Antimicrobial Resistance and Infectious Diseases Laboratory, Murdoch University, Murdoch, WA, Australia
New South Wales Department of Primary Industries, Wollongbar, NSW, Australia.
Appl Environ Microbiol. 2021 Apr 27;87(10). doi: 10.1128/AEM.03037-20.
Enterococci are ubiquitous opportunistic pathogens that have become a major public health issue globally. The increasing prevalence of antimicrobial resistance in hospital-adapted enterococci had been thought to originate from livestock. However, this association between livestock and hospital-adapted enterococci is currently unclear. This study investigates the antimicrobial susceptibilities of enterococci isolated from pig cecal samples and compares the genomic characteristics of from pigs to those of isolates from meat chickens and from human sepsis cases. From 200 cecal samples, antimicrobial susceptibility testing was performed for ( = 84), ( = 36), and ( = 17). Whole-genome sequencing was performed for all isolates, and the sequences were compared to those of previously studied isolates from meat chickens and human sepsis cases through bioinformatics analysis. Resistance (non-wild type) to erythromycin, gentamicin, tetracycline, ampicillin, daptomycin, virginiamycin, and quinupristin-dalfopristin was identified. More importantly, except for a single isolate harboring the operon, no resistance was observed in the three species to vancomycin, teicoplanin, and linezolid, which are critically important antimicrobials used to treat enterococcal infections in humans. The isolates from chickens were genetically distinct from human and pig isolates, which were more closely related. Human strains that were closely related to pig strains were not typical "hospital-adapted strains" as previously identified. The results of this study show that enterococci from Australian finisher pigs are not a source of resistance to critically important antimicrobials and that from pigs is not part of the current human hospital-adapted population. Resistance to the critically important antimicrobials vancomycin, teicoplanin, and linezolid is not found in enterococci collected from Australian finisher pigs. However, some antimicrobial resistance was observed. In particular, resistance to quinupristin-dalfopristin, a combination of two streptogramin class antimicrobials, was identified despite the absence of streptogramin use Australia-wide since 2005. Other observed resistance among enterococci from pigs include chloramphenicol, erythromycin, and tetracycline resistance. Genomic comparison of from Australian pigs to isolates collected from previous studies on chickens and humans indicate that from pigs are genetically more similar to those of humans than those from chickens. Despite the increased genetic similarities, strains from pigs are phylogenetically distinct and did not belong to the dominant sequence types found in hospital-adapted strains causing sepsis in humans. Therefore, the results indicate that Australian finisher pigs are not a source of hospital-adapted in Australia.
肠球菌是一种普遍存在的机会致病菌，已成为全球主要的公共卫生问题。医院适应肠球菌对抗菌药物的耐药性日益增加，人们曾认为这种耐药性源自家畜。然而，目前尚不清楚家畜与医院适应肠球菌之间的这种关联。本研究调查了从猪盲肠样本中分离出的肠球菌的抗菌药物敏感性，并比较了来自猪、鸡肉鸡和人类败血症病例的 的基因组特征。从 200 个盲肠样本中，对 （ = 84）、 （ = 36）和 （ = 17）进行了抗菌药物敏感性测试。对所有 分离株进行了全基因组测序，并通过生物信息学分析将序列与先前从鸡肉鸡和人类败血症病例中研究过的分离株进行比较。鉴定出对红霉素、庆大霉素、四环素、氨苄西林、达托霉素、维吉尼亚霉素和奎奴普丁/达福普汀的耐药性（非野生型）。更重要的是，除了单个分离株携带 操纵子外，三种物种对万古霉素、替考拉宁和利奈唑胺均未表现出耐药性，这些药物是治疗人类肠球菌感染的关键抗菌药物。来自鸡的 分离株在基因上与人类和猪分离株不同，与猪分离株的关系更密切。与猪分离株密切相关的人类菌株并非以前确定的典型“医院适应株”。本研究结果表明，来自澳大利亚育肥猪的肠球菌不是对关键抗菌药物耐药的来源，而且来自猪的肠球菌也不是当前人类医院适应人群的一部分。在从澳大利亚育肥猪中收集的肠球菌中未发现对关键抗菌药物万古霉素、替考拉宁和利奈唑胺的耐药性。然而，观察到了一些抗菌药物耐药性。特别是，尽管自 2005 年以来，澳大利亚已全面停止使用两种糖肽类抗菌药物组合的奎奴普丁/达福普汀，但仍观察到对其的耐药性。猪源肠球菌中其他观察到的耐药性包括氯霉素、红霉素和四环素耐药性。对来自澳大利亚猪的 与之前在鸡和人类上的研究中收集的分离株进行基因组比较表明，来自猪的 在基因上与人类的更相似，而不是与鸡的相似。尽管遗传相似性增加，但猪源 菌株在系统发育上是不同的，不属于引起人类败血症的医院适应株的主要序列类型。因此，结果表明，澳大利亚育肥猪不是澳大利亚医院适应 的来源。
