Surveillance for Hospital Outbreaks of Invasive Group A Streptococcal Infections in Ontario, Canada, 1992 to 2000

21 August 2007 | Volume 147 Issue 4 | Pages 234-241

Background: Streptococcus pyogenes can cause severe disease in the individual patient and dramatic hospital outbreaks.

Objective: To describe the epidemiology of hospital outbreaks of invasive group A streptococcal infection in order to understand the potential benefit of proposed outbreak investigation and management strategies.

Design: Prospective, population-based surveillance.

Setting: Short-term care hospitals in Ontario, Canada.

Patients: Persons with a positive culture for group A streptococcus from a normally sterile site between 1 January 1992 and 31 December 2000.

Measurements: Laboratory-based surveillance identified patients with nosocomial invasive group A streptococcal infection. Epidemiologic and microbiological investigations were used to detect transmission.

Results: Of 2351 cases of invasive group A streptococcal disease, 291 (12%) were hospital acquired. Twenty-nine (10%) nosocomial cases occurred as part of 20 outbreaks. Seventy percent (14 of 20) of outbreaks involved nonsurgical, nonobstetric patients. Community-acquired cases initiated 25% of outbreaks; most were cases of necrotizing fasciitis in patients admitted to the intensive care unit. Outbreaks were small (median, 2 cases [range, 2 to 10 cases]) and short (median duration, 6 days [range, 0 to 30 days]). The median time between the first 2 cases was 4.5 days. The most common mode of propagation was patient-to-patient transmission. A staff carrier was the primary mode of transmission in 2 (10%) outbreaks, but 1 or more health care workers were colonized with the outbreak strain in 6 of 18 (33%) other outbreaks.

Limitations: Some outbreaks with 1 case of invasive disease may have been missed; advice provided to participating hospitals may have reduced the number and size of outbreaks.

Conclusions: Practices to prevent hospital transmission of group A streptococci should include isolation of patients admitted to the intensive care unit with necrotizing fasciitis, investigation after a single nosocomial case, and emphasis on identifying and treating health care worker carriers on surgical and obstetric services and patient reservoirs on other wards.

*For members of the Ontario Group A Streptococcal Study Group, see the Appendix.

Editors' Notes Context Hospital outbreaks of invasive group A streptococcal infection are a potentially preventable source of morbidity and mortality. Contribution In Ontario, Canada, 291 cases of hospital-acquired invasive group A infection occurred between 1992 and 2000; 10% of these infections occurred during 20 outbreaks in the hospital. Although nosocomial infections were most common in surgical and obstetric patients, most outbreaks of streptococcus A infection occurred outside of those settings. One quarter of the outbreaks was related to community-acquired infections (mostly necrotizing fasciitis) requiring intensive care; the bacteria were primarily transmitted from patient to patient. Implication Isolation of patients with necrotizing fasciitis may be an important strategy to reduce hospital outbreaks of invasive group A streptococcal infection. —The Editors

 

Author and Article Information

From the University of Toronto, Mount Sinai Hospital, Sunnybrook Health Sciences Centre, St. Joseph's Health Centre, The Scarborough Hospital, and Humber River Regional Hospital, Toronto, Ontario, Canada; Centers for Disease Control and Prevention, Atlanta, Georgia; The Ottawa Hospital, Ottawa, Ontario, Canada; National Centre for Streptococcus, Edmonton, Alberta, Canada; Hamilton Health Sciences, Hamilton, Ontario, Canada; and Grand River Hospital, Waterloo, Ontario, Canada.

Acknowledgments: The authors thank the many patients, physicians, microbiology technologists, infection control practitioners, and public health staff who have collaborated in the surveillance and outbreak investigations across Ontario. They also thank MDS Laboratories for assistance with specimen transport.

Grant Support: By Centers for Disease Control and Prevention contracts 200-91-0929 and 200-94-0877.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Allison McGeer, MD, Mount Sinai Hospital, Room 210, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada; e-mail, amcgeer{at}mtsinai.on.ca.

Current Author Addresses: Dr. Daneman: Institute for Clinical Evaluative Sciences, Sunnybrook Health Sciences Centre, G-Wing Room 106, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.

Ms. Green: Mount Sinai Hospital, Room 210, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada.

Dr. Low: Mount Sinai Hospital, Room 1487, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada.

Dr. Simor: Sunnybrook Health Sciences Centre, Room B121, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.

Ms. Willey: Mount Sinai Hospital, Room 1460, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada.

Dr. Schwartz: Centers for Disease Control and Prevention, Room 5309, 12 Corporate Boulevard, Atlanta, GA 30329.

Drs. Toye and Jessamine: The Ottawa Hospital, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.

Dr. Tyrrell: National Centre for Streptococcus, 2B3.13 WMC, 8440-112 Street, Edmonton, Alberta T6G 2J2, Canada.

Dr. Krajden: St. Joseph's Health Center, 30 The Queensway, Toronto, Ontario M6R 1B5, Canada.

Ms. Ramage: Hamilton Health Sciences Office, 50 Wing, Room 219, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada.

Dr. Rose: The Scarborough Hospital–Grace Site, 3030 Birchmount Road, Scarborough, Ontario M1W 3W3, Canada.

Ms. Schertzberg: Grand River Hospital, 835 King Street West, Kitchener, Ontario N2G 1G3, Canada.

Ms. Bragg: Humber River Regional Hospital, 2111 Finch Avenue, Toronto, Ontario M5N 1N1, Canada.

Dr. McGeer: Mount Sinai Hospital, Room 210, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada.

Author Contributions: Conception and design: K.A. Green, A. McGeer.

Analysis and interpretation of the data: N. Daneman, K.A. Green, G.J. Tyrrell, A. McGeer.

Drafting of the article: N. Daneman.

Critical revision of the article for important intellectual content: N. Daneman, K.A. Green, G.J. Tyrrell, A. McGeer.

Final approval of the article: N. Daneman, K.A. Green, P. Jessamine, D. Rose, A. McGeer.

Provision of study materials or patients: K.A. Green, B. Toye, P. Jessamine, S. Krajden, D. Rose.

Obtaining of funding: K.A. Green, A. McGeer.

Administrative, technical, or logistic support: B. Willey, B. Toye, A. McGeer.

Collection and assembly of data: K.A. Green, D. Bragg, A. McGeer.