Mao Y, Doyle M P, Chen J
Center for Food Safety and Department of Food Science and Technology, The University of Georgia, Griffin, GA 30223-1797, USA.
Lett Appl Microbiol. 2006 Jun;42(6):642-7. doi: 10.1111/j.1472-765X.2006.01875.x.
This study evaluated the production of colanic acid (CA) exopolysaccharide (EPS) by Escherichia coli O157:H7 in relation to the pathogen's ability to survive under acidic conditions simulating the environment in the human gastrointestinal tract.
Escherichia coli O157:H7 W6-13 and its CA-deficient mutant M4020 were examined for their resistance to bile salts, and their ability to survive in simulated gastric fluid containing pepsin (pH 2.0) and simulated intestinal fluid containing pancreatin (pH 8.0). The effect of acid adaptation at pH 5.5 on the survival of E. coli O157:H7 in simulated gastric fluid was also determined. The results indicated that the survivability of M4020, under conditions simulating the environment in the human gastrointestinal tract, reduced more drastically than the viability of W6-13. The presence of bile salts had a slight effect on both types of E. coli O157:H7 cells. The loss of CA did not change the ability of M4020 to respond to acid adaptation.
The EPS CA may serve as a protective barrier to E. coli O157:H7 for its survival in the human gastrointestinal tract.
The study contributes to a better understanding of the EPS affecting the ability of E. coli O157:H7 to combat acid stress.
本研究评估了大肠杆菌O157:H7产柯氏酸（CA）胞外多糖（EPS）的情况，以及该病原体在模拟人体胃肠道环境的酸性条件下的存活能力。
检测了大肠杆菌O157:H7 W6-13及其CA缺陷突变体M4020对胆盐的抗性，以及它们在含有胃蛋白酶的模拟胃液（pH 2.0）和含有胰酶的模拟肠液（pH 8.0）中的存活能力。还测定了在pH 5.5下进行酸适应对大肠杆菌O157:H7在模拟胃液中存活的影响。结果表明，在模拟人体胃肠道环境的条件下，M4020的存活率比W6-13的存活率下降得更剧烈。胆盐的存在对两种类型的大肠杆菌O157:H7细胞都有轻微影响。CA的缺失并未改变M4020对酸适应的反应能力。
EPS CA可能作为大肠杆菌O157:H7在人体胃肠道中存活的保护屏障。
该研究有助于更好地理解EPS对大肠杆菌O157:H7抵抗酸应激能力的影响。
