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

Objective. To investigate the antimicrobial susceptibility and clonal relationship of Acinetobacter baumannn 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-Iike, 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 circulat on and environmental persistence of this microorganism.