Growth and processing conditions affecting acid tolerance inEscherichia coli O157:H7
Growth and processing conditions affecting acid tolerance inEscherichia coli O157:H7
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影响大肠杆菌 O157:H7 耐酸性的生长和加工条件
DOI：
10.1006/fmic.1997.0158
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发表时间：
1998
影响因子：
5.3
通讯作者：
C. Kaspar
中科院分区：
文献类型：
--
作者：
Chorng;C. Kaspar
研究了不同生长条件（厌氧、生长期、NaCl、pH和温度）对大肠杆菌O157:H7耐酸性的直接影响（DpH1.15）和酸性磷酸酶比活性的间接影响。O157:H7菌株43895在合成瘤胃液中厌氧生长比好氧生长更早产生耐酸性。然而，好氧和厌氧培养的静止期细胞具有同等程度的耐酸能力，比厌氧培养的长周期细胞更强。这些结果与稳定期sigma因子对生长期耐酸性的调节一致[38]。NaCl（1%）的加入也增强了菌株43895的对数相细胞的耐酸能力，但对静止相细胞的耐酸能力没有增强作用。生长温度影响了耐酸性，在15、25和37°c时，在对数和固定阶段，dph1.15值逐渐增大。因此，研究了温度对大肠杆菌O157:H7菌株43895在碎牛肉中的后续存活和耐酸性的影响。菌株43895在接种后的碎牛肉中，在4°c储存时数量减少了1.14 log10cfu g-1，而在-20°c储存时数量基本保持不变。虽然在15℃预孵育4小时后再在4℃或-20℃储存不影响存活，但大肠杆菌O157:H7存活者的耐酸能力显著降低（P<0.10001）。这些结果表明，加工温度对大肠杆菌O157:H7的耐酸能力有影响。
The impact of growth conditions (anaerobiosis, growth phase, NaCl, pH, and temperature) on the development of acid tolerance in Escherichia coli O157:H7 was investigated directly (DpH1.15) and indirectly by monitoring the specific activity of acid phosphatase. Anaerobic growth of O157:H7 strain 43895 in synthetic rumen fluid resulted in earlier development of acid tolerance than aerobic growth. However, stationary-phase cells of both aerobic and anaerobic cultures had an equivalent degree of acid tolerance that was greater than that achieved in log-phase cultures grown anaerobically. These results are consistent with the growth-phase regulation of acid tolerance by the stationary-phase sigma factors38. The addition of NaCl (1%) also enhanced acid tolerance of log-phase but not stationary-phase cells of strain 43895. Growth temperature influenced the acid tolerance with progressively greater DpH1.15values obtained at 15, 25, and 37°1C, in both log and stationary phase. Therefore, the influence of temperature on the subsequent survival and acid tolerance of E. coli O157:H7 strain 43895 in ground beef was evaluated. Numbers of strain 43895 decreased c. 1.14 log10cfu g-1in inoculated ground beef stored at 4°1C, whereas numbers remained essentially unchanged during storage at -20°C. While pre-incubation at 15°1C for 4 h prior to storage at 4 or -20°C did not influence survival, the acid tolerance of E. coli O157:H7 survivors was significantly decreased (P<0.10001). These results indicate that the processing temperature can influence acid tolerance in E. coli O157:H7.