the spectrum of anitmicrobial activity action of antimicrobial drugs mechanism of antibiotics action inhibation of protein synthesis quinolones Antimeta metabolites

1. Emaneini M. PhD.
The Spectrum of Antimicrobial Activity
Narrow spectrum (limited spectrum)
 Antimicrobials effective against a (limited spectrum)
of microbial types
 A drug effective on G+ or G- bacteria
Broad spectrum (extended spectrum)
 Antimicrobials effective against a (extended spectrum) wide
variety of microbial types
 A drug effective against both G+& G- bacteria

2. Emaneini M. PhD.
The Action of Antimicrobial Drugs
Bactericidal
Kill microbes directly
Bacteriostatic
Prevent microbes from growing

3. Emaneini M. PhD.
Mechanisms of Antibiotics Action

4. Emaneini M. PhD.
1- Inhibition of Cell Wall Synthesis
2- Injuring the Plasma Membrane
3- Inhibition of Protein Synthesis
4- Inhibition of Nucleic Acid Synthesis
5- Inhibiting the Synthesis of Essential Metabolites
Mechanisms of Antibiotics Action

5. Emaneini M. PhD.
Inhibition of Cell Wall Synthesis
Transpeptidases, Carboxypeptidases, Transglycosylases
Penicillin-binding proteins (PBPs(
β-Lactam antibiotics: generally are bactericidal agents

6. Emaneini M. PhD.
1- Beta-Lactam Antibiotics
 Penicillins
 Cephalosporins
2- Glycopeptides
 Vancomycin
3- Lipopeptides
 Daptomycin
4- Polypeptides
 Bacitracin
Inhibition of Cell Wall Synthesis

7. Emaneini M. PhD.
Inhibition of Cell Wall Synthesis
Isoniazid, Ethionamide, Ethambutol, & Cycloserine
Used for the treatment of mycobacterial infections
Isoniazid
Isonicotinic acid hydrazide [INH])
Bactericidal; Blocks mycolic acid synthesis
Ethionamide
Derivative of INH
Blocks mycolic acid synthesis
Ethambutol
Interferes with the synthesis of arabinogalactan in the cell wall
Cycloserine
Inhibits D-alanine-Dalanine synthetase & Alanine racemase

8. Emaneini M. PhD.
Injuring the Plasma Membrane
1- Lipopeptides
Daptomycin
2- Polypeptides
Polymyxins

9. Emaneini M. PhD.
Inhibition of Protein Synthesis

10. Emaneini M. PhD.
Chloramphenicol
 Broad spectrum
 Bacteriostatic
 Blocking peptide elongation
 Binding reversibly to the peptidyl transferase (50S)
 Only for the treatment of typhoid fever
 Can produce aplastic anemia (1 per 24,000 treated patients)
 Resistance: plasmid-encoded chloramphenicol acetyltransferase

11. Emaneini M. PhD.
Inhibition of Nucleic Acid Synthesis
1- Quinolones
2- Rifampin
3- Metronidazole

12. Emaneini M. PhD.
 Synthetic
 Inhibit bacterial DNA gyrases (II) or topoisomerases (IV)
Nalidixic acid
Fluoroquinolones:
Ciprofloxacin Levofloxacin Gatifloxacin
Resistance: mutations in chromosomal genes of DNA gyrases (II)
or topoisomerases (IV)
Quinolones

13. Emaneini M. PhD.
Antimetabolites
Sulfonamides
 Preventing the synthesis of the folic acid
 Compete with p-aminobenzoic acid
 Mammalian organisms do not synthesize folic acid
Treatment of Nocardia, Chlamydia, & some protozoa infections
Sulfacetamide Sulfadiazine Sulfisoxazole
R Group