Detection of the viable but nonculturable Escherichia coli O157:H7 in aquatic microcosm / 中华预防医学杂志

ABSTRACT

<p><b>OBJECTIVES</b>This study is to monitor the survival of E. coli O157H7 in the aquatic microcosm from Han River and explore the feasibility of fluorescence staining, heterotrophic plate count and ELISA in detection of viable but nonculturable E. coli O157H7.</p><p><b>METHODS</b>E. coli O157H7 were added into aquatic microcosm from Han River and cultured with low temperature and oligo-nutrition. Then the survival of E. coli O157H7 were real-time monitored by acridine orange direct count (AODC), direct viable count (DVC)-CTC staining, DVC-nalidixic acid (NA) staining, heterotrophic plate count (HPC) and ELISA.</p><p><b>RESULTS</b>E. coli O157H7 can be converted to a viable but nonculturable state in the aquatic microcosm from Han River 58 days after cultured at 4°C with oligo-nutrition. The amount of viable E. coli O157H7 was measured as 1.2 × 10(5) CFU/ml by DVC-CTC and 9.0 × 10(4) CFU/ml by DVC-NA, whereas the amount of culturable bacterial determined by HPC is 0. The amounts of bacteria determined by ELISA are basically stable within 58 days around 10(6) CFU/ml.</p><p><b>CONCLUSION</b>E. coli O157H7 can be converted into a viable but nonculturable state in Han River water at 4°C with oligo-nutrition, and ELISA combined with fluorescence staining and heterotrophic plate count can be used in quantitative detection of the viable but nonculturable E. coli O157H7.</p>