Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain.
Appl Environ Microbiol. 2010 May;76(9):2799-805. doi: 10.1128/AEM.02421-09. Epub 2010 Mar 12.
To ascertain whether on animal farms there reside extended-spectrum beta-lactamase (ESBL) and plasmidic class C beta-lactamase-producing Escherichia coli isolates potentially pathogenic for humans, phylogenetic analyses, pulsed-field gel electrophoresis (PFGE) typing, serotyping, and virulence genotyping were performed for 86 isolates from poultry (57 isolates) and pig (29 isolates) farms. E. coli isolates from poultry farms carried genes encoding enzymes of the CTX-M-9 group as well as CMY-2, whereas those from pig farms mainly carried genes encoding CTX-M-1 enzymes. Poultry and pig isolates differed significantly in their phylogenetic group assignments, with phylogroup A predominating in pig isolates and phylogroup D predominating in avian isolates. Among the 86 farm isolates, 23 (26.7%) carried two or more virulence genes typical of extraintestinal pathogenic E. coli (ExPEC). Of these, 20 were isolated from poultry farms and only 3 from pig farms. Ten of the 23 isolates belonged to the classic human ExPEC serotypes O2:H6, O2:HNM, O2:H7, O15:H1, and O25:H4. Despite the high diversity of serotypes and pulsotypes detected among the 86 farm isolates, 13 PFGE clusters were identified. Four of these clusters contained isolates with two or more virulence genes, and two clusters exhibited the classic human ExPEC serotypes O2:HNM (ST10) and O2:H6 (ST115). Although O2:HNM and O2:H6 isolates of human and animal origins differed with respect to their virulence genes and PFGE pulsotypes, the O2:HNM isolates from pigs showed the same sequence type (ST10) as those from humans. The single avian O15:H1 isolate was compared with human clinical isolates of this serotype. Although all were found to belong to phylogroup D and shared the same virulence gene profile, they differed in their sequence types (ST362-avian and ST393-human) and PFGE pulsotypes. Noteworthy was the detection, for the first time, in poultry farms of the clonal groups O25b:H4-ST131-B2, producing CTX-M-9, and O25a-ST648-D, producing CTX-M-32. The virulence genes and PFGE profiles of these two groups were very similar to those of clinical human isolates. While further studies are required to determine the true zoonotic potential of these clonal groups, our results emphasize the zoonotic risk posed especially by poultry farms, but also by pig farms, as reservoirs of ESBL- and CMY-2-encoding E. coli.
为了确定动物农场中是否存在对人类具有潜在致病性的产超广谱β-内酰胺酶（ESBL）和质粒型 C 类β-内酰胺酶的大肠杆菌分离株，对来自禽场（57 株）和猪场（29 株）的 86 株大肠杆菌进行了系统发育分析、脉冲场凝胶电泳（PFGE）分型、血清分型和毒力基因分型。来自禽场的大肠杆菌分离株携带 CTX-M-9 组以及 CMY-2 编码酶的基因，而来自猪场的分离株主要携带 CTX-M-1 编码酶的基因。禽场和猪场的分离株在其系统发育群分配上存在显著差异，猪场分离株以 phylogroup A 为主，禽场分离株以 phylogroup D 为主。在 86 个农场分离株中，有 23 株（26.7%）携带两种或多种与肠外致病性大肠杆菌（ExPEC）典型的毒力基因。其中，20 株分离自禽场，仅 3 株分离自猪场。23 株分离株中有 10 株属于经典的人类 ExPEC 血清型 O2:H6、O2:HNM、O2:H7、O15:H1 和 O25:H4。尽管在 86 个农场分离株中检测到了血清型和脉冲型的高度多样性，但鉴定出了 13 个 PFGE 簇。其中 4 个簇含有携带两种或多种毒力基因的分离株，2 个簇显示出经典的人类 ExPEC 血清型 O2:HNM（ST10）和 O2:H6（ST115）。尽管来自人和动物的 O2:HNM 和 O2:H6 分离株在毒力基因和 PFGE 脉冲型上存在差异，但来自猪的 O2:HNM 分离株与来自人的 O2:HNM 分离株具有相同的序列型（ST10）。唯一的禽源 O15:H1 分离株与该血清型的人类临床分离株进行了比较。尽管它们都属于 phylogroup D，具有相同的毒力基因谱，但它们在序列型（ST362-禽和 ST393-人）和 PFGE 脉冲型上存在差异。值得注意的是，首次在禽场检测到产 CTX-M-9 的克隆群 O25b:H4-ST131-B2 和产 CTX-M-32 的 O25a-ST648-D，分别为 O25b:H4-ST131-B2 和 O25a-ST648-D。这两个群的毒力基因和 PFGE 图谱与临床人类分离株非常相似。虽然需要进一步的研究来确定这些克隆群的真正人畜共患病潜力，但我们的研究结果强调了尤其是禽场和猪场作为 ESBL 和 CMY-2 编码大肠杆菌的储存库所带来的人畜共患病风险。
