彰化地區某醫院鮑氏不動桿菌藥物敏感試驗與Class 1 integrons之探討

Study of Variation on Antimicrobial Susceptibility Test and Class 1 Integron of Acinetobacter Baumannii in A Hospital in Changhua, Taiwan

抗藥性鮑氏不動桿菌（Acinetobacter baumannii）是引起醫療照護相關感染非常重要的原因，除高致病性與致死率外，也是醫療照護相關感染主要病原菌之一，而Integron 是除了質體與轉位子之外，細菌獲得新抗藥基因有關的水平傳播單位。本研究在2008~2010 年共收集彰化秀傳醫院100 株鮑氏不動桿菌臨床血液培養菌株，針對14 種抗生素進行抗藥性的測試。並運用CS-PCR 技術來分析Class 1 integrons的分布與其所攜帶抗藥基因卡匣種類。分析後發現，鮑氏不動桿菌對cephalosporins類藥物的抗藥性明顯上升（由54% 上升為66%），且對PIP 、TZP 、SXT 、SAM 類抗生素的抗藥性也都有上升的趨勢，但同時發現對Aminoglycosides 的抗藥性則有下降的趨勢（由60% 降為48%）。 約有61.8% 的鮑氏不動桿菌臨床分離株可增幅出Class 1 integron 的cassettearray；增幅出的cassette array 有3.0 kb, 2.5 kb, 1.5 kb 和1.0 kb 四種大小，其中以帶有2.5 kb cassette array 所佔的比率最高，為所有帶integron 的菌株之87.3%。經對照抗生素的抗性測試可以發現，帶有Class 1 integron 的菌株，其具有的抗生素抗性比不具有Class 1 integron 的菌株較為多樣化。可是發現頻率最高的2.5 kb 的cassettearray ，在其他國家的報告卻極少；推測可能因素為經由醫院內長期抗生素壓力的篩選，使得帶有2.5 kb integron 的鮑氏不動桿菌，形成了台灣地區特有的臨床優勢菌株，而這種趨勢的產生應該是與醫師在治療上使用的抗生素有關。

Antibiotic-resistant Acinetobacter baumannii is a very important cause of healthcare-associated infections. Being highly pathogenic and having high mortality, it is one of the major healthcare-associated infecting pathogens. In addition to plasmid and transposon, integron is the genetic unit that confers antibiotic resistance to bacteria. In this study, 100 A. baumannii clinical blood culture isolates were collected from Show Chwan Memorial Hospital, Changhua, Taiwan from 2008 to 2010 and their antimicrobial susceptibility against 14 kinds of antibiotics were examined. Results showed a significant increase (from 54% to 66%) in drug resistance of A. baumannii to cephalosporins. An upward trend in resistance to PIP, TZP, SXT and SAM was also observed. In contrast, there was a marked decrease (from 60% to 48%) in drug resistance to aminoglycosides.
Moreover, the CS-PCR method was employed to detect the existence of class 1 integron in these isolates. It was found that 61.8% of these isolates carried the class 1 integron, and the cassette arrays they carried were of four different sizes: 3.0 kb, 2.5 kb, 1.5 kb and 1.0 kb, with the majority of isolates (87.3%) carrying the 2.5 kb cassette array. Results also showed that integron-carrying A. baumannii isolates were more resistant to various antibiotics tested than non-integron-carrying isolates. The widespread occurrence of 2.5 kb cassette array in A. baumannii isolates from the case hospital was rarely reported in other countries.This phenomenon may be linked to the hospital’s preference of certain antibiotics, causing the A. baumannii strain carrying the 2.5-kb cassette array to become the dominant antibiotic being administered.