Table 1.

Comparison of CA‑MRSA and HA-MRSA

CHARACTERISTIC	CA‑MRSA	HA-MRSA
Time and location of emergence^{2,6–8,10–14,22,23}	1980s–1990s, in the community	1960s, in hospitals
Genotype^2,23–27	SCCmec types IV and V	SCCmec types I, II, and III
Virulence factors^23,26–30	Panton-Valentine leukocidin often present; other virulence factors believed to exist	Uncommon
Common subtypes^{19,24,25,27,29}	CMRSA-10 (USA300), CMRSA-7 (USA400)	CMRSA-2 (USA100)
Predominant type of infection^2,7,27,28,31	Skin and soft tissue infections	Respiratory tract, urinary tract, bloodstream, and postsurgical infections
Infection onset^2,8,15,30,32	Typically in the community in young, healthy individuals	Typically in hospital, often associated with older age, intensive care unit stay, and central lines
Antibiotic susceptibility^4,27,30,33	Susceptible to a range of antibiotics	Limited range of antibiotic susceptibility
Risk factors	Community risk factors^25,34 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 factors^26,27 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.