School of Food Science, Washington State University, Pullman 99163, USA.
Food Microbiol. 2011 May;28(3):537-46. doi: 10.1016/j.fm.2010.11.002. Epub 2010 Nov 13.
The inactivation and sublethal injury of Escherichia coli O157:H7, Campylobacter jejuni and Pseudomonas aeruginosa at three temperatures (22 °C, 4 °C and -18 °C) were studied using traditional microbiological tests and mid-infrared spectroscopy (4000-400 cm(-1)). Bacteria were cultivated in diluted nutrient matrices with a high initial inoculation (∼10(7) CFU/ml) levels. Both E. coli O157:H7 and P. aeruginosa survived and cell numbers increased at 22 °C for 5 days while C. jejuni numbers decreased one log(10) CFU/ml. A two log CFU/ml decrease was observed for the three pathogens held at 4 °C for 12 days. C. jejuni survived poorly following incubation at -18 °C for 20 days while levels of E. coli O157:H7 and P. aeruginosa remained high (10(4) CFU/ml). Temperature stress response of microbes was observed by infrared spectroscopy in polysaccharide, protein, lipid, and nucleic acid regions and was strain specific. Level of cold injury could be predicted using cluster, discriminant function and class analog analysis models. Pathogens may produce oligosaccharides and potentially other components in response to stress as indicated by changes in spectral features at 1200-900 cm(-1) following freezing.
采用传统微生物学检测方法和中红外光谱（4000-400cm-1）研究了三种温度（22°C、4°C 和-18°C）下大肠杆菌 O157:H7、空肠弯曲菌和铜绿假单胞菌的失活和亚致死损伤。细菌在稀释的营养基质中培养，初始接种量较高（约 10（7）CFU/ml）。在 22°C 下培养 5 天，大肠杆菌 O157:H7 和铜绿假单胞菌存活并数量增加，而空肠弯曲菌数量减少一个对数（10）CFU/ml。在 4°C 下培养 12 天，三种病原体的数量减少了两个对数 CFU/ml。在-18°C 下孵育 20 天后，空肠弯曲菌存活情况较差，而大肠杆菌 O157:H7 和铜绿假单胞菌的水平仍然很高（10（4）CFU/ml）。红外光谱观察到微生物的温度应激反应在多糖、蛋白质、脂质和核酸区域，且具有菌株特异性。可以使用聚类、判别函数和类模拟分析模型预测冷损伤水平。如在光谱特征在 1200-900cm-1 处发生变化所示，病原体可能会产生低聚糖和潜在的其他成分以应对冷冻带来的应激。
