speB Gene as an early specific genetic marker for diagnosis of group a beta-hemolytic streptococcus [GABHS]: considerable virulence factor

ABSTRACT

Group A beta-hemolytic streptococcus [GABHS], which is the most common cause of pharyngeotonsilitis, is the target of most diagnostic and therapeutic strategies. Pyrogenic exotoxin B [speB] is one of the most important virulence factors of GAS as it cause destruction of host defense system proteins .Early and appropriate treatment of GABHS significantly reduces the risk of development of acute rheumatic fever which can be prevented if an early and adequate course of antibiotic is received. To evaluate the role of speB as an early genetic marker for diagnosis of S. pyogenes [GABHS] in comparison with other methods and its correlation with the post-infectious sequelae. 80 patients were included in this study, they were selected from those attending Pediatric Outpatient Clinic. They were divided into two groups 48 patients with acute follicular tonsillitis [Group I] and 32 patients with rheumatic fever or rheumatic heart disease [Group II]. They were subjected to complete clinical examination and throat swabs were collected from each patients and tested for Culture, Rapid antigen detection test [RADT] and for the expression of speB gene using PCR technique. GABHS were detected by culture in [50.0% and 71.88%] of group I and group II respectively, while by using RADT, were detected in [52.08% and 84.38%] of group I and group II respectively. speB gene were detected in [50% and 93.75%] of group I and group II respectively with significant deference [P<0.001]. In comparison to culture, PCR showed 97.87% sensitivity and 75.75% specificity, while RADT showed 91.48% sensitivity and 72.72% specificity. Detection of speB gene shows high sensitivity and specificity in comparison with other detection methods and can be used as an early marker for diagnosis of GABHS and predicting the post- infectious sequelae