Spread of the blaOXA–23-Containing Tn2008 in Carbapenem-Resistant Acinetobacter baumannii Isolates Grouped in CC92 from China

Abstract

The rapid expansion of carbapenem-resistant <i>Acinetobacter baumannii</i> (CRAB) clinical isolates is a big issue. We investigated the antibiotic susceptibility, molecular epidemiology and resistance gene of <i>A. baumannii</i> collected at two hospitals in Shanghai, China. Besides, the <i>A. baumannii</i> PCR-based replicon typing method (AB-PBRT) was conducted to categorize the plasmids into homogeneous groups on the basis of replicase genes. Most CRAB isolates showed high-level resistance to almost all antibiotics but retain susceptibility to colistin and tigecycline. A total of 101 isolates carried <i>bla</i>_OXA-51-like gene. Sequencing identified the presence of <i>bla</i>_OXA-66 for CRAB isolates. <i>bla</i>_OXA-23 gene were discovered in all CRAB isolates. Each CRAB isolate contained 1-3 of 19 different plasmid replicase (<i>rep</i>) gene homology groups (GRs) and the GR6 (<i>rep</i>Aci6) was ubiquitous. Genotyping by Multilocus Sequence Typing (MLST) showed seven defined MLST patterns and three novel STs were found. eBURST analysis indicated they were all grouped in CC92 (GCII) with the most frequent ST208 (50%). Two <i>bla</i>_OXA-23-bearing transposons were found: Tn<i>2006</i> and Tn<i>2008</i>. Tn<i>2008</i> were detected in 54 (96.4%) isolates and Tn<i>2006</i> in two remaining isolates. The <i>bla</i>_OXA-23 carbapenem gene was vitally associated with <i>rep</i>Aci6 plasmid belong to CC92 clonal group. Our survey revealed severe drug resistance in <i>A. baumannii</i> isolates. Tn<i>2008</i>-containing CC92 <i>A. baumannii</i> were endemic, which may facilitate the <i>bla</i>_oxa23 dissemination.