because they mediate communications between leukocytes (although many also act on cells other than leukocytes). Most cytokines have a wide spectrum of effects, and some are produced by several different cell types. The majority of these cytokines act on the cells that produce them (autocrine actions) or on neighboring cells (paracrine) and rarely at a distance (endocrine). Even before the antigens of a microbe are recognized by T and B lymphocytes, the microbe elicits an immune response through pattern recognition receptors expressed on innate immune cells; this is the first line of defense that also serves to activate adaptive immunity. In the case of immunization with a protein antigen, microbial mimics, called adjuvants, are given with the antigen, and these stimulate innate immune responses. During the innate response, the microbe or adjuvant activates antigen-presenting cells to express molecules called costimulators and to secrete cytokines that stimulate the proliferation and differentiation of T lymphocytes. The requirement for microbe-triggered signal 2 ensures that the adaptive immune response is induced by microbes and not by harmless substances. In immune responses to tumors and transplants, "signal 2" may be provided by substances released from necrotic cells (the "damage-associated molecular patterns" mentioned earlier). The reactions and functions of T and B lymphocytes differ in important ways and are best considered separately even though both may be activated concurrently in an immune response. Their functions are to increase leukocyte production during immune and inflammatory responses, both to increase their numbers and to replace leukocytes that die during such responses. They are produced by marrow stromal cells, T lymphocytes, macrophages, and other cells. The knowledge gained about cytokines has numerous practical therapeutic applications. Inhibiting cytokine production or actions is an approach for controlling the harmful effects of inflammation and tissue-damaging immune reactions. Many other cytokine antagonists are now approved for the treatment of various inflammatory disorders. Conversely, administration of cytokines is used to boost reactions that are normally dependent on these proteins, such as hematopoiesis and defense against some viruses. An important therapeutic application of cytokines is to mobilize hematopoietic stem cells from bone marrow to peripheral blood, from which they can be collected for stem cell transplantation. Eosinophils and mast cells bind to IgE-coated microbes such as helminthic parasites, and function to eliminate helminths. Th2 cells also induce the "alternative" Overview of Lymphocyte Activation and Immune Responses All adaptive immune responses develop in steps, consisting of: antigen recognition; activation of specific lymphocytes to proliferate and differentiate into effector and memory cells; elimination of the antigen; and decline of the response, with memory cells being the long-lived survivors. The major events in each step are summarized next; these general principles apply to protective responses against microbes as well as pathologic responses that injure the host. Display and Recognition of Antigens Microbes and other foreign antigens can enter the body anywhere. It is obviously impossible for lymphocytes to effectively patrol every possible portal of antigen entry, because there are not enough antigen-specific lymphocytes to constantly cover all of this "terrain. Dendritic cells capture microbial antigens from epithelia and tissues and transport the antigens to lymph nodes. The T cells are activated to proliferate and to differentiate into effector and memory cells, which migrate to sites of infection and serve various functions in cell-mediated immunity. Some activated T cells remain in the lymphoid organs and help B cells to produce antibodies, and some T cells differentiate into long-lived memory cells (not shown). Antibody responses to most protein antigens require T cell help and are said to be T-dependent. The dominant immune reactions elicited by each subset, and its role in host defense and immunologic diseases, are summarized. Some activated T cells produce multiple cytokines and do not fall into a distinct subset. Naïve B lymphocytes recognize antigens, and under the influence of helper T cells and other stimuli (not shown), the B cells are activated to proliferate and to differentiate into antibody-secreting plasma cells. Some of the activated B cells undergo heavy-chain class switching and affinity maturation, and some become long-lived memory cells. Antibodies of different heavy-chain classes (isotypes) perform different effector functions, shown on the right. Note that the antibodies shown are IgG; these and IgM activate complement; and the specialized functions of IgA (mucosal immunity) and IgE (mast cell and eosinophil activation) are not shown. The normal immune response and secrete cytokines, which work together to stimulate the B cells. T-independent responses are relatively simple, whereas T-dependent responses show features such as Ig isotype switching and affinity maturation (described later), which require T cell help and lead to responses that are more varied and effective. Helper T cells also stimulate the production of antibodies with high affinities for the antigen. This process, called affinity maturation, improves the quality of the humoral immune response. These two processes are initiated when activated B cells that receive signals from helper T cells during responses to protein antigens migrate into follicles and begin to proliferate to form germinal centers, which are the major sites of isotype switching and affinity maturation. Antibodies bind to microbes and prevent them from infecting cells, thus neutralizing the microbes. IgG antibodies coat (opsonize) microbes and target them for phagocytosis, since phagocytes (neutrophils and macrophages) express receptors for the Fc tails of IgG. IgG and IgM activate the complement system by the classical pathway, and complement products promote phagocytosis and destruction of microbes. IgA is secreted from mucosal epithelia and neutralizes microbes in the lumens of the respiratory and gastrointestinal tracts (and other mucosal tissues). IgG is actively transported across the placenta and protects the newborn until the immune system becomes mature. IgE and eosinophils cooperate to kill parasites, mainly by release of eosinophil granule contents that are toxic to the worms. As mentioned earlier, Th2 cytokines stimulate the production of IgE and activate eosinophils, and thus the response to helminths is orchestrated by Th2 cells. Some antibody-secreting plasma cells, particularly those that are generated in germinal centers, migrate to the bone marrow and take up residence for months or even years, continuously producing antibodies during this time. Memory cells are an expanded pool of antigen-specific lymphocytes (more numerous than the naïve cells specific for any antigen that are present before encounter with that antigen), and they respond faster and more effectively when reexposed to the antigen than do naïve cells. Innate immunity, unlike adaptive immunity, does not have fine antigen specificity or memory. The lymphocytes are activated to proliferate and differentiate into effector and memory cells. Humoral immunity is mediated by antibodies and is effective against extracellular microbes (in the circulation and mucosal lumens). The immune responses against such exogenous antigens may take several forms, ranging from annoying but trivial discomforts, such as itching of the skin, to potentially fatal diseases, such as anaphylaxis. Some of the most common reactions to environmental antigens cause the group of diseases known as allergy. Immune responses against self, or autologous, antigens, cause autoimmune diseases. In fact, in many hypersensitivity diseases, it is suspected that the underlying cause is a failure of normal regulation. The problem in hypersensitivity is that these reactions are poorly controlled, excessive, or misdirected. The brief outline of basic immunology presented here provides a foundation for considering the diseases of the immune system. We first discuss the immune reactions that cause injury, called hypersensitivity reactions, and then disorders caused by the failure of tolerance to self antigens, called autoimmune disorders, and the rejection of transplants.

