Occurrence, molecular confirmation, and multidrug resistance of methicillin-resistant Staphylococcus aureus and Staphylococcus pseudintermedius in companion animals in Indonesia

Background and Aim: Methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus pseudintermedius (MRSP) are increasingly recognized as important pathogens in companion animals, with significant zoonotic and public health implications. Data on methicillin-resistant staphylococci in pets in Indonesia remain scarce, particularly from clinical settings. This study aimed to determine the occurrence, molecular identity, and antimicrobial resistance (AMR) profiles of MRSA and MRSP isolated from companion animals presenting with clinical infections using an integrated phenotypic and genotypic diagnostic approach. Materials and Methods: We collected 100 clinical swab samples from dogs (n = 26), cats (n = 67), and rabbits (n = 7) presenting with signs of bacterial infection at veterinary clinics in Central Java and the Special Region of Yogyakarta, Indonesia. Isolates were identified using standard biochemical tests and confirmed molecularly by PCR targeting the 23S rRNA and nuc genes for S. aureus and PCR–restriction fragment length polymorphismof the pta gene for S. pseudintermedius. Methicillin resistance was screened using oxacillin resistance screening agar base, phenotypically confirmed by disk diffusion (cefoxitin or oxacillin), and genotypically verified by detection of the mecA gene. The Kirby–Bauer method was used to perform antimicrobial susceptibility testing against 11 commonly used antibiotics. Results: Of the 100 samples, 41 S. aureus and 14 S. pseudintermedius isolates were confirmed. Based on mecA detection, 27/41 (65.9%) S. aureus isolates were classified as MRSA and 13/14 (92.9%) S. pseudintermedius isolates were classified as MRSP. MDR was highly prevalent, observed in 92.6% of MRSA and 92.3% of MRSP isolates. High resistance rates were noted against β-lactam antibiotics, including penicillin, ampicillin, and amoxicillin. Several isolates carried mecA despite being phenotypically susceptible, indicating silent or low-expression resistance determinants. Conclusion: This study reveals a great burden of methicillin- and multidrug-resistant staphylococci among companion animals with clinical infections in Indonesia. The detection of mecA-positive MRSA and MRSP underscores a substantial zoonotic risk and highlights the limitations of phenotypic methods. These findings emphasize the need for routine molecular diagnostics, strengthened antimicrobial stewardship in veterinary practice, and integrated One Health surveillance to mitigate the spread of AMR across animal–human interfaces. Keywords: Antimicrobial resistance, companion animals, Indonesia, mecA gene, methicillin-resistant Staphylococcus aureus, methicillin-resistant Staphylococcus pseudintermedius, multidrug resistance, One Health.