Pour plates

• Membrane filtration

• Surface spread plates

• The "most probable number" approach

Pour plates and membrane filtration are widely used; surface spread plates are more commonly used for counting microorganisms in pure culture work. The most probable number approach is a method of last resort and its supporting statistical tables are limited, as they do not properly address mold recovery. Each of these four approaches splits into two methods.

• Counting numbers of aerobic bacteria per unit weight or volume of product

• Counting numbers of yeasts and moulds per unit weight or volume of product

Microbiologists debate endlessly whether the two methods are mutually exclusive, and how to derive a total count if they are not. Most of this debate is only of academic interest. For quality control (QC) purposes safe conservative assumptions are that:

• Bacteria are never recovered in the test for yeasts and molds

• Yeasts and molds are never recovered in the test for aerobic bacteria

• The total count is the sum of the two

With properly formulated preparations manufactured under controlled GMP conditions, actual recoverable numbers are rarely within a decimal order of magnitude of the specified limits. Any manufacturer producing a nonsterile aqueous-based preparation close to (or frequently failing) the pharmacopoeial limits for numbers of microorganisms, is already in trouble!

Was this article helpful?

0 0
Reasons, Remedies And Treatments For Heartburns

Reasons, Remedies And Treatments For Heartburns

Find Out The Causes, Signs, Symptoms And All Possible Treatments For Heartburns!

Get My Free Ebook


Post a comment