The changing susceptibilities of methicillin-resistant Staphylococcus aureus at a midwestern hospital: the emergence of "community-associated" MRSA.
BACKGROUND
The emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been well described; however, few studies have reviewed long-term hospital-wide data.


METHODS
This retrospective study of adult patients used the first culture per patient per visit positive for MRSA for 1996 to 2005. Isolates were categorized as community-associated or health care-associated phenotype based on antibiotic susceptibilities. chi(2) tests for trend and linear regression analyses were performed.


RESULTS
The annual prevalence of CA-MRSA increased significantly over the 10-year study period (from 43 of 507 [8.9%] MRSA cultures in 1996 to 672 of 1697 [39.6%] MRSA cultures in 2005; P < .01). The proportion of MRSA cultures obtained within 48 hours of hospital admission increased from 50.5% to 79.5% (P < .01). The median age of patients with MRSA decreased, from 60 to 49 years (P < .01). Among the CA-MRSA cases, the proportion of non-Caucasian patients increased from 30.2% to 60.4% (P < .01) and the proportion of patients categorized as low socioeconomic status increased from 25.6% to 35.6% (P < .01). Significant consistent trends were not observed for patient sex or body sites of the cultures.


CONCLUSIONS
An increasing number of MRSA with a community-associated phenotype occurred during the 10-year study period. Patterns of decreasing age, increasing non-Caucasian races, and decreasing socioeconomic status were observed among patients with MRSA.
McMullen
Kathleen M
KM
Hospital Infection and Epidemiology Department, Barnes Jewish Hospital, St. Louis, MO, USA. kmm2742@bjc.org
Warren
David K
DK
Woeltje
Keith F
KF
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D005006:Ethnicity; D005260:Female; D006761:Hospitals; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015146:Midwestern United States / Q000453:epidemiology; D015995:Prevalence; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D055815:Young Adult