Page 46 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

4- Alcohols

• It dissolves lipid membranes and denature proteins.

• They are effective against most fungi and bacterial cells, but cannot kill

endospore-formers. (Intermediate-level disinfectants or antiseptics)

• The most effective concentrations ranging from 60%- 90% (commonly 70%).

cidal activity drops sharply below 50% concentration

• The presence of water is essential for activity.

• Alcohols have poor penetration of organic matter, and their use is,
therefore, restricted to clean conditions.

• Use: - Antiseptic

- Disinfectant: Clinical thermometers, stethoscopes computers, rubber
stoppers of multiple-dose medication vials

The presence of water is a crucial factor in destroying or
inhibiting the growth of pathogenic microorganisms

Water enhances the effectiveness of alcohol as a disinfectant by:

- acting as a catalyst in protein denaturation
- slowing evaporation, which increases surface contact time
- 70% alcohol solutions penetrate the cell wall more completely which

permeates the entire cell, coagulates all proteins, and therefore the
microorganism dies.
o Isopropyl alcohol concentrations over 91% coagulate proteins too quickly,
creating a protective layer that reduces effectiveness

.

Alcohols are not recommended for sterilizing medical and
surgical materials, because of

- their lack of sporicidal action and
- their inability to penetrate protein-rich materials

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