Phenotypic Characterization of Antibiotic Resistance in Staphylococcus aureus from Clinical, Hospital Wastewater, and River Sources in Jakarta

Background: Antimicrobial resistance (AMR) poses a growing threat to public health, particularly in urban settings where effluents from hospital wastewater treatment plants (WWTPs) and river systems may contribute to the spread of resistant bacteria. Aim: This study aimed to characterize and compare the phenotypic antibiotic resistance profiles of Staphylococcus aureus isolated from clinical samples, hospital wastewater, and the Ciliwung River in Jakarta, to assess potential environmental dissemination and links between clinical and environmental reservoirs of resistance. Methods: S. aureus isolates were obtained from RSCM clinical samples, four points at the hospital WWTP, and six sites along the Ciliwung River between September and December 2024. Isolates were identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry, and antibiotic susceptibility testing was performed via automated systems. Results: Two river isolates showed resistance only to penicillin. Among 14 WWTP isolates, resistance to penicillin (43%), tetracycline (19%), and gentamicin (3%) was observed, with evidence of multidrug resistance (MDR). Clinical isolates showed a higher prevalence of resistance, with 32% classified as MDR. All methicillin-resistant S. aureus isolates exhibited MDR, with a greater prevalence in clinical (22%) than environmental samples (6%). A vancomycin-resistant S. aureus isolate was detected at the WWTP inlet, the first such report in Indonesian wastewater. Half of the environmental isolates were susceptible to all antibiotics tested. Conclusion: Similar resistance patterns in clinical and environmental S. aureus suggest potential transmission between these reservoirs. However, larger studies are needed to confirm these findings and better assess environmental AMR risks.