HealthDay News — A new strain of Streptococcus pyogenes is causing scarlet fever, according to a study published online Sept. 10 in The Lancet Infectious Diseases.

Nicola N. Lynskey, PhD, from the Medical Research Council Centre for Molecular Bacteriology & Infection in London, and colleagues used regional and national data to analyze changes in S pyogenes emm genotypes by analyzing genomes from 135 noninvasive and 552 invasive emm1 isolates compared with 2880 global emm1 sequences.

The researchers observed a significant increase in emm1 S pyogenes upper respiratory tract isolates in northwest London in the March to May period, coinciding with national increases in scarlet fever and invasive disease notifications, from 5% in 2014 to 19% in 2015 and 33% in 2016. Increases were noted in invasive emm1 isolates collected nationally, from 31% in 2015 to 42% in 2016. Emergence of a new emm1 lineage (M1UK) was observed in sequences of emm1 isolates from 2009 to 2016, which could be genotypically differentiated from pandemic emm1 isolates (M1global) by 27 single nucleotide polymorphisms. Among M1UK vs M1global isolates, the median streptococcal pyrogenic exotoxin A protein concentration in supernatant was 9 times higher. In 2016, M1UK expanded nationally to represent 84% of all emm1 genomes.

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“Wider national and global surveillance will provide clearer understanding of the lineage’s geographical reach and longer-term fitness, and permit enhanced public health readiness where necessary,” the authors write.

One author disclosed financial ties to the biotechnology industry.

Abstract/Full Text