The antibiotics, important considerations for their use, their classification, synergistic and antagonistic effect, hypersensitivity reactions and development of resistance to these agents.

1. 1© Capt Dr Muhammad Aamir Farooq | Pak Army

2. Antibiotics
2© Capt Dr Muhammad Aamir Farooq | Pak Army

3. Introduction
• Chemical substance produced by microorganism
• Having bactericidal or bacteriostatic action
• Antibiotics are produced by
• Moulds
• Actinomyces
• Bacteria
• Synthesized
• Excessive use creates resistance to these drugs
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4. Sequence
• History
• Classification of Antibiotics
• Combination of Drugs
• Hypersensitivity
• Antimicrobial Resistance (AMR)
• Imp Considerations for Antibiotic Use
• conclusion
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5. History
• In 19th century Pasteur noted antagonistic effect of organism on
others
• Paul Ehrlich developed idea of selective toxicity
• In 1928 Sir Alexander Fleming observed effect of Penicillium
notatum on Staphylococcus
• Penicillin was isolated in 1939
• In 1944 Selman Waksman & Albert Schatz isolated streptomycin
from Streptomyces griseus
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6. Classification of Antibiotics
• CHEM Structure
• Tetracycline
• Penicillin
• Aminoglycosides
• Macrolides etc
• Spectrum of Activity
• Narrow spectrum
• Broad spectrum
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7. Classification of
Antibiotics
Activity Against Bacteria
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8. Classification of
Antibiotics
Mechanism of Action
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9. combinations of Drugs
• Antibiotic Synergism
• Activity of two drugs in combinations is greater to sum of their
independent activity
• Antibiotics having synergistic effect includes:-
• Penicillin
• Cephalosporin
• Bactracin
• Vancomycin
• Aminoglycosides
• Polymyxins 9
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10. Combinations of Drugs
• Antibiotic Antagonism
• Activity of two drugs in combinations is less to sum of their
independent activity
• Antibiotics having antagonistic effect include
• Chloramphenicol
• Tetracycline
• Erythromycin
• Clindamycin
• Sulphnamides 11

11. Hypersensitivity
• Exaggerated response of immune system to antibiotic
• Reactions may be damaging, uncomfortable, or occasionally fatal
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12. Hypersensitivity
• Desensitization protocols are designed to treat type-1 hypersensitivity
• Induction of drug tolerance without an adverse reaction
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13. Antimicrobial Resistance (AMR)
• Ability of a microbe to resist the effect of medication to which they
were once sensitive
• Resistance arises through one of the following ways:-
• Natural resistance
• Genetic mutation
• Misuse of antibiotics
• Resistant microbes are inc difficult to treat
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14. AMR
15
Mechanism of AMR
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15. AMR
• Causes of AMR
• Inappropriate prescribing of antibiotics
• Uncontrolled sale in many low income countries
• Missing doses when taking antibiotics
• Antibiotic use in livestock
• Lack of hygiene
• Vol of antibiotic prescribed
16
© Capt Dr Muhammad Aamir Farooq | Pak Army

16. (AMR)
• Prevention
• Decreased duration of antibiotic treatment
• Limit use of antibiotics in animals
• Min antibiotic usage
• Alternate therapy
• Development of new drugs
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17. Reasons for Failure of Antibiotic Therapy
• Wrong diagnosis e.g. viral not bacterial infection
• Unsusceptible organism
• Susceptible organism later develop resistance
• Mixed infection & insufficient antibiotic cover
• combinations of incompatible antibiotics
• Super infection by resistant opportunistic pathogen occurred
• Re-infection by original or by other pathogen
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18. Reasons for Failure of Antibiotic Therapy
• Inadequate drainage or presence of foreign body in surgeries
• Access to site of infection because of inflammation, cellular debris,
tissue destruction & abscessation
• Animal deficient mechanism weakened due to disease,
malnutrition
• Incorrect dosage or route of administration
• Expired or substandard products
• Poor nursing & inadequate nutrition
• Stress of disease
19© Capt Dr Muhammad Aamir Farooq | Pak Army

19. Imp Considerations for Antibiotic Use
• Obtaining an accurate diagnosis of infection
• Ident opportunities to switch to narrow spectrum
• Understanding drug pharmacodynamics & efficacy
• Recognizing the adverse effect of drugs on the host
• Correct dosage & route of administration
• Nutrition state of animal especially protein & vitamins
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20. Conclusion
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21. 21
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22. 22
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23. Classification of Antibiotics
• β-Lactam Drugs
• Drugs which have β-Lactam ring in their structure
• These include following
• Penicillin
• Cephalosporins
• Involved in inhibition of cell wall synthesis
• May be inhibited by lactamases enzymes
© Capt Dr Muhammad Aamir Farooq | Pak Army

