Askari Nasrin, Ghanbarpour Reza
Department of Pathobiology, Faculty of Veterinary Medicine, Shahid Bahonar University of Kerman, Kerman, Iran.
Molecular Microbiology Research Group, Faculty of Veterinary Medicine, Shahid Bahonar University of Kerman, Kerman, Iran.
BMC Vet Res. 2019 Jan 7;15(1):14. doi: 10.1186/s12917-018-1771-y.
Escherichia coli O157:H7 is a highly virulent human pathogen with severe consequences following infection, which claims many lives worldwide. A suggested method for controlling this bacterium is the competitive elimination through using probiotic bacteria that prevent its colonization. Some nonpathogenic E. coli strains that produce antibacterial colicins are among these probiotic bacteria. We aimed to isolate and characterize the colicinogenic E. coli strains from diarrheic and healthy sheep that inhibit E. coli O157:H7, which could be used as possible probiotic sources. A total of 292 E. coli isolates (146 from each diarrheic and healthy sheep) were screened for the presence of colicin and virulence genes. The phylogenetic group/subgroup determination was performed by PCR. In vitro evaluation of inhibitory effect of colicinogenic isolates on E. coli O157:H7 was done phenotypically.
The frequency of diarrhea associated colicinogenic E. coli isolates was significantly higher than those isolated from healthy sheep. An association between ETEC and the genes coding for colicin-V & colicin-Iab in diarrheic E. coli isolates was observed. Moreover, there was an association between ipaH and Colicin-V encoding genes. Furthermore, E. coli isolates showing bacteriocinogeny while possessing no virulence genes had a frequency of 97.67 and 11.94% in healthy and diarrheic isolates, respectively. Of these strains, five isolates (3.42%) from diarrheic and twenty-five isolates (17.12%) from healthy sheep inhibited O157:H7 strain. Additionally, colicin E1 and colicin Iab genes were more prevalent in B1 phylogroup.
These results signified that healthy sheep could be considered as a potential source for anti-O175:H7 bacterial isolates.
大肠杆菌O157:H7是一种高致病性人类病原体，感染后会造成严重后果，在全球导致许多人死亡。一种建议的控制这种细菌的方法是通过使用能阻止其定植的益生菌进行竞争性消除。一些产生抗菌性大肠杆菌素的非致病性大肠杆菌菌株属于这些益生菌。我们旨在从腹泻和健康绵羊中分离并鉴定出能抑制大肠杆菌O157:H7的产大肠杆菌素的大肠杆菌菌株，这些菌株可作为潜在的益生菌来源。总共筛选了292株大肠杆菌分离株（腹泻和健康绵羊各146株），以检测大肠杆菌素和毒力基因的存在情况。通过聚合酶链反应（PCR）进行系统发育组/亚组的测定。对产大肠杆菌素的分离株对大肠杆菌O157:H7的抑制作用进行了表型体外评估。
与腹泻相关的产大肠杆菌素的大肠杆菌分离株的频率显著高于从健康绵羊中分离出的菌株。在腹泻的大肠杆菌分离株中观察到肠毒素大肠杆菌（ETEC）与编码大肠杆菌素-V和大肠杆菌素-Iab的基因之间存在关联。此外，侵袭性质粒抗原H（ipaH）与大肠杆菌素-V编码基因之间也存在关联。此外，在健康和腹泻分离株中，不具有毒力基因但具有产细菌素能力的大肠杆菌分离株的频率分别为97.67%和11.94%。在这些菌株中，来自腹泻绵羊的5株分离株（3.42%）和来自健康绵羊的25株分离株（17.12%）抑制了O157:H7菌株。此外，大肠杆菌素E1和大肠杆菌素Iab基因在B1系统发育组中更为普遍。
这些结果表明，健康绵羊可被视为抗O175:H7细菌分离株的潜在来源。
