Faruque S M, Ahmed K M, Abdul Alim A R, Qadri F, Siddique A K, Albert M J
Molecular Genetics Laboratory, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
J Clin Microbiol. 1997 Mar;35(3):624-30. doi: 10.1128/jcm.35.3.624-630.1997.
The emergence of Vibrio cholerae O139 Bengal in 1993, its rapid spread in an epidemic form, in which it replaced existing strains of V. cholerae O1 during 1992 and 1993, and the subsequent reemergence of V. cholerae O1 of the El Tor biotype in Bangladesh since 1994 have raised questions regarding the origin of the reemerged El Tor vibrios. We studied 50 El Tor vibrio strains isolated in Bangladesh and four other countries in Asia and Africa before the emergence of V. cholerae O139 and 32 strains isolated in Bangladesh during and after the epidemic caused by V. cholerae O139 and 32 strains isolated in Bangladesh during and after the epidemic caused by V. cholerae O139 to determine whether the reemerged El Tor vibrios were genetically different from the El Tor vibrios which existed before the emergence of V. cholerae O139. Analysis of restriction fragment length polymorphisms in genes for conserved rRNA, cholera toxin (ctxA), and zonula occludens toxin (zot) or in DNA sequences flanking the genes showed that the El Tor strains isolated before the emergence of V. cholerae O139 belonged to four different ribotypes and four different ctx genotypes. Of 32 El Tor strains isolated after the emergence of O139 vibrios, 30 strains (93.7%) including all the clinical isolates belonged to a single new ribotype and a distinctly different ctx genotype. These results provide evidence that the reemerged El Tor strains represent a new clone of El Tor vibrios distinctly different from the earlier clones of El Tor vibrios which were replaced by the O139 vibrios. Further analysis showed that all the strains carried the structural and regulatory genes for toxin-coregulated pilus (tcpA, tcpI, and toxR). All strains of the new clone produced cholera toxin (CT) in vitro, as assayed by the GM1-dependent enzyme-linked immunosorbent assay, and the level of CT production was comparable to that of previous epidemic isolates of El Tor vibrios. Further studies are required to assess the epidemic potential of the newly emerged clone of V. cholerae O1 and to understand the mechanism of emergence of new clones of toxigenic V. cholerae.
1993年霍乱弧菌O139孟加拉型的出现，它以流行形式迅速传播，在1992年和1993年期间取代了现有的霍乱弧菌O1菌株，以及自1994年以来孟加拉国埃尔托生物型霍乱弧菌O1的再次出现，引发了关于再次出现的埃尔托弧菌起源的问题。我们研究了在霍乱弧菌O139出现之前在孟加拉国以及亚洲和非洲其他四个国家分离的50株埃尔托弧菌菌株，以及在霍乱弧菌O139引起的疫情期间和之后在孟加拉国分离的32株菌株，以确定再次出现的埃尔托弧菌在基因上是否与霍乱弧菌O139出现之前存在的埃尔托弧菌不同。对保守rRNA、霍乱毒素（ctxA）和小带闭合毒素（zot）基因中的限制性片段长度多态性或基因侧翼的DNA序列进行分析表明，在霍乱弧菌O139出现之前分离的埃尔托菌株属于四种不同的核糖体分型和四种不同的ctx基因型。在O139弧菌出现后分离的32株埃尔托菌株中，30株（93.7%）包括所有临床分离株属于单一的新核糖体分型和明显不同的ctx基因型。这些结果提供了证据，表明再次出现的埃尔托菌株代表了埃尔托弧菌的一个新克隆，与被O139弧菌取代的早期埃尔托弧菌克隆明显不同。进一步分析表明，所有菌株都携带毒素共调节菌毛的结构和调节基因（tcpA、tcpI和toxR）。通过GM1依赖性酶联免疫吸附测定法检测，新克隆的所有菌株在体外都产生霍乱毒素（CT），并且CT产生水平与之前埃尔托弧菌疫情分离株相当。需要进一步研究来评估新出现的霍乱弧菌O1克隆的流行潜力，并了解产毒霍乱弧菌新克隆的出现机制。
