title: Efficient detection and long-term persistence of the carriage of methicillin-resistant Staphylococcus aureus.
abstract: The natural history of the carriage of methicillin-resistant Staphylococcus aureus (MRSA) was examined in a 9-year retrospective cohort study of 102 known carriers. The populations studied consisted of patients admitted to a university hospital from 1989 through 1991; a review extending back to January 1983 was conducted. The focuses of the study included the duration of carriage among patients who were known to have carried MRSA previously and who were readmitted to the hospital (36 patients) and the optimal anatomic site for screening (66 patients). Cultures of the nares (sensitivity, 93%; negative predictive value, 95%) were considerably more valuable for the detection of MRSA colonization than were cultures of cutaneous sites of the axilla, groin, and perineum (sensitivity, < or = 39%; negative predictive value, < or = 69%). The estimated half-life of MRSA colonization in this special population of patients was approximately 40 months. Restriction enzyme analysis of plasmid types of paired isolates from the 12 patients with MRSA carriage persisting for > 12 months revealed five instances (42%) in which both isolates were of the same type. In summary, our results indicate that the majority of readmitted carriers harbor MRSA for > 3 years and that, in this population, culture of the anterior nares alone (with culture of wound or sputum, when present) is a valid and efficient method for the detection of persistent MRSA carriage.
authors.affiliation: Department of Pathology, University of Iowa College of Medicine, Iowa City 52242.
authors.forename: M D
authors.initials: MD
authors.lastname: Sanford
authors.forename: A F
authors.initials: AF
authors.lastname: Widmer
authors.forename: M J
authors.initials: MJ
authors.lastname: Bale
authors.forename: R N
authors.initials: RN
authors.lastname: Jones
authors.forename: R P
authors.initials: RP
authors.lastname: Wenzel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002353:Carrier State; D002648:Child; D002675:Child, Preschool; D003428:Cross Infection / Q000175:diagnosis / Q000382:microbiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D009297:Nasal Mucosa / Q000382:microbiology; D015995:Prevalence; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D013530:Surgical Wound Infection / Q000382:microbiology