Therapeutic use of antibiotics

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Therapeutic use of antibiotics

  1. 1. THERAPEUTIC USEOF ANTIBIOTICSDr.Salam Daradkeh,MDDepartment of General Surgery
  2. 2. Definition of antibiotic Chemical substances produced by various species of micro-organisms (bacteria,fungus,actinomycetes)that suppress the growth of other micro- organisms and they eventually destroy them. antibiotics≈ Antimicrobials(sulfonamide,quinolones)
  3. 3. Classification &mechanism ofaction Inhibition of cell wall synthesis:→cell lysis penicillin,cephalosporins,vancomycin,bacitracin, miconazole,ketoconazole and clotrimazole. Alteration of cell membrane permeability: polymyxin,colisthemate,nystatin,amphotericine B. Affect the function of bacterial ribosomes: chloramphenicol,tetracycline,erythromycine,clin damycin.
  4. 4. Classification &mechanism ofaction Binding to 30S ribosomal subunit:alter protein synthesis. Aminoglycosides. Affect nucleic acid metabolism: rifampicine,quinolones. Anti-metabolites: sulfonamides, trimetoprim. Nucleic acid analogs: Zidovudine ,acyclovir ganciclovir,vidarabine.
  5. 5. Eradication of surgicalinfection? Debridement of necrotic tissue. Drainage of abscess. Removal of infected foreign bodies. Maintenance of adequate nutritional status. Use of antibiotics or antimicrobials.
  6. 6. Classes of antibiotics Penicillins:effective against group A streptococcus,pneumococcus,clostridiu m,D streptococcus.no role against G negative with the exception of Neisseria . - Peni.G - Anti-staph.:carbenicillin,methicillin, oxacillin,nafcillin. - easy gram - :ampicillin,amoxycillin.
  7. 7. COURSE&DURATION OFTHERAPY Continuous monitoring. Chronicity of infections:liver abscess, osteomyelitis. Site &source of infection. Virulence of infecting micro-organisms. Host response to microbial challenge.
  8. 8. Factors influencing favorableoutcome Level of antimicrobial agent at site of infection. Dose must be sufficient to produce the necessary effect but must be below the toxic level. In-vitro sensitivity. Location of infection.
  9. 9. Indications of anti-microbialcombination Treatment of mixed bacterial infections: intra-abdominal,liver, brain,UTI. Therapy of severe infections in which a specific cause is unknown. Enhancement of antibacterial activity in the treatment of specific infections. Prevention of the emergence of resistant micro-organisms.
  10. 10. Disadvantages ofcombinations of anti-microbials Risk of toxicity. ↑ cost. Risk of antagonism. Risk of superinfection.
  11. 11. Factors influencing selection ofantimicrobials Susceptibility of the infecting micro- organisms. Bactericidal vs bacteriostatic agents. Dose,route,duration of therapy. Allergy & toxicity. Site of infection. Combination therapy , synergism, antagonism.
  12. 12. Reasons of failure ofantimicrobial therapy Failure to adjust the dose of the antibiotic. Treatment of nonbacterial infections. Superinfections. Drug reaction. Incorrect drugs. Defects in host resistance.

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