For example symptoms of gastritis back pain order 300 mg ranitidine otc, the large number of capsular sero types (currently 98) and the frequent resistance to betalactam antibiotics gastritis diet zinc buy genuine ranitidine line, including penicillin gastritis for 6 months generic ranitidine 150 mg without a prescription, in S gastritis diet 7 up order ranitidine 300 mg amex. The crucial factor in any attempt to study the population genetic structure of bacteria is the sample chronic gastritis gallbladder ranitidine 300 mg order with mastercard. It must faithfully represent the popula tion chosen for analysis and reflect the parameters under study, whether this is disease association or geographic or temporal variations. In contrast to many other infections in humans, studies of the etiology of oral diseases like periodontitis and caries pose significant problems due to the complex ity of the microbiome, and because these diseases are not caused by individ ual pathogens but rather by polymicrobial communities. Conversely, an isolate from an apparently healthy subject is not necessarily nonpathogenic. If the bac terial population under study has a clonal population structure, this will usually disclose particular diseaseassociated clones or subpopulations if such occur. Conversely, in a population characterized by frequent recom bination, pathogenic isolates may not cluster together but are character ized by distinct genes that encode virulence. These studies utilized large collections of isolates that were clinically, geographically, and temporally diverse. In contrast, isolates from Old World monkeys are closely related to human isolates. Isolates for which pathogenicity has been demonstrated in animal models are randomly distributed across the population. Screenings of comprehensive col lections of isolates from clinically welldefined situations using micro array technology are required to identify specific combinations of genes that determine a virulent phenotype. However, the population structure is clearly clonal, with only limited evidence of genetic recombination. This con clusion is based on the observation that strains cluster according to serotype and that there is clear evidence of genetic linkage disequilibrium. In an anal ysis based almost entirely on isolates from Europeans, there was no evidence of single clonal types being responsible for multiple cases of periodontitis or systemic infections, nor was there evidence of diseaseassociated isolates clustering separately from isolates obtained from healthy individuals. These observations are compatible with the conclusion that, in the exam ined human populations, both P. Thus, if etiologically involved in the pathogenesis of periodontal disease, they play the role of an opportunistic (endogenous) pathogen. This notion is consistent with the recent understanding that periodontitis is not an infection in the classical sense of the term but rather a dysbiotic disease arising from polymicrobial synergy within bacterial communities, where P. Nevertheless, studies have sur prisingly revealed that a large number of isolates of A. The enhanced production of leuko toxin is due to a single deletion of 530 bp in the promoter region of the leukotoxin gene operon. The clone is endemically present in Morocco, where it is associated with an unusually high prevalence of periodontal disease (15%) among adolescents (odds ratio, 29. It has also been detected in dental biofilms from a group of Israeli children with an unusually high prevalence (38%) of earlyonset periodontitis. Two different genetic events have resulted in enhanced leukotoxin production in par ticular clones of A. The very strong association with earlyonset aggressive periodontitis strongly supports its etiologic significance in this disease. These findings emphasize that observations obtained in one geographic locality or in human populations consisting of individuals of a certain ra cial or ethnic background are not necessarily applicable worldwide. They further suggest that earlyonset aggressive periodontitis may be a disease with dual etiology and epidemiology. In at least some persons of African descent, disease is associated with a particular clone of A. If this assumption is correct, it has important implications for treatment strategies. While eradication of the pathogenic clone with anti biotics or through vaccination may be relevant in the former situation, the most logical treatment in the latter situation would be to attempt to restore the natural balance in the commensal microbiome by hygienic measures. The evolutionary process has included optimization of the bacterial genome, often leading to loss of metabolic versatility and, thereby, enhanced dependency on the host. For bacteria that form part of the commensal microbiome on mucosal membranes, the major mechanism of transmission is vertical. Molecular genetics has demonstrated a degree of biodiversity in the oral microbiome far exceeding earlier expectations and has provided new insight into the patterns of acquisition, transmission, and dynamics of oral bacteria. Combined with the recent realiza tion that individual clones within bacterial species may have widely diferent properties, including widely difering virulence, this implies a remarkable degree of individuality of dental biofilms. This new realization implies that previous attempts to identify etiologic agents of oral diseases by searching for associations between presence of particular cultivable bacteria and disease activity were too simplistic. Conversely, species considered nonpathogenic have been almost neglected, though there may be functionally important diferences within such species. Even ubiquitous species, which are usually dismissed as lacking interest as potential pathogens, may include virulent subpopulations. Population genetics analysis of oral bacteria on a broad scale can reveal new insight into the genetic mechanisms of the genetic and phenotypic diversity that exists in the oral microbiome and provide a better basis for our understanding of the etiology of oral diseases. Bacterial species can be viewed as populations of individual strains that share basic housekeeping functions but otherwise may have very diferent properties. Genetic diversification can result from accumulation of point mutations in the bacterial genome or from recombinational replacements. Species in which accumulation of mutations is the dominant mechanism of genetic diversification consist of discrete phyloge netic lineages or clones. Genome analyses shows that species have a core genome comprising genes present in all strains, typically housekeeping genes, and a pangenome comprising the entire set of genes, some of which may be variably present, such as virulence genes. If recombination in a bacterial population is very