How Anti Microbial Work And treat you ? Principle of Anti Microbials

 PRINCIPLE OF ANTI-MICROBIAL THERAPY

Selection of Anti-microbial therapy 

1)organism‟s identity 

2)organism‟s susceptibility to particular agent 3)site of infection 

4)patient‟s factor

 5)safety of agent 

6) cost of therapy

Empiric therapy 

In emergency situation, before the identification of organism Broad spectrum antibiotics used called as empiric therapy . 

Bacteriostatic Antibiotics that arrest the Growth & Replication of bacteria at serum level thus limiting spread of infection until body‟s immune sys. Attack, immobilize & eliminate it from body

e.g Chloramphenicol bacteriostatic against Gram –Ve rod 

Bactericidal Antibiotic Kill bacteria at drug serum level e.g Chloramphenicol bactericidal against S.pneumonia

Minimum Inhibitory Concentration MIC=Lowest conc. Require to inhibit bacterial growth

Minimum Bactericidal Concentration MBC=Minimum conc. That kills the bacteria 

✔️ Chloramphenicol + Metronidazole cross B.B.B having lipid solubility 

✔️ Pencillin doesnot cross B.B.B but cross in Meningitis 

✔️ Erthromycin and Tetracyclline used with caution in Liver dysfunction

✔️ Tetracycline cause tooth dysplasia & ϴ bone growth in fetus…

✔️ Some Anthelmentic are embryotoxic & teratogenic

✔️ Aminoglycoside cause ototoxicity in fetus

Conc. Dependent killing by Aminoglycoside

Time-dependent killing by β-lactam, Macrolide, Glycopeptide, Clindamycin, Linezolid.

Post-antibiotic effect: persistent suppression of microbial growth after levels of antibiotic have fallen below MIC…e.g Aminoglycoside, Flouroquinolones

Narrow-Spectrum Antibiotics:  against one or limited group of micro-organism e.g Isoniazid against Mycobacteria 

Extended-Spectrum Antibiotics: effective against gram-+Ve bacteria e.g Ampicillin 

Broad-Spectrum Antibiotics: effect a wide variety of microbial species e.g Tetracycline, Chloramphenicol 

Superinfection:

 Administration of Broad-Spectrum antibiotics cause destruction of normal flora & precipitate growth of Clostridium Difficile, the growth of which normally kept in check by the presence of other organism 

Drug Resistance: 

1) Genetic alteration 

2) mutation in DNA 

3)DNA transfer of drug resistance by R factor 

4)modification of target site 

5)decreased accumulation or by ↑ efflux 

6)enzyme inactivation .