GAS isolates from the five patients yielded four distinct PFGE patterns. The patterns of isolates from two patients were identical, while each pattern of the isolates from the other three patients was unique. No epidemiologic relation between the two patients with identical isolates could be established. Prophylactic antibiotic treatment of close contacts was not pursued, and no secondary cases were identified. Investigators from Spokane and the state health department used PFGE in their investigation to determine that these cases were not caused by a common source.
GAS is a common cause of pharyngeal, skin, and other soft tissue infections.
Transmission of GAS is generally person to person through contaminated secretions. Four of the women with invasive GAS infection described in this report were obese. Obesity has not been associated previously with invasive GAS infection and merits further study. In this investigation, PFGE results were concordant with traditional typing methods, performed locally, and available within 4 days of submission of the isolates. The investigators used PFGE to determine that the five cases, despite their similarities, did not represent a common-source outbreak but were a clustering of sporadic cases.