FAQ: Group A Streptococcus Study

• Which group A streptococcus cases get reported to the Ontario group A streptococcal surveillance study? 
• What is a sterile site culture? 
• Do we report all these cases to the Public Health Department? 
• If a lab reports an isolate from a non-sterile site culture, how can I tell whether the patient has toxic shock syndrome (STSS)? 
• Do contacts of GAS cases need to receive prophylactic antibiotics? 
• Sometimes physicians do not make a diagnosis of necrotizing fasciitis until several days after a case is admitted to the hospital – is it too late to start prophylactic antibiotics at that time? 
• If a severe case of group A streptococcal disease occurs in an institution (e.g. hospital or nursing home), should some people (e.g. roommates, health care workers) be treated similarly to household contacts?

Response by Allison McGeer, MD, [Investigator, Ontario Group A Streptococcal Study.]
Mount Sinai Hospital

» Which group A streptococcus cases get reported to the Ontario group A streptococcal surveillance study?

All group A streptococcus (GAS) identified from cultures of normally sterile sites, or cases of STSS or necrotizing fasciitis, with a positive culture from a non-sterile site are reported to the study office at Mount Sinai Hospital (phone number 416-586-3144 or 1-800-668-6282).

» What is a sterile site culture?

A sterile site culture is a culture obtained from a normally sterile site such as blood, synovial or pleural fluid or sterile aspirates. Confusion sometimes arises in determining whether a swab or aspirate is sterile or superficial (that is, not from a sterile site). Generally the only swabs which are from sterile sites are those which are taken in the operating room during surgery - if this is not the case, it is safe to assume that the isolate is from a non-sterile site. Aspirates are usually from sterile sites, and such cases are included in the surveillance definition. An aspirate culture can be obtained through needle aspiration or during a percutaneous drainage procedure.

» Do we report all these cases to the Public Health Department?

Since June 1995, all cases of invasive group A Streptococcal disease are reported to the Public Health Department (PHD). The PHD requires a report for any case where a group A Streptococcus is isolated from a normally sterile site AND any case which meets the clinical definition for soft tissue necrosis (necrotizing fasciitis, necrotizing myositis, gangrene), meningitis, or streptococcal toxic shock syndrome and has a positive culture (sterile or non-sterile) for group A streptococci.

» If a lab reports an isolate from a non-sterile site culture, how can I tell whether the patient has toxic shock syndrome (STSS)?

In Ontario surveillance to date, 95% of patients with STSS either died within 48 hours of admission to hospital, or were admitted to the ICU. If the patient meets neither of these criteria, it is safe to assume that they do not have STSS, and if they don't meet any of the other criteria for clinical severity listed above, you do not need to report the case to the Public Health Department. The detailed criteria for toxic shock syndrome can be viewed in the Ontario Ministry of Health guidelines for management of contacts of cases of invasive GAS.

» Do contacts of GAS cases need to receive prophylactic antibiotics?

In Ontario, antibiotic prophylaxis is recommended for household and close contacts of cases of severe GAS infection (necrotizing fasciitis, STSS, or death within 7 days of infection). A household contact is anyone living in the same household as a case within 7 days prior to the case patient becoming ill. Close contacts are persons who share the same sleeping arrangements or who have had direct mucous membrane contact with the oral or nasal secretions of a case within 7 days prior to case patient illness. Prophylaxis consists of 10 days of Cefalexin, Penicillin VK or Erythromycin. Criteria for prophylaxis and antibiotic dosage recommendations can be found in Ontario Ministry of Health guidelines for management of contacts of cases of invasive GAS.

» Sometimes physicians do not make a diagnosis of necrotizing fasciitis until several days after a case is admitted to the hospital – is it too late to start prophylactic antibiotics at that time?

It is sometimes difficult to make a diagnosis of necrotizing fasciitis, and both surgery and a definitive diagnosis may be delayed for several days. Fortunately, these cases are usually representative of less severe disease. Since most illness in household contacts occurs in the first two weeks after exposure, prophylaxis should be initiated if a diagnosis is made within the first 10 days.

» If a severe case of group A streptococcal disease occurs in an institution (e.g. hospital or nursing home), should some people (e.g. roommates, health care workers) be treated similarly to household contacts?

No. There is no evidence to suggest that prophylaxis is required in these situations. Transmission in institutions is different from that in households. If a case occurs in a nursing home, guidelines such as those from the Ontario Nursing Home Association may be used to guide investigation. No followup is needed in hospitals unless either (i) the case is nosocomial (in which case the investigation will depend on the particular circumstances) or (ii) a health care worker sustains a direct exposure of skin or mucous membranes with the blood or body fluids of a newly infected patient (e.g. facial splash while irrigating a wound in a patient with necrotizing fasciitis).