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Extended-spectrum β-lactamase (ESBL)- and carbapenemase-producing Enterobacterales are a critical global health problem and wastewater treatment plants (WWTPs) can promote their spread into the environment; yet their efficacy is not well characterized. Here, we have used conventional culturing to monitor coliform bacteria and quantitative PCR to monitor 2 ESBL and 5 carbapenemase (CP) genes and 4 enteric opportunistic pathogens (EOPs) in the influent and effluent of 7 Croatian WWTPs in two seasons. In general, levels of total, cefotaxime- and carbapenem-resistant coliforms were significantly reduced but not eliminated by conventional treatment in most WWTPs. Most WWTPs efficiently removed EOPs such as K. pneumoniae and A. baumannii , while E. coli and Enterococcus spp. were reduced but still present in relatively high concentrations in the effluent. ESBL genes (bla TEM and bla CTX-M-32) were only slightly reduced or enriched after treatment. CP genes, bla KPC-3 , bla NDM and bla OXA-48 -like, were sporadically detected, while bla IMP and bla VIM were frequently enriched during treatment and correlated with plant size, number or size of hospitals in the catchment area, and COD effluent concentration. Our results suggest that improvements in wastewater treatment technologies are needed to minimize the risk of environmental contamination with top priority EOPs and ARGs and the resulting public health. [Display omitted] • WWTPs reduce but do not eliminate total and resistant E. coli and other coliforms. • Good removal of A. baumannii and K. pneumoniae was reported in most WWTPs. • ESBL genes were only slightly reduced or even enriched after treatment. • CP genes such as bla IMP and bla VIM were frequently enriched during the process. • Concentrations of bla IMP and bla VIM were affected by specific WWTP characteristics. [ABSTRACT FROM AUTHOR]