Characterisation of Streptococcus pyogenes on the basis of pyrotoxin exotoxin genes in north India

Abstract

Introduction: Scarlet fever and toxic shock syndrome are two major clinical entities caused due to the action of pyrogenic exotoxin. We screened the clinical isolates of Streptococcus pyogenes for the presence of major exotoxin encoding genes SpeA, SpeB and SpeC. Materials and Methods: Isolates of S. pyogenes obtained from clinical samples were characterised on the basis of pyrogenic exotoxin encoding genes SpeA, SpeB, and SpeC. The sample was cultured and identified by conventional biochemical test and further confirmed by latex agglutination test kit (Remel, USA). On confirmed group A streptococci isolates, deoxyribonucleic acid extraction and polymerase chain reaction were performed. Antimicrobial susceptibility testing and detection of inducible clindamycin resistance for all clinical isolates were performed using Clinical and Laboratory Standard Institute guidelines by Kirby–Bauer disk diffusion method. Results: Thirty-one confirmed isolates of S. pyogenes were tested; out of which, the respective prevalence values of SpeB and SpeC genes were 80.6 and 35.5%. SpeA gene was detected in only single isolate. All the isolates were susceptible to penicillin, but resistance was seen with erythromycin, tetracycline and levofloxacin. Inducible clindamycin resistance was seen in two isolates. Conclusion: The present study found that the genes encoding pyrogenic exotoxin is circulating in the S. pyogenes isolates present in north India and have the potential of causing scarlet fever that is not reported so far from the country. A significant percentage of drug resistance was noted for the alternative drugs required for the treatment of penicillin allergic patients. The recent upsurge in the cases of scarlet fever in south-east Asia warns us to keep a check on gene profile of these isolates in the community.