Comparing 2005-06 invasive group A Streptococcus (iGAS) to current iGAS populations
In 2015, an outbreak of hypervirulent invasive group A Streptococcus (iGAS) emm-type 59, was identified at a local hospital in Arizona. The emm-59 strain was responsible for a large nationwide outbreak in Canada from 2006-2009, as well as some smaller outbreaks in California, Minnesota, Montana and Colorado. The emm-59 strain is known to cause necrotizing fasciitis, septicemia, soft tissue infections, and in some cases death. During the collection of the outbreak iGAS case isolates, we discovered there were multiple emm-types that had caused invasive disease. We then wanted to understand which GAS emm-types had caused invasive disease prior to the emm-59 outbreak, compare them with the current set of isolates, and look for any outbreaks within the emm-types not emm-59. The Arizona Department of Health (AZDH) had reported an increase in iGAS starting in 2004 and peaking in 2006. AZDH recently reported that another iGAS spike is underway. For this study, we selected random iGAS isolates from an AZDH collection dated 2005-06, to compare to the recent collection from 2015-16. We then performed whole genome sequencing and various data analyses to characterize the population structures of each set and discern the relative abundances of each emm-type.