College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi, China.
College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi, China.
Poult Sci. 2020 Jul;99(7):3688-3696. doi: 10.1016/j.psj.2020.04.015. Epub 2020 Apr 25.
Commensal Escherichia coli from the poultries have been considered as reservoirs of extended-spectrum β-lactamases (ESBL)-encoding genes. Between May 2018 and March 2019, a total of 340 E. coli isolates were obtained from apparently healthy broiler chickens from 20 to 40 D old, distributed in 17 small-scale commercial farms. Finally, 45 isolates (8 from 20-day-old broiler chickens, 14 from 30-day-old ones, and 23 from 40-day-old ones) were identified as ESBL producers, which were further investigated to shed light on the virulence gene profiles, phylogenetic groups, and multilocus sequence types and to detect the ESBL plasmid-mediated quinolone resistance determinant (PMQR) genes as well as the mutations in the quinolone resistance-determining regions (QRDR) of gyrA and parC. Molecular analysis showed that phylogenic group A and B1 accounted for 66.7% of the ESBL producers. The overall occurrence of virulence genes ranged from 5.1% (cva) to 86.7% (papC). Twenty (44.4%) ESBL producers were considered as biofilm producers with moderate or heavy biofilm formation. The most predominant specific CTX-M subtype was bla (n = 19), followed by bla (n = 17), bla (n = 9), bla (n = 6), bla (n = 5), and bla (n = 4). Additionally, PMQR genes were identified in 86.7% of ESBL producers, qnrS (n = 21) was the most dominant PMQR gene, followed by the aac(6')-Ib-cr (n = 15), qnrB (n = 12), and qnrA (n = 9), and all of them co-expressed with β-lactamase genes. All PMQR-positive isolates harbored simultaneously at least 1 mutation in the QRDR of gyrA and parC. Forty-five ESBL producers were assigned to 33 sequence types, and the most frequent sequence types (STs) was ST10 (n = 5) and followed by ST95 (n = 3). Additionally, ST302, ST88, ST410, ST187, and ST23 were represented by 2 ESBL producers, respectively, and the remaining ones exhibited diverse ST. Moreover, the prevalence of ESBL producers, the biofilm-forming ability, and the occurrence of the QRDR mutations among the E. coli isolates were characterized by gradually increased with advancing age of broiler chickens.
从家禽中分离到的共生大肠杆菌已被认为是具有扩展谱β-内酰胺酶（ESBL）编码基因的储库。在 2018 年 5 月至 2019 年 3 月期间，从 20-40 日龄的健康肉鸡中总共获得了 340 株大肠杆菌分离株，分布在 17 个小型商业农场中。最后，鉴定出 45 株（8 株来自 20 日龄肉鸡，14 株来自 30 日龄肉鸡，23 株来自 40 日龄肉鸡）为 ESBL 产生菌，进一步研究了这些产生菌的毒力基因谱、系统发育群、多位点序列类型以及检测 ESBL 质粒介导的喹诺酮耐药决定因子（PMQR）基因和喹诺酮耐药决定区（QRDR）中的突变。分子分析表明，系统发育群 A 和 B1 占 ESBL 产生菌的 66.7%。毒力基因的总发生率为 5.1%（cva）至 86.7%（papC）。20（44.4%）株 ESBL 产生菌被认为是生物膜产生菌，具有中度或重度生物膜形成。最主要的特定 CTX-M 亚型为 bla（n = 19），其次为 bla（n = 17）、bla（n = 9）、bla（n = 6）、bla（n = 5）和 bla（n = 4）。此外，在 86.7%的 ESBL 产生菌中鉴定出了 PMQR 基因，qnrS（n = 21）是最主要的 PMQR 基因，其次是 aac(6')-Ib-cr（n = 15）、qnrB（n = 12）和 qnrA（n = 9），它们都与β-内酰胺酶基因共同表达。所有 PMQR 阳性分离株的 gyrA 和 parC 的 QRDR 中均至少存在 1 个突变。45 株 ESBL 产生菌被分配到 33 个序列型，最常见的序列型（ST）是 ST10（n = 5），其次是 ST95（n = 3）。此外，ST302、ST88、ST410、ST187 和 ST23 分别由 2 株 ESBL 产生菌代表，其余则表现出不同的 ST。此外，ESBL 产生菌、生物膜形成能力以及 QRDR 突变在肉鸡中的发生率随着肉鸡日龄的增加而逐渐增加。
