Persistence of Multidrug-resistant Bacteria and Resistance Genes following Tertiary Treatment of Hospital Wastewater in Malaysia

Antibiotic-resistant bacteria (ARB) in hospital wastewater pose serious environmental and public health risks due to their potential to persist through treatment processes and disseminate resistance genes. This study investigated the occurrence and persistence of ARB and antibiotic resistance genes (ARGs) in the wastewater treatment system of a teaching hospital in Malaysia. Samples were collected from five treatment stages across two sampling periods and analyzed using culture-based isolation, 16S rRNA gene sequencing, and antimicrobial susceptibility testing according to CLSI and EUCAST guidelines. A total of 28 isolates consisting of 11 different bacterial species were identified, including representative species such as Klebsiella pneumoniae, Acinetobacter baumannii, Aeromonas hydrophila, and members of the Stenotrophomonas maltophilia complex. K. pneumoniae exhibited multidrug-resistance and mutations in the gyrA gene (S83R, D87N), associated with fluoroquinolone resistance. Detected ARGs included blaSHV, blaCTX-M, blaTEM, blaNDM, and gyrA. The persistence of resistant bacteria and ARGs in the final effluent indicates incomplete elimination by tertiary treatment. These findings highlight hospital wastewater as a critical reservoir for antimicrobial resistance and underscore, from a One Health perspective, the need for integrated monitoring and improved wastewater treatment strategies to limit environmental dissemination of resistance determinants.

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