#streptococcus pyogenes

Tonsillitis and pharyngitis are infections often caused by Streptococcus pyogenes, a member of the group A Streptococcus. The aim of this study was to isolate S. pyogenes and identify the virulence genes associated with its pathogenesis in a local population of Lahore, Pakistan. The samples (n=110) were collected from patients suffering from tonsillitis and pharyngitis. They were proceeded on 5 % sheep blood agar and crystal violet agar for the subsequent isolation and purification of S. pyogenes. The biochemical characterization, determination of antibiogram and serum opacity factor (SOF) was performed by using standard procedures. The amplification of the selected virulent genes was carried out by PCR. Results demonstrated β- hemolytic colonies of S. pyogenes in 18.8 % (n=20) of the samples, which was also confirmed by coagulation with specific antisera. The 62.5 % of the strains were notably tested positive for serum opacity factor (SOF), whereas 37.5 % of the strains were tested negative. The antibiogram of S. pyogenes revealed sensitivity to cefotaxime (62.5 %), gentamicin (37.5 %), penicillin G (87. 5 %), clindamycin (87.5 %) and erythromycin (100 %). All strains were found to be resistant to tetracycline. PCR amplification yielded product sizes of 700 bp, 290 bp, 780 bp, 820 bp, 510 bp, 409 bp, 550 bp and 580 bp for emm, sagA, speA, speB, scpA, slo, hylA and ska genes, respectively. The presence of these virulent genes confirmed their incidence in the local population, which can be studied further to gain deeper insights into the molecular mechanisms of S. pyogenes pathogenicity.