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

Authors
  • Principe, Luigi
  • Piazza, Aurora
  • Giani, Tommaso
  • Bracco, Silvia
  • Caltagirone, Maria Sofia
  • Arena, Fabio
  • Nucleo, Elisabetta
  • Tammaro, Federica
  • Rossolini, Gian Maria
  • Pagani, Laura
  • Luzzaro, Francesco
Type
Published Article
Journal
Journal of Clinical Microbiology
Publisher
American Society for Microbiology
Publication Date
Aug 01, 2014
Volume
52
Issue
8
Pages
3004–3010
Identifiers
DOI: 10.1128/JCM.00291-14
PMID: 24920776
Source
Medline
License
Unknown

Abstract

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.

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