title: Community-associated methicillin-resistant Staphylococcus aureus: trends in case and isolate characteristics from six years of prospective surveillance.
abstract: OBJECTIVE
  In 2000, the Minnesota Department of Health (MDH) implemented active, sentinel site surveillance for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Data from 2000-2005 were analyzed to determine trends in case characteristics, pulsed-field types (PFTs), and antimicrobial susceptibilities including inducible clindamycin resistance (ICR).
  
  
  METHODS
  Active sentinel site surveillance was initiated in 2000 at 12 hospital laboratories that served inpatients and outpatients. Patient medical records were reviewed to determine if they met the epidemiologic case criteria for CA-MRSA; isolates were obtained from patients meeting these criteria. The MDH Public Health Laboratory performed pulsed-field gel electrophoresis subtyping and antimicrobial susceptibility testing, including ICR.
  
  
  RESULTS
  The proportion of MRSA cases classified as CA increased from 11% to 33% (p<0.01). The proportion of cases with skin or soft tissue infections also increased compared with other infection types from 75% to 87% (p<0.01). During the surveillance period, USA300 replaced USA400 as the dominant PFT. With the change in dominant PFT, the proportion of isolates susceptible to erythromycin (45% to 13%, p<0.01) and ciprofloxacin (80% to 59%, p<0.01) decreased. The proportion of erythromycin-resistant/clindamycin-susceptible isolates with ICR (93% to 14%, p<0.01) decreased. The proportion of susceptible isolates also changed within the USA300 PFT; the proportion of isolates susceptible to erythromycin (33% vs. 3%) and the proportion susceptible to ciprofloxacin (67% to 62%) decreased significantly.
  
  
  CONCLUSIONS
  CA-MRSA increased dramatically from 2000 to 2005. Changes in the predominant PFT have impacted susceptibility profiles of CA-MRSA, including ICR. Continued surveillance is needed to monitor the changing epidemiology of CA-MRSA and to inform clinical decisions.
authors.affiliation: Infection Control and Antibiotic Resistance Unit, Acute Disease Investigations and Control, Minnesota Department of Health, Orville L. Freeman Building, 625 Robert St. N, PO Box 64975, St. Paul, MN 55164-0975, USA. kathy.como-sabetti@state.mn.us
authors.forename: Kathryn
authors.initials: K
authors.lastname: Como-Sabetti
authors.forename: Kathleen H
authors.initials: KH
authors.lastname: Harriman
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Buck
authors.forename: Anita
authors.initials: A
authors.lastname: Glennen
authors.forename: David J
authors.initials: DJ
authors.lastname: Boxrud
authors.forename: Ruth
authors.initials: R
authors.lastname: Lynfield
mesh_terms: D000328:Adult; D002648:Child; D002939:Ciprofloxacin / Q000494:pharmacology; D002981:Clindamycin / Q000494:pharmacology; D017714:Community-Acquired Infections / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D004917:Erythromycin / Q000494:pharmacology; D006801:Humans; D016106:Methicillin Resistance; D011159:Population Surveillance; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects*; D014481:United States / Q000453:epidemiology
chemical_list: D002981:Clindamycin; D002939:Ciprofloxacin; D004917:Erythromycin