Page 22 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

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

• For example, endospore-forming bacteria will take longer to kill than non-
endospore forming bacteria.

5) Physical and Chemical Factors

• Type of water (hard vs. soft): Hard water may reduce the rate of killing
of microorganisms.
- Hard water reduces the rate of kill of certain disinfectants because
divalent cations (e.g., magnesium, calcium) interact with the

disinfectant to form insoluble precipitates
• Temperature: An increase in the temperature at which chemical acts often

enhances its activity.
• pH: An increase in pH improves the antimicrobial activity of some
disinfectants (e.g., glutaraldehyde, quaternary ammonium

compounds) but decreases the antimicrobial activity of others.

6) Activity level of the method or agent

Agents that are cidal will be more effective at reducing
microbial contamination than agents that are static.

7) Nature of the object
- porous vs. nonporous surface

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