Methicillin-resistant Staphylococcus aureus Fomite Survival

Christa Williams; Diane L Davis

doi:10.29074/ascls.22.1.34

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Christa Williams, MT (ASCP)
1. Clinical Laboratory Science Program, Health Sciences Department, Salisbury University, Salisbury MD
Diane L Davis, PhD CLS(NCA) MT SC SLS (ASCP)⇑
1. Professor of the Clinical Laboratory Science Program, Health Sciences Department, Salisbury University, Salisbury MD

Address for correspondence: Diane L Davis PhD CLS(NCA), professor, Clinical Laboratory Science Program, Health Sciences Department, Salisbury University, 1101 Camden Avenue, Salisbury, MD 21801. (410) 548-4787, (410) 548-9185 fax. dldavis{at}salisbury.edu

Abstract

OBJECTIVE: To assess survival of methicillin-resistant Staphylococcus aureus (MRSA) on fomites encountered by health students.

DESIGN: Three suspensions of MRSA were made to mimic lab splashes: a 0.5 McFarland trypticase soy broth, whole blood with 50 colony forming units/mL and body fluid/serum with 2,000 colony forming units/mL. These were seeded onto three environmental surfaces (glass, vinyl floor tile, and countertop) and wet swabbed for 60 days. High touch areas of student stethoscopes were also wet swabbed. MRSA selective CHROMagar® was used to identify organism survival.

SETTING: Salisbury University, Salisbury MD

PARTICIPANTS: Salisbury University nursing and respiratory therapy students who volunteered to have their stethoscopes swabbed anonymously.

MAIN OUTCOME MEASURE: Detection of pink colonies on MRSA-selective CHROMagar®.

RESULTS: MRSA in 0.5 McFarland broth lived for >60 days on all surfaces. MRSA in blood was undetectable on any surface, and MRSA in serum survived 41 days on glass, 45 days on tile, and >60 days on countertop. Five of thirty-three stethoscopes (15%) tested were positive for MRSA.

CONCLUSIONS: Previous studies showed fomite survival of MRSA for about two weeks using contact plate sampling and MRSA on 7.4% of stethoscopes. We showed longer MRSA survival times by wet swab sampling and a higher stethoscope contamination rate. As expected, higher organism loads survived longer.

ABBREVIATIONS: ATCC = American Type Colony Collection; CFUs = colony forming units; MRSA = methicillin-resistant Staphylococcus aureus; MSSA = methicillin-sensitive Staphylococcus aureus; TS = trypticase soy.