title: Low prevalence of meticillin-resistant Staphylococcus aureus carriage at hospital admission: implications for risk-factor-based vs universal screening.
abstract: BACKGROUND
  There is debate over the optimal policy for detecting meticillin-resistant Staphylococcus aureus (MRSA) colonization at hospital admission. The emergence of community-associated (CA)-MRSA may compromise targeted screening strategies based on risk factors for healthcare-associated (HA)-MRSA.
  
  
  OBJECTIVE
  To determine the prevalence of MRSA colonization at admission, and the genotype and molecular epidemiology of the strains involved.
  
  
  METHODS
  A 12-month observational study was performed at a 1200-bed London tertiary referral hospital from 1 April 2008 to 1 March 2009. All available MRSA isolates were genotyped by spa and staphylococcal cassette chromosome mec (SCCmec) typing.
  
  
  RESULTS
  The overall MRSA colonization rate was 2.0% of 28,892 admissions (range 6.6% in critical care to 0.8% in obstetrics/gynaecology/neonatology). The overall frequency of previously unknown carriage of MRSA on admission was 1.4%. Most colonizing strains were epidemic HA-MRSA-15 and -16. However, heterogeneous CA strains accounted for 18% of recovered isolates, including 37.5% of MRSA from accident and emergency and 23.1% of MRSA from surgery. The CA-MRSA strain types had significantly different epidemiological associations from the HA-MRSA strains, so risk factors used for the identification of HA-MRSA may not detect CA-MRSA reliably.
  
  
  CONCLUSIONS
  The low rate of HA-MRSA in the UK increases the relative proportion due to CA-MRSA, for which conventional risk-factor-based screening strategies may be less effective. Cost-benefit analyses of universal MRSA admission screening will need to take account of this new epidemiology.
authors: Centre for Clinical Infection and Diagnostics Research, Department of Infectious Diseases, King's College London, Guy's and St. Thomas' Hospital NHS Foundation Trust, London, UK. jonathan.otter@kcl.ac.uk
authors: J A
authors: JA
authors: Otter
authors: M T
authors: MT
authors: Herdman
authors: B
authors: B
authors: Williams
authors: O
authors: O
authors: Tosas
authors: J D
authors: JD
authors: Edgeworth
authors: G L
authors: GL
authors: French
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002353:Carrier State / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008131:London / Q000453:epidemiology; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D010343:Patient Admission; D015995:Prevalence; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology*; D062606:Tertiary Care Centers; D055815:Young Adult