College of Animal Science and Technology, State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Universitygrid.256609.e, Nanning, China.
Microbiol Spectr. 2022 Aug 31;10(4):e0054522. doi: 10.1128/spectrum.00545-22. Epub 2022 Jul 19.
In this study, we aimed to investigate the occurrence and molecular characteristics of fosfomycin-resistant isolates from pig, chicken and pigeon farms in Guangxi Province of China. A total of 200 fosfomycin-resistant strains were obtained from food animals and their surrounding environments, with the , , and genes being detected in 26% (52/200), 10% (20/200), and 5% (10/200), respectively. Surprisingly, three -producing E. coli isolates were found to be concomitant with . Most of the -like-gene-positive isolates were multidrug-resistant strains and consistently possessed , , and genes. Only was successfully transferred to the recipient strains, and the 29 -carrying transconjugants exhibited high-level resistance to fosfomycin (MIC ≥ 512 μg/mL). Multilocus sequence typing (MLST) combined with enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) analyses indicated that or genes were spread by horizontal transfer as well as via clonal transmission between E. coli. We used the PCR mapping method to explore the genetic contexts of -like genes, and two representative strains (fEc.1 and fEcg99-1) were fully sequenced. Six different genetic structures surrounding were detected and one infrequent context was discovered among the conjugable -positive E. coli isolates. The five genetic environments of were identified and found to be highly similar to the partial sequence of transposon Tn. Furthermore, whole-genome sequencing (WGS) results showed that was colocalized with , , , (A), , and a number of virulence-related factors on the same chromosomes of strains, and various insertion sequences (IS/IS) were detected upstream or downstream of . The phylogenetic analysis revealed that both - and -carrying E. coli ST602 and -carrying E. coli ST2599 were closely related to E. coli isolates from humans, which may indicate that they pose a threat to human health. Here, we report the widespread and complex genetic environments of -like genes in animal-derived strains in China. The gene was identified in this study and was found to confer resistance to fosfomycin. The high prevalence of -like genes in farms indicates that food animals serve as a potential reservoir for the resistance genes. This study also discovered that fosfomycin resistance genes were always associated with mobile elements, which would accelerate the transmission of -like genes in strains. Importantly, E. coli ST602 and ST2599 carrying or from food animals had high similarity to E. coli isolates from humans, suggesting that -like genes can be transmitted to humans through the food chain, thus posing a serious threat to public health. Therefore, the prevalence of -like genes isolated from animals should be further monitored.
在这项研究中，我们旨在调查中国广西省猪、鸡和鸽子养殖场中产 物 磷霉素耐药分离株的发生和分子特征。从食用动物及其周围环境中获得了 200 株磷霉素耐药株，其中 26%（52/200）、10%（20/200）和 5%（10/200）检测到了 、 、 基因。令人惊讶的是，发现了 3 株产 E. coli 分离株同时携带 。大多数 -like- 基因阳性分离株是多药耐药株，一致携带 、 、 基因。仅 成功转移到受体菌株，29 株携带 的转导子对磷霉素表现出高水平耐药（MIC≥512μg/ml）。多位点序列分型（MLST）结合肠杆菌重复基因间一致性聚合酶链反应（ERIC-PCR）分析表明， 或 基因通过水平转移以及 E. coli 之间的克隆传播而传播。我们使用 PCR 图谱法探讨了-like 基因的遗传环境，对两个代表性菌株（fEc.1 和 fEcg99-1）进行了全序列测序。检测到 周围存在六种不同的遗传结构，在可接合的 - 阳性 E. coli 分离株中发现了一种罕见的结构。鉴定了 5 种 的遗传环境，发现它们与转座子 Tn 的部分序列高度相似。此外，全基因组测序（WGS）结果表明， 在菌株的同一染色体上与 、 、 （A）、 、和许多毒力相关因子共定位，并且在 上下游检测到各种插入序列（IS/IS）。系统发育分析表明，携带 和 的 E. coli ST602 以及携带 的 E. coli ST2599 与来自人类的 E. coli 分离株密切相关，这可能表明它们对人类健康构成威胁。 在这里，我们报告了中国动物源性菌株中 -like 基因广泛而复杂的遗传环境。本研究鉴定了 基因，并发现其赋予磷霉素耐药性。农场中-like 基因的高流行率表明食用动物是耐药基因的潜在储存库。本研究还发现，磷霉素耐药基因总是与移动元件相关，这将加速菌株中-like 基因的传播。重要的是，来自食用动物的携带 或 的 E. coli ST602 和 ST2599 与来自人类的 E. coli 分离株具有很高的相似性，这表明-like 基因可以通过食物链传播给人类，从而对公众健康构成严重威胁。因此，应进一步监测从动物中分离出的-like 基因的流行率。
