Hegde A, Bhat G K, Mallya S
Department of Microbiology, Kasturba Medical College, Mangalore - 575 001, India.
Indian J Med Microbiol. 2009 Oct-Dec;27(4):325-8. doi: 10.4103/0255-0857.55446.
Enterotoxigenic Escherichia coli (ETEC) is an important pathogen responsible for secretory diarrhoea. The production of heat labile enterotoxin (LT), by ETEC, is largely responsible for the pathogenesis of diarrhoea. In the present study we investigated the effect of stress factors such as temperature, pH, osmotic stress and nutritional limitation on the production of LT by ETEC using in-house GMI-ELISA. Four strains of E. coli consisting, one standard strain MTCC 723 and three clinical isolates were used in the study. Maximum amount of LT (OD 3.285) was produced at 37 0 C followed by 40 0 C (OD 3.305). Growth of E. coli in medium with pH 8.6 resulted in maximum amount of LT production (OD 3.489). LT was not detectable when bacteria were grown in medium with pH < or =7.2 and > or = 9.2. Sodium chloride concentration of 0.2 M stimulated maximum amount of LT production. Maximum amount of LT was produced when the bacteria were grown in medium containing 2.5 g/l of glucose. All the stress factors had a significant effect on the LT production by E. coli , though quantitative differences in the various strains were observed.
产肠毒素大肠杆菌（ETEC）是导致分泌性腹泻的重要病原体。ETEC产生的不耐热肠毒素（LT）在很大程度上导致了腹泻的发病机制。在本研究中，我们使用内部GMI-ELISA研究了温度、pH值、渗透应激和营养限制等应激因素对ETEC产生LT的影响。研究中使用了四株大肠杆菌，包括一株标准菌株MTCC 723和三株临床分离株。在37℃时产生的LT量最大（OD 3.285），其次是40℃（OD 3.305）。大肠杆菌在pH 8.6的培养基中生长时，LT产量最高（OD 3.489）。当细菌在pH≤7.2或≥9.2的培养基中生长时，未检测到LT。0.2M的氯化钠浓度刺激了最大量的LT产生。当细菌在含有2.5g/l葡萄糖的培养基中生长时，产生的LT量最大。所有应激因素对大肠杆菌产生LT均有显著影响，尽管各菌株之间存在数量差异。
