Respective Roles of Culturable and Viable-but-Nonculturable Cells in the Heterogeneity of Salmonella enterica Serovar Typhimurium Invasiveness

The existence of Salmonella enterica serovar Typhimurium viable-but-nonculturable (VBNC) cells is a public health concern since they could constitute unrecognized sources of infection if they retain their pathogenicity. To date, many studies have addressed the ability of S. Typhimurium VBNC cells to...

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Bibliographic Details
Published in:Applied and Environmental Microbiology 2009-08, Vol.75 (16), p.5179-5185
Main Authors: Passerat, Julien, Got, Patrice, Dukan, Sam, Monfort, Patrick
Format: Article
Language:English
Subjects:
Apoptosis
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Biological and medical sciences
Cell culture
Centrifugation, Density Gradient - methods
Colony Count, Microbial
Culture Media
DNA-Binding Proteins - genetics
DNA-Binding Proteins - metabolism
Fundamental and applied biological sciences. Psychology
Gene expression
Gene Expression Regulation, Bacterial
HeLa Cells - microbiology
Humans
Infections
Microbial Viability
Microbiology
Public Health Microbiology
Salmonella
Salmonella enterica
Salmonella typhimurium - genetics
Salmonella typhimurium - growth & development
Salmonella typhimurium - pathogenicity
Salmonella typhimurium - physiology
Trans-Activators - genetics
Trans-Activators - metabolism
Transcription Factors - genetics
Transcription Factors - metabolism
Virulence
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Summary:The existence of Salmonella enterica serovar Typhimurium viable-but-nonculturable (VBNC) cells is a public health concern since they could constitute unrecognized sources of infection if they retain their pathogenicity. To date, many studies have addressed the ability of S. Typhimurium VBNC cells to remain infectious, but their conclusions are conflicting. An assumption could explain these conflicting results. It has been proposed that infectivity could be retained only temporarily after entry into the VBNC state and that most VBNC cells generated under intense stress could exceed the stage where they are still infectious. Using a Radioselectan density gradient centrifugation technique makes it possible to increase the VBNC-cell/culturable-cell ratio without increasing the exposure to stress and, consequently, to work with a larger proportion of newly VBNC cells. Here, we observed that (i) in the stationary phase, the S. Typhimurium population comprised three distinct subpopulations at 10, 24, or 48 h of culture; (ii) the VBNC cells were detected at 24 and 48 h; (iii) measurement of invasion gene (hilA, invF, and orgA) expression demonstrated that cells are highly heterogeneous within a culturable population; and (iv) invasion assays of HeLa cells showed that culturable cells from the different subpopulations do not display the same invasiveness. The results also suggest that newly formed VBNC cells are either weakly able or not able to successfully initiate epithelial cell invasion. Finally, we propose that at entry into the stationary phase, invasiveness may be one way for populations of S. Typhimurium to escape stochastic alteration leading to cell death.
ISSN:0099-2240
1098-5336
1098-6596
DOI:10.1128/AEM.00334-09