title: Contaminations of laboratory surfaces with Staphylococcus aureus are affected by the carrier status of laboratory staff.
abstract: OBJECTIVE
  As a biosafety laboratory, we take samples from surfaces in microbiological laboratories to survey the handling of micro-organisms. Whereas contaminations with other micro-organisms were rare, Staphylococcus aureus was found in the working environment of many laboratories. As 20-60% of the healthy population are carriers of S. aureus we wanted to asses the effect of carriers on our sampling results.
  
  
  RESULTS
  Nasal swabs of staff members in nonmicrobiological laboratories and offices as well as surface samples from their personal work environment were taken and analysed for S. aureus DNA. In addition S. aureus strains were isolated using S. aureus-specific agar plates and analysed by randomly amplified polymorphic DNA (RAPD)-PCR and multilocus sequence typing (MLST). Our data show that contaminations with S. aureus in nonmicrobiological environments are common with 29% of the surface samples containing S. aureus DNA. In the working environment of carriers, the number of contaminations was significantly increased compared to the environment of noncarriers.
  
  
  CONCLUSIONS
  The carrier status of staff members significantly affects the number of contaminations on laboratory surfaces. Therefore, even in the absence of intentional handling of S. aureus, contaminations can be detected on a substantial amount of surfaces.
  
  
  CONCLUSIONS
  Sampling procedures need to be adapted based on these results with respect to the locations where samples are taken and the threshold for significant contaminations. Because of its wide distribution, S. aureus can serve as a marker for hygienic standards in laboratories.
authors.affiliation: State Laboratory Basel City, Biosafety Laboratory, Basel, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Schmidlin
authors.forename: M
authors.initials: M
authors.lastname: Alt
authors.forename: G
authors.initials: G
authors.lastname: Vogel
authors.forename: U
authors.initials: U
authors.lastname: Voegeli
authors.forename: P
authors.initials: P
authors.lastname: Brodmann
authors.forename: C
authors.initials: C
authors.lastname: Bagutti
mesh_terms: D002353:Carrier State / Q000382:microbiology*; D019411:Clinical Laboratory Techniques; D006801:Humans; D007753:Laboratories / Q000592:standards*; D058885:Multilocus Sequence Typing; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D000078329:Workforce