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Survival and gene expression of enterotoxigenic Escherichia coli during long-term incubation in sea water and freshwater.

Journal article
Authors Åsa Lothigius
Åsa Sjöling
Ann-Mari Svennerholm
Ingrid Bölin
Published in Journal of applied microbiology
Volume 108
Issue 4
Pages 1441-1449
ISSN 1365-2672
Publication year 2010
Published at Institute of Biomedicine, Department of Microbiology and Immunology
Pages 1441-1449
Language en
Keywords ETEC, gene expression, survival, VBNC, water
Subject categories Microbiology


Abstract Aims: In this study, the main objective was to verify the hypothesis of induction of 'viable but non-culturable' (VBNC) forms of enterotoxigenic Escherichia coli (ETEC) during incubation in water. Methods and Results: Six clinically isolated ETEC strains were studied. Viable counts showed culturable ETEC bacteria for up to 3 months in freshwater but only two out of six strains were culturable in seawater at this time point. Although the bacterial cells remained intact, no production or secretion of heat-labile (LT) or heat-stable (ST) enterotoxins was observed using GM1-ELISA methods. However, genes encoding ETEC toxins (STh and LT), colonization factors (CS7 and CS17), gapA and 16S RNA were expressed during 3 months in both sea water and freshwater microcosms as determined by real-time RT-PCR on cDNA derived from the bacteria. Conclusions: Clinically isolated ETEC strains can survive for long periods in both sea water and freshwater. The bacterial cells remain intact, and the gene expression of virulence genes and genes involved in metabolic pathways are detected after 3 months. Significance and Impact of the Study: These results indicate that ETEC bacteria can enter a VBNC state during stressful conditions and suggest that ETEC has the potential to be infectious after long-term incubation in water.

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