Ecological and molecular-epidemiological studies of Vibrio cholerae related bacteria in Indian Subcontinent

霍乱弧菌在印度次大陆，特别是恒河流域的水环境中定殖，并周期性地引起霍乱流行。在霍乱弧菌的206个血清型中，只有O 1和139引起流行性霍乱，而非O 1/非O 139菌株不会引起流行性霍乱，尽管观察到零星的霍乱病例。为了阐明该地区霍乱的流行特征，对来自环境和临床来源的霍乱弧菌进行了分离和分析。对孟加拉地区两个来源的霍乱弧菌分离株进行了分析，特别强调了分子流行病学特征。用PCR方法检测菌株的毒力基因ctxA、tcpA和toxR。脉冲场凝胶电泳（PFGE）进行，以确定临床和环境菌株之间的克隆关系。临床和环境来源的O 1和O 139菌株均为3种毒力基因阳性，而非O 1/非O 139菌株除1株外，ctxA和tcpA均为阴性，而toxR为阳性。最近分离的O 1和O 139的PFGE模式是相似的，在每个血清型，无论起源，虽然与过去的分离株比较显示出一些差异。非O 1/非O 139菌株。经典型ctxA、tcpA阳性。这些结果表明，有一个临床和环境菌株之间的克隆关系和水生环境作为水库的致突变霍乱弧菌。

Vibrio cholerae colonizes aquatic environments in Indian-subcontinent, especially in Ganges Basin, and causes cholera epidemics periodically. Of the 206 serovars of V.cholerae, only O1 and 139 cause epidemic cholera, whereas non-O1/non-O139 strains do not, although sporadic diarrheal cases are observed. To clarify epidemic feature of cholera in these area, V.cholerae strains were isolated from from environmental and clinical origins and analysed.V.cholerae isolates from both origins in the Bengal region were analyzed with particular emphasis on the molecular epidemiological feature. Presence of the virulence genes (ctxA,tcpA and toxR) in the isolates was analyzed by PCR(polymerase chain reaction) method. PFGE (pulsed-field gel electrophoresis) was performed to determine the clonal relationships between clinical and environmental strains. O1 and O139 strains from both clinical and environmental sources were all positive for the three virulence genes while nonO1/non-O139 strains from both sources were all negative for ctxA and tcpA, except a strain, but positive for toxR. PFGE patterns of recent isolates of O1 and O139 were similar in each serovar regardless of origins, although comparison with past isolates showed some differences. An exceptional non-O1/non-O139 strain. was positive for ctxA and tcpA of classical type. These results indicate that there is a clonal relationship between clinical and environmental strains and the aquatic environments serve as reservoirs of toxigenic V.cholerae.