Characterization of resistance mechanisms and genetic relatedness of carbapenem-resistant Acinetobacter baumannii isolated from blood, Italy

Diagn Microbiol Infect Dis. 2013 Feb;75(2):180-6. doi: 10.1016/j.diagmicrobio.2012.11.002. Epub 2012 Dec 21.


The aim of this study was to characterize the resistance mechanisms and genetic relatedness of 21 carbapenem-resistant Acinetobacter baumannii blood isolates collected in Italy during a 1-year multicenter prospective surveillance study. Genes coding for carbapenemase production were identified by polymerase chain reaction (PCR) and sequencing. Pulsed-field gel electrophoresis (PFGE), multiplex PCRs for group identification, and multilocus sequence typing (MLST) were used to determine genetic relationships. Carbapenem resistance was consistently related to the production of oxacillinases, mostly the plasmid-mediated OXA-58 enzyme. Strains producing the OXA-23 enzyme (chromosomally mediated) were also detected. Seven PFGE clones were identified, some of which being related to international (ICL- I and ICL-II) or national clonal lineages. Multiplex PCRs identified 4 different groups (group 2 being dominant), further distinguishable in 6 sequence types by MLST. The heterogeneity of profiles highlights the diffusion of international and national clonal lineages in Italy. Continuous surveillance is needed for monitoring the spread of these worrisome strains equipped with multiple drug resistance mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter Infections / microbiology*
  • Acinetobacter baumannii / drug effects
  • Acinetobacter baumannii / enzymology*
  • Acinetobacter baumannii / genetics*
  • Acinetobacter baumannii / isolation & purification
  • Bacterial Proteins / genetics
  • Cluster Analysis
  • Electrophoresis, Gel, Pulsed-Field
  • Humans
  • Italy
  • Multilocus Sequence Typing
  • Polymerase Chain Reaction
  • beta-Lactam Resistance
  • beta-Lactamases / genetics


  • Bacterial Proteins
  • beta-Lactamases
  • carbapenemase
  • oxacillinase