Changes in the prevalence of nasal colonization with Staphylococcus aureus in the United States, 2001-2004.
BACKGROUND
Staphylococcus aureus is a common cause of infection, particularly in persons colonized by this organism. Virulent strains of methicillin-resistant S. aureus (MRSA) have emerged in the general community.


METHODS
A nationally representative survey of nasal colonization with S. aureus was conducted from 2001 through 2004 as part of the National Health and Nutrition Examination Survey. MRSA isolates were identified by the oxacillin disk-diffusion method. The pulsed-field gel electrophoresis (PFGE) type was determined for all MRSA isolates. A t statistic was used to compare the prevalence of colonization across biennia and across population subgroups. Cofactors independently associated with colonization were determined with backward stepwise logistic modeling.


RESULTS
The prevalence of colonization with S. aureus decreased from 32.4% in 2001-2002 to 28.6% in 2003-2004 (P < .01), whereas the prevalence of colonization with MRSA increased from 0.8% to 1.5% (P < .05). Colonization with MRSA was independently associated with healthcare exposure in males and with having been born in the United States, age > or =60 years, diabetes, and poverty in females. In 2003-2004, a total of 19.7% (95% confidence interval, 12.4%-28.8%) of MRSA-colonized persons carried a PFGE type associated with community transmission.


CONCLUSIONS
Nasal colonization with MRSA has increased in the United States, despite an overall decrease in nasal colonization with S. aureus. PFGE types associated with community transmission only partially account for the increase in MRSA colonization.
Gorwitz
Rachel J
RJ
National Center for Preparedness, Detection, and Control of Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. rgorwitz@cdc.gov
Kruszon-Moran
Deanna
D
McAllister
Sigrid K
SK
McQuillan
Geraldine
G
McDougal
Linda K
LK
Fosheim
Gregory E
GE
Jensen
Bette J
BJ
Killgore
George
G
Tenover
Fred C
FC
Kuehnert
Matthew J
MJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D003625:Data Collection; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D009666:Nose / Q000382:microbiology*; D015995:Prevalence; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000254:growth & development* / Q000302:isolation & purification; D014481:United States / Q000453:epidemiology
D004269:DNA, Bacterial