Occurrence, characteristics, and antibiotic sensitivity of Staphylococcus aureus isolated from wild birds in the Kasur district of Punjab, Pakistan

Staphylococcus aureus is gaining worldwide attention because of its substantial impact on public health. The current study aimed to characterize S. aureus strains isolated from wild birds in the Kasur district of Punjab, Pakistan from 2021 to 2022. A total of one hundred samples were collected from five wild bird species. The samples were enriched, inoculated on selective agars and cultured for 24 hr at 37.00 ˚C. All isolates were verified by matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS) and polymerase chain reaction (PCR) after Gram staining. Positive isolates were screened for phenotypic (Kirby-Bauer disk diffusion and minimum inhibitory concentration s), genotypic antibiotic resistance, and virulence genes. These samples yielded 30 (30.00%) S. aureus isolates, confirmed by polymerase chain reaction utilizing the 16S rRNA gene. Staphylococcus aureus was more prevalent in cloacal samples (16.00%) than oral samples (14.00%). Various S. aureus isolates showed varying degrees of resistance to three different antibiotics. Oxacillin (56.66%; n = 17) and tetracycline (33.33%; n = 10) showed the highest resistance rates with the lowest susceptibility (43.33%; n = 13). In contrast, vancomycin, rifampicin, linezolid, and daptomycin were 100% susceptible. Further disc diffusion study revealed resistance to tetracycline (33.33%), erythromycin (16.66%), and gentamicin (10.00%). The tetK gene was found in 33.33% of wild bird samples, while the ermA gene was found in 16.66% of samples. The aacA-D gene was only found in three (10.00%) isolates. None of the isolates tested positive for virulence genes. In conclusion, S. aureus is carried by wild birds in this area, posing a potentail threat to both humans and animals.