Carbapenem-resistant Acinetobacter baumannii (CRAB) has increased significantly in recent decade in Taiwan. This study investigated the molecular epidemiology of CRAB with focus on the mechanisms of resistance and spread in isolates with blaOXA-23-like or blaOXA-24-like All 555 CRAB isolates in our 2002-2010 multi-centered collection were tested for the presence of class A, B and D carbapenemase genes. All isolates with blaOXA-23-like or blaOXA-24-like were subjected to PFGE and 82 isolates (60 blaOXA-23-like and 22 blaOXA-24-like) were selected for MLST to determine sequence type (ST) and clonal group (CG), and detection of additional beta-lactamase and aminoglycoside genes. The flanking regions of carbapenem and aminoglycoside resistance genes were identified by PCR mapping and sequencing. The localization of blaOXA was determined by S1 nuclease and I-CeuI assays. CRAB isolates carrying blaOXA-23-like or blaOXA-24-like increased significantly from 2008 onward, especially those with blaOXA-23-like The blaOXA-23-like gene was carried by AbGRI1-type structures located in plasmid and/or chromosome in isolates of different STs (CG92 and novel CG786) whereas blaOXA-24-like was carried on plasmids in CRAB isolates of limited ST (CG92). No class A or B carbapenemase genes were identified. Multiple aminoglycoside resistance genes coexisted in CRAB. Tn6180-borne armA was found in 74 (90.2%) CRAB and 58 (70.7%) had upstream Tn6179, constituting AbGRI3. The blaTEM was present in 38 (46.3%) of tested CRAB with 35 (92.1%) in AbGRI2-type structures and 61% of ampC had upstream ISAba1 We conclude that dissemination and spread of a few dominant lineages of CRAB containing various resistance island structures occurred in Taiwan.
日期:
2018-03
關聯:
Antimicrobial Agents and Chemotherapy. 2018 Mar;62(3):Article number e01215-17.
