Clonal complexes 104, 109 and 113 playing a major role in the dissemination of OXA-carbapenemase-producing Acinetobacter baumannii in Southeast Brazil

Abstract

Carbapenem resistance among Acinetobacter baumannii strains isolated from clinical settings in Brazil has increased dramatically in the last 10 years due to the emergence and dissemination of OXA-type carbapenemase encoding genes. This study aimed to characterize the presence of carbapenem-hydrolyzing class D β-lactamases (CHDL)-encoding genes and clonal complexes playing a major role in the dissemination of OXA-carbapenemase-producing A. baumannii in Southeast Brazil. A total of 74 A. baumannii strains isolated from patients admitted to 4 hospitals in Southeast Brazil were analyzed. Molecular characterization of strains revealed that 67 strains carried blaOXA-23 (72%), blaOXA-143 (25%) or both genes (3%). PFGE analysis identified 12 PFGE clusters, grouping 26 pulsotypes. Two PFGE clusters were predominant, comprising more than 66% of OXA-producing A. baumannii isolates. Among 23 representative strains characterized by MLST-UO (Multilocus Sequence Typing Scheme - University of Oxford, http://pubmlst.org/abaumannii/), 14 different STs were identified, of which six were confirmed as novel sequence types (designated as STs 402-407). Most of these isolates belonged to clonal complexes CC104,CC109 or CC113, whereas three STs were singletons (ST339, 403 and 407). In conclusion, the presence of blaOXA-23- and blaOXA-143-like genes was not related to specific ST/CC, suggesting that the dissemination of OXA-carbapenemase-encoding genes may involve different STs, in which the spread of OXA-23-like is most likely due to mobile elements (i.e., plasmids). In this regard, CC104, CC109 and CC113 played a major role as predominant CDHL-carrying clones, instead of CC92, which was not identified.

Keywords: Acinetobacter baumannii; Carbapenem resistance; Molecular epidemiology; Multilocus sequence typing; PFGE, OXA carbapenemases.