Department of Biological Science, Faculty of Science, University of Bamenda, Bamenda, Cameroon.
Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon.
PLoS One. 2020 Dec 15;15(12):e0235583. doi: 10.1371/journal.pone.0235583. eCollection 2020.
Escherichia coli O157 is an emerging foodborne pathogen of great public health concern. It has been associated with bloody diarrhoea, haemorrhagic colitis and haemolytic uremic syndrome in humans. Most human infections have been traced to cattle and the consumption of contaminated cattle products. In order to understand the risk associated with the consumption of cattle products, this study sought to investigate the prevalence and identify virulence genes in E. coli O157 from cattle in Cameroon.
A total of 512 rectal samples were obtained and analysed using conventional bacteriological methods (enrichment on modified Tryptone Soy Broth and selective plating on Cefixime-Tellurite Sorbitol Mac-Conkey Agar) for the isolation of E. coli O157. Presumptive E. coli O157 isolates were confirmed serologically using E. COLIPROTM O157 latex agglutination test and molecularly using PCR targeting the rfb gene in the isolates. Characterisation of the confirmed E. coli O157 strains was done by amplification of stx1, stx2, eaeA and hlyA virulence genes using both singleplex and multiplex PCR.
E. coli O157 was detected in 56 (10.9%) of the 512 samples examined. The presence of the virulence genes stx2, eaeA and hylA was demonstrated in 96.4% (54/56) of the isolates and stx1 in 40 (71.4%) of the 54. The isolates exhibited three genetic profiles (I-III) with I (stx1, stx2, eaeA and hlyA) being the most prevalent (40/56; 71.4%) while two isolates had none of the virulence genes tested.
A proportion of cattle slaughtered in abattoirs in Buea are infected with pathogenic E. coli O157 and could be a potential source of human infections. We recommend proper animal food processing measures and proper hygiene be prescribed and implemented to reduce the risk of beef contamination.
大肠杆菌 O157 是一种新兴的食源性病原体，对公众健康构成了极大的威胁。它已被证实与人类的血性腹泻、出血性结肠炎和溶血尿毒症综合征有关。大多数人类感染都可以追溯到牛身上，以及食用受污染的牛产品。为了了解与食用牛产品相关的风险，本研究旨在调查喀麦隆牛中大肠杆菌 O157 的流行情况并鉴定其毒力基因。
采集了 512 份直肠样本，通过常规细菌学方法（在改良的 Tryptone Soy Broth 上富集，然后在 Cefixime-Tellurite Sorbitol Mac-Conkey Agar 上选择性平板分离）来分离大肠杆菌 O157。使用 E. COLIPROTM O157 乳胶凝集试验对疑似大肠杆菌 O157 分离株进行血清学确认，然后使用针对分离株 rfb 基因的 PCR 进行分子鉴定。通过单重和多重 PCR 扩增 stx1、stx2、eaeA 和 hlyA 毒力基因，对确认的大肠杆菌 O157 菌株进行特征分析。
在所检查的 512 个样本中，检测到大肠杆菌 O157 56 株（10.9%）。在 54 株（96.4%）分离株中检测到 stx2、eaeA 和 hylA 毒力基因，在 40 株（71.4%）分离株中检测到 stx1 毒力基因。分离株显示出三种遗传图谱（I-III），其中 I 型（stx1、stx2、eaeA 和 hlyA）最为常见（40/56；71.4%），而两株分离株则未检测到所测试的任何毒力基因。
在 Buea 的屠宰场中，一部分屠宰牛感染了致病性大肠杆菌 O157，可能是人类感染的潜在来源。我们建议采取适当的动物食品加工措施和规定并实施适当的卫生措施，以降低牛肉污染的风险。
