title: Cross-colonisation with Pseudomonas aeruginosa of patients in an intensive care unit.
abstract: BACKGROUND
  Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa is usually preceded by colonisation of the respiratory tract. During outbreaks, colonisation with P aeruginosa is mainly derived from exogenous sources. The relative importance of different pathways of colonisation of P aeruginosa has rarely been determined in non-epidemic settings.
  
  
  METHODS
  In order to determine the importance of exogenous colonisation, all isolates of P aeruginosa obtained by surveillance and clinical cultures from two identical intensive care units (ICUs) were genotyped with pulsed field gel electrophoresis.
  
  
  RESULTS
  A total of 100 patients were studied, 44 in ICU 1 and 56 in ICU 2. Twenty three patients were colonised with P aeruginosa, seven at the start of the study or on admission and 16 of the remaining 93 patients became colonised during the study. Eight patients developed VAP due to P aeruginosa. The incidence of respiratory tract colonisation and VAP with P aeruginosa in our ICU was similar to that before and after the study period, and therefore represents an endemic situation. Genotyping of 118 isolates yielded 11 strain types: eight in one patient each, two in three patients each, and one type in eight patients. Based on chronological evaluation and genotypical identity of isolates, eight cases of cross-colonisation were identified. Eight (50%) of 16 episodes of acquired colonisation and two (25%) of eight cases of VAP due to P aeruginosa seemed to be the result of cross-colonisation.
  
  
  CONCLUSIONS
  Even in non-epidemic settings cross-colonisation seems to play an important part in the epidemiology of colonisation and infection with P aeruginosa.
authors: Department of Internal Medicine, University Hospital Maastricht, The Netherlands.
authors: D C
authors: DC
authors: Bergmans
authors: M J
authors: MJ
authors: Bonten
authors: F H
authors: FH
authors: van Tiel
authors: C A
authors: CA
authors: Gaillard
authors: S
authors: S
authors: van der Geest
authors: R M
authors: RM
authors: Wilting
authors: P W
authors: PW
authors: de Leeuw
authors: E E
authors: EE
authors: Stobberingh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015373:Bacterial Typing Techniques; D002648:Child; D002675:Child, Preschool; D003428:Cross Infection / Q000635:transmission*; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D018410:Pneumonia, Bacterial / Q000382:microbiology / Q000635:transmission*; D011446:Prospective Studies; D011552:Pseudomonas Infections / Q000382:microbiology / Q000635:transmission*; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000302:isolation & purification*; D012121:Respiration, Artificial / Q000009:adverse effects