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GAS clone source of invasive infections in Wyoming
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A newly emerged, highly virulent clone of group A Streptococcus type emm59, previously seen in Canada and parts of the United States, has been identified as the source of highly invasive infections in Wyoming, according to recent findings.
In the study, the researchers analyzed four cases of severe invasive infection caused by group A Streptococcus (GAS) in rural northeastern Wyoming. The cases occurred within a similar time frame, and there was a direct link between two of the cases.
Case-patient four, a 46-year-old woman, contracted the illness from a family member with whom she lived, case-patient two. Case-patient two was a 78-year-old man with various medical problems who died within 48 hours after hospitalization. Case-patient three was a 46-year-old physician who treated patients one and two. Case-patient one was an otherwise healthy man, aged 19 years.
Because these infections took place in close proximity to an area where a cluster of six invasive emm59 infections were diagnosed in Montana in 2010, the researchers sought to determine whether genetically related emm59 strains were culpable. Strains extracted from patients two and four were sent to Houston Methodist Hospital for genome sequencing, which revealed that the two emm59 case strains differed by only 15 single nucleotide polymorphisms.
In a separate analysis, the researchers evaluated a convenience sample of 17 GAS strains extracted from patients with pharyngitis or skin infections in the geographic area near the community where the invasive infections occurred. However, none of these strains were emm59.
According to the researchers, the uncharacteristic virulence of this emm59 strain is a matter of concern and should be studied further.
“We document that an unusually virulent emm59 clone has now emerged to cause severe infections and one death in rural northeastern Wyoming,” the researchers wrote. “Given the speed and modest cost of full-genome sequencing and its role in human health, we remain interested in studying the spread of this clone.”
Disclosure: The researchers report no relevant financial disclosures.
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