Development of a sensitive detection method for stressed E. coli O157:H7 in source and finished drinking water by culture-qPCR

Environ Sci Technol. 2011 Mar 15;45(6):2250-6. doi: 10.1021/es103365b. Epub 2011 Feb 22.


A sensitive and specific method that also demonstrates viability is of interest for detection of E. coli O157:H7 in drinking water. A combination of culture and qPCR was investigated. Two triplex qPCRs, one from a commercial source and another designed for this study were optimized from 5 different assays to be run on a single qPCR plate. The qPCR assays were specific for 33 E. coli O157:H7 strains tested and detected 500 cells spiked in a background of 10(8) nontarget bacterial cells. The qPCR detection was combined with an enrichment process using Presence Absence (P/A) broth to detect chlorine and starvation stressed cells. qPCR analysis performed post-enrichment allowed the detection of 3-4 cells/L as indicated by a sharp increase in fluorescence (lowering of Ct values) from pre-enrichment levels, demonstrating a 5-6 log increase in the number of cells. When six vulnerable untreated surface water samples were examined, only one was positive for viable E. coli O157:H7 cells. These results suggest that the culture-PCR procedure can be used for rapid detection of E. coli O157:H7 in drinking water.

MeSH terms

  • Bacterial Typing Techniques / methods*
  • Chlorine / toxicity
  • Disinfectants / toxicity
  • Escherichia coli O157 / drug effects
  • Escherichia coli O157 / genetics
  • Escherichia coli O157 / isolation & purification*
  • Fresh Water / chemistry
  • Fresh Water / microbiology*
  • Polymerase Chain Reaction
  • Stress, Physiological
  • Water Pollutants, Chemical / toxicity
  • Water Purification
  • Water Supply / analysis*


  • Disinfectants
  • Water Pollutants, Chemical
  • Chlorine