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ANTIBIOTICS Slide 2 The selection of antibiotic therapy for an infection requires a knowledge of: 1The infecting organism, including the pathogen most likely to be present in given clinical or geographical circumstances 2The local patterns of antimicrobial resistance in common pathogens 3 An understanding of the pharmacokinetics of the antimicrobials selected 4 The physiology of the patient, metabolic upset, renal or hepatic dysfunction, age and available routes of administration. The clinical history should determine the systems of the body most likely to be involved in disease. Figure 6.3 (p. 133) shows common pathogens found in different systems.Figure 6.3p. 133 The Selection of Antibiotic Slide 3 Slide 4 ENDOGENOUS INFECTIONS-RESERVOIRS OF INFECTIONS IN ADULTS The human body is in contact with many potentially infectious agents: bacteria, viruses, fungi or protozoa. Most are harmless colonisers causing no clinical upset but forming a natural reservoir of potential infection in the human host Slide 5 Common Infecting Organisms. Slide 6 Selection of Antibiotics Identification of Infecting organism Slide 7 Empirical treatment Prior to Identification of Organism 1.The Acutely Ill patient 2. Selecting a Drug Slide 8 C.Determining the Antimicrobial Susceptibility of the Organism Bacteriostatic vs Bacteriocidal MIC MBC D. Effect of Site of Infection on Therapy: Blood Brain Barrier Lipid solubility of drug Mol wt Protein Binding Slide 9 E. Patient Factors Immune system Renal dysfunction Hepatic dysfunction Poor perfusion Age Pregnancy Lactation F. Drug Safety G. Cost of therapy Slide 10 Route of Administration Determination of Rational Dosing 1 Concentration dependent killing 2. Post antibiotic effect Slide 11 Slide 12 SITES OF MICROBIAL ACTION Slide 13 Chemotherapeutic Spectra Narrow Extended Broad Combination of Antimicrobials Advantages Disadvantages Slide 14 DRUG RESISTENCE 1.Genetic alteration Spontaneous mutation DNA transfer of drug resistence 2. Altered expression of proteins in drug resistant organisms Modification of target sites Decreased accumulation Enzyme inactivation Slide 15 PROPHYLACTIC ANTIBIOTICS Rheumatic heart disease Dental work in pts with valves, prosthesis TB Surgery Pregnant mother - zidovudine Slide 16 COMPLICATIONS OPF ANTIBIOTIC THERAPY Hypersensitivity Direct toxicity Superinfections Slide 17 Inhibitors of Cell Wall Synthesis Slide 18 PENICILLIN Slide 19 PENICILLIN G Slide 20 Extended Penicillins ORAL - Amoxycillin IV -Ampicillin Wider range Broken down by penicillinase Combined with penicillinanse (BETA LACTAMASE) inhibitors - Clavulanic acid Sulbactam Tazobactam Augmentin- Amoxy+sulbactam Slide 21 Anti Staphylococcal Penicillins Oral & Not inactivated by penicillinases ( BETA LACTAMASE ) Cloxacillin Dicloxacillin Flucloxacillin Slide 22 ADVERSE EFFECTS OF PENICILLINS Slide 23 Stability of penicillins to acid & penicillinases Slide 24 CEPHALOSPORINS Slide 25 Slide 26 OTHER BETA LACTAM ANTIBIOTICS- CARBAPENEMS& MONOBACTAMS Slide 27 OTHER CELL WALL INHIBITORS- VANCOMYCIN SIDE-EFFECTS