Ground beef contamination with Escherichia coli is usually a result of carcass faecal contamination during the slaughter process. Carcasses are contaminated when they come into contact with soiled hides or intestinal leakage content during dressing and the evisceration processes. A more recent and compelling hypothesis is that, when lymph nodes are present in manufacturing beef trimmings, they can be a potential source of Enterobacteriaceae contamination of ground beef. The aim of this study was to investigate the occurrence of E. coli in lymph nodes from beef carcasses used for ground meat production, in six slaughter plants situated in central Italy A total of 597 subiliac (precrural) lymph nodes were obtained from 597 cattle carcasses and screened for E. coli by culture. Furthermore, E. coli isolates (one per positive carcass) were tested for stx1, stx2 eaeA and hlyA genes that are commonly used to identify and characterise shiga toxin-producing E. coli (STEC). In addition, the E. coli isolates were profiled for antimicrobial susceptibility. A proportion of 34.2% (204/597) carcasses were positive for E. coli. PCR revealed that 29% (59/204) of E. coli possessed stx1 or stx2 which corresponded to 9.9% of the cattle sampled. Moreover, a combination of stx1 or stx2 and eaeA was found in in 4 isolates (2% among E. coli positive samples and 1% among cattle sampled) and a combination of stx1 or stx2 and eaeA and hly in 1 isolate (0.5% and 0.2%). More than 95% of isolates were susceptible to gentamicin, ceftriaxone, cyprofloxacin and cefotaxime while high rates of resistance were recorded for cephalotin, ampicillin, tetracycline, tripe sulfa and streptomycin. The multivariate analysis identified “age” as the factor most closely related to E. coli positivity (either generic E. coli or STEC) in bovine lymph nodes. In conclusion, subiliac lymph nodes represent a source of E. coli for ground beef. These results are of major importance for risk assessment and improving good manufacturing practices during animal slaughter and ground meat production.

大肠杆菌对碎牛肉的污染通常是屠宰过程中of体粪便污染的结果。当屠体在敷料和内脏处理过程中与脏的生皮或肠泄漏物接触时会受到污染。最新的和令人信服的假说是，当在牛肉切边中存在淋巴结时，它们可能是碎牛肉肠杆菌科污染的潜在来源。这项研究的目的是调查位于意大利中部的六家屠宰场中，用于生产绞肉的牛肉尸体的淋巴结中大肠杆菌的发生情况。从597头牛cattle体中共获得597个ilia下（前壁）淋巴结并筛选大肠杆菌的培养。此外，大肠杆菌分离物（每正胎体一个），用于进行测试STX1，STX2 EAEA和靶向hlyA通常用于鉴定和表征志贺毒素的基因的大肠杆菌（STEC）。此外，对大肠杆菌分离物的抗菌敏感性进行了分析。的34.2％（597分之204）屠体的比例进行阳性大肠杆菌。PCR显示29％（59/204）的大肠杆菌拥有stx1或stx2，相当于所采样牛的9.9％。而且，stx1或stx2的组合和EAEA物在4株（其中2％发现大肠杆菌正样本和取样牛中1％）的组合和STX1或志贺毒素和EAEA和hly启动在1株（0.5％和0.2％）。超过95％的分离株对庆大霉素，头孢曲松，环丙沙星和头孢噻肟敏感，而对头孢菌素，氨苄青霉素，四环素，磺基曲普和链霉素的耐药率很高。多元分析确定“年龄”是与牛淋巴结中大肠杆菌阳性（通用大肠杆菌或STEC）最密切相关的因素。总之，sub下淋巴结代表了大肠杆菌的来源用于碎牛肉。这些结果对于动物屠宰和绞肉生产过程中的风险评估以及改善良好的生产实践具有至关重要的意义。