Healthcare-Associated Group A Streptococcal Bacteremia: A Sentinel Event?

Background:   Healthcare-associated infections (HAIs) due to Group A streptococci (GAS) are often severe and can be associated with a common healthcare personnel source.  The CDC recommends that a single case of postsurgical or postpartum invasive GAS infection should prompt further epidemiologic investigation to identify potential common sources.  Others have recommended that a single healthcare-associated bacteremia due to GAS represents a sentinel event and warrants investigation.  Such investigations are labor-intensive and may detract from other efforts at HAI surveillance and prevention.    

Objective: To review cases of healthcare-associated GAS bacteremia over a 10 year period to determine sources and to identify potential clusters of infection that may not have been recognized.

Methods: All positive blood cultures for GAS from 1999-2008 were obtained from microbiology laboratory records.  Medical records of patients with positive blood cultures were reviewed.  GAS bacteremia was considered to be healthcare-associated if it occurred > 24 hours after admission and the patient did not have evidence of GAS infection incubating on admission, or if it was linked to a procedure performed on a previous admission.  Infection preventionists continuously reviewed microbiology records to evaluate for clusters of other GAS infections during the study period.

Results: During the study period, there were 69 patients with GAS bacteremia, of which 10 (14%) were healthcare-associated.   The epidemic curve for healthcare-associated GAS bacteremia is shown in the figure.  Nine cases (90%) occurred within 6 months of another episode of bacteremia.  However, none of these were epidemiologically related based on patient location or shared healthcare personnel.  Three episodes (33%) were related to endometritis, but each infection occurred > 2 years apart.  Two bacteremias (20%) occurred after nasogastric or endoscopic procedures, and 2 (20%) occurred after respiratory infections.  Two cases (20%) represented primary bacteremia with unclear source, and one (10%) represented secondary bacteremia from a surgical site infection.  No other clustering of GAS infections was noted during the study period.  All patients recovered uneventfully, except for the patient with surgical site infection, who died after a complicated course following renal transplantation.  Molecular typing of isolates was not performed.

Conclusions: Healthcare-associated GAS bacteremia was an infrequent occurrence at our hospital over a 10 year period.  Temporal relationship of cases during 6 month periods did occur, but these were not epidemiologically related.  Therefore, investigation of a single episode of healthcare-associated GAS bacteremia is not warranted in most cases.  Infection preventionists should remain alert to clustering of GAS infections in postsurgical and postpartum patients to identify potential common sources.