Chemical Methods of Microbial Control

Chemotherapeutic Drug

Any chemical used in the treatment, relief, or prophylaxis of a disease

Prophylaxis

Use of a drug to prevent potential infection in a person at risk

Antimicrobial Chemotherapy

The use of chemotherapeutic drugs to control infection

Antimicrobials

Any antimicrobial drug, regardless of its origin

Antibiotic

A substance produced by microbes that can inhibit growth or destroy other microbes

Semisynthetic Drugs

Compounds chemically modified in the laboratory after being isolated from natural sources

Synthetic Drugs

Compounds synthesized entirely in the laboratory through chemical reactions

What test can be done instead of the Kirby Bauer test?

Minimum Inhibitory Concentration Test

Kirby-Bauer Method

Uses antibiotics containing disks to test whether particular bacteria are susceptible to specific antibiotics

Kirby-Bauer Antibiotic Sensitivity Test

Media - Mueller-Hinton agar

Media pH - 7.2-7.4

Amount of bacteria - 150 million bacterial cells/ml of liquid

Age of culture for st-up - 2-6 hours old

Times plates are incubated - 18-24 hours

Temperature of incubation - 35-37 °C

Spreading technique - bacterial lawn

Bacterial Lawn

spread 3 different times on agar plate

Zone of Inhabitation (mm)

Measurement of circular area around the antibiotic disk

Results of Kirby-Bauer Test: Resistant

Antibiotic has no effect on the bacteria

Results of Kirby-Bauer Test: Intermediate

Antibiotic is only moderately effective against the bacteria

Results of Kirby-Bauer Test: Sensitive

Antibiotic is effective against the bacteria (prevents growth)

Broad Spectrum Antibiotics

Effective against a large range of bacteria

Narrow Spectrum Antibiotics

Effective against a small group of bacteria

Bactericidal

Kills bacteria

Bacteriostatic

Inhibit reproduction of bacteria, allows immune system to eliminate them

What are the General Actions of Antibiotics?

1. Cell wall inhibitors

2. Cell membrane

3. DNA/RNA

4. Protein synthesis inhibitors acting on ribosomes

5. Metabolic pathways & products