Inoculation of Beef with Low Concentrations of Escherichia coli O157:H7 and Examination of Factors That Interfere with Its Detection by Culture Isolation and Rapid Methods
Inoculation of Beef with Low Concentrations of Escherichia coli O157:H7 and Examination of Factors That Interfere with Its Detection by Culture Isolation and Rapid Methods
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DOI：
10.4315/0362-028x-73.12.2180
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发表时间：
2010-12-01
影响因子：
2
通讯作者：
Koohmaraie, Mohammad
中科院分区：
文献类型：
--
作者：
Bosilevac, Joseph M.;Kalchayanand, Norasak;Koohmaraie, Mohammad
目前使用的行业测试程序需要能够检测到大肠杆菌O 157：H7的牛肉或碎牛肉样品中的水平低至1 CFU/375 g。我们提出了一个可靠的方案，用于在此低浓度下生成用于验证试验的对照接种物，并评价其使用。结果显示，当1CFU为目标浓度时，所有样品中有一半没有接受细胞，并且大于3CFU的目标更可靠。通过培养物分离和两种商业检测试剂盒（Qualicon BAX-MP和BioControl GDS）进行检测，分别检出94% +/-11%、92% +/-10%和92% +/- 7%接种5.4 CFU（范围1 - 9 CFU）的样品。我们还研究了背景需氧平板计数（APC）细菌和脂肪含量对E。coli O157：H7。在APC浓度低于6 log CFU/g时，快速方法检测到所有接种26 CFU E.大肠杆菌O 157：H7。在6.7 log CFU/g的APC下，培养、BAX-MP和GDS分别检测到100%、75%和13%的接种样品。商业方法均未检出E.大肠杆菌O 157：H7的检出率为63%。大肠杆菌O 157：H7。脂肪含量的增加与免疫磁珠回收率的降低相关，但未观察到这会干扰E。大肠杆菌O 157：H7。
Currently used industry testing programs require the ability to detect Escherichia coli O157:H7 in samples of beef trim or ground beef at levels as low as 1 CFU/375 g. We present a reliable protocol for generating a control inoculum for verification testing at this low concentration and evaluate its use. Results show that half of all samples received no cells when 1 CFU was the target concentration and that targets greater than 3 CFU were much more reliable. Detection by culture isolation and two commercial assays, Qualicon BAX-MP and BioControl GDS, detected 94% +/- 11%, 92% +/- 10%, and 92% +/- 7% of samples inoculated with 5.4 CFU (range 1 to 9 CFU), respectively. We also examined the effect of background aerobic plate count (APC) bacteria and fat content effects on the detection of E. coli O157:H7. At APC concentrations below 6 log CFU/g, the rapid methods detected all beef trim samples inoculated with 26 CFU of E. coli O157:H7 per 65 g. At an APC of 6.7 log CFU/g, culture, BAX-MP, and GDS detected 100, 75, and 13%, respectively, of inoculated samples. Neither commercial method detected E. coli O157:H7 in the samples when APC was 7.7 log CFU/g, whereas culture was able to detect 63% of E. coli O157:H7 in the samples when APC was at this concentration. Increased fat content correlated with decreasing recovery of immunomagnetic separation beads, but this was not observed to interfere with detection of E. coli O157:H7.