| 摘要: | 本研究目的是對中部兩家醫院多重抗藥性鮑氏不動桿菌 ( A. baumannii ) 之抗藥機制和散播因子進行分析。首先由台中仁愛醫院 2004-2005 年間收集的 31 株抗 carbapenem 的鮑氏不動桿菌。利用脈衝式電泳以 Asc I 限制酶酵素分型，可將 A 群分成 I (11/31)、II (16/31)兩群集，另有 4 株 sporadic。經由等電點聚焦電泳、聚合酶連鎖反應和核酸序列分析偵測出A 群菌主要帶有 Class-B 的 metallo β-lactamases 的bla IMP-8-like 比例是87% (27/31)。在散播因子發現在A群都帶有class 1 integron，可分為四種不同的片段，分別是1.4 kb、2.2 Kb、2.5 kb、和5 kb，其中1.4 kb 包含有 bla IMP-8-like 基因。接著在2007 年由童綜合醫院所收集的 29 株抗 carbapenem 的鮑氏不動桿菌和 13 株不抗 carbapenem 的鮑氏不動桿菌作為對照菌株，共 42 株稱為B 群。同樣以 Asc I 限制酶酵素進行脈衝式電泳分型， B 群可分成 I (19/42)、II (2/42)、III (7/42)、IV (2/42)、V (2/42)、VI (6/42) 群集另有 4 株 sporadic 。同樣對 B 群菌進行乙內醯胺酶偵測，發現除了29 株抗 carbapenem 的鮑氏不動桿菌中帶有 Class-B 金屬乙內醯胺酶的bla IMP-8-like 比例是66% (19/29)，並同時偵測到 37 菌株帶有Class D 乙內醯胺酶 OXA-23。在散播因子發現 28 株帶有 OXA-23 乙內醯胺酶基因其上游具有 ISAba1 因子。在 B 群有 90% (38/42) 的菌株存在有三種 integron 片段，分別是2.2 kb 、2.5 kb、還有 5 kb。由以上結果中部兩家醫院的鮑氏不動桿菌院內和醫院間散布著相似的 PFGE types，而且經由不同型的乙內醯胺酶對 carbapenem 產生抗性；在散播因子方面攜帶型別大部分不同，但都有同樣基因片匣的 2.5 kb 的 integron。
The prevalence of carbapenem-resistant isolates of Acinetobacter baumannii and the dissemination factors were investigated at 2 district hospitals (A, B) in central Taiwan. During the period from 2004-2005, total 31 A. baumannii nonduplicate isolates were selected from A hospital because of resistance to carbapenems , also named A group strains. The 31 A. baumannii strains belong to 2 different clusters I (11/31), II (16/31) and 4 sporadic strains were classified by Asc I Pulse Field Gel Electrophoresis (PFGE). Screening for carbapenem-resistant beta-lactamase production was performed in the isolates by the combined disk method, isoelectric focusing, PCR amplification, and DNA sequence. Of carbapenems resistant 27 of A. baumannii were found with IMP-8-like, a Class-B metallo-beta-lactamase. Polymerase chain reaction (PCR) analysis showed the presence of four types of cassette arrays of 1.4 kb, 2.2 kb, 2.5 kb and 5 kb on class 1 integron. DNA sequencing was used to identify the genetic structures of the variable combination cassette region. The 1.4 kb fragment contain with gene of bla IMP-8-like. In 2007, another 42 A. baumannii nonduplicate isolates were selected from B hospital including 29 carbapenem-resistant isolates and 13 noncarbapenem-resistant isolates as control. The 42 A. baumannii strains were also classified by Asc I Pulse Field Gel Electrophoresis (PFGE). Type I was the dominant isolate, including subtypes I (19/42), II (2/42), III (7/42), IV (2/42), V (2/42), VI (6/42) and 4 sporadic strains. Screening for carbapenem-resistant beta-lactamase production indicated that 66% (19/29) of the carbapenem-resistant isolates carried the bla IMP-8-like gene, and 37 carried the bla OXA-23 gene in all 42 A. baumannii nonduplicate isolates. The OXA-23 -encoding gene was located 34 bp downstream of ISAba1. Three class I integron fragments of 2.2 kb, 2.5 kb and 5 kb were found in 90% (38/42) in A. baumannii isolates of B hospital. Only the 2.5 kb fragment of class 1 integron contains cassette arrays same in the isolates from A hospital. No plasmids were detected and conjugal transfer of resistance was not demonstrated in all of isolates. These results suggest that carbapenem-resistant A. baumanni strains epidemic clones have been intra- and inter-hospital spread. More efforts, including other ß-lactamase and searching antibiotic -resistance factor should be further identified to understand the revolution of multiple resistance in A. baumanni. |
