由2014至2017年從就診臺大動物醫院的犬貓所分離帶有超廣譜性乙內醯胺酶大腸桿菌的盛行率及特性分析

Abstract

超廣譜性乙內醯胺酶（extended-spectrum-β-lactamases, ESBLs）為可以水解β-內醯胺類抗菌藥物的酵素，包括第三代頭孢子菌素，如獸醫常用的ceftiofur。ESBL的產生主要是藉由質體傳遞，並且此類質體通常包含對其他種類的抗生素如胺基配糖體和氟喹諾酮類具有抗藥性的基因，限制了可用於治療的有效抗微生物劑的選擇。ESBLs廣泛分佈於腸桿菌科的成員中，特別是在大腸桿菌中。在犬貓中最常見的疾病為尿路感染，然而引起尿路感染 (urinary tract infections, UTIs) 的病原體又以大腸桿菌居多，這時就需要抗生素的治療，進而可能會導致ESBL-producing E. coli的產生。儘管帶有ESBL的微生物是全球性問題，但在臺灣，目前對於在獸醫中產ESBL的微生物的報告有限。因此，本研究目的在於分析2014至2017年間，就診臺大動物醫院的狗貓所分離帶有超廣譜性乙內醯胺酶大腸桿菌的盛行率及特性。本研究收集了285個大腸桿菌的檢體，並經由臨床與實驗室標準協會所規範的雙盤紙錠試驗去鑑定ESBL表現型，結果發現有65株大腸桿菌帶有ESBL (22.8%)。所有的65株分離株都對ampicillin呈抗藥性，對β-lactams類的ceftiofur、四環素類的doxycycline以及喹諾酮類的enrofloxacin、ciprofloxacin，則分別呈現93.8%、73.8%、80%，以及78.5% 的抗藥性。對於β-lactams類的imipenem與胺基配糖體類的gentamicin，則有相對較高的感受性。CTX-M-1和CTX-M-2 group為最主要的ESBL基因型。屬於CTX-M-1 group的分離株共有38株 (58.5%)，以CTX-M-55 (24/65, 36.9%) 為主要的ESBL基因。屬於CTX-M-2 group的分離株共12株 (18.5%)，其ESBL基因均為CTX-M-124 (12/65, 18.5%)。多重基因座序列分型法結果顯示ST457、ST131、ST648為最常見的無性繁殖系 (clone)。其中ST131、ST648又是屬於全球流行高危險群的無性繁殖系。然而，ST131 O25b是引起全球人畜共通傳染並造成公共衛生問題的clone。在本研究中發現有8株大腸桿菌屬於ST131 O25b，又以CTX-M-14和CTX-M-15的衍生物為主要ESBL基因型。伴侶動物如犬貓與人類會有親密的接觸，有可能成為人類產生ESBL細菌的潛在來源。因此，從公共衛生和獸醫學角度來看，鑑定與分析ESBL細菌的抗藥性問題與流行病學，是一個值得繼續深入探討的議題。

Extended-spectrum-β-lactamases (ESBLs) is a group of enzymes that can hydrolyze β-latctams antimicrobial agents, including the third generation cephalosporins such as ceftiofur frequently used in veterinary medicine. Production of ESBL is primarily plasmid-mediated and such plasmids often comprise the genes that exhibit resistance to other classes of antimicrobials like aminoglycosides and fluoroquinolones, limiting the choice of effective antimicrobial agents available for treatment. ESBLs are widely distributed in the members of the family Enterobacteriaceae, particularly in Escherichia coli. In both dogs and cats, the most common pathogen was E. coli, which could cause urinary tract infections (UTIs) and should be treated by antimicrobial agents. Urinary tract infections (UTIs) is the most common disease in dogs and cats, and the most commonly seen pathogen is E. coli. Therapy of UTIs requires antimicrobials; however, usage of such antimicrobials may also result in producing of ESBL-producing E. coli. Although presence of ESBL-producing microorganisms is a global problem, the information regarding the ESBL-producing E. coli is limited in veterinary medicine in Taiwan. Therefore, the objective of this study is to characterize the E. coli strains isolated in National Taiwan University Veterinary Hospital (NTUVH) from 2014 to 2017 in dogs and cats, analyzing the prevalence of ESBL-producing E. coli, the ESBL gene groups, and the sequence type of these ESBL producers. The double disc test specified by Clinical and Laboratory Standards Institute (CLSI) detected 65 ESBL-producing E. coli (22.8%) from 285 E. coli isolates recovered from dogs and cats in this study. All the 65 ESBL-producing E. coli were resistant to ampicillin. The resistant rate to ceftiofur, doxycycline, enrofloxacin, and ciprofloxacin was 93.8%, 73.8%, 80%, and 78.5% respectively. The ESBL-producing E. coli were relatively more sensitive to imipenem and gentamicin. The CTX-M-1 and CTX-M-2 was the most commonly found ESBL gene groups. A total of 38 isolates belonged to CTX-M-1 group; the main ESBL gene was CTX-M-55 (24/65, 36.9%). Twelve isolates belonged to CTX-M-2 group and the ESBL gene were all CTX-M-124 (12/65, 18.5%). Multilocus sequence typing (MLST) showed that ST457, ST131 and ST648 were the most commonly found clones, and the ST131 and ST648 were the globally distributed high risk clones. The E. coli ST131/O25b is a zoonotic global clone of public health concern and our study found 8 E. coli ST131/O25b isolates whose major ESBL genes were CTX-M-14 and CTX-M-15 variants. Since companion animals like dogs and cats are in close contact with humans, From the perspective of public health and veterinary medicine, characterization of the ESBL-producers and epidemiology is an issue warrants further investigation.