Edrington Tom S, Long Melissa, Ross Tim T, Thomas Jack D, Callaway Todd R, Anderson Robin C, Craddock Frank, Salisbury Mike W, Nisbet David J
Food and Feed Safety Research Unit, Southern Plains Agricultural Research Center, U.S. Department of Agriculture, Agricultural Research Service, College Station, Texas 77845, USA.
J Food Prot. 2009 Aug;72(8):1713-7. doi: 10.4315/0362-028x-72.8.1713.
The present study examined the incidence of Escherichia coli O:H7 and Salmonella in feedlot lambs. Fifty-six feedlot lambs from eight sheep farming operations were grouped in a single drylot pen, fed, and managed as is typical in the southwestern United States. Fecal samples were collected on days 0, 46, 87, and 122 of the feeding period via rectal palpation. Wool samples (ventral midline) were collected one time only at the feedlot, immediately prior to shipping to the processing plant, and carcass swabs were collected following slaughter. All samples were cultured for E. coli O157:H7, Salmonella, and fecal coliforms, and select isolates were examined for antimicrobial susceptibility. Overall, the percentages of fecal and wool samples positive for E. coli O157:H7 averaged 9 and 18%, respectively. One carcass swab was E. coli O157:H7 positive. Of the 155 fecal samples collected, 11 (7%) were Salmonella positive. Salmonella was detected in nearly 50% of the wool samples collected prior to slaughter, while none of the carcasses were Salmonella positive 24 h postslaughter. All isolates (E. coli O157:H7, Salmonella, and fecal coliforms) were susceptible to ceftiofur, enrofloxacin, and trimethoprim-sulfamethoxazole. One E. coli O157:H7 isolate cultured from a carcass swab was resistant to seven antibiotics, and seven wool E. coli O157:H7 isolates were multidrug resistant. Results of this research demonstrate that feedlot sheep are naturally colonized with E. coli O157:H7 and Salmonella and wool can be a source of carcass contamination; however, in-plant processing procedures and intervention strategies were largely effective in preventing carcass contamination.
本研究调查了饲养场羔羊中大肠杆菌O157:H7和沙门氏菌的感染率。来自八个养羊场的56只饲养场羔羊被集中圈养在一个干燥圈舍中，按照美国西南部的典型方式进行喂养和管理。在饲养期的第0天、46天、87天和122天，通过直肠触诊采集粪便样本。仅在饲养场装运至加工厂之前，一次性采集羊毛样本（腹中线），屠宰后采集胴体拭子。所有样本均培养检测大肠杆菌O157:H7、沙门氏菌和粪大肠菌群，并对选定的分离株进行药敏试验。总体而言，粪便和羊毛样本中大肠杆菌O157:H7阳性率分别平均为9%和18%。一份胴体拭子大肠杆菌O157:H7呈阳性。在采集的155份粪便样本中，11份（7%）沙门氏菌呈阳性。在屠宰前采集的近50%的羊毛样本中检测到沙门氏菌，而屠宰后24小时胴体均未检测出沙门氏菌呈阳性。所有分离株（大肠杆菌O157:H7、沙门氏菌和粪大肠菌群）对头孢噻呋、恩诺沙星和甲氧苄啶-磺胺甲恶唑敏感。从一份胴体拭子培养出的一株大肠杆菌O157:H7分离株对七种抗生素耐药，七株羊毛大肠杆菌O157:H7分离株具有多重耐药性。本研究结果表明，饲养场绵羊自然携带大肠杆菌O157:H7和沙门氏菌，羊毛可能是胴体污染的来源；然而，厂内加工流程和干预策略在很大程度上有效地防止了胴体污染。
