Invasive Streptococcal Infections in Hospitals in Ontario, Canada, 1992 to 2000

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The summary below is from the full report titled "Surveillance for Hospital Outbreaks of Invasive Group A Streptococcal Infections in Ontario, Canada, 1992 to 2000." It is in the 21 August 2007 issue of Annals of Internal Medicine (volume 147, pages 234-241). The authors are N. Daneman, K.A. Green, D.E. Low, A.E. Simor, B. Willey, B. Schwartz, B. Toye, P. Jessamine, G.J. Tyrrell, S. Krajden, L. Ramage, D. Rose, R. Schertzberg, D. Bragg, A. McGeer, and the Ontario Group A Streptococcal Study Group.

What is the problem and what is known about it so far?

Invasive streptococcal infections are serious infections that can be difficult to treat and deadly. Necrotizing fasciitis is a type of invasive streptococcal infection that has recently become more common. This infection involves the skin and underlying tissues. In addition to causing infection in a single patient, invasive streptococcal infections can spread from patient to patient in hospitals. Hospital outbreaks can occur with little warning. Knowing more about hospital outbreaks might help hospitals to develop better ways to prevent and treat them.

Why did the researchers do this particular study?

To learn about hospital outbreaks of streptococcal infections in Ontario, Canada.

Who was studied?

The researchers studied all invasive streptococcal infections that had occurred in Ontario from 1992 through 2000. They focused on infections that involved patients in hospitals.

How was the study done?

From 1992 through 2000, the researchers contacted microbiology laboratories to identify all reported cases of invasive streptococcal infection that occurred in Ontario. For infections that involved a hospitalized patient, they contacted the hospital's infection control department and provided suggestions about preventing spread of infection. They also conducted laboratory tests to determine whether one infection was related to another.

What did the researchers find?

During the study, 2351 invasive streptococcal infections were reported in microbiology laboratories in Ontario. Of these, 291 involved patients in hospitals. The researchers also identified 20 hospital outbreaks. Outbreaks were small, involving an average of 2 patients, and lasted an average of 6 days. In most outbreaks, the bacteria were transmitted from patient to patient, most likely on the hands of staff. One fifth of the outbreaks involved patients with necrotizing fasciitis admitted to intensive care units.

What were the limitations of the study?

The advice that the researchers provided to the hospitals may have influenced the size and length of the outbreaks. Outbreaks in other settings may differ from those reported in this study.

What are the implications of the study?

Potential ways to reduce hospital outbreaks of invasive streptococcal infections include isolation of patients hospitalized with necrotizing fasciitis, looking for infection in other patients after a case occurs, and identifying and treating patients and health care workers who carry the bacteria that cause these infections.