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


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.


CONCLUSIONS
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.
Lothigius
A
A
WHO Collaborating Centre for Research on Enterotoxigenic Escherichia coli (ETEC), and Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden. asa.lothigius@microbio.gu.se
Sjöling
A
A
Svennerholm
A-M
AM
Bölin
I
I
D058491:Bacterial Load; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism; D054307:Enterotoxigenic Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D004768:Enterotoxins / Q000235:genetics / Q000378:metabolism; D005618:Fresh Water / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D050296:Microbial Viability; D012623:Seawater / Q000382:microbiology*
D001426:Bacterial Proteins; D004768:Enterotoxins; D002265:Carboxylic Ester Hydrolases; C098953:EstA protein, bacteria