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U.S. Department of Health and Human Services


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Questions and Answers on Method for E. sakazakii in Powdered Infant Formula

Note: E. sakazakii has been renamed to Cronobacter. Please see Chapter 29 of the Bacterial Analytical Manual (BAM).


August 2002

Question: Does FDA intend to use this method to test ingredients during the inspection?

Answer: FDA inspectors will be collecting specific raw material components along with finished product. Our analysts will use the above method to determine presence/absence only of the organism in the raw material. Quantitative determination will only be performed on the finished product.

Question: Is it possible to make a quantitative determination (MPN) of E. sakazakii if a non-selective pre-enrichment step is used?

Answer: Yes. Performed correctly, the method will result in a quantitative E. sakazakii determination.

Question: Can we get clarification on the FDA procedure for performing the DNase agar. The medium manufacture (BBL Microbiology Systems) for the DNase Agar with Toluidine Blue recommends looking for bright rose-pink zones surrounding colonies or band inoculum in a Prussian blue medium. The FDA has stated to look for the growth surrounded by clear zone is as typical of positive deoxyribonuclease production.

Answer: The DNase agar test along with two other tests were added to the method as E. Additional tests to further distinguish E. sakazakii from other species of the genus Enterobacter. FDA laboratories will be using the API 20E biochemical identification system (along with Table 1 attached to the method--see note below) to make the distinction between the various Enterobacter species. To avoid any confusion, we will remove E. Additional testing from the method.

Note: The original Table 1 attached to the method contained an error. The reaction on yellow pigment for E. sakazakii should read "+", not "-".

Isolation and Enumeration of Enterobacter sakazakii from Dehydrated Powdered Infant Formula July 2002; Revised August 2002