Too close for comfort: screening strategy to detect methicillin-resistant Staphylococcus aureus conversion in exposed roommates.

All 899 roommates exposed to methicillin-resistant Staphylococcus aureus (MRSA) index cases were studied over 57 months. MRSA detection is better at approximately 3 days (50%-55%) or 7 days (56%) after contact has been broken than day 0 (30%). Polymerase chain reaction testing at day 3 performs similarly to culture at day 7. Nasal/rectal screening provides superior detection than nasal alone. Those exposed >48 hours are at significantly greater risk of colonization.