FAQ: Group A Streptococcus Study
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
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
» What is a sterile site
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
» 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
» 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
» 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
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