Albert M J, Ansaruzzaman M, Talukder K A, Chopra A K, Kuhn I, Rahman M, Faruque A S, Islam M S, Sack R B, Mollby R
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka-1000, Bangladesh.
J Clin Microbiol. 2000 Oct;38(10):3785-90. doi: 10.1128/JCM.38.10.3785-3790.2000.
Aeromonads are causative agents of a number of human infections. Even though aeromonads have been isolated from patients suffering from diarrhea, their etiological role in gastroenteritis is unclear. In spite of a number of virulence factors produced by Aeromonas species, their association with diarrhea has not been clearly linked. Recently, we have characterized a heat-labile cytotonic enterotoxin (Alt), a heat-stable cytotonic enterotoxin (Ast), and a cytotoxic enterotoxin (Act) from a diarrheal isolate of Aeromonas hydrophila. Alt and Ast are novel enterotoxins which are not related to cholera toxin; Act is aerolysin related and has hemolytic, cytotoxic, and enterotoxic activities. We studied the distribution of the alt, ast, and act enterotoxin genes in 115 of 125 aeromonads isolated from 1, 735 children with diarrhea, in all 27 aeromonads isolated from 830 control children (P = 7 x 10(-4) for comparison of rates of isolation of aeromonads from cases versus those from controls), and in 120 randomly selected aeromonads from different components of surface water in Bangladesh. Aeromonas isolates which were positive only for the presence of the alt gene had similar distributions in the three sources; the number of isolates positive only for the presence of the ast gene was significantly higher for the environmental samples than for samples from diarrheal children; and isolates positive only for the presence of the act gene were not found in any of the three sources. Importantly, the number of isolates positive for both the alt and ast genes was significantly higher for diarrheal children than for control children and the environment. Thus, this is the first study to indicate that the products of both the alt and ast genes may synergistically act to induce severe diarrhea. In 26 patients, Aeromonas spp. were isolated as the sole enteropathogen. Analysis of clinical data from 11 of these patients suggested that isolates positive for both the alt and ast genes were associated with watery diarrhea but that isolates positive only for the alt gene were associated with loose stools. Most of the isolates from the three sources could be classified into seven phenospecies and eight hybridization groups. For the first time, Aeromonas eucrenophila was isolated from two children, one with diarrhea and another without diarrhea.
气单胞菌是多种人类感染的病原体。尽管已从腹泻患者中分离出气单胞菌，但其在肠胃炎中的病因学作用尚不清楚。尽管气单胞菌属产生了多种毒力因子，但其与腹泻的关联尚未明确。最近，我们从一株嗜水气单胞菌腹泻分离株中鉴定出一种热不稳定细胞紧张性肠毒素（Alt）、一种热稳定细胞紧张性肠毒素（Ast）和一种细胞毒性肠毒素（Act）。Alt和Ast是与霍乱毒素无关的新型肠毒素；Act与气溶素相关，具有溶血、细胞毒性和肠毒性活性。我们研究了从1735名腹泻儿童中分离出的125株气单胞菌中的115株、从830名对照儿童中分离出的全部27株气单胞菌（病例中气单胞菌分离率与对照中气单胞菌分离率比较，P = 7×10⁻⁴）以及从孟加拉国地表水不同成分中随机选取的120株气单胞菌中alt、ast和act肠毒素基因的分布情况。仅alt基因呈阳性的气单胞菌分离株在这三个来源中的分布相似；仅ast基因呈阳性的分离株在环境样本中的数量显著高于腹泻儿童样本中的数量；在这三个来源中均未发现仅act基因呈阳性的分离株。重要的是，腹泻儿童中alt和ast基因均呈阳性的分离株数量显著高于对照儿童和环境样本。因此，这是第一项表明alt和ast基因产物可能协同作用诱导严重腹泻的研究。在26名患者中，气单胞菌属被分离为唯一的肠道病原体。对其中11名患者的临床数据分析表明，alt和ast基因均呈阳性的分离株与水样腹泻有关，而仅alt基因呈阳性的分离株与稀便有关。来自这三个来源的大多数分离株可分为7个表型种和8个杂交组。首次从两名儿童中分离出嗜泉气单胞菌，一名患有腹泻，另一名未患腹泻。
