title: Increasing role of Staphylococcus aureus and community-acquired methicillin-resistant Staphylococcus aureus infections in the United States: a 10-year trend of replacement and expansion.
abstract: BACKGROUND
  There is the need to properly characterize the temporal trend of U.S. Staphylococcus aureus infections, including methicillin-resistant S. aureus (MRSA) and community-acquired (CA) MRSA in inpatient and outpatient settings.
  
  
  METHODS
  The study used the Surveillance Network(®) surveillance database (Eurofins Medinet) and the National Hospitalization Discharge Survey for the period 1998-2007. CA-MRSA phenotype was defined by a resistance profile that includes susceptibility to gentamicin and cotrimoxazole, and coresistance to ciprofloxacin/clindamycin. Adjusted rates, rate ratios, and 95% confidence intervals (CIs) were computed using multivariate logistic regression.
  
  
  RESULTS
  The study consisted of 1,761,991 S. aureus isolates. Annual MRSA prevalence continuously increased over the 10-year period from 32.7% in 1998 to 53.8% in 2007 (odds ratio 2.4, 95% CI 2.3-2.5). CA-MRSA replaced competing strains by increasing its share of MRSA from 22.3% in 1998 to 66.1% in 2007 (odds ratio 6.7, 95% CI 6.5-6.9). MRSA-related hospitalization rate per 1,000 discharges doubled from 3.5 ± 0.9 in 1998 to 7.6 ± 1.5 in 2007 (RR 2.2, 95% CI 1.8-3.1), whereas CA-MRSA increased from 0.4 ± 0.14 hospitalizations per 1,000 discharges in 1998 to 3.1 ± 0.5 in 2007 (RR 8.1, 95% CI 5.2-14.1), By 2007, 81.5% of all MRSA isolates were categorized as CA-MRSA among children, whereas CA-MRSA represented 48.9% of MRSA isolates from the elderly.
  
  
  CONCLUSIONS
  MRSA not only replaced methicillin susceptible S. aureus (MSSA) isolates as a percentage of all S. aureus isolates, but its hospitalization rates increased over and above the replacement process. This trend also applies to CA-MRSA over hospital-acquired (HA) MRSA.
authors.affiliation: Research Statistics Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709, USA. robertino.mera@gsk.com
authors.forename: Robertino M
authors.initials: RM
authors.lastname: Mera
authors.forename: Jose A
authors.initials: JA
authors.lastname: Suaya
authors.forename: Heather
authors.initials: H
authors.lastname: Amrine-Madsen
authors.forename: Cosmina S
authors.initials: CS
authors.lastname: Hogea
authors.forename: Linda A
authors.initials: LA
authors.lastname: Miller
authors.forename: Emily P
authors.initials: EP
authors.lastname: Lu
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Sahm
authors.forename: Patrick
authors.initials: P
authors.lastname: O'Hara
authors.forename: Camilo J
authors.initials: CJ
authors.lastname: Acosta
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002939:Ciprofloxacin / Q000494:pharmacology; D017714:Community-Acquired Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission; D016208:Databases, Factual; D005260:Female; D005839:Gentamicins / Q000494:pharmacology; D006760:Hospitalization / Q000706:statistics & numerical data / Q000639:trends; D006801:Humans; D007223:Infant; D007297:Inpatients / Q000706:statistics & numerical data; D008137:Longitudinal Studies; D008297:Male; D008712:Methicillin / Q000494:pharmacology*; D016106:Methicillin Resistance / Q000187:drug effects*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D008875:Middle Aged; D015999:Multivariate Analysis; D010045:Outpatients / Q000706:statistics & numerical data; D010641:Phenotype; D011159:Population Surveillance; D015995:Prevalence; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology; D014481:United States
chemical_list: D005839:Gentamicins; D002939:Ciprofloxacin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D008712:Methicillin