Emergence of extensively drug-resistant international clone IC-6 Acinetobacter baumannii carrying bla and bla in the Brazilian Amazon region.

Objectives: The extensively drug-resistant (XDR) Acinetobacter baumannii international clone VI (IC-6) has been identified worldwide since 2006. This study reports the emergence of IC-6 in the Brazilian Amazon region and reveals the particular genomic features considering its mobilome and resistome.

Methods: A total of 32 carbapenem-resistant A. baumannii strains recovered from Boa Vista city (Roraima, Brazil) in 2016 were characterised by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The whole genome sequences of the Brazilian IC-6 strains were obtained. The mobilome and resistome were assessed by in silico analyses.

Results: PFGE and MLST demonstrated that the 32 A. baumannii strains belonged to four clones. One XDR clone corresponded to the high-risk pandemic IC-6 lineage from ST944/78. The IC-6 resistome was composed of aadA5, aac(3'')-IIa, aph(3')-Ia, armA, aadB, msrE, bla, IS15DIV-bla-IS15DIV, bla, ISAba1-bla, bla, qacEΔ1 and sul1. Mobilome prediction revealed that bla was embedded in a 15.5-kb plasmid and that it was flanked by putative XerC/D-binding sites, possibly involved in bla mobilisation. Several resistance genes were in a 48-kb multidrug resistance genomic island inserted in the chromosome, which also harboured genes involved in host pathogenicity and adaptive traits. Interestingly, the Brazilian strains shared the bla and bla with IC-6/ST944/78 recovered in a distinct spatiotemporal context, pointing to an epidemiological link among them.

Conclusion: This study highlights the importance of surveillance of XDR A. baumannii strains, even outside of densely populated cosmopolitan regions, to reveal the epidemiology of pandemic lineages, stressing their threat to public health.