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Abstract
group A streptococci (GAS) are human pathogens causing 650,000 annual deaths among humans. Recently, hypervirulent, invasive GAS strains have emerged and their emergence was correlated with the carriage streptodornase gene variants, which encode secreted nucleases that degrade neutrophil extracellular traps, protecting the bacteria from phagocytosis. So far, five major streptodornase classes have been discovered, four of which are phage-encoded: Spd2, Spd3, Spd4, and Sda; the fifth is the chromosomally encoded Spd. To date, no method is available for rapid and accurate genotyping of all five classes in clinical GAS isolates. To rapidly investigate the distribution of phage-encoded streptodornases among clinical isolates, we initiated this study to develop a polymerase chain reaction (PCR)-based genotyping approach. First, a bioinformatics analysis was conducted to screen GAS genomes for known streptodornase patterns. Next, clinical isolates from Egypt were cultured and tested for nuclease activity by subculture on DNA-agar plates containing methylene blue, then by an agarose gel electrophoresis-based method to test the extent of DNA degradation