Investigation of two sewersheds in Belo Horizonte, Brazil reveals hospital and municipal wastewaters in a hospital-dominated sewershed as priority sources for antibiotic resistance spread to the environment

The proliferation of antibiotic resistant bacteria (ARB) and genes (ARGs) is a threat to global public health and has been associated with environmental release of wastewater (WW), with healthcare facilities suspected as primary sources of generation. This study found similar ARB abundance in WW collected from two hospitals (5.7 ± 0.7-log CFU mL⁻¹) and two municipal wastewater treatment plants (WWTPs, 5.3 ± 0.8-log CFU mL⁻¹). However, there was significantly higher (p < 0.05) meropenem-resistance in hospital WW (5.77 ± 0.35-log CFU mL-1) than in municipal WW (4.58 ± 0.34-log CFU mL-1). Similarly, ARGs intI1, sul1, ermB, qnrB, and bla_TEM were higher in hospital WW, (8.4 ± 1.03-log gene copies mL-1) than in untreated municipal WW (7.60 ± 1.15-log gene copies mL-1), with significant correlations observed between the effluent ARGs of a hospital used as a reference facility for infectious diseases and the ARGs in its corresponding WWTP influent. During treatment, low-energy systems demonstrated an average reduction of 52 % for ARBs and 48 % for ARGs, while conventional activated sludge achieved 98 % and 86 %, respectively. Multi-drug resistance was observed in 76 % of 18 isolated bacterial strains, particularly for E. coli and K. pneumoniae. The results of this study implicate hospitals as hotspots of antimicrobial resistance, suggesting the potential for discretionary guidelines when determining whether to treat hospital WW prior to discharge to local sewersheds and highlight the need to determine the best methods to reduce their release from WWTPs.