title: Multiple site surveillance cultures as a predictor of methicillin-resistant Staphylococcus aureus infections.
abstract: OBJECTIVE
  To determine the relationship between methicillin-resistant Staphylococcus aureus (MRSA) colonization density, colonization site, and probability of infection in a frequently screened cohort of intensive care unit (ICU) patients.
  
  
  METHODS
  Patients had swab samples tested for MRSA at admission to the ICU, discharge from the ICU, and twice weekly during their ICU stay, and they were followed up for development of MRSA infection. Swab test results were analyzed to determine the proportion of patients colonized and the proportion colonized at each screening site. Hazard of MRSA infection (rate of infection per day at risk) was calculated using a Cox proportional hazards analysis, and risk factors for MRSA infection, including presence of MRSA, degree of colonization, and pattern of colonization were determined.
  
  
  RESULTS
  Among the 4,194 patient episodes, 238 (5.7%) had screening results that were positive for MRSA, and there were 34 cases of MRSA infection. The hazard ratio (HR) for developing an infection increased as more sites were colonized (HR, 3.4 for being colonized at more than 1 site compared with colonization at 1 site [95% confidence interval, 1.2-9.9]). Colonization site was predictive of developing infection (HR for nose or throat colonization compared with no colonization, 168 [95% confidence interval, 69-407]).
  
  
  CONCLUSIONS
  This study demonstrated that the hazard of developing an infection was higher when more sites were colonized and that certain sites were more predictive of infection than others. These results may be useful for predicting infection in ICU patients and may influence treatment.
authors.affiliation: Victorian Infectious Diseases Service, Royal Melbourne Hospital, Melbourne, Australia.
authors.forename: Benedict Lim Heng
authors.initials: BL
authors.lastname: Sim
authors.forename: Emma
authors.initials: E
authors.lastname: McBryde
authors.forename: Alan C
authors.initials: AC
authors.lastname: Street
authors.forename: Caroline
authors.initials: C
authors.lastname: Marshall
mesh_terms: D001365:Axilla / Q000382:microbiology; D002353:Carrier State / Q000175:diagnosis* / Q000382:microbiology; D003422:Critical Care; D003428:Cross Infection / Q000175:diagnosis* / Q000382:microbiology; D005260:Female; D006119:Groin / Q000382:microbiology; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008875:Middle Aged; D009666:Nose / Q000382:microbiology; D010614:Pharynx / Q000382:microbiology; D011159:Population Surveillance; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology