emm Typing Clinical Samples of Group A Streptococcus to Understand the Epidemiology of Cyclic Outbreaks in Utah

Background: Invasive Group A Streptococcus (GAS) infections’ average mortality rate is 10-15%, although some strains can approach 35%. The ability to determine strain type and understand corresponding lethality may be of vital importance in guiding clinical decisions. For as yet undefined reasons, Utah has experienced higher than average rates of invasive GAS disease. Typing of the cell surface M virulence protein (“emm” typing) has been used to identify related strains of GAS.

Methods: This study was approved by the Institutional Review Boards of the University of Utah and Primary Children’s Medical Center. GAS isolates from children with invasive GAS disease were emm typed by PCR and sequencing. emm type was determined by comparison to the CDC emm typing database. A comparison was made between emm type and site of disease to determine if specific emm types were associated with particular manifestations.

Results: The current sample size incorporates 22 specimens from a variety of clinical manifestations. These include 4 samples from septicemia, 2 from neck abcesses and retropharyngeal abcesses, and one from each of the following: abdominal fluid, foot tissue, left cervix, left ear, pelvis fluid, protected brush, ear pus, right humerous, sternal abcess, synovial ankle, synovial knee, tonsilar abcess and wound. emm typing is still underway.

Conclusions: emm typing of our samples has the potential to identify strains which carry disproportionate virulence. This will enable clinicians to treat patients more efficaciously. Additionally, the epidemiological value of this may guide future research regarding the means through which these strains become hypervirulent.