frequent compared to the mutation rate, a panmictic population structure arises. This is characterized by a random (or nearly random) assortment of alleles and the absence of distinct phylogenetic lineages. Hence, no single property will be able to identify a virulent phenotype in such bacteria unless that property is uniquely responsible for the pathogenic potential. Diferent parts of a bacterial genome, or even of a single gene, may have a phylogenetic history diferent from that of the remaining genome. For example, surface proteins often demonstrate antigenic diversity as a result of local recombination. In addition, complete virulence genes or whole pathogenicity islands may spread through a basically clonal population of bacteria by horizontal genetic transfer to confer the same virulence properties on otherwise evolutionarily distinct lineages. Many bacteria appear to have coevolved with their hosts and have speciated in synchrony. The mouth forms the entry to the alimentary tract and is in continuity with the pharynx. Therefore, the physical and functional integrity of the oral mucosa is important both for oral and systemic health. A particularly susceptible area, however, is the junction between the teeth and the gingiva, which potentially constitutes a "breeding ground" for periodontal bacteria. This article is divided into two sections-"Oral Secretory Immunity" and "Subgingival Immunity"-to better reflect the peculiarities of the respec tive anatomical areas and the immune mechanisms operating therein. About 65% of the whole saliva is produced by the submandibular gland, 23% by the parotid gland, and 4% by the sublingual gland. The minor salivary glands collectively contribute the remaining 8% of the salivary production. The basic secretory unit of salivary glands is represented by the acinus, a cluster of epithelial cells that secrete a fluid comprised of water, electrolytes, mucins, and proteins, including enzymes. There are two basic types of aci nar epithelial cells: the serous cells, which produce a watery fluid devoid of mucus material, and the mucous cells, which produce a mucusrich secretion. Salivary glands secrete mucins and other innate antimicrobial factors that protect mucosal and tooth surfaces. The sali vary glands also constitute a mucosal effector site where B cells terminally differenti ate into polymeric IgAsecreting plasma cells. T and B cells also localize in inflamed gingivae, and B cells differentiate into plasma cells that secrete mainly IgG (also IgM or monomeric IgA). These, as well as immunoglobulins derived from the circulation, can transude into the gingival crevice. Antimicrobial peptides and cytokines are also produced by leukocytes present in the gingival connective this sue, the junctional epithelium, or the gingival crevice, where leukocytes are chemotac tically recruited. The gingival crevice also contains functional complement, which is activated by subgingival bacteria or antigenantibody complexes. The other salivary glands contain both types of acini, although acini of the mucus type predominate in the sublingual glands. From the acini, secretions are initially collected into small collecting ducts, which lead to larger ducts and finally to a single large duct that secretes the salivary contents into the oral cavity. These include both inorganic (electro lytes, such as chloride, potassium, sodium, and bicarbonate) and organic components. The latter include a number of proteins, such as the digestive enzyme amylase, mucous glycoproteins, acidic prolinerich and tyrosine rich proteins, and numerous humoral host defense factors. Overview of Innate Host Defense Factors in Saliva the oral cavity contains an array of innate antimicrobial factors that are secreted by salivary glands but also by epithelial cells and neutrophils. These antimicrobial molecules can kill or inhibit the growth of microor ganisms and have broadspectrum antibacterial, antifungal, and antiviral properties. Therefore, at least in principle, they can efficiently protect the oral mucosal surfaces from pathogens. Innate defense mechanisms addi Immunology of the Oral Cavity 229 tionally determine the minimal requirements for successful microbial col onization. Those organisms that cannot adapt to these conditions will fail to maintain themselves within the host. Many of the earlier studies on innate defense systems in mucosal secretions were performed using saliva or milk, which are accessible and available in large quantities. Major innate host factors found in the oral cavity are listed in Table 1 and are briefly discussed below. Cationic Antimicrobial Peptides Cationic antimicrobial peptides are small peptides (generally between 12 and 50 amino acids) with a net positive charge, owing to an excess of basic amino acids, such as arginine, lysine, and histidine. This property allows them to interact with bacterial membranes, which constitutes their common tar get, despite different modes of action. Several other peptides, originally appreciated for their neural or neuroendocrine signaling functions, appear to also exhibit potent antimi crobial activities, at least in vitro. Such peptides include the calcitonin gene related peptide, substance P, neuropeptide Y, and vasoactive intestinal peptide. Its immunoregulatory activities include both pro and anti inflammatory effects that vary depending on several factors, such as the cell type involved. Gene polymorphisms of the salivary agglutinin have been associated with a high incidence of caries. It is also expressed in human salivary glands and can agglutinate bacteria and neutralize the influenza virus via its sialic acid residues. Its levels in the salivary glands are upregulated in patients with chronic sialadenitis, suggesting a role in the innate host defense of sal ivary glands. This pentapeptide was shown to inhibit the sucroseinduced decrease of dental plaque pH in vitro. It is also found in saliva, where it mediates bac terial agglutination and controls bacterial colonization. Reduced levels of fibronectin are correlated with periodontitis in adults and with high levels of S. The dimer of calgranulin A and B, termed calprotectin, is expressed in the cytosol of various cell types (neutrophils, monocytes, and keratinocytes) and has host defense activity. Lactoferrin binds iron (Fe3+) in association with bicarbonate and, therefore, can deprive microorganisms (bacteria, viruses, fungi and parasites) of this essential nutrient. Bactericidal activity, independent of iron binding, has been reported for lactoferrin and probably involves increased membrane permeability in targeted bacteria. This bactericidal function is mediated by the basic ami noterminal region, since the isolated lactoferricin peptides from this region 232 Chapter 10 of the molecule are particularly active. Gene polymorphisms