title: Spread of a carbapenem- and colistin-resistant Acinetobacter baumannii ST2 clonal strain causing outbreaks in two Sicilian hospitals.
abstract: BACKGROUND
  Infections caused by multidrug-resistant (MDR) Acinetobacter baumannii have become an important healthcare-associated problem, particularly in intensive care units (ICUs).
  
  
  OBJECTIVE
  To investigate the emergence of carbapenem- and colistin-resistant A. baumannii infections in two Sicilian hospitals.
  
  
  METHODS
  From October 2008 to May 2011, a period which included two Italian Nosocomial Infections Surveillance in ICUs network (SPIN-UTI) project surveys, all carbapenem-resistant A. baumannii isolates from the ICUs of two hospitals in Catania, Italy, were prospectively collected. Minimum inhibitory concentrations (MICs) were measured by agar dilution, and phenotypic testing for metallo-β-lactamase (MBL) production was performed. Carbapenem resistance genes and their genetic elements were identified by polymerase chain reaction and sequencing. Genotypic relatedness was assessed by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing. Patient-based surveillance was conducted using the SPIN-UTI protocol and previous antibiotic consumption was recorded.
  
  
  RESULTS
  Twenty-six carbapenem-resistant A. baumannii were identified. Imipenem and meropenem MICs ranged from 4 to >32 mg/L, and 15 isolates exhibited high-level colistin resistance (MICs >32 mg/L). PFGE demonstrated that all isolates belonged to a unique clonal type and were assigned to ST2 of the international clone II. They harboured an intrinsic blaOxA-51-like carbapenemase gene, blaOxA-82, which was flanked upstream by ISAba1.
  
  
  CONCLUSIONS
  The dissemination of clonally related isolates of carbapenem-resistant A. baumannii in two hospitals is described. Simultaneous resistance to colistin in more than half of the isolates is a problem for effective antibiotic treatment. Prior carbapenem and colistin consumption may have acted as triggering factors.
authors.affiliation: University of Catania, Department GF Ingrassia, Catania, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Agodi
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Athens, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Voulgari
authors.affiliation: University of Catania, Department GF Ingrassia, Catania, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Barchitta
authors.affiliation: University of Catania, Department GF Ingrassia, Catania, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Quattrocchi
authors.affiliation: Azienda Ospedaliero - Universitaria 'Policlinico - Vittorio Emanuele', Catania, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Bellocchi
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Athens, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Poulou
authors.affiliation: Azienda Ospedaliero - Universitaria 'Policlinico - Vittorio Emanuele', Catania, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Santangelo
authors.affiliation: Azienda Ospedaliero - Universitaria 'Policlinico - Vittorio Emanuele', Catania, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Castiglione
authors.affiliation: Azienda Ospedaliera Cannizzaro, Catania, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Giaquinta
authors.affiliation: Azienda Ospedaliera Cannizzaro, Catania, Italy.
authors.forename: M A
authors.initials: MA
authors.lastname: Romeo
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Athens, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Vrioni
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Athens, Greece. Electronic address: atsakris@med.uoa.gr.
authors.forename: A
authors.initials: A
authors.lastname: Tsakris
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology* / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000145:classification* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology; D003091:Colistin / Q000494:pharmacology; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006761:Hospitals; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D016133:Polymerase Chain Reaction; D012802:Sicily / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D003091:Colistin
keywords: Acinetobacter; Carbapenemase; Colistin resistance