We reviewed susceptibility of 840 A. baumannii complex isolates at two academic medical centers and explored their mechanism of carbapenem resistance. Carbapenem resistance rates among A. baumannii increased from <5% before 2005 to 55% in 2011 and declined thereafter. We subjected 86 isolates for further antibiotic susceptibility testing using E-test, screened for MBL and carbapenemase production, and performed PCR for blaOXA genes. Statistical analyses included correlation of resistance genes with susceptibility. Sixty-one isolates were non-susceptible to carbapenems (MIC >2 μg/mL). Phenotypic screening showed carbapenemase production in 50 isolates, but none was positive for MBL. Among carbapenem non-susceptible isolates, the CHDL (group D carbapenemase) encoding genes blaOXA-23 (52%) and blaOXA-40 (28%) were the most frequent genes. In conclusion, carbapenem resistance rates in A. baumannii peaked in 2011 and have since declined in our region. Carbapenem resistance among A. baumannii was primarily associated with production of acquired CHDLs including OXA-23 and OXA-40.

中文翻译：

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在伊利诺伊州中部生产OXA-23和OXA-40的耐碳青霉烯的鲍曼不动杆菌。

我们审查了两个学术医学中心对840鲍曼不动杆菌复合物的敏感性，并探讨了它们对碳青霉烯耐药的机制。鲍曼不动杆菌对碳青霉烯的耐药率从2005年之前的<5％上升到2011年的55％，之后下降。我们对86个分离株进行了进一步的抗生素敏感性测试（使用E-test），筛选了MBL和碳青霉烯酶的产生，并对blaOXA基因进行了PCR。统计分析包括耐药基因与药敏性的相关性。六十一种分离物对碳青霉烯类药物不敏感（MIC> 2μg/ mL）。表型筛选显示50个分离物中产生碳青霉烯酶，但MBL均无阳性。在碳青霉烯类非敏感分离株中，编码基因blaOXA-23（52％）和blaOXA-40（28％）的CHDL（D组碳青霉烯酶）是最常见的基因。总之，鲍曼不动杆菌对碳青霉烯的耐药率在2011年达到峰值，此后一直在下降。鲍曼不动杆菌对碳青霉烯的耐药性主要与获得的CHDL的产生有关，包括OXA-23和OXA-40。