Faruque Shah M, Biswas Kuntal, Udden S M Nashir, Ahmad Qazi Shafi, Sack David A, Nair G Balakrish, Mekalanos John J
Molecular Genetics Laboratory, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka-1212, Bangladesh.
Proc Natl Acad Sci U S A. 2006 Apr 18;103(16):6350-5. doi: 10.1073/pnas.0601277103. Epub 2006 Apr 6.
The factors that enhance the waterborne spread of bacterial epidemics and sustain the epidemic strain in nature are unclear. Although the epidemic diarrheal disease cholera is known to be transmitted by water contaminated with pathogenic Vibrio cholerae, routine isolation of pathogenic strains from aquatic environments is challenging. Here, we show that conditionally viable environmental cells (CVEC) of pathogenic V. cholerae that resist cultivation by conventional techniques exist in surface water as aggregates (biofilms) of partially dormant cells. Such CVEC can be recovered as fully virulent bacteria by inoculating the water into rabbit intestines. Furthermore, when V. cholerae shed in stools of cholera patients are inoculated in environmental water samples in the laboratory, the cells exhibit characteristics similar to CVEC, suggesting that CVEC are the infectious form of V. cholerae in water and that CVEC in nature may have been derived from human cholera stools. We also observed that stools from cholera patients contain a heterogeneous mixture of biofilm-like aggregates and free-swimming planktonic cells of V. cholerae. Estimation of the relative infectivity of these different forms of V. cholerae cells suggested that the enhanced infectivity of V. cholerae shed in human stools is largely due to the presence of clumps of cells that disperse in vivo, providing a high dose of the pathogen. The results of this study support a model of cholera transmission in which in vivo-formed biofilms contribute to enhanced infectivity and environmental persistence of pathogenic V. cholerae.
目前尚不清楚增强细菌流行病通过水传播并在自然环境中维持流行菌株的因素。尽管已知流行性腹泻病霍乱是由被致病性霍乱弧菌污染的水传播的，但从水生环境中常规分离致病菌株具有挑战性。在此，我们表明，致病性霍乱弧菌的条件性存活环境细胞（CVEC）以部分休眠细胞的聚集体（生物膜）形式存在于地表水中，这些细胞通过常规技术难以培养。将这种水接种到兔肠道中，可将CVEC作为完全有活力的细菌回收。此外，当在实验室中将霍乱患者粪便中排出的霍乱弧菌接种到环境水样中时，这些细胞表现出与CVEC相似的特征，这表明CVEC是霍乱弧菌在水中的感染形式，并且自然界中的CVEC可能源自人类霍乱粪便。我们还观察到，霍乱患者的粪便中含有霍乱弧菌的生物膜样聚集体和自由游动的浮游细胞的异质混合物。对这些不同形式的霍乱弧菌细胞相对感染性的估计表明，人类粪便中排出的霍乱弧菌感染性增强主要是由于存在在体内分散的细胞团块，从而提供了高剂量的病原体。本研究结果支持一种霍乱传播模型，即体内形成的生物膜有助于增强致病性霍乱弧菌的感染性和在环境中的持久性。
