Determination of Enterobacteriaceae

Laboratory Procedure MFLP-43
September 1997

1. Application

This method is applicable to the enumeration of viable Enterobacteriaceae in accordance with the requirements of Sections 4 and 7 of the Food and Drugs Act. This revised method replaces MFLP-43 dated May, 1988.

2. Description

This method has been shown to produce satisfactory results with naturally-contaminated foods for the detection of

Enterobacteriaceae (11.1-11.4). The MPN method applies in the analysis of foods containing small numbers of coliforms, since the sensitivity is not limited by the amount of food homogenate that can be introduced into a Petri dish.

3. Principle

This method estimates the numbers of viable Enterobacteriaceae per g or mL of product. A portion of the product is mixed with a specified agar medium and incubated under specified conditions of time and temperature. It is assumed that each viable microorganism will multiply under these specified conditions of incubation and give rise to a visible colony which can be counted.

4. Definitions of Terms

See Appendix A of Volume 3.

5. Collection of Samples

See Appendix B of Volume 3.

6. Materials and Special Equipment

1) 0.1% Peptone Water.

2) Petri dishes, glass (100 x 15 mm) or plastic (90 x 15 mm).

3) 1-, 5-, and 10-mL bacteriological pipettes, sterile.

4) Water bath or air incubator for tempering agar, 44-46°C.