Harada Kazuki, Shimizu Takae, Mukai Yujiro, Kuwajima Ken, Sato Tomomi, Kajino Akari, Usui Masaru, Tamura Yutaka, Kimura Yui, Miyamoto Tadashi, Tsuyuki Yuzo, Ohki Asami, Kataoka Yasushi
Department of Veterinary Internal Medicine, Tottori University, Tottori, Japan.
Laboratory of Veterinary Microbiology, Nippon Veterinary and Life Science University, Tokyo, Japan.
PLoS One. 2017 Mar 22;12(3):e0174178. doi: 10.1371/journal.pone.0174178. eCollection 2017.
The emergence of antimicrobial resistance among Enterobacter spp., including resistance to extended-spectrum cephalosporins (ESC), is of great concern in both human and veterinary medicine. In this study, we investigated the prevalence of antimicrobial resistance among 60 isolates of Enterobacter spp., including E. cloacae (n = 44), E. aerogenes (n = 10), and E. asburiae (n = 6), from clinical specimens of dogs and cats from 15 prefectures in Japan. Furthermore, we characterized the resistance mechanisms harbored by these isolates, including extended-spectrum β-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR); and assessed the genetic relatedness of ESC-resistant Enterobacter spp. strains by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Antimicrobial susceptibility testing demonstrated the resistance rates to ampicillin (93.3%), amoxicillin-clavulanic acid (93.3%), cefmetazole (93.3%), chloramphenicol (46.7%), ciprofloxacin (43.3%), tetracycline (40.0%), ceftazidime (33.3%), cefotaxime (33.3%), trimethoprim/sulfamethoxazole (28.3%), gentamicin (23.3%), and meropenem (0%). Phenotypic testing detected ESBLs in 16 of 18 ESC-resistant E. cloacae isolates but not in the other species. The most frequent ESBL was CTX-M-15 (n = 8), followed by SHV-12 (n = 7), and CTX-M-3 (n = 1). As for AmpC β-lactamases, CMY-2 (n = 2) and DHA-1 (n = 2) were identified in ESC-resistant E. cloacae strains with or without ESBLs. All of the ESC-resistant E. cloacae strains also harbored one or two PMQRs, including qnrB (n = 15), aac(6')-Ib-cr (n = 8), and qnrS (n = 2). Based on MLST and PFGE analysis, E. cloacae clones of ST591-SHV-12, ST171-CTX-M-15, and ST121-CTX-M-15 were detected in one or several hospitals. These results suggested intra- and inter-hospital dissemination of E. cloacae clones co-harboring ESBLs and PMQRs among companion animals. This is the first report on the large-scale monitoring of antimicrobial-resistant isolates of Enterobacter spp. from companion animals in Japan.
肠杆菌属细菌中出现的抗菌药物耐药性，包括对超广谱头孢菌素（ESC）的耐药性，在人类医学和兽医学中都引起了极大关注。在本研究中，我们调查了从日本15个县的犬猫临床标本中分离出的60株肠杆菌属细菌的抗菌药物耐药性情况，其中包括阴沟肠杆菌（n = 44）、产气肠杆菌（n = 10）和阿氏肠杆菌（n = 6）。此外，我们对这些分离株所携带的耐药机制进行了表征，包括超广谱β-内酰胺酶（ESBLs）和质粒介导的喹诺酮耐药性（PMQR）；并通过多位点序列分型（MLST）和脉冲场凝胶电泳（PFGE）评估了耐ESC肠杆菌属菌株的遗传相关性。抗菌药物敏感性测试显示，对氨苄西林的耐药率为93.3%，阿莫西林-克拉维酸为93.3%，头孢美唑为93.3%，氯霉素为46.7%，环丙沙星为43.3%，四环素为40.0%，头孢他啶为33.3%，头孢噻肟为33.3%，甲氧苄啶/磺胺甲恶唑为28.3%，庆大霉素为23.3%，美罗培南为0%。表型测试在18株耐ESC的阴沟肠杆菌分离株中的16株中检测到了ESBLs，而在其他菌种中未检测到。最常见的ESBL是CTX-M-15（n = 8），其次是SHV-12（n = 7）和CTX-M-3（n = 1）。至于AmpCβ-内酰胺酶，在有或无ESBLs的耐ESC阴沟肠杆菌菌株中鉴定出了CMY-2（n = 2）和DHA-1（n = 2）。所有耐ESC的阴沟肠杆菌菌株还携带一种或两种PMQRs，包括qnrB（n = 15）、aac(6')-Ib-cr（n = 8）和qnrS（n = 2）。基于MLST和PFGE分析，在一家或几家医院中检测到了ST591-SHV-12、ST171-CTX-M-15和ST121-CTX-M-15的阴沟肠杆菌克隆。这些结果表明，携带ESBLs和PMQRs的阴沟肠杆菌克隆在伴侣动物中存在医院内和医院间传播。这是日本关于伴侣动物中肠杆菌属抗菌药物耐药分离株大规模监测的首次报告。