of lactoferrin have been associated with aggressive periodontitis. Lactoferrin also has antiinflammatory effects by binding and neutralizing the lipid A compo nent of bacterial lipopolysaccharide, a major proinflammatory molecule. Seven of these genes express salivary proteins that are contributed by the subman dibular and sublingual salivary glands. Their antimicrobial action involves inhibition of bacterial cysteine proteases, such as the gingipains of P. Bacterial proteases play a major role in nutrient acquisition, and their inhibition by cystatins can lead to suppression of bacterial growth. Cys tatins also inhibit human lysosomal cathepsins, which under inflammatory conditions contribute to periodontal tissue destruction. It exerts anti bacterial, antifungal, and antiinflammatory properties through its serine protease inhibitor properties. The protein can kill both Grampositive and Gramnegative bacteria, activity that requires the presence of both domains. In terms of enzymatic activity, lysozyme is a muramidase that hydrolyzes the 1,4 glycosidic bond between Nacetylmuramic acid and Nacetylglucosamine residues in the peptidoglycan of the cell wall of Grampositive bacteria. Although few species of bacteria are directly lysed by lysozyme, the cell walls of oral streptococci, weakened by cleavage of peptidoglycan, become susceptible to lysis by the addition of monovalent anions, such as bicarbonate, fluoride, thiocyanate, and chloride, which are abundant in saliva. Other functions of Immunology of the Oral Cavity 233 lysozyme include activation of autolysins in the cell wall, agglutination of microorganisms, blocking of bacterial adherence, and inhibition of acid production by oral microorganisms. Moreover, lysozyme synergizes with other innate or immunoglobulin defense factors. Despite these functions, there is no clear evidence that salivary levels of lysozyme are related to the occurrence of dental caries or periodontal disease.

In gingivitis gastritis diet of speyer discount 150 mg ranitidine amex, the inflammatory process is reversible and is limited to the gingival epithelium and connective tissue gastritis diet ��� cheap 300 mg ranitidine otc. In contrast gastritis elimination diet generic ranitidine 300 mg with mastercard, periodontitis is characterized by an immunoinflamma tory infiltrate of the deeper compartments of the periodontium gastritis symptoms worse night order generic ranitidine pills, resulting in loss of gingival tissue attachment to the tooth gastritis diet 2012 purchase generic ranitidine canada, deepening of the gingival crevice (called here the periodontal pocket), and destruction of the peri odontal ligament and alveolar bone. In the absence of appropriate ther apy, this destructive process can lead to tooth loss. Although a dense infiltrate of inflammatory myeloid cells and lymphocytes is invariably as sociated with gingivitis, this condition can remain stable without neces sarily progressing to periodontitis, which apparently requires a susceptible host. Bacteria that colonize the teeth below the gingival margin are impli cated in periodontal disease, although their perceived roles and mecha nisms have been a matter of debate and different theories have been proposed over the years. Recent human microbiome analyses and mecha nistic studies in relevant preclinical models indicate that periodontitis is not, strictly speaking, a bacterial infection. Rather, the microbial etiology of periodontitis entails synergistic interactions between different indigenous species with distinct roles in a dysbiotic microbial community. Dysbiosis represents an alter ation in the abundance or dynamics of individual species within a poly microbial community (relative to their abundance or influence in health) leading to dysregulated hostmicrobial interactions and destructive inflam mation. Keystone pathogens, colonization by which is facilitated by accessory pathogens, initially subvert the host response, leading to a dysbiotic microbiota in which pathobionts overactivate the in flammatory response and cause periodontal tissue degradation, including resorption of the supporting alveolar bone. Inflammation and dysbiosis positively reinforce each other because inflammatory tissue breakdown products. This process generates a selfperpetuating pathogenic cycle that may underlie the chronicity of periodontitis. Reprinted from Ha jishengallis G, Nat Rev Immunol 15:30­44, 2015, with permission of the publisher. Certain commensals, though nonpathogenic by them selves in the oral environment, can promote keystone pathogen metabolic activity and colonization and, as such, are implicated as accessory patho gens. In this regard, inflammatory tissue breakdown products generate a nutritionally favorable environment where pathobionts can thrive at the expense of species that cannot take advantage of, or are suppressed by, the environmental changes. The blooming pathobionts, including keystone pathogens that undermine host immunity through subversive tactics, may further exacerbate dysbiotic inflammation, eventually caus ing overt periodontitis in susceptible individuals. From the above, it becomes evident that commensal or pathogenic properties of microorganisms are not intrinsic features and, therefore, have to be considered within the context of both the microbial community in which they reside and the host immune status. The health or disease associated properties of an organism should be viewed as a spectrum from commensalism to pathogenicity that includes newly recognized categories such as those discussed above. Rather, periodontal health is a proactive symbiotic state maintained by homeostatic immunity to the local microbiota. Susceptibility to periodontitis, and hence the transition from symbiosis to dysbiosis, is determined by a variety of factors (genetic or epigenetic factors; environmental factors such as smoking, stress, and diet; systemic diseases such as diabetes; aging) that may modify the host response in either a protective or a destructive direction. Recent evidence from human and animal modelbased studies is consistent with the view that periodontitis is not caused by specific pathogens (upper panel). Rather, periodontitis is a dysbiotic disease arising from disruption of the homeo static immunity that can maintain a balance between the host response and the indige nous microbial community (lower panel). Susceptibility to periodontitis, and hence the transition from symbiosis to dysbiosis, is determined by a variety of factors, as indicated. Immunopathogenic Mechanisms in Periodontal Disease 337 posed, it remains uncertain whether individual genes (as opposed to complex combinations of genes) play important roles in periodontal disease patho genesis. Overall, the pathogenic potential of a periodontal mi crobial community, termed