Molecular typing of XDR Acinetobacter baumannii strains in an Italian ICU.

OBJECTIVE: To investigate the antimicrobial susceptibility and clonal relationship of Acinetobacter baumannii strains isolated in an Italian ICU. DESIGN: Epidemiological, observational, retrospective, longitudinal study. SETTING AND PARTICIPANTS: The ICU of the University Hospital of Sassari, Italy. MAIN OUTCOME MEASURES: Pulsed Field Gel Electrophoresis (PFGE) and Multi Locus Sequence Typing (MLST) were used to evaluate the genomic features of the isolated strains. RESULTS: Drug susceptibility testing for all isolated strains showed the same resistance pattern, characterized by resistance to the most important antibiotics, with the only exception of colistin. PFGE showed a very poor between-strain variability; three distinct clusters, 11, 4, and 1 isolates in size, were identified (Dice's coefficient: 92.11%). MLST showed that all isolated strains belonged to sequence type 2 (ST2). All isolates collected from the environment and the human samples were positive for the following genes: blaOXA-23, blaOXA-51-like, blaVIM-like, blaIMP-like, andISAba1; however, blaOXA-24-like, blaOXA-58-like, and blaNDM-like were not detected. CONCLUSIONS: The survey identified XDR strains belonging to the same cell clone, confirming the wide circulation and environmental persistence of this microorganism.