Molecular identification of antibiotic resistance profile and virulence genes in Staphylococcus aureus from human and animal sources

Staphylococcus aureus is a common cause of infection in both animals and human. It often resists many antibiotics. This resistance is partly due to efflux pumps and genes like mecA. This study aimed to detect S. aureus in humans and animals, test its antibiotic resistance, and identify some important virulence genes. A total of 14 samples were collected between December 2022 and August 2023. Seven came from humans in Dhi Qar, Iraq. The other seven came from animals in Al-Najaf. Five isolates were confirmed as S. aureus. where. Diagnosis used blood agar and mannitol salt agar, followed by Gram stain and biochemical tests. VITEK 2 was used for confirmation. Antibiotic sensitivity was tested using Muller Hinton agar and VITEK 2 Ast card. PCR was used to detect virulence and resistance genes, including mecA (60.0%), nuclease (80.0%), lipase (100.0%), Saphylokinase (100.0%), invasive protease (60.0%), and Enterotoxin A (100.0%). A phylogenetic tree was done. Five isolates (35.7%) were identified as S. aureus. All five carried lipase, Enterotoxin A, and staphylokinase genes. Most had mecA and nuc genes. Three isolates carried invasive protease. Resistance was highest to penicillin, oxacillin, and cefoxitin. No resistance was found to gentamicin 0(0%), ciprofloxacin 0(0%), or linezolid. Phylogenetic analysis showed genetic diversity among strains. This study showed that S. aureus strains from humans and animals can carry multiple virulence genes and resist many antibiotics. The high rate of mecA gene indicates MRSA is present in both sources.