Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa, Israel. Division of Bacteriology, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo 162-8640, Japan. Department of Gastrointestinal Sciences, Christian Medical College, Vellore, India. Department of Biology, Faculty of Science and Science Education, University of Haifa, Oranim, Tivon 36006, Israel.
Environ Microbiol Rep. 2010 Feb;2(1):96-103. doi: 10.1111/j.1758-2229.2009.00109.x. Epub 2009 Dec 21.
Environmental Vibrio cholerae strains belonging to the non-O1/non-O139 serogroups are natural inhabitants of freshwater including estuarine environments. Recent findings indicated that chironomids (Diptera: Chironomidae), the most widely distributed insects in freshwater, serve as a natural reservoir of these bacteria. Here we study the role of chironomids, particularly exuviae as carriers and as a monitoring tool for the distribution of V. cholerae in the environment. During a survey conducted in India (June 2006), 326 V. cholerae non-O1/non-O139 isolates were isolated from chironomid egg masses, larvae and exuviae. In addition, a heat-stable enterotoxin (nag-st) positive strain was isolated from exuviae during the local cholera outbreak. We identified 62 different strains in a subset of 102 isolates by analysis of variable number of tandem repeats (VNTR), demonstrating a high variation of V. cholerae on hosting chironomids. Our results show that chironomids can both maintain and distribute this overwhelming diversity of environmental V. cholerae strains, including toxigenic ones. Exuviae proved to be an efficient tool for the monitoring of environmental V. cholerae, offering simple, direct and practical access for on-shore collection. Finally, finding toxigenic V. cholerae on chironomids in endemic areas, together with molecular typing, may potentially improve monitoring of cholera in the future.
环境中的霍乱弧菌非 O1/O139 血清群菌株是淡水包括河口环境的自然居民。最近的研究结果表明，摇蚊（双翅目：摇蚊科）是淡水分布最广泛的昆虫，是这些细菌的天然宿主。在这里，我们研究了摇蚊（尤其是其蜕壳）作为细菌载体和监测工具在环境中分布的作用。在印度进行的一项调查中（2006 年 6 月），从摇蚊卵块、幼虫和蜕壳中分离出了 326 株非 O1/O139 霍乱弧菌。此外，在当地霍乱爆发期间，从蜕壳中分离出了一株耐热肠毒素（nag-st）阳性菌株。我们通过分析可变数串联重复（VNTR）对 102 个分离株中的一个子集进行分析，鉴定出了 62 种不同的菌株，表明霍乱弧菌在宿主摇蚊上的变异很高。我们的结果表明，摇蚊既可以维持又可以传播这种环境中霍乱弧菌的多样性，包括产毒性菌株。蜕壳被证明是监测环境中霍乱弧菌的有效工具，为岸上采集提供了简单、直接和实用的方法。最后，在流行地区在摇蚊上发现产毒性霍乱弧菌，与分子分型相结合，可能有助于未来更好地监测霍乱。
