title: Pseudomonas aeruginosa acquisition on an intensive care unit: relationship between antibiotic selective pressure and patients' environment.
abstract: BACKGROUND
  The purpose of this study was to investigate the relationship among Pseudomonas aeruginosa acquisition on the intensive care unit (ICU), environmental contamination and antibiotic selective pressure against P. aeruginosa.
  
  
  METHODS
  An open, prospective cohort study was carried out in a 16-bed medical ICU where P. aeruginosa was endemic. Over a six-month period, all patients without P. aeruginosa on admission and with a length of stay >72 h were included. Throat, nasal, rectal, sputum and urine samples were taken on admission and at weekly intervals and screened for P. aeruginosa. All antibiotic treatments were recorded daily. Environmental analysis included weekly tap water specimen culture and the presence of other patients colonized with P. aeruginosa.
  
  
  RESULTS
  A total of 126 patients were included, comprising 1,345 patient-days. Antibiotics were given to 106 patients (antibiotic selective pressure for P. aeruginosa in 39). P. aeruginosa was acquired by 20 patients (16%) and was isolated from 164/536 environmental samples (31%). Two conditions were independently associated with P. aeruginosa acquisition by multivariate analysis: (i) patients receiving ≥3 days of antibiotic selective pressure together with at least one colonized patient on the same ward on the previous day (odds ratio (OR) = 10.3 ((% confidence interval (CI): 1.8 to 57.4); P = 0.01); and (ii) presence of an invasive device (OR = 7.7 (95% CI: 2.3 to 25.7); P = 0.001).
  
  
  CONCLUSIONS
  Specific interaction between both patient colonization pressure and selective antibiotic pressure is the most relevant factor for P. aeruginosa acquisition on an ICU. This suggests that combined efforts are needed against both factors to decrease colonization with P. aeruginosa.
authors.affiliation: Service de Réanimation Médicale, Hôpital Pellegrin-Tripode, place Amélie Raba Léon, 33076 Bordeaux Cedex, France. alexandre.boyer@chu-bordeaux.fr
authors.forename: Alexandre
authors.initials: A
authors.lastname: Boyer
authors.forename: Adélaïde
authors.initials: A
authors.lastname: Doussau
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Thiébault
authors.forename: Anne Gaëlle
authors.initials: AG
authors.lastname: Venier
authors.forename: Van
authors.initials: V
authors.lastname: Tran
authors.forename: Hélène
authors.initials: H
authors.lastname: Boulestreau
authors.forename: Cécile
authors.initials: C
authors.lastname: Bébéar
authors.forename: Frédéric
authors.initials: F
authors.lastname: Vargas
authors.forename: Gilles
authors.initials: G
authors.lastname: Hilbert
authors.forename: Didier
authors.initials: D
authors.lastname: Gruson
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Rogues
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D003428:Cross Infection / Q000453:epidemiology* / Q000517:prevention & control; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000517:prevention & control; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification*; D014871:Water Microbiology
chemical_list: D000900:Anti-Bacterial Agents