nososymbiocity, depends both on host suscepti bility and on the community composition and dynamics. Although required for periodontal disease pathogenesis, the subgingi val microbial communities are not sufficient by themselves to cause dis ease. Indeed, periodontal tissue damage is predominantly inflicted by the host inflammatory response to the subgingival microbial challenge rather than by direct microbial toxic activities. This article examines the inter actions between the subgingival dysbiotic microbiota and elements of both innate immunity (complement, phagocytes) and adaptive immunity (regu latory and effector lymphocytes) that contribute to periodontitis. We focus on the most important immune players, which, while aiming to control the microbial challenge, actually cause bystander tissue damage and thereby drive periodontal disease pathogenesis. The bacteria do not have to invade the under lying connective tissue to activate immune mechanisms for recruitment of innate and adaptive immune cells to the gingiva. This barrier is actually highly porous, as the junctional epithelial cells are interconnected by only a few desmosomes and occasional gap junctions. Moreover, subgingival bacteria can activate the gingival crevicular epithelial cells, which can respond by releasing anti microbial peptides and chemokines that, in turn, recruit neutrophils to the gingival crevice or periodontal pocket. Overall, the subgingival environ ment is replete with immune and inflammatory mediators. These include cytokines, chemokines, antimicrobial peptides, complement proteins, and antibodies, which are produced locally by resident or recruited cells or are even derived from plasma exudate into the pockets. Periodontal health is characterized by a controlled immunoinflam matory state that maintains hostmicrobe homeostasis, thereby prevent ing development of clinically evident disease (for details, see Chapter 10). However, as discussed above, the immune response can become dys regulated, leading to destructive inflammation while failing to control bacterial outgrowth. This figure aims to illustrate an appreciation of the com plexity of the periodontal host response. Periodontitis arises from highly complex interactions between the subgingival dysbiotic microbiota and the host. These interac tions involve elements of both innate (complement, phagocytes) and adaptive immu nity (regulatory and effector lymphocytes), as well as stromal cells (fibroblasts and osteoblasts). Shown is a complex (albeit simplified compared to the actual) view of cytokine and chemokinemediated cross talk interactions between the indicated cell types that result in inflammationdriven destruction of connective tissue and alveolar bone (see text for details). The development of periodon titis correlated with increased complexity of the cellular infiltrate composi tion from one dominated by neutrophils (initial lesion) to one containing elevated numbers of macrophages and T lymphocytes (early lesion) and, additionally, plasma cells, which predominated in the established and ad vanced lesions. Page and Schroeder moreover described cytopathologic alterations in fibroblasts and increasing loss of collagen in the gingival connective tissue as the inflammatory cell infiltrate became heavier. The Page and Schroeder model of the 1970s remains fundamentally valid, although the subsequent dissection of cross talk interactions between innate and adaptive leukocytes has offered a more nuanced and mecha nistic understanding of periodontal disease pathogenesis with profound implications for treatment (see Chapter 21). The neutrophils, protagonists of the initial lesion and traditionally regarded as merely antimicrobial cells in acute infections, are now appreciated for their functional versatility and critical roles in chronic inflammation. Also, the role of complement was uncertain in the early 1970s, although it was suspected to play a role in the initial lesion. It is now well accepted that complement plays a key role in many aspects of periodontal disease pathogenesis. Moreover, it is now firmly established that T lymphocytes (as well as innate immune cell types) exist in functionally specialized subsets (see Chapter 2) with different or even conflicting roles in immunity and inflammation. Also well appreci ated is that local tissues have a "regulatory say" over the host inflamma tory response through several mechanisms, including local production of homeostatic molecules, the absence (or scarcity) of which can potentially precipitate or exacerbate periodontitis. Finally, an entirely new field of research, osteoimmunology, has developed, which studies the effects of immunoinflammatory events on the cells that mediate bone resorption (osteoclasts), thus being of central importance in periodontitis. Whereas complement may contrib ute to hostmicrobe homeostasis in clinically healthy periodontium, it appears to be dysregulated in periodontitis, where it can actually contribute to tissue destruction. Studies with several periodontitisassociated bacteria indicate that they interact with complement in complex ways that include both inhibi tory and stimulatory effects. For instance, Porphyromonas gingivalis, Tannerella forsythia, and Prevotella intermedia express proteases that inhibit complement 340 Chapter 15 mediated phagocytosis and killing. As a conse quence of complement inhibition, the deposition of opsonins and the formation of the membrane attack complex on the bacterial surface are suppressed. Interestingly, these organisms have alternative mechanisms for protection against activated complement. Treponema denticola expresses a protein that binds and exploits factor H, another major soluble inhibitor of complement. Even under con ditions that suppress the canonical activation of the complement cascade, P. The same proteases readily destroy the C5b component of C5, thus preventing the generation of the membrane attack complex. However, disruption of these regulatory mechanisms by specific complement gene mutations or by subversive pathogens can lead to complement overactivation and hence un warranted inflammation and damage to host tissues. Periodontal bacteria not only can hijack soluble negative regulators to protect themselves against complement attack, as discussed above, but also can degrade cellassociated regulatory molecules that would otherwise protect host tissues or cells. Republished from Hajishengallis G, Nat Rev Immunol 15:30­44, 205, with permission of the publisher. The association of complement with periodontitis is supported by both clinical and animal experimentation studies. A causeandeffect relationship between complement and periodontitis was supported by interventional and mechanistic studies in preclinical models of periodontitis. Specifically, genetic and pharmacological studies