Contamination of potable water distribution systems by multiantimicrobial-resistant enterohemorrhagic Escherichia coli.
BACKGROUND
The contamination of processed or unprocessed drinking water by fecal coliform bacteria has been reported worldwide. Despite a high incidence of waterborne diseases, entero-hemorrhagic Escherichia coli (EHEC) is an underacknowledged pathogen of concern to public health in India. Although the presence of EHEC is recorded in surface water resources of India, drinking water sources are yet to be investigated.


OBJECTIVE
The goal of this study was to analyze potable water samples for the presence of virulence determinants of EHEC and to determine the sensitivity of the virulence determinants to antimicrobials.


METHODS
We enumerated coliform bacteria in potable water samples collected from six locations in Lucknow, a major city in northern India, using the most probable number method. E. coli (n = 81), randomly isolated by membrane-filtration technique from four sites, were identified by biochemical characterization. E. coli were not detected in samples from two other sites. We screened 15 randomly selected isolates from each site for virulence determinants of EHEC using polymerase chain reaction (PCR). The isolates positive for virulence determinants (n = 18) were screened for sensitivity to 15 antimicrobials by the disk diffusion method.


RESULTS
Both stx1 and stx2 genes were present in 33.3% of isolates, whereas others possessed either stx1 (11.1%) or stx2 (55.6%). eaeA, hlyA, and chuA genes were present in 100, 23.3, and 16.7% of isolates, respectively. Resistance to multiple antimicrobials was observed in potential EHEC.


CONCLUSIONS
The occurrence of multiantimicrobial-resistant EHEC in potable water is an important health concern because of the risk of waterborne outbreaks.
Ram
Siya
S
Environmental Microbiology Division, Industrial Toxicology Research Centre, Mahatma Gandhi Marg, Lucknow, India.
Vajpayee
Poornima
P
Shanker
Rishi
R
D018829:Adhesins, Bacterial / Q000235:genetics; D000890:Anti-Infective Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics; D006460:Hemolysin Proteins / Q000235:genetics; D007194:India; D011956:Receptors, Cell Surface / Q000235:genetics; D022622:Shiga Toxin 1 / Q000235:genetics; D022641:Shiga Toxin 2 / Q000235:genetics; D014774:Virulence; D014871:Water Microbiology; D014881:Water Supply / Q000032:analysis*
D018829:Adhesins, Bacterial; D000890:Anti-Infective Agents; D001425:Bacterial Outer Membrane Proteins; C423457:ChuA protein, E coli; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D011956:Receptors, Cell Surface; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; C073819:eaeA protein, E coli