Molecular study of two virulence factors genes in staphylococcus aureus isolated from burn and respiratory system infections

The present study is aimed at isolating and identifying: the clinical isolates S. aureus collectng from burn and tonsillitis samples, investigating two virulence factors genes of S.aureus by polymerase chain reaction technique (PCR) technique, identifying the genetic polymorphisms of the clumping factor A (clfA) and fibronectin-binding protein A (fnbA) genes in the of S. aureus. The observed variants have been localized according to their positions within the referring genomic DNA sequences. The current study includes 80 swabs that are collected from burn patients and swabs extracting from patients with tonsillitis during the period from February to July 2020 at Al-Hussein Teaching Hospital in Thi-Qar province, Iraq. The complete isolates of Staphylococci isidentified by microscopic, morphological, and biochemical tests. Only 65 isolates (81.25 %) have showed positive growth on mannitol salt agar and diagnosed as S. aureus. The results explain a high rate of S. aureus and they are registered in the age group of (≤ 10 years), while the lowest frequency for burn and tonsillitis samples has observed in (51-60 years) age group of with 2 (2.5 %) patients. The results of molecular diagnosis have displayed that 81.54 % of S. aureus isolates and have clf A gene, while the prevalence of fnb gene is 18.46 %. The percentage of clf A and fnb genes relates with site of isolation is differenced, which has been divided to 82.86 % and 80 % of isolates recovers from burn and tonsillitis samples gaving positive results for clf A gene, while fnb gene present in 20 % and 16.67 %, which divides to 7/35 from burn and 5/30 from burn and tonsillitis samples. The current results indicate the absence of any detectable nucleic acid variations in the amplified 288 bp fragment of the clfA gene. Meanwhile, several mutations are identified in the fnbA gene. Both generated clfR-based and fnbA-based phylogenetic trees indicate accurate positioning with regard to both investigated samples. These comprehensive trees have been constructed to allocate the identified mutations with their related organisms. The currently constructed phylogenetic provides informative comprehensive data, in terms of the accurate positioning of S. aureus samples and their relative sequences. Therefore, both generated clfA-based and fnbA-based phylogenetic trees provide a confirmed identity with respect to the phylogenetic relationships among the investigated samples.