The demonstration of method suitability should be performed using the challenge organisms listed (see Tables IIa–b) in accordance
with the recommendations found in USP Chapter ‹1227› (9). Growth promotion is an area of some ambiguity in the compendial text. Although media-growth promotion
is not described in the tests, it is required. USP Chapter ‹1117› (10) provides assistance in designing the studies using 10–100 CFUs of the challenge organisms.
Table IIa: Aspects of the current and harmonized microbial limits tests (enumeration).
A major concern of many quality control workers is whether the changes in the harmonized chapter will necessitate the revalidation
of existing assays to meet harmonized test requirements. Several considerations might lead to revalidation: a required change
in media, in the volume of material required for testing, or in general testing conditions. It is difficult to determine whether
all product types would require revalidation, and thus a summary table (see Tables IIa–b) is included in this article to describe
the critical aspects of the current "Microbial Limits Tests (Enumeration)" and the draft harmonization text. This table is
provided only as an aid. The decision of whether or not revalidation is necessary rests with each individual facility for
its particular products.
Table IIb: Aspects of the current and harmonized microbial limits tests (enumeration).
USP ‹62› "Absence of Specified Microorganisms"
There is a significant controversy in the United States over the intent of this evaluation. FDA is bound by the concern expressed
in the Code of Federal Regulations (21 CFR 211.113 and 21 CFR 211.165) relating to the importance of "objectionable microorganisms." This issue is addressed in the final section of this
review because the harmonized Chapter ‹1111› deals with "other organisms."
Tables IIIa–c presents the existing "Microbial Limits—Absence of Specified Microorganisms" tests from the current USP and Pharm Eur, as well as the harmonized document. It is presented as an aid to evaluation, and may assist in determining whether revalidation
of method suitability studies is needed. It should be noted that this harmonized chapter represents a true compromise by all
parties, with (at least in the author's opinion) significant changes from the current USP, Pharm Eur, and JP chapters. Table IV provides guidance about the media-growth promotion expectations of the new chapters.
Table IIIa: Absence of specified microorganisms.
As the reader reviews these sections, it is reasonable to consider the current validation (or microbial recovery or method
suitability) studies performed for currently marketed products. It is very likely that many of these studies may need to be
performed again to meet the expectations of the harmonized procedure.