Guangdong Provincial Key Laboratory of Microbial Safety and Health, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, China.
Guangdong Provincial Key Laboratory of Microbial Safety and Health, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, China.
Int J Food Microbiol. 2022 Oct 2;378:109805. doi: 10.1016/j.ijfoodmicro.2022.109805. Epub 2022 Jun 17.
Escherichia coli O157 belongs to a diverse serogroup including different H serotypes. E. coli O157: H7 is the most common serotype that can cause acute gastroenteritis, hemorrhagic colitis (HC), and hemolytic-uremic syndrome (HUS) in humans. In recent years, some E. coli O157:non-H7 strains have been reported to cause sporadic cases and outbreaks of diarrheal diseases. However, the phenotypic and genotypic characteristics of E. coli O157:non-H7 are poorly understood. In this study, E. coli O157:non-H7 strains were isolated from retail food sold on markets in 13 cities in China during 2012-2016 and characterized systematically in terms of their H serotypes, virulence genes, antibiotic resistance, and genotypes. Six H serotypes (H26, H42, H11, H38, H4, and H5) were identified, of which, O157:H42 (31.4 %) and O157:H26 (28.6 %) were the most prevalent. Most of the isolates (82.9 %) carried virulence genes. Ten isolates (28.6 %) carried the eae gene and were identified as atypical enteropathogenic E. coli. Multilocus sequence typing showed that the E. coli O157:non-H7 strains demonstrated diverse sequence types with different evolutionary trends than E. coli O157:H7. All the isolates exhibited multidrug resistance. The isolates showed a high prevalence of resistance to AMC, AMP, CTX, CIP, T/S, TE, and FFC. The predominant antibiotic-resistance genes were TEM-1 (40.0 %), CTX-M-55 (34.3 %), aadA (74.3 %), sul2 (62.9 %), floR (91.4 %), tetA (85.7 %), qnrS (37.1 %), oqxA (62.9 %), and oqxB (62.9 %). For the first time, we identified IncI2 plasmid-mediated colistin-resistant strains (six O157:H26 and one O157:H4). These strains co-harbored plasmid-mediated mcr-1 gene, CTX-M-55, OXA-4, PMQR, and other resistant genes, which is of great concern. Colistin and cefotaxime are generally used as the last defense to treat complicated infections. The emergence of virulent and multidrug resistant strains in food poses a serious threat to human health. The strict monitoring and surveillance of multiple-drug resistant strains in food are needed to prevent their dissemination to humans.
大肠杆菌 O157 属于一个多样化的血清群，包括不同的 H 血清型。大肠杆菌 O157：H7 是最常见的血清型，可导致人类急性肠胃炎、出血性结肠炎（HC）和溶血性尿毒综合征（HUS）。近年来，一些大肠杆菌 O157：非-H7 菌株已被报道引起散发性病例和腹泻病暴发。然而，大肠杆菌 O157：非-H7 的表型和基因型特征了解甚少。在这项研究中，从 2012-2016 年在中国 13 个城市的零售食品中分离出大肠杆菌 O157：非-H7 菌株，并从 H 血清型、毒力基因、抗生素耐药性和基因型等方面对其进行了系统表征。鉴定出 6 种 H 血清型（H26、H42、H11、H38、H4 和 H5），其中 O157：H42（31.4%）和 O157：H26（28.6%）最为流行。大多数分离株（82.9%）携带毒力基因。10 株（28.6%）携带 eae 基因，被鉴定为非典型肠致病性大肠杆菌。多位点序列分型显示，大肠杆菌 O157：非-H7 菌株的序列类型具有不同的进化趋势，与大肠杆菌 O157：H7 不同。所有分离株均表现出多重耐药性。分离株对 AMC、AMP、CTX、CIP、T/S、TE 和 FFC 的耐药率较高。主要的抗生素耐药基因是 TEM-1（40.0%）、CTX-M-55（34.3%）、aadA（74.3%）、sul2（62.9%）、floR（91.4%）、tetA（85.7%）、qnrS（37.1%）、oqxA（62.9%）和 oqxB（62.9%）。我们首次发现了携带 IncI2 质粒介导的粘菌素耐药基因的大肠杆菌 O157：H26（6 株）和 O157：H4（1 株）。这些菌株共同携带质粒介导的 mcr-1 基因、CTX-M-55、OXA-4、PMQR 和其他耐药基因，这令人担忧。粘菌素和头孢噻肟通常被用作治疗复杂感染的最后手段。食品中出现毒力和多药耐药菌株对人类健康构成严重威胁。需要对食品中的多药耐药菌株进行严格监测和监测，以防止其传播给人类。
