title: An outbreak of extremely drug-resistant Pseudomonas aeruginosa in a tertiary care pediatric hospital in Italy.
abstract: BACKGROUND
  Extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) isolates are susceptible to only one or two classes of antibiotics. In 2011-2012, we investigated an outbreak of XDR-PA affecting children with onco-hematological diseases.
  
  
  METHODS
  Outbreak investigation included ascertainment of cases, tracing of intestinal carriers and environmental surveillance. Contact precautions were adopted for patients with infection or colonization. Isolates were tested for antimicrobial susceptibility; phenotypic confirmation of carbapenemase production was performed, and carbapenemase genes were tested by multiplex polymerase-chain-reaction (PCR). Genotypes were determined by pulsed-field gel electrophoresis (PFGE).
  
  
  RESULTS
  XDR-PA was isolated from 27 patients; 12 had bacteremia, 6 other infections and 9 were colonized. Severe neutropenia was significantly associated with bacteremia. Bloodstream-infection mortality rate was 67%. All isolates were resistant to carbapenems, cephalosporins and penicillins + β-lactamase inhibitors. Isolates were susceptible only to colistin in 22 patients, to colistin and amikacin in 4, and to ciprofloxacin and colistin in 1. PFGE results identified 6 subtypes of a single genotype, associated with clusters of cases, and 4 sporadic genotypes. Two sporadic isolates were metallo-β-lactamase producers, negative to PCR. All other isolates were metallo-β-lactamase producers due to the presence of a VIM carbapenemase. Incidence of XDR-PA infections decreased from 0.72 cases/1,000 inpatient-days in March 2011-March 2012, to 0.34/1,000 in April-December 2012, after implementation of active finding of intestinal carriers on all onco-hematological inpatients.
  
  
  CONCLUSIONS
  Control measures targeting intestinal carriers are crucial in limiting in-hospital transmission of XDR-PA polyclonal strains, protecting more vulnerable patients, such as severely neutropenic children, from developing clinical infections.
authors.affiliation: Unit of Clinical Epidemiology, Medical Direction, Bambino Gesù Children's Hospital, Piazza S, Onofrio, 4, Rome 00161, Italy. marta.ciofidegliatti@opbg.net.
authors.forename: Marta
authors.initials: M
authors.lastname: Ciofi Degli Atti
authors.forename: Paola
authors.initials: P
authors.lastname: Bernaschi
authors.forename: Michaela
authors.initials: M
authors.lastname: Carletti
authors.forename: Ida
authors.initials: I
authors.lastname: Luzzi
authors.forename: Aurora
authors.initials: A
authors.lastname: García-Fernández
authors.forename: Alice
authors.initials: A
authors.lastname: Bertaina
authors.forename: Annamaria
authors.initials: A
authors.lastname: Sisto
authors.forename: Franco
authors.initials: F
authors.lastname: Locatelli
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Raponi
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D003428:Cross Infection / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006776:Hospitals, Pediatric / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D007558:Italy / Q000453:epidemiology; D008297:Male; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D063128:Tertiary Health Care / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems