Summary Tigecycline and colistin are few of ‘last‐resort’ antibiotic defences used in anti‐infection therapies against carbapenem‐resistant bacterial pathogens. The successive emergence of plasmid‐borne tet (X) tigecycline resistance mechanism and mobile colistin resistance ( mcr ) determinant, renders them clinically useless. Here, we report that co‐carriage of tet (X6) and mcr‐1 gives co‐resistance to both classes of antibio...

Summary The transferability of bacterial resistance to tigecycline, the ‘last‐resort’ antibiotic, is an emerging challenge of global health concern. The plasmid‐borne tet (X) that encodes a flavin‐dependent monooxygenase represents a new mechanism for tigecycline resistance. Natural source for an ongoing family of Tet(X) resistance determinants is poorly understood. Here, we report the discovery of 26 new variants [ tet (X18)...

Summary MCR‐4 and MCR‐8 are two recently identified members of an ongoing MCR family of colistin resistance. Although that aquatic reservoir for MCR‐4 is proposed, the origin and mechanism of MCR‐8 is poorly understood. Here we report a previously unrecognized non‐mobile colistin resistance enzyme, termed NMCR‐2, originating from the plant pathogen Kosakonia pseudosacchari . NMCR‐2 (551aa) gives 67.3% identity to MCR‐8 (565aa)...