Vibrio mimicus are the reservoirs of the heat-stable enterotoxin gene (nag-st) among species of the genus Vibrio

P. Yuan, A. Ogawa, T. Ramamurthy, G. B. Nair, T. Shimada, S. Shinoda, T. Takeda

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Using a 0.27 kb DNA probe specific for the heat-stable enterotoxin gene (nag-st) of Vibrio cholerae non-O1, 1109 strains representing 17 species of the genus Vibrio, isolated from clinical and environmental sources were examined. The nag-st gene was preponderantly associated with strains classified as V. mimicus; 16.8% of these strains hybridized. It was more frequent in the clinical isolates (22.6%) than in the environmental isolates (13.7%). The incidence of nag-st gene-positive strains of V. mimicus isolated from different countries was uniformly high and ranged between 8.7% (Bangladesh) and 57.1% (environmental strains from USA). The incidence of the nag-st gene was much lower among strains of V. cholerae non-O1 (3.6%). Probe-positive and-negative strains of V. mimicus and V. cholerae non-O1 were used to evaluate the performance of the conventional suckling mouse assay for detection of the NAG-ST enterotoxin. Of the 31 probe-positive strains, only five (16.1%) yielded a positive fluid accumulation ratio (FA ratio) when neat heated culture supernatant was used to perform the suckling mouse assay. All the 31 probe-positive strains gave a positive FA ratio when 20-fold concentrated and heated culture supernatants of the strains were used to perform the suckling mouse assay. The need to concentrate (by at least 20-fold) the culture supernatant of strains of V. mimicus and V. Cholerae non-O1 was identified as an important step to obtain consistent results when using the suckling mouse assay for detection of NAG-ST.

Original languageEnglish
Pages (from-to)59-63
Number of pages5
JournalWorld Journal of Microbiology & Biotechnology
Issue number1
Publication statusPublished - Jan 1 1994



  • DNA probe
  • NAG-ST
  • Vibrio
  • Vibrio mimicus
  • heat-stable enterotoxin

ASJC Scopus subject areas

  • Biotechnology
  • Physiology
  • Applied Microbiology and Biotechnology

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