Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, CH-8057 Zurich, Switzerland.
J Food Prot. 2022 May 1;85(5):740-746. doi: 10.4315/JFP-21-431.
The use of florfenicol in farm animals may select enterococci that carry resistance genes that confer resistance to linezolid, a critically important oxazolidinone antibiotic used in human medicine. This cross-sectional study aimed to assess the occurrence of oxazolidinone resistance genes in florfenicol-resistant enterococci from fattening pigs in Switzerland and to characterize a subset of the isolates using whole genome sequencing. A total of 31 florfenicol-resistant enterococcal isolates were obtained from 27 (5%) of 565 cecal samples of fattening pigs from seven (11%) of 62 farms. Screening by PCR revealed the presence of cfr-poxtA in 1 of 31, optrA in 15 of 31, and poxtA in 15 of 31 enterococcal isolates. One randomly selected isolate per PCR-positive Enterococcus species and positive farm was selected for further analysis (n = 10). In nine of the 10 isolates, the presence of oxazolidinone resistance genes did not result in phenotypic resistance. Whole genome sequencing analysis showed the presence of E. faecalis (n = 1), E. faecium (n = 1), and E. hirae (n = 1), harboring optrA18, optrA7, and a new optrA allele, respectively. E. durans (n = 1), E. faecium (n = 4), and E. hirae (n = 1) carried the wild-type poxtA, and E. faecalis (n = 1) coharbored cfr(D) and poxtA2. Except for optrA7, all oxazolidinone resistance genes were found on plasmids. Multilocus sequence typing analysis identified E. faecalis ST19 and ST376, E. faecium ST80 belonging to hospital-adapted clade A1, and E. faecium ST21, ST55, ST269, and ST416 belonging to clade A2, which represents human commensals and animal strains. The occurrence of cfr(D), optrA, and poxtA in various porcine Enterococcus spp. demonstrates the spread of oxazolidinone resistance genes among enterococci from fattening pigs in Switzerland. The presence in one sample of poxtA-carrying E. faecium ST80 emphasizes the potential risk to human health through dissemination of strains carrying oxazolidinone resistance genes into the food chain.
在农场动物中使用氟苯尼考可能选择携带对线唑醇耐药基因的肠球菌，而后者是一种在人类医学中至关重要的恶唑烷酮类抗生素。本横断面研究旨在评估瑞士育肥猪粪便中产氟苯尼考耐药肠球菌中恶唑烷酮类耐药基因的发生情况，并通过全基因组测序对其中一部分分离株进行特征描述。从 62 个农场中的 7 个（11%）的 565 个盲肠样本中，共获得 31 株氟苯尼考耐药肠球菌分离株。通过 PCR 筛选发现，1 株 31 株肠球菌分离株中存在 cfr-poxtA，15 株 31 株肠球菌分离株中存在 optrA，15 株 31 株肠球菌分离株中存在 poxtA。从每个 PCR 阳性肠球菌种和阳性农场中随机选择 1 株分离株进行进一步分析（n = 10）。在 10 株分离株中，有 9 株的存在的恶唑烷酮类耐药基因并未导致表型耐药。全基因组测序分析显示，分别有 1 株屎肠球菌、1 株粪肠球菌和 1 株海氏肠球菌携带 optrA18、optrA7 和新的 optrA 等位基因。1 株缓症肠球菌、4 株粪肠球菌和 1 株屎肠球菌携带野生型 poxtA，1 株屎肠球菌同时携带 cfr(D)和 poxtA2。除 optrA7 外，所有的恶唑烷酮类耐药基因均位于质粒上。多位点序列分型分析鉴定出屎肠球菌 ST19 和 ST376、医院适应型 clade A1 的粪肠球菌 ST80 以及 clade A2 的粪肠球菌 ST21、ST55、ST269 和 ST416，这些菌分别为人类共生菌和动物菌株。在不同的猪源肠球菌中发现 cfr(D)、optrA 和 poxtA，表明了氟苯尼考耐药基因在瑞士育肥猪肠球菌中的传播。在一个样本中发现携带 poxtA 的粪肠球菌 ST80，强调了通过携带恶唑烷酮类耐药基因的菌株传播到食物链中对人类健康的潜在风险。
