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J Clin Microbiol. 2014 Aug;52(8):3004-10. doi: 10.1128/JCM.00291-14. Epub 2014 Jun 11.

Epidemic diffusion of OXA-23-producing Acinetobacter baumannii isolates in Italy: results of the first cross-sectional countrywide survey.

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  • 1Microbiology and Virology Unit, Department of Laboratory Medicine, A. Manzoni Hospital, Lecco, Italy.
  • 2Department of Clinical, Surgical, Diagnostic, and Pediatric Sciences, Section of Microbiology, University of Pavia, Pavia, Italy.
  • 3Department of Medical Biotechnologies, University of Siena, Siena, Italy.
  • 4Department of Medical Biotechnologies, University of Siena, Siena, Italy Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy Clinical Microbiology and Virology Unit, Department of Laboratory Medicine, Careggi University Hospital, Florence, Italy.
  • 5Microbiology and Virology Unit, Department of Laboratory Medicine, A. Manzoni Hospital, Lecco, Italy


Carbapenem-resistant Acinetobacter baumannii (CRAb) is emerging worldwide as a public health problem in various settings. The aim of this study was to investigate the prevalence of CRAb isolates in Italy and to characterize their resistance mechanisms and genetic relatedness. A countrywide cross-sectional survey was carried out at 25 centers in mid-2011. CRAb isolates were reported from all participating centers, with overall proportions of 45.7% and 22.2% among consecutive nonreplicate clinical isolates of A. baumannii from inpatients (n = 508) and outpatients (n = 63), respectively. Most of them were resistant to multiple antibiotics, whereas all remained susceptible to colistin, with MIC50 and MIC90 values of ≤ 0.5 mg/liter. The genes coding for carbapenemase production were identified by PCR and sequencing. OXA-23 enzymes (found in all centers) were by far the most common carbapenemases (81.7%), followed by OXA-58 oxacillinases (4.5%), which were found in 7 of the 25 centers. In 6 cases, CRAb isolates carried both bla(OXA-23-like) and bla(OXA-58-like) genes. A repetitive extragenic palindromic (REP)-PCR technique, multiplex PCRs for group identification, and multilocus sequence typing (MLST) were used to determine the genetic relationships among representative isolates (n = 55). Two different clonal lineages were identified, including a dominant clone of sequence type 2 (ST2) related to the international clone II (sequence group 1 [SG1], SG4, and SG5) and a clone of ST78 (SG6) previously described in Italy. Overall, our results demonstrate that OXA-23 enzymes have become the most prevalent carbapenemases and are now endemic in Italy. In addition, molecular typing profiles showed the presence of international and national clonal lineages in Italy.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

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