BackgroundThe contribution of community and hospital sources to the transmission of extended-spectrum β-lactamase producing Enterobacterales (ESBL-PE) remains elusive.AimTo investigate the extent of community dissemination and the contribution of hospitals to the spread of ESBL-PE by exploring their spatiotemporal distribution in municipal wastewater of the central European city of Basel.MethodsWastewater samples were collected monthly for two consecutive years throughout Basel, Switzerland, including 21 sites across 10 postcode areas of the city collecting either community wastewater (urban sites,n= 17) or community and hospital wastewater (mixed sites,n= 4). Presumptive ESBL-PE were recovered by selective culture methods. Standard methodologies were applied for species identification, ESBL-confirmation, and quantification.ResultsNinety-five percent (477/504) of samples were positive for ESBL-PE. Among these isolates,Escherichia coli(85%, 1,140/1,334) andKlebsiella pneumoniae(11%, 153/1,334) were most common. They were recovered throughout the sampling period from all postcodes, withE. coliconsistently predominating. The proportion ofK. pneumoniaeisolates was higher in wastewater samples from mixed sites as compared to samples from urban sites, while the proportion ofE. coliwas higher in samples from urban sites (p= 0.003). Higher numbers of colony forming units (CFUs) were recovered from mixed as compared to urban sites (median 3.2 × 102vs. 1.6 × 102CFU/mL).E. coli-counts showed moderate correlation with population size (rho = 0.44), while this correlation was weak for other ESBL-PE (rho = 0.21).ConclusionESBL-PE are widely spread in municipal wastewater supporting that community sources are important reservoirs entertaining the spread of ESBL-PE. Hospital-influenced abundance of ESBL-PE appears to be species dependent.