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

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

World Journal of Microbiology and Biotechnology 10(1): 59-63

1994


ISSN/ISBN: 0959-3993
PMID: 24420888
DOI: 10.1007/bf00357565
Accession: 009723947

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Abstract
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.

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