MOLECULAR MICROBIOLOGY
Group A Streptococcus: introducing a rapid molecular POC test
Streptococcus pyogenes, also known as Group A Streptococcus, is the prime cause of bacterial pharyngitis and results in major disease worldwide. Ranging from non-invasive disease to severe invasive disease such as necrotising fasciitis, toxic shock syndrome and scarlet fever, the infection is associated with high morbidity and mortality. Here, Naomi Mason and colleagues investigate the use of a new near-patient test.
For decades, the clinical history, clinical examination and a throat swab for microbiological culture have been the only tools clinicians have had to rule in/ out pharyngitis caused by Streptococcus pyogenes infection (also known as Group A Streptococcus [GAS]). The microbiology departments within the authors’ trust use traditional culture techniques to isolate S. pyogenes (Fig 1). With a minimum incubation time of 18 hours and follow-on confirmatory tests as well as antimicrobial susceptibility testing, the turnaround time is three days.
Since 2014, England has seen
increased scarlet fever activity, unprecedented in modern times. Mutations seen within the M protein (emm1) and the emergence of M1UK (a sublineage of emm1) were seen to be prevalent in patients with pharyngitis before the COVID-19 pandemic. The emm1 S. pyogenes strains are highly virulent and disproportionately associated with invasive infections;1 most worryingly there is a recognised association between emm1 S. pyogenes and fatal outcome of invasive infection.1 Furthermore, M1UK
has been strongly
associated with scarlet fever and invasive infection,1
no doubt because of its
increased production of streptococcal pyrogenic exotoxin A-SpeA.2
Fig 1. Streptococcus pyogenes (Group A Streptococcus [GAS]) growing on Columbia blood agar.
WWW.PATHOLOGYINPRACTICE.COM APRIL 2024 During the COVID-19 pandemic GAS 35
Nathan Reading from Halesowen, UK CC BY 2.0 Wikimedia Commons
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