Wastewater is considered a hotspot for MDR bacteria and plays a role in their spread and impact on human, animal and environmental health (One-Health). As detailed information on the contribution of each sector is lacking, we investigated the occurrence of ESKAPE-/ESBL-producing bacteria from wastewater of livestock slaughterhouses and their municipal wastewater-treatment plants. The target species were ubiquitously identified along the slaughter and wastewater chains, but showed a wide variety of resistance patterns. Clinically important isolates were mainly recovered from municipal wastewater (i.e. CRE). Wastewater-treatment plants appear to be failing to eliminate these bacteria, resulting in their discharge into the preflooder and subsequent dissemination into the environment. However, further analysis of the wastewater also revealed the presence of natural enemies (bacteriophages) of the target bacteria. Lytic phages of different species were found to specifically attack their target bacteria and are able to significantly reduce the number of bacteria in-vitro. The genetic diversity of the phages obtained against a target species (e.g. K. pneumoniae) allows the development of suitable/safe cocktails with phage-members targeting different receptor binding proteins on the surface of the bacteria to avoid the development of phage-resistant clones. In addition, careful adaptation of the phage application to the specific purposes is necessary to develop efficient application strategies. Identified phage-members did not seem to be limited to wastewater treatment purposes, as bacteria for different sectors could be tackled using them in different combinations out of the developed phage-collection and can therefore be adapted to a wide variety of One Health approaches.