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Introduction to Antibiotics 1 st yr( Respiratory block) Prof. Azza Elmedany

Introduction to Antibiotics 1 st yr( Respiratory block) Prof. Azza Elmedany. Chemical substances produced by various microorganisms that have the capacity to inhibit ( bacteriostatic ) or destroy ( bacteriocidal ) other microorganisms Now a day they are chemically synthesized drugs.

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Introduction to Antibiotics 1 st yr( Respiratory block) Prof. Azza Elmedany

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  1. Introduction to Antibiotics1st yr( Respiratory block)Prof. Azza Elmedany

  2. Chemical substances produced by various microorganisms that have the capacity to inhibit (bacteriostatic ) or destroy ( bacteriocidal ) other microorganisms Now a day they are chemically synthesized drugs. Antibiotics will not cure infections caused by viruses. Definition of Antibiotics

  3. CLASSIFICATION OF ANTIBIOTICSACCORDING TO MECHANISM OF ACTION • INHIBITION OF CELL WALLSYNTHESIS e.g. Penicillins • INHIBITION OFPROTEIN SYNTHESISe.g.Macrolides • INHIBITION OF NUCLEIC ACIDSYNTHESIS e.g. Quinolones.

  4. According to spectrum • Narrow spectrum , e.g.: penicillin G , aminoglycosides • Broad spectrum , e.g.: ampicillin ,amoxicillin

  5. Antibiotic Prescription Clinical situation Microbiologicalinformation Pharmacological consideration

  6. Choice of Antimicrobial Drugs • Clinical diagnosis e.g. Syphilis 2. Bacteriological identification a) infecting organism is notidentified (UTIs ,meningitis). b) infecting organism is identified but sensitivity to antibiotic isn’t known (T.B) 3. Site of infection

  7. Choice of Antimicrobials ( Cont.) 4. Host factors a) Immune system e.g. diabetes, HIV, malnutrition, advanced age. b) Genetic factors e.g. Patients with G-6-PD deficiency treated with sulfonamides c) Pregnancy and Lactation Aminoglycosides- hearing loss in the child Tetracyclines- injury to the developing teeth ( child ) d) Age of the patient e.g. Grey baby Syndrome (chloramphenicol) Discoloration of teeth (tetracycline) e) Renal function e.g. Aminoglycosides in renal failure f)Liver function e.g. Erythromycin in hepatic failure

  8. Choice of Antimicrobials ( Cont.) 5. Drug Allergy 6. Potential Side Effects (Drug safety) Chloramphenicol ( a plastic anaemia) Tetracyclines in children Flouroquinolones in children &pregnancy ( cartilage damage ) 7. The cost of therapy

  9. MISUSES OF ANTIBIOTICS • Treatment of untreatable infections e.g. viral infections • Improper dosage. • Therapy of fever of unknown origin. • Reliance on chemotherapy with omission of surgical drainage ( pus or necrotic tissues ). • Excessive use of prophylactic antibiotics intravelers. • Lack of adequate bacteriological information.

  10. BACTERIAL RESISTANCE Definition Concentration of antibiotic required to inhibit or kill the bacteria is greater than the concentration that can safely be achieved in the plasma.

  11. Administer drug in full dose, atproper interval and by the best route Apparent cure achieved-continue for about 3 days further to avoid relapse Two or more antimicrobials should not be used without good reason, e.g.: Mixed bacterial infections Ill patient of unknown etiology To prevent emergence of resistance (e.g. TB ) To achieve synergism e.g. piperacillin+ gentamicin (p. aeruginosae) General Principles of Chemotherapy

  12. Benefit of chemotherapeutic combination • Broaden the spectrum of antibacterial activity • Reduce the doses • Reduce the side effects • Overcome microbial resistance (TB ) • Produce a more potent compound ( co-trimoxazole) • produce a synergistic effect (penicillin with gentamycin • Treatment of severe infections (septicaemia )

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