Emergence and Distribution of Plasmids Bearing the bla _OXA-51 -Like Gene with an Upstream IS Aba1 in Carbapenem-Resistant Acinetobacter baumannii Isolates in Taiwan

Abstract

The bla OXA-51 -like gene with an upstream ISAba1 (ISAba1-bla OXA-51 -like gene) was originally found on the chromosomes of carbapenem-resistant or -susceptible Acinetobacter baumannii isolates. However, a plasmidborne ISAba1-bla OXA-51 -like gene has recently been identified in Acinetobacter genomic species 13TU and several A. baumannii isolates in Taiwan, and all of the isolates are carbapenem resistant. This study aimed to characterize the plasmids bearing the ISAba1-bla OXA-51 -like gene and their significance in A. baumannii. Among the 117 ISAba1-bla OXA-51 -like-harboring isolates collected from 10 hospitals in Taiwan, 58 isolates (49.6%) from 24 clones had the genes located on plasmids that likely originated from a common progenitor. Among the 58 isolates, four had additional copy of the ISAba1-bla OXA-51 -like gene on their chromosomes. Based on the analysis of these four isolates, the plasmid-located ISAba1-bla OXA-51 -like gene appeared to be acquired via one-ended transposition (Tn6080). The isolates with a plasmid bearing the ISAba1-bla OXA-51 -like gene had higher rates of resistance to imipenem (98% versus 46.6%; P < 0.001) and meropenem (98% versus 69%; P ‫؍‬ 0.019) than those with the genes chromosomally encoded, which is most likely due to increased gene dosage provided by the higher copy number of associated plasmids. Transformation with a recombinant plasmid harboring only the ISAba1-bla OXA-51 -like gene was enough to confer a high level of carbapenem resistance to A. baumannii, eliminating the possible contribution of other factors on the original plasmids. This study demonstrated that the carbapenem resistance-associated plasmids carrying the ISAba1-bla OXA-51 -like gene are widespread in A. baumannii strains in Taiwan.

Prevalence of carbapenem resistance genes inAcinetobacter baumanniiisolated from clinical specimens obtained from an academic hospital in South Africa

“…33 However, it is important to note that in a recent publication by Chen et al, 49.6% (58/117) of A. baumannii isolates that were obtained from 10 Taiwanese hospitals contained the OXA-51-like gene on a plasmid which conferred increased rates of resistance to imipenem and meropenem. 34 This phenomenon can be explained by the increased gene expression because of the higher copy number on the plasmids. 34 During M-PCR II, one of the isolates (isolate number 36) tested positive for the VIM-like gene, as well as for OXA-23 and OXA-51, indicating that this was a highly drug-resistant isolate of A. baumannii.…”

“…34 This phenomenon can be explained by the increased gene expression because of the higher copy number on the plasmids. 34 During M-PCR II, one of the isolates (isolate number 36) tested positive for the VIM-like gene, as well as for OXA-23 and OXA-51, indicating that this was a highly drug-resistant isolate of A. baumannii. Antimicrobial susceptibility testing with the Vitek 2 Automated System ® confirmed that isolate number 36 was resistant to gentamicin, ceftazidine, piperacillin-tazobactam, ciprofloxacin, imipenem, cefepime and meropenem.…”

The role of the genetic elements bla oxa and IS Aba 1 in the Acinetobacter calcoaceticus-Acinetobacter baumannii complex in carbapenem resistance in the hospital setting

“…The bacterial genus Acinetobacter is recognized as a key HAI-causing pathogen that is associated with high mortality rates in hospital settings (2) (4) . Acinetobacter has considerable capacity to spread and develop new antibiotic resistance mechanisms (5) . Consequently, numerous HAI outbreaks caused by multidrug-resistant (MDR) representatives of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex have been reported in several countries, including Brazil (2) (5) (6) .…”

A Case of IMP-4-, OXA-421-, OXA-96-, and CARB-2-Producing Acinetobacterpittii Sequence Type 119 in Australia

“…1). This gene had a genetic environment identical to that of the chromosomal bla OXA-51 gene in A. baumannii (19), which includes two genes that are usually present upstream and downstream of bla OXA-51 in A. baumannii, the phosphinothricin Nacetyltransferase-encoding gene and fxsA, respectively. bla has 95% identity with the previously reported bla OXA gene (GenBank accession number CP002177, locus tag BDGL_000903) from the genome of A. calcoaceticus PHEA-2 (20), which is the closest neighbor of our CR12-42 isolate, as previously mentioned.…”