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Individual cell lag time distributions of Cronobacter (Enterobacter sakazakii) and impact of pooling samples on its detection in powdered infant formula.

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Article
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Miled, R.B. ; Guillier, L. ; Neves, S. ; Augustin, J.C. ; Colin, P. ; Besse, N.G.

FOOD MICROBIOLOGY

Ecole Nationale Veterinaire d'Alfort, Unite Microbiologie des Aliments - Securite et Qualite (MASQ), 7 avenue du General de Gaulle, F-94704 Maisons-Alfort Cedex, France.Agence nationale de securite sanitaire Anses Laboratoire de securite des aliments, Anses 23 Avenue du General de Gaulle, 94706 Maisons Alfort Cedex, France.

2011

Article

Abstract: Cells of six strains of Cronobacter were subjected to dry stress and stored for 2.5 months at ambient temperature. The individual cell lag time distributions of recovered cells were characterized at 25degreesC and 37degreesC in non-selective broth. The individual cell lag times were deduced from the times taken by cultures from individual cells to reach an optical density threshold. In parallel, growth curves for each strain at high contamination levels were determined in the same growth conditions. In general, the extreme value type II distribution with a shape parameter fixed to 5 (EVIIb) was the most effective at describing the 12 observed distributions of individual cell lag times. Recently, a model for characterizing individual cell lag time distribution from population growth parameters was developed for other food-borne pathogenic bacteria such as Listeria monocytogenes. We confirmed this model's applicability to Cronobacter by comparing the mean and the standard deviation of individual cell lag times to populational lag times observed with high initial concentration experiments. We also validated the model in realistic conditions by studying growth in powdered infant formula decimally diluted in Buffered Peptone Water, which represents the first enrichment step of the standard detection method for Cronobacter. Individual lag times and the pooling of samples significantly affect detection performances.
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