Outbreak of a carbapenem-resistant XDR Acinetobacter baumannii belonging to the International Clone II (IC2) in a clinical setting in Brazil, 2022

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a leading cause of nosocomial infections worldwide, and the occurrence of extensively drug-resistant (XDR) lineages among them is increasing. Most of A. baumannii pandemic lineages, known as International clones, are represented by MDR/XDR CRAB strains. The IC2 is considered one of the most successful and widespread pandemic clones, however, it is rare in South America, where IC1, IC4 and IC5 are prevalent. In Brazil, besides sporadic reports, an IC2 outbreak was reported only once in Sao Paulo city during the COVID-19 pandemics. This study characterized an outbreak caused by IC2 strains (n=16) in a hospital in Rio de Janeiro in 2022. MLST (MLST Pasteur scheme) analysis revealed that all strains recovered from nosocomial infections belonged to ST2 and corresponded to CRAB presenting the XDR phenotype. In general, this broad resistance spectrum was explained by the presence of several antibiotic resistance genes (ARGs) (armA, blaTEM, blaOXA-23, blaOXA-66, and aacA4-catB8-aadA1-qacE{Delta}1/sul1 carried in class 1 integron). Interestingly, the strains characterized here presented a broader resistance spectrum compared to those of the unique other and contemporary IC2 outbreak in Brazil, although they shared most of the ARGs. This study stressed the possibility of the successful establishment of IC2 in Brazilian clinical settings during and after the COVID-19 pandemics in response to a series of events, such as the overuse of antibiotics, during that period.