Efficacy of anaerobic digestion wastewater treatment systems in reducing antimicrobial resistance bacteria in wastewater from swine farms in Thailand

The study aimed to evaluate the antimicrobial resistance (AMR) patterns among the fecal indicator bacteria and analyze the characteristics of wastewater from anaerobic digestion (AD) wastewater treatment systems in swine farms. Escherichia coli and Enterococcus spp. were identified by conventional and molecular methods. AMR profiles and wastewater quality were analyzed using standard methods. The results indicated that the primary resistances observed in E. coli were against AM, TE, SXT, and DO. Among Enterococcus spp., the highest resistance was noted for TE, followed by E, CIP, and NX. Enterococcus faecium showed the highest resistance to CIP, NX, and TE. Multidrug-resistant-E. coli and enterococci were 64.2 and 32.6%, respectively. Furthermore, CL-resistant E. coli and VA-resistant Enterococcus spp. were reported. Compared with influent, the proportion of AMR E. coli and Enterococcus spp. in effluent was decreased. This decline suggested that AD effectively removed antimicrobial-resistant bacteria (ARB). However, high influent biochemical oxygen demand, total suspended solids, and chemical oxygen demand levels demonstrated significant pollution. Therefore, swine farms should prioritize waste management and regular maintenance of treatment systems to enhance the removal of ARB and pollutants. This study analyzed data from only three farms, highlighting the need for future research with a larger sample.