A high mortality rate associated with multidrug-resistant Acinetobacter baumannii ST79 and ST25 carrying OXA-23 in a Brazilian intensive care unit

The global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) strains has restricted the therapeutic options available to treat infections due to this pathogen. Understanding the prevalence of such infections and the underlying genetic mechanisms of resistance may help in the implementation of adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting. This study describes the molecular characteristics and risk factors associated with OXA-23-producing A. baumannii infections. A case-control study was undertaken from September/2013 to April/2015. Acquisition of OXA-23-producing A. baumannii was found to be associated with the use of nasogastric tubes, haemodialysis, and the use of cephalosporins. These isolates were only susceptible to amikacin, gentamicin, tigecycline, and colistin, and contained the ISAba1 insertion sequence upstream ofbla(OXA-23) and bla(OXA-51) genes. Twenty-six OXA-23-producing A. baumannii strains belonged to the ST79 (CC79) clonal group,and patients infected or colonised by these isolates had a higher mortality rate (34.6%). In conclusion, this study showed a dissemination of OXA-23-producing A. baumannii strains that was associated with several healthcare-related risk factors and high mortality rates among intensive care unit patients.