建立超廣譜乙內醯胺?(ESBL)病原菌與整合子之分子分型資料庫 Database Establishment of ESBL Pathogens Molecular Fingerprinting and Related Integron Family
中文摘要
超廣效乙內醯胺?（extended-spectrum β-lactase，ESBL）是一種由突變 基因（bla），所媒介的新一類乙內醯胺?（β-lactamase） ，一般位於質體
（plasmid）上。這些酵素可經由一個或多個氨基酸的改變，就能水解更多 cephalosporin 類抗生素，所以這些能製造 ESBLs 的細菌就可以抵抗更多抗 生素，包括較新的第三代cephalosporin、penicillin 以及
aztreonam。ESBLs 常見於克雷白氏肺炎菌（Klebsiella pneumoniae）、大 腸桿菌（Escherichia coli，E. coli）等腸道菌，可水解 carbapenem 以外的 β-lactam 類抗生素，使得臨床上的治療倍受挑戰。由於 ESBL 的抗藥性基因一 般位於質體中，故此抗藥性基因可在細菌間相互轉移、傳遞，進一步造成抗藥性 的擴散。
在另一方面，ESBL 類抗藥性菌株已不僅只限制於 Klebsiella pneumoniae 以 及E. coli，在其他細菌如沙門氏菌（Salmonella enterica）、綠膿桿菌
（Pseudomonas aeruginosa）、黏質沙雷氏桿菌（Serratia
marcescens）等也都相當常見。大部分的革蘭氏陰性菌（Gram negative）
都會產生ESBL，並對我們現今所用的大部分抗生素產生抗藥性。當細菌產生這
類ESBL 的酵素時，像是 cefotaxime，ceftazidime 以及 ceftriaxone 等第 三代頭孢菌素(3rd generation cephalosporins)，對於細菌就無法產生抑制 作用，因此也使得在現今臨床醫療上遭遇到很大的困難。
除此之外，整合子（integron）是近年來被認為繼抗藥性質體（plasmid）和 轉位子（transposon）外，另一個與細菌獲得新抗藥性基因及抗藥性基因散佈 有關的機制。基因卡匣（gene cassettes）上帶有抗藥基因，許多不同的抗藥
性基因是位於一基因卡匣內，細菌之質體或是genomic DNA 的基因序列能夠
透過integron 主導基因卡匣透過進行特定部位重組作用的方式嵌入或移出
integron，達到基因卡匣的整合，此種特定部位重組作用造成 integron 所攜
帶之抗藥性基因的改變和抗藥性基因的散佈，因此integron 和基因卡匣在臨
床菌株抗藥性中扮演著重要角色。
E. coli 及 Klebsiella pneumoniae 為 ESBL 中常見的菌種，其盛行率在國內 有越來越高的趨勢。近年來在台灣，一些革蘭氏陰性菌，都陸續出現抗藥性的問 題，對於目前所使用的抗生素均已有抗藥性的產生。在本實驗中，我們將全國各 主要醫學中心及北醫附設醫院所收集的ESBL 檢體，利用 ERIC 以及 REP-PCR 分子指紋圖譜分型技術（molecular fingerprinting），針對 E. coli 及
Klebsiella pneumoniae 來做基因多樣性之分析鑑定。結果證實這兩種分型法 可以對台灣地區之E coli 以及 Klebsiella pneumoniae 臨床分離菌株提供良
好的區分能力，在分子流行病學上比對出菌株種源相關性，進而希望能發展出 一套能夠提供臨床進行快速準確的菌種鑑別的系統平台。此外，我們更針對 integron 來探討細菌具有哪些抗藥性基因，進而釐清細菌抗藥性之機制。
英文摘要
Infections caused by multidrug-resistant bacteria expressing extended -spectrum - lactamases (ESBLs) pose serious challenges to clinicians. Extended-spectrum - lactamases (ESBLs) are plasmid-mediated bacterial enzymes that confer resistance to a broad range of -lactams. Most ESBLs have evolved by genetic mutation from native -lactamases, such as TEM-1, TEM-2, and SHV-1. These parent enzymes are commonly found in Gram-negative bacteria, particularly enterobacteriaceae; they are highly active against penicillins and modestly active against early-generation
cephalosporins.
The prevalence of infections caused by extended-spectrum -lactamase (ESBL)–
producing Enterobacteriaceae is increasing worldwide. Because ESBL-producing strains are resistant to a wide variety of commonly used antimicrobials, their proliferation poses a serious global health concern that has complicated treatment strategies for a growing number of hospitalized patients. Although ESBLs have been reported most frequently in Escherichia coli and Klebsiella species , they have been found in other bacterial species as well, including Salmonella enterica, Pseudomonas aeruginosa, and Serratia marcescens .
Bacterial resistance to an increasing number of antimicrobial agents is a well- established problem. In recent years, a novel group of DNA elements able to incorporate antibiotic resistance genes by a site-specific recombination have been identified in Gram-negative bacteria. These elements have been termed integrons.
Gene transfer into small genomes and into plasmids is via site-specific recombination.
Integron act as reporters of antibiotic resistance cassettes. As such, integron-driven gene capture is likely to be an important factor in the more general process of horizontal gene transfer in the evolution of bacterial genomes.
An increase in the number of cases of ESBL has been observed over the past few years in the hospital of major medical center in Taiwan, and will be the great challenge to overcome this threatens. There are total 323 drug-resistant ESBL have collected, in which 223 clinical isolates are from the Taipei Medical University Hospital. Other 100 samples were kindly provided by Dr. P. R. Hsueh (NTU, School of Medicine) which collected from the major medical centers in Taiwan including north, central, south, and east regions. The objectives of this proposed project are (i) to investigate the molecular epidemiology of ESBL colonization and infection in the hospital, (ii) to evaluate the diffusion of integron types among clinical isolates of
ESBL in Taiwan and to carry out a molecular characterization of their gene cassette arrays, (iii) to study the molecular epidemiology of ESBL antimicrobial resistance, (iv) to evaluate the contribution of integrons and efflux pump to the multiple antibiotic resistance and nosocomial spread of ESBL strains, and (v) to identify clinical and therapeutic factors contributing to the selection of multidrug-resistant ESBL in the hospital environment.
