pH-dependent stationary-phase acid resistance response of enterohemorrhagic Escherichia coli in the presence of various acidulants.
pH-dependent stationary-phase acid resistance response of enterohemorrhagic Escherichia coli in the presence of various acidulants.
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DOI：
10.4315/0362-028x-62.3.211
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发表时间：
1999-03
影响因子：
2
通讯作者：
R. Buchanan;S. G. Edelson
中科院分区：
文献类型：
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作者：
R. Buchanan;S. G. Edelson
研究了酸化剂种类对肠出血性大肠杆菌pH依赖性稳定相耐酸性反应的影响。9株E.大肠杆菌（7株O 157：H7，1株O 111：H-，1株生物型1参考菌株）分别在加1%葡萄糖的胰蛋白酶大豆肉汤（TSB）和不加葡萄糖的TSB中于37 ℃培养18小时，以分别产生酸抗性诱导的和非诱导的静止期细胞。然后将这些培养物接种到补充有0.5%柠檬酸、苹果酸、乳酸或乙酸并用HCl调节至pH 3.0的脑心浸液肉汤（BHI）中。将BHI管在37 ° C下孵育长达7小时，并在0、2、5和7小时后取出样品，并在BHI琼脂和麦康凯琼脂（MA）上铺板以计数CFU。将结果与先前仅用HCl获得的数据进行比较。菌株的耐酸性差异很大，依赖于菌株，酸化剂，和诱导pH依赖性的耐酸性。盐酸始终是对细胞损伤最小的;乳酸是最有害的。其他酸的相对活性是菌株依赖性的。诱导pH依赖性的耐酸性增加了固定相E已经相当大的耐酸性。杆菌损伤程度也随酸和菌株而变化，BHI琼脂和MA CFU计数之间有多达5个对数周期的差异。肠出血性大肠杆菌存活率的准确测定。酸性食品中的大肠杆菌必须考虑到微生物的生物变异性，即其耐酸性和通过诱导生理应激反应提高存活率的能力。
The effect of acidulant identity on the pH-dependent stationary-phase acid resistance response of enterohemorrhagic Escherichia coli was studied. Nine strains of E. coli (seven O157:H7, one O111:H-, and one biotype 1 reference strain) were cultured individually for 18 h at 37 degrees C in tryptic soy broth (TSB) plus 1% dextrose and in TSB without dextrose to yield acid resistance induced and noninduced stationary-phase cells, respectively. These cultures were then inoculated into brain heart infusion broth (BHI) supplemented with 0.5% citric, malic, lactic, or acetic acid and adjusted to pH 3.0 with HCl. The BHI tubes were incubated at 37 degrees C for up to 7 h and samples were removed after 0, 2, 5, and 7 h and plated for counting CFU on BHI agar and MacConkey agar (MA). The results were compared to data previously obtained with HCl only. Acid resistance varied substantially among the isolates, being dependent on the strain, the acidulant, and the induction of pH-dependent acid resistance. Hydrochloric acid was consistently the least damaging to cells; lactic acid was the most detrimental. The relative activity of the other acids was strain dependent. Inducing pH-dependent acid resistance increased the already substantial acid tolerance of stationary-phase E. coli. The extent of injury also varied with acid and strain, with as much as a 5-log-cycle differential between BHI agar and MA CFU counts. The accurate determination of the survival of enterohemorrhagic E. coli in acidic foods must take into account the biological variability of the microorganism with respect to its acid resistance and its ability to enhance survival through the induction of physiological stress responses.