Colistin‐resistant Enterobacter kobei carrying mcr‐9.1 and blaCTX‐M‐15 infecting a critically endangered franciscana dolphin (Pontoporia blainvillei), Brazil.

The emergence of mobile mcr genes mediating resistance to colistin is a critical public health issue that has hindered the treatment of serious infections caused by multidrug‐resistant pathogens in humans and other animals. We report the emergence of the mcr‐9.1 gene in a polymyxin‐resistant extended‐spectrum β‐lactamase (ESBL)‐producing Enterobacter kobei infecting a free‐living franciscana dolphin (Pontoporia blainvillei), threatened with extinction in South America. Genomic analysis confirmed the presence of genes conferring resistance to clinically relevant β‐lactam [blaCTX‐M‐15, blaACT‐9, blaOXA‐1 and blaTEM‐1B], aminoglycoside [aac(3)‐IIa, aadA1, aph(3'')‐Ib and aph(6)‐Id], trimethoprim [dfrA14], tetracycline [tetA], quinolone [aac(6')‐Ib‐cr and qnrB1], fosfomycin [fosA], sulphonamide [sul2] and phenicol [catA1 and catB3] antibiotics. The identification of mcr‐9.1 in a CTX‐M‐15‐producing pathogen infecting a critically endangered animal is of serious concern, which should be interpreted as a sign of further spread of critical priority pathogens and their resistance genes in threatened ecosystems. [ABSTRACT FROM AUTHOR]