Isolation of Vibrio mimicus producing cholera toxin from stools in Shanxi province

Objective To isolate Vibrio mimicus (V.mimicus) from stool sample of cholera-like case, and detect whether it carried cholera toxin gene or not. Methods A diarrhea case with cholera-like symptom was investigated in Shanxi province. The stool and environmental samples were collected, cultured and isolated according to WS 289 - 2008 and cholera prevention and control manual (5th edition), suspected colonies were detected with serum agglutination test of Vibrio cholerae (V. cholerae), and API20E system was used to identify the bacteria. Meanwhile, the O1, O139 V. cholerae-specificity and cholera toxin gene of suspected colonies were detected by PCR. Results Stool samples were inoculated with selective medium, suspected colonies of V. cholerae were found in both gentamicin and alkaline agar, but in TCBS agar, green, transparent, medium size, smooth, moist colonies were observed; and in blood agar, gray, moist colonies and clear zone of hemolysis could be seen; After staining, no meteor-like movement of bacteria was observed on wet film under dark field. Oxidase and sticky silk test were positive, The serum agglutination test to detect V.cholerae O1,O139 and O141 were negative. The strain was identified as V. mimicus (93.5% possibility) with API20E. No V.mimicus was detected in environmental samples. PCR detection indicated the V. mimicus strain carried cholera toxin genes, but without V.cholerae O1, O139-specificity. Conclusion For specimens from cases of cholera like illness, when serum agglutination test of V.cholerae was negative, further detection of cholera toxin should be taken.