Beta-lactam non-susceptible GAS from clinical samples in Guyana. β-lactam non-susceptible Group A Streptococcus isolated from clinical samples in Guyana

Introduction: Streptococcus pyogenes (or Group A streptococci [GAS]), is the causative agent of pharyngitis and various other syndromes involving cellulitis, streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis. Methods: In this study, we sought to use Sanger sequencing to identify mutations in PBP genes of Streptococcus pyogenes isolated from hospitalised patients that could confer reduced PBP affinity for penicillin and/or cephalosporin antibiotics. All isolates were screened for resistance to penicillin, amoxicillin, and cefazolin using E-test strips. Results: While there no documented cases of reduced susceptibility to penicillin or amoxicillin. There were 13 isolates were cefazolin non-susceptible. Examination of pbp1a by Sanger sequencing revealed several isolates with single amino acid substitutions, which could potentially reduce the affinity of PBP 1A for cefazolin and possibly other first generation cephalosporins. Conclusion: Penicillin and penicillin-derived antibiotics remain effective treatment options for GAS infections, but active surveillance is needed to monitor for changes to susceptibility patterns against these and other antibiotics and understand the genetic mechanisms contributing to them.