Phenotypic and Genotypic Characterization of Antibiotic Resistance in Staphylococcus aureus Isolated from Different Sources

Background: Staphylococcus aureus is a bacterial pathogen that can cause a wide range of nosocomial infections. Nasal colonization by S. aureus plays an important role both in the epidemiology and pathogenesis of infection. Objectives: This study aimed at detecting the biofilm-forming capacity of clinical isolates and detection of icaA and agr genes. Methods: A total of 150 clinical specimens was collected from patients in different hospitals in Baghdad. The clinical samples included wounds, abscess, sputum, and ear infections. The suspected isolates were cultured for one day at 37 °C on mannitol salt agar in an aerobic environment. Results: The results showed that of 150 samples, 44 isolates were S. aureus (29.3%), of wounds samples, 22 isolates (45.83%) were S. aureus, 13 (37.14%) were from abscess, 7 (17.95%) from sputum, and 2 isolates (7.14%) from ear samples. This study found that most isolates formed biofilm, but the levels of biofilm were distributed across three ranges. The results also indicated that 47.7% of the isolates produced a strong biofilm, as well as 38.6 and 13.6% produced moderate and weak biofilms, respectively. The present molecular results showed that S. aureus from different samples were 13 (59.1%), 4 (30.77%), 3 (42.85%), 0 (0%) from wounds, abscess, sputum, ear, respectively, were positive for agr gene. While the results showed 18 (81.8%), 10 (76.9%), 5 (71.4%), 1 (50%), respectively, were positive for icaA gene. Conclusions: Most S. aureus isolates isolated from wound were biofilm positive. These isolates bore icaA and agr genes in a high quantity.