Molecular Detection and Expression of the blaZ Gene in Clinical Staphylococcus aureus Isolated from Hospital Patients

Abstract

This study aimed to investigate the presence and expression of the blaZ gene in clinical Staphylococcus aureus isolates obtained from patients attending hospitals in Iraq. A total of 140 clinical specimens were collected, including wound swabs (71), vaginal swabs (35), urine samples (20), and sputum samples (14). Bacterial isolation was performed using Mannitol Salt Agar (MSA), followed by morphological and biochemical identification and confirmation using the VITEK-2 Compact system. Among the collected specimens, 25 S. aureus isolates were identified. β-Lactamase production was assessed using the Nitrocefin disk test, with 20 isolates showing positive results. These β-lactamase-positive isolates were selected for molecular analysis. PCR was performed for detection of the blaZ, mecA and 16S rRNA genes, and the blaZ gene was detected in all 20 examined isolates. The mecA gene was also detected in all selected isolates. The expression of blaZ was subsequently analyzed by real-time quantitative PCR using 16S rRNA as the reference gene. The results revealed considerable variation in blaZ expression among the examined isolates, with fold-change values ranging from 0.001953 to 128 and an overall mean of 17.90. Overall, the study demonstrated the presence of blaZ among the selected β-lactamase-positive clinical S. aureus isolates and showed considerable variation in its expression between isolates. These findings provide molecular characterization of blaZ expression among the clinical isolates examined in this study.

Keywords: Staphylococcus aureus; blaZ; β-Lactamase; Antimicrobial resistance; mecA; 16S rRNA.