24. • Penicillin
Penicillin binds at active site of transpeptidase that cross-links
peptidoglycan strands by mimicking D-alanyl-D-alanine residues that
normally bind to this site
Classification of Antibiotics
© Capt Dr Muhammad Aamir Farooq | Pak Army

25. Classification of Antibiotics
• Penicillin
Drugs Family Static Cidal Action
Ampicillin
Penicillin
- +
Inhibit
Cell wall
synthesis
Carbenicillin - +
Cloxacillin - +
Methicillin - +
Nafcillin - +
Penicillin-G - +
© Capt Dr Muhammad Aamir Farooq | Pak Army

26. Classification of Antibiotics
• Cephalosporins
• Semi-synthetic antimicrobial agents which are derivatives of 7-
amino cephalosporanic acid
• Closely related in structure to penicillin
• Have a beta-lactam ring
• Highly resistant to penicillinase
• Transpeptidation-inhibited by cephalosporins
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27. 1st Generation (Gram +ve)
Staphylococci Streptococci
Cephalosporins
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28. 1st Generation (Gram –ve)
E-coli Proteus Klebsiella(Not All)
Salmonella Shigella Enterobacter(Not All)
Cephalosporins© Capt Dr Muhammad Aamir Farooq | Pak Army

29. • 2nd Generation
• All 1st Generation
• Haemophilus influenza
• Enterobacter aerogenes
• Neisseria
Cephalosporins
© Capt Dr Muhammad Aamir Farooq | Pak Army

30. • 3rd Generation (Gram -ve)
• All 1st & 2nd Generations organisms plus
• Hospital Acquired Infections
• Pseudomonas aeruginosa
• Urinary tract infection
• Hospital-acquired pneumonia
• Vancomycin-resistant Enterococcus
Cephalosporins
© Capt Dr Muhammad Aamir Farooq | Pak Army

31. • Aminoglycosides
Classification of Antibiotics
31© Capt Dr Muhammad Aamir Farooq | Pak Army

32. • Aminoglycosides
Drugs Family Static Cidal Action
Gentamycin
Aminoglycosi-
des
- +
Inhibit
Protein
Synthesis
Kenamycin - +
Neomycin - +
Streptomycin - +
Classification of Antibiotics
32© Capt Dr Muhammad Aamir Farooq | Pak Army

33. • Quinolones
Block bacterial DNA synthesis by inhibiting topoisomerase II (DNA
gyrase) in G -ve organisms or topoisomerase IV in G +ve
organisms such as Staph. aureus
Classification of Antibiotics© Capt Dr Muhammad Aamir Farooq | Pak Army

34. Classification of Antibiotics
• Macrolides
Inhibit protein synthesis by binding on ribosomal subunits
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35. Classification of Antibiotics
Drugs Family Static Cidal Action
Erythromycin
Macrolide
+ -
Inhibit
Protein
Synthesis
Azithromycin + -
Tylosin + -
• Macrolides
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36. Classification of Antibiotics
• Tetracycline
Inhibit protein synthesis by binding on 50 S ribosomal subunits
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37. Classification of Antibiotics
Drugs Family Static Cidal Action
Tetracycline Tetracyclins + -
Inhibit
Protein
Synthesis
• Tetracycline
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38. Dihydropteroic acid
Dihyrofolic acid
Tetrahydrofolic acid
PABA+ Pteridine
Sulfonamide
TrimethoprimDihydrofolate Reductase
Dihydrofolate Synthetase
Dihydropteroate Synthetase
Classification of Antibiotics
• Sulphonamides
© Capt Dr Muhammad Aamir Farooq | Pak Army
38

39. Drugs Family Static Cidal Action
Sulphadiazine
Sulpho-
namides
+ -
Inhibit
Cytoplasmic
Function
Sulphamerazine + -
Sulphadimetho-
xIine
+ -
Classification of Antibiotics
• Sulphonamides
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40. Gram-negative
Gram-positive
Anaerobic
P. aeruginosa
H. influenzaeNeissseria spp
E. Coli
(coliforms)
S. aureus
Streptococcus spp
Bacteroides spp
Clostridium spp
Enterococcus spp
Classification of Antibiotics
• Sulphonamides
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41. Classification of Antibiotics
• Vancomycin
It also inhibit cell wall synthesis by same mechanism as penicillins
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42. Classification of Antibiotics
• Bacitracin
It interferes with dephosphorylation of bactoprenol pyrophosphate
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43. Classification of Antibiotics
• Polymyxins
After binding to lipopolysaccharide (LPS) in outer membrane,
polymyxins disrupt both outer & inner membranes
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44. Classification of Antibiotics
• Rifampin
Rifampicin inhibits bacterial DNA-dependent RNA synthesis by
inhibiting bacterial DNA-dependent RNA polymerase
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