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Adjunctive and Prophylactic Use of Antibacterial Agents in Dentistry

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OverviewLearning ObjectivesIntroductionMicrobiology of Odontogenic InfectionsPharmacology of Systemic Antibacterial AgentsInhibitors of Bacterial Cell Wall SynthesisInhibitors of DNA Synthesis or Integrityzithromycin has an extended spectrum that includes some anaerobic gram-positive cocci and gram-negative bacilli.or TranslationStrategies for the Treatment of Odontogenic InfectionsPrimary Dental CareAdjunctive Antibacterial ChemotherapyProphylactic Antibacterial ChemotherapyPrescription-precautions Associated with Antibacterial AgentsAntibacterial Drug-resistanceGastrointestinal DistressHypersensitivity ReactionsCardiovascular EffectsCentral Nervous System EffectsOral CandidiasisAntibacterial Drugs and PregnancyAntibacterial Drugs and NursingDrug-drug InteractionsConclusionIntroduction – Antibacterial Agents in DentistryParticipants in Adjunctive and Prophylactic Use of Antibacterial Agents in Dentistry will be introduced to evidence-based information related to the microbiology of odontogenic infections, the pharmacology of systemic antibacterial agents, and the rationale for the selection of an antibacterial agent for the treatment of odontogenic infections.OverviewParticipants in this course will be introduced to evidence-based information related to the microbiology of odontogenic infections, the pharmacology of systemic antibacterial agents, and the rationale for the selection of an antibacterial agent for the treatment of odontogenic infectionsand for prophylactic therapy.Learning ObjectivesUpon completion of this course, the dental professional should be able to:- Discuss the microbiology of odontogenic infections.- Discuss the pharmacology of systemic antibacterial agents.- Discuss indications for the adjunctive administration of antibacterial agent.o Select the most appropriate agent.- Discuss indications for antibacterial prophylaxis.o Select the most appropriate regiment.- Discuss potential ADEs associated with the administration of antibacterial agents.IntroductionThe human foetus is free of microorganisms.1 After initial exposure at birth, most organisms are soon eliminated, but others become permanently established and the dynamic process of colonization begins. The adult body harbours a dense, diverse, indigenous flora that includes bacteria, viruses, fungi and protozoa. Interaction between these various microbial ecosystems determines the normal flora. Microorganisms of the normal flora establish symbiotic relationships (mutualism, commensalisms, or parasitism) with their human host and each other.2,3Factors that modify or shift the balanced environment of the normal flora (age, altered anatomy, diet, local and systemic conditions, or pharmacotherapy) may predispose an individual to infection.4,5 Infection, the invasion and multiplication of microorganisms in body tissues, results in cellular injury due to competitive metabolism, toxin production, or immune-mediated reactions. An infection may be autogenous, caused by the body’s normal flora; or it may be a cross-infection, related to the proliferation of transient organisms.6Microbiology of Odontogenic InfectionsPredicated on their metabolic characteristics, i.e., their metabolic demand for oxygen, bacteria are classified as aerobic, facultative, or anaerobic. Morphologically, they are characterized as cocci or bacilli (rods). Based on Gram’s Method of staining (Box 1), bacteria are further classified as gram-positive or gram-negative. The distinct staining properties of bacteria are related to their architectural and biochemical differences.7Box 1. Gram’s Method of Staining.7Step 1. Apply a thin film of the specimen to a glass slide and allow it to dry.Step 2.Fix the slide in methanol for 1 minute or fix by quickly passing the slide through a flame several times.Step 3. Flood the slide with crystal violet stain for 30 seconds.Step 4. Rinse gently with running water.Step 5. Flood the slide with Gram’s iodine wash for 30 seconds.Step 6. Rinse gently with running water.Step 7. Apply acetone decolorizer so it runs over stained areas until no more color washes out.Step 8. Rinse gently with running water.Step 9. Flood the slide with safranin counterstain for 30 seconds.Step 10.Rinse gently under running water and allow the slide to air dry.Gram-positive bacteria possess a thick peptidoglycan cell wall interspersed with lipoteichoic acid underlain by the cytoplasmic membrane (Figure 1).8 Gram-negative bacteria have an outer membranewith lipopolysaccharides and a lipoprotein layer underlain by a thin peptidoglycan layer and the cytoplasmic membrane (Figure 2).8 The ability of antibacterial agents to diffusion into bacteria is also affected by these structural differences.Figure 1. Gram-positive Bacteria.Figure 2. Gram-negative Bacteria.Figures 1&2, modified from Kasmar AG, Hooper D. Pharmacology of bacterial infections: cell wall synthesis. In Golan DE, Tashjian, Jr. AH, Armstrong EJ, Armstrong AW. Ed. Principles of pharmacology. The pathophysiologic basis of drug therapy. 2nd ed. 2008. Wolters Kluwer/Lippincott Williams & Wilkins. Baltimore, MD.8During staining, crystal violet interacts with iodine forming a complex. Acetone extracts lipids from the outer membrane, cell wall, and cytoplasmic membrane of bacteria.7 The damage to gram-negative organisms is more extensive and they lose their crystal violet-iodine complexes, i.e., they are decolorized; and when counterstained with safranin, they appear red (Figure 3).7 Gram-positive bacteria retain their crystal violet-iodine complexes and appear deep purple (Figure 4).7Figure 3. Gram-negative Organisms.Figure 4. Mixed Gram-positive and Gram-negative Organisms.An average adult harbors at least 300 oral bacterial species and more than 700 strains of bacteria have been isolated from test cases.9-11 Most odontogenic infections are polymicrobial. The number of strains per infection ranges from 1 to 10 with an average number of 4 isolates.9,12-24 The predominant flora creates an ecosystem of synergism by elaborating a more favorable acidic environment and decreased oxygenation to support the growth and proliferation of its members. Ultimately, facultative and anaerobic gram-positive and gram-negative cocci and bacilli predominate in all types of odontogenic infections (Table 1).9-31Table 1. Bacteria Detected in Odontogenic Infections.26,27Gram-staining and morphologic characteristics Facultative anaerobes Obligate anaerobesGram-positive


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