Environmental Section of the Evandro Chagas Institute, Ananindeua, Pará, Brazil.
PLoS One. 2013 Nov 26;8(11):e81372. doi: 10.1371/journal.pone.0081372. eCollection 2013.
Vibrio cholerae is a natural inhabitant of many aquatic environments in the world. Biotypes harboring similar virulence-related gene clusters are the causative agents of epidemic cholera, but the majority of strains are harmless to humans. Since 1971, environmental surveillance for potentially pathogenic V. cholerae has resulted in the isolation of many strains from the Brazilian Amazon aquatic ecosystem. Most of these strains are from the non-O1/non-O139 serogroups (NAGs), but toxigenic O1 strains were isolated during the Latin America cholera epidemic in the region (1991-1996). A collection of environmental V. cholerae strains from the Brazilian Amazon belonging to pre-epidemic (1977-1990), epidemic (1991-1996), and post-epidemic (1996-2007) periods in the region, was analyzed. The presence of genes related to virulence within the species and the genetic relationship among the strains were studied. These variables and the information available concerning the strains were used to build a Bayesian multivariate dependency model to distinguish the importance of each variable in determining the others. Some genes related to the epidemic strains were found in environmental NAGs during and after the epidemic. Significant diversity among the virulence-related gene content was observed among O1 strains isolated from the environment during the epidemic period, but not from clinical isolates, which were analyzed as controls. Despite this diversity, these strains exhibited similar PFGE profiles. PFGE profiles were significant while separating potentially epidemic clones from indigenous strains. No significant correlation with isolation source, place or period was observed. The presence of the WASA-1 prophage significantly correlated with serogroups, PFGE profiles, and the presence of virulence-related genes. This study provides a broad characterization of the environmental V. cholerae population from the Amazon, and also highlights the importance of identifying precisely defined genetic markers such as the WASA-1 prophage for the surveillance of cholera.
霍乱弧菌是世界许多水生环境中的天然居民。携带相似毒力相关基因簇的生物型是流行性霍乱的病原体，但大多数菌株对人类无害。自 1971 年以来，对潜在致病性霍乱弧菌的环境监测导致从巴西亚马逊水生生态系统中分离出许多菌株。这些菌株大多数来自非 O1/非 O139 血清群（NAG），但在该地区的拉丁美洲霍乱流行期间（1991-1996 年）分离出了产毒性 O1 菌株。对属于该地区流行前（1977-1990 年）、流行期（1991-1996 年）和流行后期（1996-2007 年）的巴西亚马逊环境中霍乱弧菌的环境菌株进行了收集和分析。研究了该物种内与毒力相关的基因的存在以及菌株之间的遗传关系。利用这些变量以及有关菌株的信息，构建了一个贝叶斯多元依存模型，以区分每个变量在确定其他变量方面的重要性。在流行期间和之后，在环境 NAG 中发现了一些与流行菌株相关的基因。在流行期间从环境中分离出的 O1 菌株中观察到与毒力相关基因含量显著不同，但从临床分离株中未观察到，这些分离株被作为对照进行分析。尽管存在这种多样性，但这些菌株表现出相似的 PFGE 图谱。PFGE 图谱在将潜在的流行克隆与土著菌株分开时具有重要意义。未观察到与分离源、地点或时期有显著相关性。WASA-1 噬菌体的存在与血清群、PFGE 图谱和毒力相关基因的存在显著相关。本研究广泛描述了亚马逊地区的环境霍乱弧菌种群，还强调了确定 WASA-1 噬菌体等明确遗传标记对霍乱监测的重要性。
