Global emergence of Acinetobacter baumannii International Clone 12 predominantly found in the Middle East

Infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) are of great concern, as mortality is high, and treatment options are very limited. Despite having among the highest rates reported worldwide, scarce genomic data are available on CRAB strains from the Middle East. Here, we report the global emergence of a novel International Clone (IC), designated IC12, based on the epidemiological, phenotypic and genome sequencing data (short reads and long reads) of a set of 60 A. baumannii isolates belonging to multilocus sequence type 158 (Pasteur scheme). IC12, prevailing in the Middle East since 2007, has also been found in Europe, Asia and South America. Alleles OXA-65 and ADC-117, coded by the bla _OXA-51-like and bla _ADC A. baumannii-intrinsic genes, respectively, were hallmarks shared by all the isolates. Plasmid pIC12-2 (80,000 bp), which carries a repAci6 replication initiator (RP-T1) and a type IV conjugative transfer system, played a major role in the antimicrobial resistance profile of 54/60 of the IC12 isolates. This resistance was mediated by three mobile genetic elements, namely Tn2008, MITEAb-IC12 and TnaphA6. All four Peruvian IC12 isolates lacked pIC12-2 and carried a different set of plasmids. Two of the Peruvian isolates carried a chromosomal resistance island of 79,396 bp long (designated IC12-RI) marked by the occurrence of tet(X3). The global spread of IC12 is worrying and calls for further studies on the virulence features and clinical impact of this clone.