in rodents have shown that complement is involved both in the dysbiotic transfor 342 Chapter 15 mation of the periodontal microbiota and in the inflammatory process that leads to the destruction of alveolar bone. The critical involvement of the central complement component C3 in periodontal pathogenesis was confirmed in nonhuman primates, where local administration of a C3 in hibitor drug blocked naturally occurring periodontitis. The involvement of complement in periodontitis is unlikely to be re stricted to the proinflammatory activities of the complement cascade it self. Although transmigrating neutrophils initially follow the chemokine gradient deposited by the endothelium, they then have to move towards a gradient existing in the infected or inflamed tissue. Neutrophils make up the majority of leukocytes (95%) in the gingi val crevice, where they form a "defense wall" against the bacteria, presum ably to block their access to the underlying connective tissue. Although there is persistent and heavy recruitment of neutrophils to the periodontal pocket, they fail to control a dysbiotic microbial community despite their capacity to elicit immune and inflammatory responses. This implies that periodontitisassociated bacteria can largely escape neutrophilmediated killing in an inflammatory environment, which, as discussed above, provi des the bacteria with precious nutrients derived from inflammatory tissue breakdown. Because inflammation is important for the persistence of periodontitisassociated bacterial communities, bacteria have developed mechanisms whereby they can uncouple neutrophilmediated bacterial clearance from neutrophilmediated inflammation. Bacterial species that are otherwise susceptible to neutrophil killing are able to evade immune clearance in the presence of P. This "by stander protection" mechanism may, in part, account for the ability of Immunopathogenic Mechanisms in Periodontal Disease 343 P. There is adequate clinical evidence that neutrophils mediate a substan tial portion of periodontal tissue destruction and that their numbers corre late positively with the severity of the disease. Consistent with the clinical studies, mice that are genetically deficient in Del1, an endothelial cell secreted protein that regulates neutrophil recruitment from the circulation, display heavy neutrophil infiltration in the periodontium and spontane ously develop periodontitis. In contrast, littermate control mice that ex press Del1 remain periodontally healthy. Activated neutrophils can cause collateral tissue damage by releasing proinflammatory cytokines, cyto toxic reactive oxygen species, and matrixdegrading enzymes, such as colla genase. In this regard, neutrophils dwell and become activated within the gingival connective tissue under severe inflammatory conditions; therefore, neutrophils are literally in a position to contribute to connective tissue deg radation through the release of collagenase. Although neutrophils have been traditionally associated with acute in flammation, recent research has revealed previously unsuspected roles, in cluding regulatory interactions with both innate and adaptive immune leukocytes, also in settings of chronic inflammation. In an in vivo inflam matory environment, neutrophils may not be as shortlived as previously thought, and neutrophils from patients with chronic periodontitis live lon ger than those from healthy subjects. Rather than being rapidly exhausted at peripheral tissues, neutrophils are currently considered capable of mi grating to lymph nodes, where they can interact with dendritic cells to modulate antigen presentation to T cells. Therefore, neutrophils can par ticipate in the regulation of adaptive immunity, a notion that is supported by emerging evidence. In addition to stored granulederived antimicrobial molecules and enzymes, neutrophils are now appreciated for their de no vo biosynthetic capacity for chemokines and cytokines with proinflam matory, antiinflammatory, or immunoregulatory activities. Consequently, neutrophils have the potential to contribute to gingivitis and periodontitis not only by ini tiating the lesion but also by becoming involved in disease progression, i. Of course, neutrophils also perform protective functions in the perio dontium, and this becomes evident from the development of aggressive forms of periodontal disease in conditions associated with defects in the production, function, and life cycle of these cells. Being 344 Chapter 15 congenital, these disorders lead to periodontal inflammation and bone loss early in life, thus affecting both the primary and permanent dentition. Because of this deficiency, neutrophils fail to adhere to blood vessel walls and thus cannot extravasate to sites of infec tion or inflammation. Overall, although historically viewed as merely a first line of defense in acute infection or injury, neutrophils are now appreciated to have im munoregulatory roles and to play a critical role in chronic conditions. As there is a fine balance between homeostatic immunity and inflammatory pathology, periodontitis is particularly affected by alterations in neutro phil numbers or function. Periodontal health therefore requires "normal" numbers of neutrophils­­neither "too few" nor "too many. Moreover, the numbers of macrophages have been positively correlated with collagen breakdown and the severity of periodontal dis ease. In normal individuals, on the other hand, the re cruitment of neutrophils regulates the expression of the same cytokine cascade main taining homeostasis in terms of periodontal health and granulopoiesis. Interestingly, macrophage depletion also causes significant reduction in the levels of P. Mature macrophages display functional versatility (plasticity) as they can alter their activities, in response to local microenvironmental factors, to function appropriately in distinct conditions. In this context, macro phages can undergo M1 (classical) or M2 (alternative) activation. Relative to M2, M1 macrophages dis play increased ability for phagocytosis of microbes and enhanced expres sion of proinflammatory cytokines and antimicrobial molecules. M1 macrophages are therefore important for protection against bacterial pathogens and are early play ers in the course of infection or inflammation. Therefore, M2 macrophages have immunoregulatory properties and promote cell prolif eration and tissue regeneration. However, M1 and M2 represent extremes of a continuum of different activation states. A subset of macrophages associated with resolution of acute inflammation (resolving macrophages) shares properties of both M1 and M2. Given that nonresolving inflammation underlies the pathogenesis of many chronic diseases, including periodontitis, the ability of the host to resolve the inflammatory response in a timely manner becomes critical.

