Kagkli D M, Vancanneyt M, Vandamme P, Hill C, Cogan T M
Moorepark Food Research Centre, Teagasc, Fermoy, Ireland.
J Appl Microbiol. 2007 Nov;103(5):1393-405. doi: 10.1111/j.1365-2672.2007.03338.x.
To determine the contribution of enterococci and coliforms from bovine faeces and teats to contamination of raw milk.
Putative enterococci (n = 301) and coliforms (n = 365) were isolated from bovine faeces (n = 20), cows' teats (n = 20), the raw milk (n = 1) and the milking environment (n = 4) on one farm. The clonal relationships of each bacterial group were investigated using Pulsed-Field Gel Electrophoresis of genomic macrorestriction fragments. Representatives of the different clusters of enterococci were identified by molecular techniques including rep-PCR, SDS protein profiling, Fluorescent Amplified Fragment Length Polymorphism (FAFLP), phenylalanyl-tRNA synthase (pheS) sequence analysis and/or 16S rDNA gene sequencing. Coliforms were identified by API 20E strips.
The majority of the bovine faecal enterococcal isolates were identified as a potential new species of Aerococcus (100 isolates); E. faecium (28 isolates), and Aerococcus viridans (28 isolates) were also found. All coliform isolates from the bovine faeces were identified as Escherichia coli. The coliforms present in the milk were Hafnia alvei, Serratia liquefaciens, Yersinia enterocolitica and Enterobacter amnigenus. No E. coli, Enterococcus or Aerococcus from the bovine faeces were found in the milk. A single clone of H. alvei was found in the water, the milking equipment and the milk, suggesting that the water was the source of the organism in the milk. No vancomycin-resistant aerococci or enterococci were found while most of the isolates tested showed the presence of at least one virulence gene. The milk-sock retained strains that adhered to particulate faecal material. Coliforms were present at approx. 2 orders of magnitude greater than enterococci in the bovine faeces.
The results imply that bovine faeces are not an important source of contamination of raw milk with enterococci or coliforms.
The results confirm those of two previous studies (Gelsomino et al. 2001, Int J Food Microbiol71, 177-188 and Kagkli et al. 2007, Int J Food Microbiol114, 243-251) on two other farms. The three studies show that contamination of milk by enterococci, lactobacilli and coliforms of bovine faecal origin is extremely low. The results also suggest that where raw milk is implicated in food infection, other factors in addition to faecal contamination must be involved.
确定牛粪和奶牛乳头中的肠球菌及大肠菌群对生乳污染的影响。
从一个农场的牛粪（n = 20）、奶牛乳头（n = 20）、生乳（n = 1）和挤奶环境（n = 4）中分离出假定的肠球菌（n = 301）和大肠菌群（n = 365）。使用基因组酶切片段脉冲场凝胶电泳研究每个细菌群体的克隆关系。通过包括重复聚合酶链反应（rep-PCR）、SDS蛋白质谱分析、荧光扩增片段长度多态性（FAFLP）、苯丙氨酰 - tRNA合成酶（pheS）序列分析和/或16S rDNA基因测序等分子技术鉴定不同肠球菌簇的代表菌株。通过API 20E条带鉴定大肠菌群。
大多数牛粪中分离出的肠球菌被鉴定为气球菌属的一个潜在新物种（100株）；还发现了屎肠球菌（28株）和绿色气球菌（28株）。从牛粪中分离出的所有大肠菌群均被鉴定为大肠杆菌。生乳中存在的大肠菌群是蜂房哈夫尼亚菌、液化沙雷氏菌、小肠结肠炎耶尔森菌和栖水肠杆菌。在生乳中未发现来自牛粪的大肠杆菌、肠球菌或气球菌。在水、挤奶设备和生乳中发现了单一克隆的蜂房哈夫尼亚菌，这表明水是生乳中该菌的来源。未发现耐万古霉素的气球菌或肠球菌，而大多数测试菌株显示至少存在一个毒力基因。奶套保留了附着在粪便颗粒物质上的菌株。牛粪中大肠菌群的数量比肠球菌大约高2个数量级。
结果表明牛粪不是生乳中肠球菌或大肠菌群污染的重要来源。
结果证实了之前在另外两个农场进行的两项研究（Gelsomino等人，2001年，《国际食品微生物学杂志》71卷，第177 - 188页；Kagkli等人，2007年，《国际食品微生物学杂志》114卷，第243 - 251页）的结果。这三项研究表明，牛粪来源的肠球菌、乳酸菌和大肠菌群对牛奶的污染极低。结果还表明，在生乳涉及食物感染的情况下，除了粪便污染外，还必须涉及其他因素。
