title: The role of patient-to-patient transmission in the acquisition of imipenem-resistant Pseudomonas aeruginosa colonization in the intensive care unit.
abstract: BACKGROUND
  Imipenem-resistant Pseudomonas aeruginosa (IRPA) is an emerging problem. The causal role of antibiotic selective pressure versus patient-to-patient transmission has not been assessed using a large cohort.
  
  
  METHODS
  Patients who were admitted to the medical and surgical intensive care units (ICUs) at the University of Maryland Medical Center from 2001 through 2006 had multiple perianal culture samples collected. Using pulsed-field gel electrophoresis (PFGE), the number of patients who acquired IRPA as a result of patient-to-patient transmission was determined. We also analyzed a subset of patients who had a previous surveillance culture that grew an imipenem-susceptible P. aeruginosa (ISPA) and a subsequent culture that grew IRPA.
  
  
  RESULTS
  Our cohort consisted of 7071 patients. Three hundred patients were colonized with IRPA. 151 patients had positive culture findings at ICU admission, and 149 patients acquired an IRPA. Among the patients who acquired IRPA, 46 (31%) had a PFGE pattern similar to that for another isolate, and 38 (26%) were found to be colonized with an ISPA on the basis of earlier culture results. Of the 38-patient subset, 28 (74%) had identical PFGE patterns.
  
  
  CONCLUSIONS
  Our data showed that, of those cases of IRPA acquisition, 46 (31%) were defined as cases of patient-to-patient transmission, and 28 (19%) were cases of acquisition by the patients' endogenous flora.
authors: Department of Pathology, Institute of Genomic Sciences, University of Maryland School of Medicine, 10 South Pine Street, Baltimore, MD 21201, USA. jkjohnson@som.umaryland.edu
authors: J Kristie
authors: JK
authors: Johnson
authors: Gwen
authors: G
authors: Smith
authors: Mary S
authors: MS
authors: Lee
authors: Richard A
authors: RA
authors: Venezia
authors: O Colin
authors: OC
authors: Stine
authors: James P
authors: JP
authors: Nataro
authors: William
authors: W
authors: Hsiao
authors: Anthony D
authors: AD
authors: Harris
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003428:Cross Infection / Q000382:microbiology / Q000635:transmission; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D015378:Imipenem / Q000494:pharmacology*; D007362:Intensive Care Units; D011552:Pseudomonas Infections / Q000382:microbiology / Q000635:transmission*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D015378:Imipenem