gms | German Medical Science

Carbapenem resistance in Acinetobacter baumannii is commonly conferred by carbapenem-hydrolysing oxacillinases (OXA), including the intrinsic OXA-51 subclass and the acquired subclasses OXA-23, OXA-40, OXA-58, OXA-143 and OXA-235. In the present study we characterized OXA-143 variants in two carbapenem-resistant A. baumannii isolates originated from Honduras (OXA-253) and Brazil (OXA-231), as well as a carbapenem-susceptible A. pittii isolate (OXA-255) from the USA. In contrast to other OXA subclasses, the genetic environment of bla_OXA-143-like showed great diversity. 5´-RACE identified the same transcription initiation site and revealed differences in the putative promoter regions (Figure 1 [Fig. 1]). However, cloned bla_OXA-143-like conferred carbapenem resistance in the A. baumannii reference strain ATCC 17978. Furthermore, OXA-255 conferred carbapenem resistance in the A. pittii reference strain SH024, which was associated with overexpression of the gene. In summary, this is the first report of OXA-143 variants from Honduras and the USA, which indicates further spread of this subclass on the American continent. The variability of the bla_OXA-143-like genetic context suggests different origins of the investigated genes. OXA-255-mediated carbapenem resistance in A. baumannii and A. pittii highlights the potential of this variant to spread in the genus Acinetobacter.