4.1 Numerous ASTM test methods and practices (for example: Test Methods D5259 and D5392, and Practices D6974 and E2563) report colony counts as their measured parameter.

4.2 These practices provide a uniform set of counting, calculating, and reporting procedures for ASTM test methods in microbiology.

Section

A—Counting Colonies on Membrane Filters

6

B—Counting Colonies on Pour Plates

7

C—Counting Colonies on Spread Plates

8

4.3 The counting rules provide a best attainable estimate of microorganisms in the sample, since the samples cannot be held and reanalyzed at a later date.

1.1 These practices cover recommended procedures for counting colonies and reporting colony-forming units (CFU) on membrane filters (MF) and standard pour and spread plates.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.