Syndromes

• Encephalitis (brain inflammation and infection)
• Reactions to medicines
• Females over 14 years: 3.0 mg/day
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Many of these in fections are extremely difficult to treat due to the high incidence of multi ple antibiotic resistance gastritis symptoms vs. heart attack buy ranitidine overnight delivery. The most frequently isolated bacterial agents in these infections include Enterococcus spp gastritis diet 3 day cheap ranitidine 150 mg online. This rate has dropped somewhat in the last few years chronic gastritis symptoms treatment purchase genuine ranitidine on-line, presumably due to targeted surveillance and increased awareness of infection control procedures gastritis low blood pressure buy generic ranitidine 300 mg online. Although the prevalence of antibioticresistant bacterial strains is likely lower in the community than in hospital settings gastritis diet ����� buy ranitidine 150 mg fast delivery, the trend toward preva lence of pathogens resistant to multiple antibiotics is an especially serious public health issue that is likely to have increasing implications for the den tal profession, especially in designing appropriate treatment for patients with a higher susceptibility to infection. For several reasons, infection control in hospitals is a much more com plex process than is infection control in the typical dental practice setting. Patient care in the hospital setting, including dental care, usually involves large numbers of staff with differing levels of training and understanding of infection control. Moreover, like hospitalized patients, dental patients receiving treatment in a hospital setting are at higher risk for exposure to antibioticresistant bacterial pathogens than are dental patients treated in the private practice setting. Despite these differences, the principles on which infection control practices are based are essentially identical in the two situations. The goal of this chapter is to identify risks for the transmission of infec tion in dental treatment settings, define strategies for managing these risks based on scientific evidence, and provide protocols for risk management. It is crucial for dental practitioners to realize that in addition to dealing with real risks of crossinfection during dental treatment, they must also address risk perception. Perception of risk has played a significant and not always positive role in shaping public health policy and has at times dra matically affected the relationship between the health professions and the public. As new potential risks are identified, policy makers, patients, and Infection Prevention and Control in Dentistry 527 health care practitioners are prone to either under or overreact based on fear. As scientific evidence becomes available on the actual risk of infec tion from newly identified potential threats, it is important that risk man agement strategies be revised and that health professionals and the public be educated. These sources are updated regularly as new information in the field is assessed and procedures for minimizing the risk of iatrogenic infections in dentistry evolve. DentalCheck was developed directly from the Infection Prevention Checklist for Dental Set tings (Table 1). It was designed specifically for use by dental health pro fessionals to periodically assess practices in their facility and ensure that they are meeting expectations for safe care. Practice of appro priate infection control procedures is an important part of overall assur ance of quality care. Outcome data from quality assurance assessments provide the evidence that the dentist and staff members are meeting ethi cal and legal obligations to patients and society. Cross-Infection Control Is Essentially a Set of Management Strategies for Risk Control Infection prevention in dentistry uses a singletier approach whereby all patients are treated as though they are a potential source of infectious pathogens. Whereas all patients are treated equally in terms of the quality assurance mechanisms that constitute infection control, the importance of medical history for determining best patient care must not be overlooked. Standard precautions are intended to prevent parenteral mucous mem brane and nonintact skin exposures of health care workers to blood borne pathogens. Specifically, dental health care workers should consider blood, saliva, and gingival fluid from all patients to be infectious. For the purposes of dental practice, crossinfection control equals risk man agement. The control of crossinfection involves a particular application of a risk management decisionmaking process, with risk identification, as sessment, or analysis, and implementation of risk control procedures. Al though quantitative data on the actual risks associated with many specific procedures are somewhat limited, the design of infection control protocols takes into account several important factors, including the following: · Known risks and hazards of specific dental procedures. Hazard is the potential harm (including the number of people exposed and the severity of conse quences) that may be suffered due to some particular incident or proce dure. Risk is the quantification of a hazard in terms of probability of the occurrence of harm. Risk assessment also considers the likelihood of trans mission of the infectious agent and the severity of the outcome of being infected. Perceptions of risk are influenced by many factors other than scientifically determined risk. These determinants of perceived risk tend to involve beliefs and feelings that are most easily understood from a socio logical or psychological perspective. A common example of perceived risk is that riding in an automobile is safer than flying in an airplane. The statis tics on passenger injury or death in airplane and automobile crashes do not support this perception, but it is nevertheless widespread. In designing effective risk management strategies for infection control in dentistry, it is necessary to address actual hazards and risks as well as to acknowledge the importance of perceived risks to the community and its confidence in the profession. Cer tain types of infectious agents are more likely to be transmitted by one route than another, so it is important to understand the significance and possible consequences of a failure of infection control procedures in any of the following transmission routes. The major potential risks include contamination of wounds during surgery and contamination of sterilized instruments during storage. In past incidents involving release of weaponized anthrax spores, this was an important fac tor that made the spores highly infectious and difficult to remove from contaminated locations. Elimination or limitation of organisms at source: · Postpone elective treatment during infective period. Infection Prevention and Control in Dentistry 531 · Flush ultrasonic scalers and air/water syringes for 2 minutes at the start of the practice day and for 30 seconds between patients. Typical standards for adequate ventilation are in the range of 5 to 8 liters/second per occupant, or approximately six air changes per hour. Direct Contact Routes of Cross-Infection Equipment · Dental instruments, chairs and units, and impression materials · Risk: bacterial and viral infectious agents · Prevention: 1. Disinfection of dental materials in contact with patients (impressions, for example) 4. The bulk containers should be disinfected between patients, unless the ma terial is dispensed into a disposable container (disclosing solution in cups, for example). Note the two disposable cups that are available to cover the dental handpiece when a bur is in place. Inoculation injury may be via eye, mucous membranes, breach in intact skin, or other sharps injury. The level of inoculation and infective dose of the particular organism determine the actual risk to the operator. While this would seem to be an obvious strategy given the education and training of health care professionals, it is an area in which there is room for improvement. In recent years, annual vaccination against viral influenza has become the recommended stan dard. Flu vaccination (which is typically effective only against current var iants of the