Jajarmi Maziar, Askari Badouei Mahdi, Imani Fooladi Abbas Ali, Ghanbarpour Reza, Ahmadi Ali
Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran.
Department of Pathobiology, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran.
BMC Vet Res. 2018 Mar 16;14(1):97. doi: 10.1186/s12917-018-1407-2.
All over the world, Shiga toxin-producing Escherichia coli (STEC) are considered as important zoonotic pathogens. Eight serogroups have the greatest role in the outbreaks and diseases caused by STEC which include O26, O45, O103, O111, O113, O121, O145 and O157. Ruminants, especially cattle are the main reservoirs but the role of small ruminants in the epidemiology of human infections has not been thoroughly assessed in many countries. The objective of this research was to investigate the pathogenic potential of the STEC strains isolated from slaughtered goats. In this study, a total of 57 STEC strains were recovered from 450 goats and characterized by subtyping of stx genes, O-serogrouping, phylo-typing and DNA fingerprinting.
Amongst 57 STEC strains isolated from goats, the prevalence of stx1 was significantly more than stx2 (98.2% vs. 24.5%; P ≤ 0.05), and 22.8% of strains harbored both stx1 and stx2 genes. Three (5.2%) isolates were characterized as EHEC, which carried both eae and stx genes. A total of five stx-subtypes were recognized namely: stx1c (94.7%), stx1a (53.7%), stx2d (21%), stx2c (17.5%), and stx2a (15.7%). In some parts of the world, these subtypes have been reported in relation with severe human infections. The stx subtypes predominantly occurred in four combinations, including stx1a/stx1c (35%), stx1c (31.5%), stx1c/stx2a/stx2c/stx2d (5.2%) and stx1c/stx2c/stx2d (%5.2%). In serogrouping, the majority of STECs from goats did not belong to the top 8 serogroups but two strains belonged to O113, which has been recognized as an important pathogenic STEC in Australia. Interestingly, none of stx eae isolates belonged to the tested serogroups. In phylo-typing the isolates mostly belonged to phylo-group B1 (82.4%), followed by phylo-group A (12.3%). STEC strains showed a substantial diversity in DNA fingerprinting; there were 24 unique ERIC-types (with a ≥95% similarity) among the isolates.
Despite the fact that the top 8 STEC serogroups were uncommon in caprine strains, the presence of highly pathogenic stx subtypes indicates that small ruminants and their products can be considered as an overlooked public health risk for humans, especially in developing countries which consume traditional products.
在全球范围内，产志贺毒素大肠杆菌（STEC）被视为重要的人畜共患病原体。八个血清群在由STEC引起的疫情和疾病中起最大作用，包括O26、O45、O103、O111、O113、O121、O145和O157。反刍动物，尤其是牛是主要宿主，但在许多国家，小型反刍动物在人类感染流行病学中的作用尚未得到充分评估。本研究的目的是调查从屠宰山羊中分离出的STEC菌株的致病潜力。在本研究中，从450只山羊中总共分离出57株STEC菌株，并通过stx基因亚型分析、O血清群分型、系统发育分型和DNA指纹分析进行了鉴定。
在从山羊中分离出的57株STEC菌株中，stx1的流行率显著高于stx2（98.2%对24.5%；P≤0.05），22.8%的菌株同时携带stx1和stx2基因。三株（5.2%）分离株被鉴定为肠出血性大肠杆菌（EHEC），它们同时携带eae和stx基因。总共识别出五种stx亚型，即：stx1c（94.7%）、stx1a（53.7%）、stx2d（21%）、stx2c（17.5%）和stx2a（15.7%）。在世界某些地区，这些亚型与严重的人类感染有关。stx亚型主要以四种组合出现，包括stx1a/stx1c（35%）、stx1c（31.5%）、stx1c/stx2a/stx2c/stx2d（5.2%）和stx1c/stx2c/stx2d（5.2%）。在血清群分型中，来自山羊的大多数STEC不属于前8个血清群，但有两株属于O113，O113在澳大利亚已被确认为重要的致病性STEC。有趣的是，没有一株stx+eae分离株属于测试的血清群。在系统发育分型中，分离株大多属于系统发育群B1（82.4%），其次是系统发育群A（12.3%）。STEC菌株在DNA指纹分析中表现出很大的多样性；分离株中有24种独特的ERIC型（相似度≥95%）。
尽管前8个STEC血清群在山羊菌株中不常见，但高致病性stx亚型的存在表明小型反刍动物及其产品可被视为对人类被忽视的公共卫生风险，尤其是在消费传统产品的发展中国家。
