Concurrent epidemics of skin and soft tissue infection and bloodstream infection due to community-associated methicillin-resistant Staphylococcus aureus.
BACKGROUND
Since its emergence in 2000, epidemic spread of the methicillin-resistant Staphylococcus aureus (MRSA) clone USA300 has led to a high burden of skin and soft tissue infections (SSTIs) in the United States, yet its impact on MRSA bloodstream infections (BSIs) is poorly characterized.


METHODS
To assess clonality of the MRSA isolates causing SSTI and BSI during the epidemic period, a stratified, random sample of 1350 unique infection isolates (from a total of 7252) recovered at the Community Health Network of San Francisco from 2000 to 2008 were selected for genotyping. Risk factors and outcomes for 549 BSI cases caused by the USA300 epidemic clone and non-USA300 MRSA clones were assessed by retrospective review of patient medical records.


RESULTS
From 2000 to 2008, secular trends of USA300 SSTI and USA300 BSI were strongly correlated (Pearson r = 0.953). USA300 accounted for 55% (304/549) of BSIs as it was the predominant MRSA clone that caused community-associated (115/160), healthcare-associated community-onset (125/207), and hospital-onset (64/182) BSIs. Length of hospitalization after BSI diagnosis and mortality rates for USA300 and non-USA300 were similar. Two independent risk factors for USA300 BSI were identified: concurrent SSTI (adjusted relative risk, 1.4 [95% confidence interval {CI}, 1.2-1.6]) and anti-MRSA antimicrobial use in the preceding 30 days (0.7 [95% CI, .6-.8]). Isolates from concurrent SSTI were indistinguishable genotypically from the USA300 isolates that caused BSI.


CONCLUSIONS
USA300 SSTIs serve as a source for BSI. Strategies to control the USA300 SSTI epidemic may lessen the severity of the concurrent USA300 BSI epidemic.
Division of Infectious Diseases, Department of Medicine, University of California, San Francisco, USA.
Pierre
P
Tattevin
Brian S
BS
Schwartz
Christopher J
CJ
Graber
Joann
J
Volinski
Akta
A
Bhukhen
Arti
A
Bhukhen
Thuy T
TT
Mai
Nhung H
NH
Vo
Denise N
DN
Dang
Tiffany HaiVan
TH
Phan
Li
L
Basuino
Françoise
F
Perdreau-Remington
Henry F
HF
Chambers
Binh An
BA
Diep
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology; D058872:Epidemics; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D008875:Middle Aged; D058889:Molecular Typing; D012189:Retrospective Studies; D012495:San Francisco / Q000453:epidemiology; D018461:Soft Tissue Infections / Q000453:epidemiology* / Q000382:microbiology; D013207:Staphylococcal Skin Infections / Q000453:epidemiology* / Q000382:microbiology; D055815:Young Adult