virus) was originally recommended for members of specific highrisk groups, including the elderly and young children. Current recom mendations are that all persons aged 6 months and older be vaccinated annually. The actual vaccination rates are much lower (44% for adults and 60% for children in the United States in 2015­2016), with the elderly being vaccinated at much higher rates than other age groups. From the standpoint of infection control, placing patients at risk by failure of health care workers to be immunized against preventable com municable diseases cannot be professionally or ethically justified. While there are no available data specific to the dental profession in North America, there is no reason to assume that the levels of vaccina tion in this group are significantly different. Among health care personnel working in settings where vaccination was neither required, promoted, nor offered onsite, vaccination coverage continued to be low (44. There appear to be several fac tors contributing to relatively low levels of influenza vaccination in the health care professions, including the variable yeartoyear effectiveness of the vaccine, unsubstantiated claims of harmful effects of this and other vac cines, and persistent antivaccine efforts in some segments of the population. These issues need to be directly addressed by the dental community at the preprofessional, graduate, and postgraduate education levels. With all of these diseases, there has been emphasis on both identify ing potentially infected persons within the population and designing specific infection control methodologies to minimize the risks of transmission. It is important to note that there is very limited evidence available to date to suggest that dental procedures conducted with rigorous attention to infection control standards present a risk to the public or to the practi tioner. Even so, infec tion control standards are constantly evolving in response to new informa tion on specific infectious agents and newly available technologies. This service provides open access to extensive and uptodate training and educational materials. Several other recently identified emerging infectious diseases have been in the public eye in recent years. To date, there are no published reports implicating these agents in the practice of dentistry, and thus they do not necessitate measures beyond the current standard pre cautions to prevent disease transmission in health care settings. Standard practice already indicates postponing dental treatment for contagious indi viduals, whatever the disease. To date, there have been no significant changes in infection control measures in North America in response to the possible threat posed by prionassociated dis eases. In this context, the response of the European dental community may prove instructive. The disease was first observed in 1996 in humans and was found to be associated with the consumption of infected bovine tissue. For this reason, British practice standards recommend disposable products or, in instances when decontamination is necessary, extremely high levels of disinfection. The recom mended chemical disinfectant is 20,000 ppm of chlorine for 1 h, 2 M sodium hydroxide for 1 h, or (for histological samples) 96% formic acid. The risks of transmission of infection from dental instruments are very low, provided that optimal standards of infection control and de contamination are maintained. In all surgical procedures, the key consid eration in minimizing any risk of transmission is ensuring the efficacy of instrument decontamination, with emphasis on cleaning the instruments, even though current methods cannot remove such risks completely. Dental equipment, such as retracting shutoff valves, antiretracting valves that tend to fail, or water lines that are inaccessible, contribute to a situation in which vir tually every standard dental unit contains water with higher numbers of bacteria than the source water for the system. The pres Infection Prevention and Control in Dentistry 537 ence of organisms apparently derived from the oral cavity has been re ported (Table 2). However, definitive casecontrolled clin ical studies to quantitate these risks have not been performed. Furthermore, over onethird of dental personnel have been found to possess serum antibodies to L. Together, these studies suggest that chronic exposure to elevated levels of Legionella spp. At pres ent, commercially available options for improving dental unit water quality are rather limited. Several infection control methods and prevention strategies designed to reduce the impact of biofilms on dental water con tamination are currently available and suitable for use in general practice. These include periodic flushing and disinfection regimens and isolated sterile water reservoirs. Inline, replaceable, pointofuse filtration systems were developed in recent years, but these have proven generally impracti cal and are not currently marketed in the United States. When sterilization is achieved by a chemical agent, the chemical is called a sterilant. Disinfection is the killing, inhibition, or removal of microorganisms that may cause disease. Disinfecting agents, usually chemical, can be used on inanimate objects or on skin and mucosal membranes prior to medical intervention. A disinfectant does not necessarily sterilize an object because viable spores and a few microorganisms may remain. In sanitization, the microbial population is reduced to levels that are considered safe by pub lic health standards. Problems Posed for Prevention of Cross-Infection in General Dental Practice There are several characteristics of dental technique and the dental opera tory itself that contribute to the overall risk of transmission of infection during the course of standard dental procedures. Even the smaller dental practices treat high numbers of patients, resulting in a rapid turnover of patients. It is not uncommon for a single practitioner to schedule more than 25 patients per day. A wide variety and number of instruments are typically used, including highspeed dental drills and sonic scaling devices that gen erate aerosols. Many invasive minor surgical procedures result in breaches of epithelial tissue with associated bleeding. Depending on the oral health of the patient, dental hygiene treatment can also result in various degrees of bleeding. The practical (as well as the financial) burden of preventing trans mission of infection rests with the practitioner. Overall success in minimiz Infection Prevention and Control in Dentistry 539 ing risk to both dental practitioners and patients relies on the design and rigorous implementation of infection control policies and procedures that must be a seamless part of normal daily procedures involving all members of the staff. Personal protection for staff Physical design and written infection control policies Rigorous implementation of infection control policies Interactions with patients during treatment: importance of medi cal histories Note that the risk to be assessed is associated with the dental pro cedure, not the patient; i. Physical design and written infection control policies · Design the operatory to allow zoning and ease of handwashing and disinfection of surfaces. While maintaining standard precautions such that infec tion control is driven by the dental procedures, it is necessary to take individual patient health issues into account when designing treatment. This is to ensure that patients at higher risk for health carerelated infections due to dental procedures are protected at a level that is appropriate for their situation. For instance, antibiotic prophylaxis to reduce the risk of secondary infection may be in dicated for certain classes of patients: the immunocompromised, patients with implanted and prosthetic medical devices, and those with a history of certain cardiac valvular diseases or disorders. Note, 540 Chapter 22 however, that in many countries, the routine use of antibiotic pre medication has declined due to changes in coverage guidelines. Standard Precautions this section provides an example of the specific procedures and behaviors required to implement standard precautions in the dental care setting.

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