O'Brien S B, Duffy G, Daly D, Sheridan J J, Blair I S, McDowell D A
The National Food Centre, Teagasc, Ashtown, Dublin, Ireland.
Lett Appl Microbiol. 2005;41(1):88-93. doi: 10.1111/j.1472-765X.2005.01667.x.
To assess the detection and recovery rates achieved with commonly used cultural methods for the enumeration and recovery of Escherichia coli O157:H7 from minced beef and bovine hide.
Minced beef and bovine hide were inoculated with varying concentrations (log(10) 1.58-2.58 CFU g(-1) and log(10) 2.42-4.49 CFU 100 cm(2) respectively) of E. coli O157:H7 and recovered using a direct plate method or an enrichment/immunomagnetic separation (IMS) method and then plated onto SMAC or SMAC-CT in both cases. The direct plate method detected the pathogen consistently from minced beef samples with an average recovery of 69.2-91.2%. From faecal material on the bovine hide the recovery of the pathogen ranged from 1.80 to 64.5% with fresh faeces depending on the inocula while from dried faeces on hide the results ranged from no recovery at all to 25.1%. Enrichment/IMS recovered E. coli O157:H7 at all inocula levels tested in minced beef while the pathogen was only detected consistently at an average inocula level of log(10) 2.73 CFU 100 cm(2) from fresh faeces and log(10) 4.49 CFU 100 cm(2) from dried faeces on bovine hide.
The direct count enumeration method for E. coli O157:H7 underestimated the numbers of pathogens present. The enrichment/IMS procedure consistently detected the pathogen from minced beef but did not always detect E. coli O157:H7 from faeces on bovine hide.
Overall this study highlights that any microbial data, used in either predictive microbiology or risk assessment, must take account of the sensitivity and associated performance of the methods employed, in order to make an accurate reflection of the true microbiology of the examined sample.
评估常用培养方法对碎牛肉和牛皮中大肠杆菌O157:H7进行计数和回收的检测率及回收率。
用不同浓度（碎牛肉中分别为log(10) 1.58 - 2.58 CFU g(-1)，牛皮中分别为log(10) 2.42 - 4.49 CFU 100 cm(2)）的大肠杆菌O157:H7接种碎牛肉和牛皮，并通过直接平板法或富集/免疫磁珠分离（IMS）法进行回收，然后两种方法均接种到SMAC或SMAC - CT平板上。直接平板法能持续检测到碎牛肉样本中的病原体，平均回收率为69.2% - 91.2%。对于牛皮上的粪便物质，新鲜粪便中病原体的回收率在1.80%至64.5%之间，具体取决于接种量，而对于牛皮上的干粪便，回收率从完全未回收至25.1%不等。富集/IMS法在碎牛肉中所有测试接种水平下均能回收大肠杆菌O157:H7，而该病原体仅在牛皮新鲜粪便平均接种水平为log(10) 2.73 CFU 100 cm(2)以及干粪便接种水平为log(10) 4.49 CFU 100 cm(2)时能持续检测到。
大肠杆菌O157:H7的直接计数法低估了样本中病原体的数量。富集/IMS程序能持续检测到碎牛肉中的病原体，但并非总能检测到牛皮粪便中的大肠杆菌O157:H7。
总体而言，本研究强调在预测微生物学或风险评估中使用的任何微生物数据，必须考虑所采用方法的灵敏度及相关性能，以便准确反映被检测样本的真实微生物情况。
