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Chromosomal co-carriage of blaOXA-23 and blaOXA-500 in a carbapenem-resistant Acinetobacter pittii isolate

Year: 2025
Type: article
Abstract: Carbapenem resistance in non- baumannii Acinetobacter has been increasingly reported worldwide. This study investigated the genetic basis of carbapenem resistance in Acinetobacter pittii isolate KBN12P06770 carrying bla OXA-23 and bla OXA-500 using whole-genome sequencing. Two carbapenemase genes were located on the chromosome. Two copies of bla OXA-23 located on Tn 2006 were identified. Additional chromosomally encoded antimicrobial resistance genes, including bla ADC-18 and ant(3“)-IIc , as well as efflux pump genes ( adeIJK , adeFGH , abeM , and abaQ ), were identified, with the exception of plasmid-borne ant(2”)-Ia . qPCR analysis revealed that the bla OXA-23 was more highly expressed than bla OXA-500 . Notably, bla OXA-23 featured the Ser225Pro substitution, first characterized in this study, which may enhance β-lactamase activity based on structural modeling. Furthermore, multilocus sequence typing (MLST) assigned KBN12P06770 to ST1611 within clonal complex 63 (CC63), with close clustering to ST2737 indicating recent divergence. The comprehensive genomic analysis of A. pittii isolate KBN12P06770 highlights the complex genetic architecture underlying carbapenem resistance. • Whole-genome sequencing revealed chromosomal co-carriage of bla OXA-23 and bla OXA-500 . • Two Tn2006-borne copies of bla OXA-23 with ~4.5-fold higher expression than bla OXA-500 . • A novel OXA-23 Ser225Pro substitution predicted to affect β-lactamase activity. • MDR genome with bla ADC-18 , ant(3“)-IIc , multiple efflux pumps, and plasmid ant(2”)-Ia . • MLST assigned the isolate to the rare ST1611 (CC63), closely related to ST2737, suggesting recent divergence.
DOI: 10.1016/j.meegid.2025.105845
Language: English
Open Access status: gold
Estimated APC paid: $2,730
OpenAlex ID: W4415653678
FWCI: 0.234
Cites: 23
Cited by: 1
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