Abstract：
Shiga toxin-producing Escherichia coli (STEC) are zoonotic pathogens frequently carried by cattle, responsible in humans of mild to bloody diarrhoea, haemolytic uraemic syndrome (HUS) and even death. In 2023-2024, a study on STEC contamination of hide and carcasses of dairy cattle at slaughter was planned in Emilia-Romagna region (northern Italy). When the study was still in progress and 60 animals were sampled, the detection of STEC O177 isolates reached high rates and gained our attention. A total of five O177 STEC strains were detected, namely four from three carcasses (5.0 %) and one from a hide sample (1.7 %). The isolates were typed by WGS as following: 1) STEC O177:H11 sequence type (ST) 765 (stx2a+, eae+), detected from one carcass; 2) STEC O177:H25 ST659 (stx2c+, eae+) detected from three carcasses and one hide sample. One carcass was contaminated by both STEC serotypes. The isolates carried other virulence determinants often found in STEC strains associated with HUS, namely the exha, astA and espP genes, together with genes for adhesion to the epithelial cells of the gut (lpfA, fdeC, fimH) and non-Locus for Enterocyte Effacement (LEE) effector protein genes (nleA, nleB). The STEC O177:H11 isolate harboured antimicrobial resistance (AMR) genes to β-lactams (blaTEM-1A), aminoglycosides (aadA1, aph(3″)-Ib, aph(6)-Id), trimethoprim (dfrA1), sulphonamides (sul1, sul2), tetracyclines (tetA), (tetB), streptothricin (sat2), and quaternary ammonium compounds (qacEdelta1). On the contrary, the STEC O177:H25 isolates carried no AMR genes. Persistent carriage of STEC O177:H25 ST659 (stx2c+, eae+) at farm level was assessed by testing animals of the same herd sent to slaughter. Interestingly, the colonies of STEC O177:H11 and STEC O177:H25 had different morphology on CHROMagar™ STEC plates, being mauve and colourless, respectively. Since mauve is the colour STEC colonies commonly have on the CHROMagar™ STEC medium, our findings can help microbiologists in the selection of uncommon serotypes. To the best of our knowledge, this is the first detection of STEC O177 from carcasses and hides of dairy cattle at slaughter. Noteworthy, the STEC-positive hide was classified as \"very dirty\" thus stressing the need of clean animals entering the slaughter chain, as required by Regulation (EC) No 853/2004. Since STEC O177 has been responsible of HUS in Europe, our data could add information on the source of uncommon serogroups in human infections.
摘要：
产志贺毒素的大肠杆菌（STEC）是牛经常携带的人畜共患病原体，在人类中负责轻度至血性腹泻，溶血性尿毒综合征（HUS）甚至死亡。在2023-2024年，计划在艾米利亚-罗马涅地区（意大利北部）进行一项关于屠宰时奶牛皮和尸体的STEC污染的研究。当研究仍在进行中，对60只动物进行了采样时，STECO177分离株的检测率很高，引起了我们的关注。共检出5株STECO177株,即三个屠体中的四个（5.0％）和一个生皮样本中的一个（1.7％）。分离株通过WGS分型如下：1）STECO177：H11序列型（ST）765（stx2a，eae+),从一个car体检测到；2）STECO177：H25ST659（stx2c+，eae）从三个尸体和一个皮革样本中检测到。一个car体被两种STEC血清型污染。分离株携带其他毒力决定子，通常在与HUS相关的STEC菌株中发现，即exha，astA和espP基因，连同粘附到肠道上皮细胞的基因(lpfA，fdeC,fimH）和肠细胞效应（LEE）效应蛋白基因的非基因座（nleA，nleB）。STECO177：H11分离株对β-内酰胺（blaTEM-1A）具有抗菌素抗性（AMR）基因，氨基糖苷类(aadA1，aph(3″)-Ib，aph(6)-Id)，甲氧苄啶（dfrA1），磺酰胺(sul1,sul2),四环素（tetA），（tetB），链霉素（sat2），和季铵化合物(qacEdelta1)。相反,STECO177:H25分离株不携带AMR基因。STECO177:H25ST659(stx2c+,eae）在农场一级是通过测试被送往屠宰的同一畜群的动物来评估的。有趣的是,STECO177:H11和STECO177:H25的菌落在CHROMagar™STEC平板上具有不同的形态，是淡紫色和无色的，分别。由于紫红色是STEC菌落在CHROMagar™STEC培养基上通常具有的颜色，我们的发现可以帮助微生物学家选择不常见的血清型.据我们所知,这是首次从屠宰的奶牛尸体和皮革中检测到STECO177。值得注意的是,STEC阳性兽皮被归类为“非常脏”，因此强调需要干净的动物进入屠宰链，根据法规（EC）No853/2004的要求。自从STECO177在欧洲负责HUS以来，我们的数据可以增加人类感染中不常见血清群来源的信息.
