Table 1.

Comparison of CA‑MRSA and HA-MRSA

Time and location of emergence2,68,1014,22,231980s–1990s, in the community1960s, in hospitals
Genotype2,2327SCCmec types IV and VSCCmec types I, II, and III
Virulence factors23,2630Panton-Valentine leukocidin often present; other virulence factors believed to existUncommon
Common subtypes19,24,25,27,29CMRSA-10 (USA300), CMRSA-7 (USA400)CMRSA-2 (USA100)
Predominant type of infection2,7,27,28,31Skin and soft tissue infectionsRespiratory tract, urinary tract, bloodstream, and postsurgical infections
Infection onset2,8,15,30,32Typically in the community in young, healthy individualsTypically in hospital, often associated with older age, intensive care unit stay, and central lines
Antibiotic susceptibility4,27,30,33Susceptible to a range of antibioticsLimited range of antibiotic susceptibility
Risk factorsCommunity risk factors25,34
  • Living or working in a group setting (such as military barracks, subsidized housing, or a shelter)

  • Use of illegal drugs within the past year

  • History of CA‑MRSA infection or colonization

  • Regular contact with somebody who lives or works in a group setting, has used drugs in the past year, or has a history of CA‑MRSA

  • Absence of in-home water service

  • Recent antibiotic use

  • Being HIV positive

  • Playing contact sports

Health care risk factors26,27
  • Surgery, hospitalization, residence in a long-term care facility, or dialysis within the past 12 months

  • The presence of an indwelling percutaneous catheter

  • Being hospitalized for more than 48 hours at time of first positive culture

  • CA‑MRSA—community-associated methicillin-resistant Staphylococcus aureus, CMRSA—Canadian epidemic strain, HA-MRSA—health care–associated methicillin-resistant Staphylococcus aureus, SCCmec—staphylococcal chromosomal cassette mec.