EpicPCR-directed cultivation strategy elucidates bacterial hosts and horizontal transfer of clinically relevant tet(X4) gene in municipal wastewater treatment plants

Great concerns have been raised by the emergency of plasmid-mediated tigecycline resistance tet(X)-variant genes in animal and human. However, the exploration of tet(X)-variants both by monitoring and genetic dissection in the environment has not been conducted. A retrospective study showcased that mobile tet(X)-variants have occurred in municipal WWTPs for a long time. A considerable level of mobile tet(X)-variants [distributed in the activated sludge, with tet(X4) exhibiting the highest detection frequency and abundance Furthermore, the combination strategy of epicPCR and targeted cultivation method revealed six genera hosting tet(X4) including three previously unreported hosts. Escherichia coli strains served as notable reservoirs for tet(X4) also in municipal WWTPs and potentially conferred referable transmission patterns amongst animal-related environments (including livestock husbandries, slaughterhouses, meat markets), clinical settings (hospitals) and municipal WWTPs, which supported by the diverse tet(X4) genetic contexts relating to IS elements on various plasmids in them. Collectively, this study provided the first glimpses of the occurrence of mobile tet(X)-variants, as well as host characteristics, genetic contexts of predominant tet(X4) in typical environment and underscored the unique role of WWTPs in disseminating mobile tet(X)-variants and their bacterial hosts from One Health perspective.