Investigation of antibiotic resistance profiles, mecA and blaZ resistance genes of staphylococcus aureus strains isolated from clinical samples at Sammara General Hospital in Iraq

This study aims to investigate the prevalence and antimicrobial resistance patterns of Staphylococcus aureus isolated from diverse clinical samples in Samarra, Iraq. 120 clinical samples (nasal swabs, ear swabs, burn swabs, wound swabs, and laryngeal swabs) were collected from both male and female patients at Samarra General Hospital between November 2023 and April 2024. Samples were cultured on blood agar, chocolate agar, and Mannitol Salt Agar (MSA) for bacterial isolation. Isolates identified as Staphylococcus aureus based on standard microbiological tests were subjected to antimicrobial susceptibility testing against eight antibiotics using the disc diffusion method. Additionally, PCR was employed to detect the presence of specific resistance genes (blaZ and mecA) and virulence factor genes. Of the 120 samples, 50 (41.7%) yielded Staphylococcus aureus growth, primarily on MSA and chocolate agar. The highest infection rate was observed in nasal swabs (46%), followed by wound swabs (28%), burn swabs (18%), ear swabs (4%), and laryngeal swabs (4%). Notably, isolates exhibited high resistance to oxacillin (96%), ampicillin (58%), and azithromycin (56%). PCR analysis revealed the presence of blaZ gene (encoding beta-lactamase) in 66.6% of isolates and mecA gene (conferring methicillin resistance) in 43.5%, indicating a significant proportion of multidrug-resistant Staphylococcus aureus (MRSA). This study highlights a concerning prevalence of Staphylococcus aureus, particularly in nasal swabs, and alarming rates of resistance to commonly used antibiotics, including oxacillin, ampicillin, and azithromycin. The detection of blaZ and mecA genes further emphasizes the presence of MRSA strains. These findings necessitate implementing stricter infection control measures and adopting alternative antimicrobial strategies to combat the growing threat of antibiotic-resistant Staphylococcus aureus in the region.