title: New genotyping method discovers sustained nosocomial Pseudomonas aeruginosa outbreak in an intensive care burn unit.
abstract: BACKGROUND
  Pseudomonas aeruginosa is a leading cause of healthcare-associated infections in the intensive care unit (ICU).
  
  
  OBJECTIVE
  To investigate an unexplained increase in the incidence of P. aeruginosa recovered from clinical samples in the ICU over a two-year period.
  
  
  METHODS
  After unsuccessful epidemiological investigation by conventional tools, P. aeruginosa clinical isolates of all patients hospitalized between January 2010 and July 2012 were typed by a novel double-locus sequence typing (DLST) method and compared to environmental isolates recovered during the investigation period.
  
  
  RESULTS
  In total, 509 clinical isolates from 218 patients and 91 environmental isolates were typed. Thirty-five different genotypic clusters were found in 154 out of 218 patients (71%). The largest cluster, DLST 1-18, included 23 patients who were mostly hospitalized during overlapping periods in the burn unit. Genotype DLST 1-18 was also recovered from floor traps, shower trolleys and the shower mattress in the hydrotherapy rooms, suggesting environmental contamination of the burn unit as the source of the outbreak. After implementation of appropriate infection control measures, this genotype was recovered only once in a clinical sample from a burned patient and twice in the environment, but never thereafter during a 12-month follow-up period.
  
  
  CONCLUSIONS
  The use of a novel DLST method allowed the genotyping of a large number of clinical and environmental isolates, leading to the identification of the environmental source of a large unrecognized outbreak in the burn unit. Eradication of the outbreak was confirmed after implementation of a continuous epidemiological surveillance of P. aeruginosa clones in the ICU.
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland. Electronic address: frederic.tissot@chuv.ch.
authors.forename: F
authors.initials: F
authors.lastname: Tissot
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: D S
authors.initials: DS
authors.lastname: Blanc
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Basset
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Zanetti
authors.affiliation: Intensive Care Service, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: M M
authors.initials: MM
authors.lastname: Berger
authors.affiliation: Intensive Care Service, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Y-A
authors.initials: YA
authors.lastname: Que
authors.affiliation: Intensive Care Service, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Eggimann
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Senn
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002053:Burn Units; D002675:Child, Preschool; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks; D004783:Environmental Microbiology; D062665:Epidemiological Monitoring; D005260:Female; D005838:Genotype; D006801:Humans; D017053:Infection Control / Q000379:methods; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology / Q000379:methods; D058889:Molecular Typing / Q000379:methods*; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D055815:Young Adult
keywords: Burns; Intensive care unit; Molecular typing; Outbreak; Pseudomonas aeruginosa