Lee Yangsoon, Yum Jong Hwa, Kim Chang-Ki, Yong Dongeun, Jeon Eun Hee, Jeong Seok Hoon, Ahn Jee Young, Lee Kyungwon
Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea.
Ann Clin Lab Sci. 2010 Winter;40(1):43-8.
This study was performed to determine the mechanisms for acquiring carbapenem resistance in six clinical isolates of Acinetobacter baumannii. All isolates showed similar SmaI-macrorestriction patterns with less than 3 band differences by PFGE. The isolates showed a high level resistance (>32 mg/L) to both imipenem and meropenem by Etest. Phe-Arg-beta-naphthylamide lowered the MICs of carbapenems. Real-time PCR experiments showed that expression levels of the adeB gene in the six A. baumannii isolates were 10- to 40-times higher than those of imipenem-susceptible strains. Direct sequencing of PCR products showed that all isolates carried the bla(OXA-23) gene, which was preceded by ISAba1. The bla(OXA-23) probe hybridized with approximately 500-kb I-CeuI chromosomal fragments, but not with a plasmid. These findings suggest that overexpression of the AdeABC efflux pump as well as chromosome-borne OXA-23 may play a role in acquiring carbapenem resistance in our A. baumannii isolates.
本研究旨在确定鲍曼不动杆菌6株临床分离株获得碳青霉烯类耐药性的机制。所有分离株通过脉冲场凝胶电泳（PFGE）显示出相似的SmaI宏观限制性图谱，条带差异少于3条。通过Etest法，这些分离株对亚胺培南和美罗培南均表现出高水平耐药（>32 mg/L）。苯丙氨酸-精氨酸-β-萘酰胺降低了碳青霉烯类药物的最低抑菌浓度（MIC）。实时荧光定量PCR实验表明，6株鲍曼不动杆菌分离株中adeB基因的表达水平比亚胺培南敏感菌株高10至40倍。PCR产物的直接测序显示，所有分离株均携带bla(OXA-23)基因，其上游为ISAba1。bla(OXA-23)探针与约500 kb的I-CeuI染色体片段杂交，但不与质粒杂交。这些发现表明，AdeABC外排泵的过表达以及染色体携带的OXA-23可能在我们的鲍曼不动杆菌分离株获得碳青霉烯类耐药性中起作用。
