Hospital-acquired invasive group a streptococcal infections in Ontario, Canada, 1992-2000.
BACKGROUND
A significant proportion of invasive group A streptococcal infections are hospital acquired. No large, prospective studies have characterized this subgroup of cases and evaluated the risk of transmission in hospitals.


METHODS
We conducted prospective, population-based surveillance of invasive group A streptococcal infections in Ontario, Canada, from 1992 to 2000. Epidemiologic and microbiologic investigations were conducted to identify cross-transmission.


RESULTS
We identified 291 hospital-acquired cases (12.4%) among 2351 cases of invasive group A streptococcal disease. Hospital-acquired invasive group A streptococcal infections are heterogeneous, including surgical site (96 cases), postpartum (86 cases), and nonsurgical, nonobstetrical infections (109 cases). Surgical site infections affected 1 of 100,000 surgical procedures and involved all organ systems. Postpartum infections occurred at a rate of 0.7 cases per 10,000 live births and exhibited an excellent prognosis. Nonsurgical, nonobstetrical infections encompassed a broad range of infectious syndromes (case-fatality rate, 37%). Nine percent of cases were associated with in-hospital transmission. Transmission occurred from 3 of 142 patients with community-acquired cases of necrotizing fasciitis requiring intensive care unit (ICU) admission, compared with 1 of 367 patients with community-acquired cases without necrotizing fasciitis admitted to the ICU and 1 of 1551 patients with other cases (P<.001). Fifteen outbreaks were identified; 9 (60%) involved only 2 cases. Hospital staff were infected in 1 of 15 outbreaks, but colonized staff were identified in 6 (60%) of 10 investigations in which staff were screened.


CONCLUSIONS
Presentation of hospital-associated invasive group A streptococcal infections is diverse. Cross-transmission is common; illness occurs in patients but rarely in staff. Isolation of new cases of necrotizing fasciitis and intervention after a single nosocomial case may also prevent transmission.
Daneman
N
N
University of Toronto, Toronto, Ontario, Canada.
McGeer
A
A
Low
D E
DE
Tyrrell
G
G
Simor
A E
AE
McArthur
M
M
Schwartz
B
B
Jessamine
P
P
Croxford
R
R
Green
K A
KA
D000328:Adult; D000368:Aged; D002648:Child; D003428:Cross Infection / Q000453:epidemiology*; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D008297:Male; D009864:Ontario / Q000453:epidemiology; D011159:Population Surveillance; D011645:Puerperal Infection / Q000453:epidemiology / Q000382:microbiology; D012307:Risk Factors; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000302:isolation & purification*; D013530:Surgical Wound Infection / Q000453:epidemiology / Q000382:microbiology