title: Pseudo-outbreaks of Stenotrophomonas maltophilia on an intensive care unit in England.
abstract: BACKGROUND
  In June 2014, a cluster of identical S. maltophilia isolates was reported in an adult intensive care unit (ICU) at a district general hospital. An outbreak control team was convened to investigate the cluster and inform control measures.
  
  
  OBJECTIVE
  To identify potential risk factors for isolation of S. maltophilia in this setting.
  
  
  METHODS
  We conducted a cohort study of ICU patients for whom a bronchoalveolar lavage (BAL) specimen was submitted between October 2013 and October 2014. Cases were patients with S. maltophilia-positive BAL. We calculated the association between isolation of S. maltophilia and patient characteristics using risk ratios (RRs) with 95% confidence intervals (95% CIs) and univariate logistic regression. Chi-squared or Fisher's exact tests were used. BAL specimens were microbiologically typed using pulse-field gel electrophoresis (PFGE).
  
  
  RESULTS
  Eighteen patients met the case definition. Two patients had clinical presentations that warranted antibiotic treatment for S. maltophilia. All cases were exposed to bronchoscopy. PFGE typing revealed clusters of two strain types. We found statistically significant elevated risks of isolating BRISPOSM-4 in patients exposed to bronchoscope A (RR: 13.56; 95% CI: 1.82-100; P < 0.001) and BRISPOSM-3 in patients exposed to bronchoscope B (RR: 16.89; 95% CI: 2.14-133; P < 0.001). S. maltophilia type BRISPOSM-4 was isolated in water used to flush bronchoscope A after decontamination.
  
  
  CONCLUSIONS
  Two pseudo-outbreaks occurred in which BAL specimens had been contaminated by reusable bronchoscopes. We cannot exclude the potential for colonization of the lower respiratory tract of exposed patients. Introduction of single-use bronchoscopes was an effective control measure.
authors.affiliation: Field Epidemiology Training Programme, Public Health England, Bristol, UK; European Programme for Interventional Epidemiology Training, Stockholm, Sweden; Field Epidemiology Service South West, Public Health England, Bristol, UK; School of Social and Community Medicine, University of Bristol, Bristol, UK. Electronic address: Thomas.waite@phe.gov.uk.
authors.forename: T D
authors.initials: TD
authors.lastname: Waite
authors.affiliation: Royal United Hospitals NHS Trust, Bath, UK.
authors.forename: A
authors.initials: A
authors.lastname: Georgiou
authors.affiliation: Royal United Hospitals NHS Trust, Bath, UK.
authors.forename: M
authors.initials: M
authors.lastname: Abrishami
authors.affiliation: Field Epidemiology Service South West, Public Health England, Bristol, UK; School of Social and Community Medicine, University of Bristol, Bristol, UK.
authors.forename: C R
authors.initials: CR
authors.lastname: Beck
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D020680:Bronchoscopes / Q000382:microbiology*; D015331:Cohort Studies; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks; D004739:England / Q000453:epidemiology; D005260:Female; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D006767:Hospitals, District; D006769:Hospitals, General; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D020615:Stenotrophomonas maltophilia / Q000302:isolation & purification*
keywords: Bronchoscope; Contamination; Intensive care unit; Pseudo-outbreak; Stenotrophomonas maltophilia