THERAPEUTIC USEOF ANTIBIOTICSDr.Salam Daradkeh,MDDepartment of General Surgery
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)
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.
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.
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.
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.
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.
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.
Disadvantages ofcombinations of anti-microbials Risk of toxicity. ↑ cost. Risk of antagonism. Risk of superinfection.
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.
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.