Clonal transmission, dual peak, and off-season cholera in Bangladesh.
Clonal transmission, dual peak, and off-season cholera in Bangladesh.
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DOI：
10.3402/iee.v1i0.7273
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发表时间：
2011
影响因子：
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通讯作者：
Cravioto A
中科院分区：
文献类型：
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作者：
Alam M;Islam A;Bhuiyan NA;Rahim N;Hossain A;Khan GY;Ahmed D;Watanabe H;Izumiya H;Faruque AS;Akanda AS;Islam S;Sack RB;Huq A;Colwell RR;Cravioto A
霍乱弧菌是一种河口细菌，与孟加拉国沿海村庄的一次霍乱高峰（3月至5月）有关。然而，由于未知原因，霍乱在达卡市以独特的双高峰（3月至5月和9月至11月）模式发生，该城市与严重污染的淡水河流系统和防洪堤接壤。2007年8月，在达卡发生极端洪水的同时，爆发了异常严重的腹泻，导致患病人数创历史新高。这项研究的目的是了解这次不寻常的暴发，以及它是否与一种新的霍乱弧菌克隆的传播有关。在2007年疫情高峰期分离的19例霍乱弧菌进行了广泛的表型和分子分析，包括通过聚合酶链反应（PCR）进行多位点遗传筛选、ctxB基因序列分型和脉冲场凝胶电泳（PFGE）。确定了与霍乱异常发病率相关的因素，并对疾病严重程度进行了分析。总体而言，微生物学和分子学数据证实，高毒力霍乱弧菌为01生物型El - Tor (ET)，具有经典生物型霍乱毒素（CT）。PFGE （NotI）和树形图聚类证实，该菌株是克隆的，与达卡和Matlab的2007年前变体ET有关，与孟加拉国河口生态系统中确认存在的变体ET的两个不同克隆之一相似。对连续三年（2006-2008年）腹泻病例数据和三十年（1980-2009年）区域水文气候学数据的分析结果清楚地表明，在达卡的两个季节性霍乱高峰期间及其之间，洪水通过粪-口途径传播传染性克隆体，而在其他流行地点未见这种霍乱模式。环形河流系统和防洪堤可能促进传染性霍乱弧菌全年传播，导致达卡人口稠密的城市生态系统突然和淡季暴发。在不断变化的气候和城市人口不断增长的地区，毒力日益增强的杂交El Tor的无性系再循环是孟加拉国面临的一个严重的公共卫生问题。
Vibrio cholerae is an estuarine bacterium associated with a single peak of cholera (March–May) in coastal villages of Bangladesh. For an unknown reason, however, cholera occurs in a unique dual peak (March–May and September–November) pattern in the city of Dhaka that is bordered by a heavily polluted freshwater river system and flood embankment. In August 2007, extreme flooding was accompanied by an unusually severe diarrhea outbreak in Dhaka that resulted in a record high illness. This study was aimed to understand the unusual outbreak and if it was related to the circulation of a new V. cholerae clone. Nineteen V. cholerae isolated during the peak of the 2007 outbreak were subjected to extensive phenotypic and molecular analyses, including multi-locus genetic screening by polymerase chain reaction (PCR), sequence-typing of the ctxB gene, and pulsed-field gel electrophoresis (PFGE). Factors associated with the unusual incidence of cholera were determined and analysis of the disease severity was done. Overall, microbiological and molecular data confirmed that the hypervirulent V. cholerae was O1 biotype El Tor (ET) that possessed cholera toxin (CT) of the classical biotype. The PFGE (NotI) and dendrogram clustering confirmed that the strains were clonal and related to the pre-2007 variant ET from Dhaka and Matlab and resembled one of two distinct clones of the variant ET confirmed to be present in the estuarine ecosystem of Bangladesh. Results of the analyses of both diarrheal case data for three consecutive years (2006–2008) and regional hydroclimatology over three decades (1980–2009) clearly indicate that the pattern of cholera occurring in Dhaka, and not seen at other endemic sites, was associated with flood waters transmitting the infectious clone circulating via the fecal-oral route during and between the dual seasonal cholera peaks in Dhaka. Circular river systems and flood embankment likely facilitate transmission of infectious V. cholerae throughout the year that leads to both sudden and off-season outbreaks in the densely populated urban ecosystem of Dhaka. Clonal recycling of hybrid El Tor with increasing virulence in a changing climate and in a region with a growing urban population represents a serious public health concern for Bangladesh.