A Novel Trimethoprim Resistance Gene, , Characterized from Escherichia coli from Calves.

Whole-genome sequencing of trimethoprim-resistant strains MF2165 and PF9285 from healthy Swiss fattening calves revealed a so far uncharacterized dihydrofolate reductase gene, Functionality and association with trimethoprim resistance were demonstrated by cloning and expressing in The DfrA35 protein showed the closest amino acid identity (49.4%) to DfrA20 from and to the Dfr determinants DfrG (41.2%), DfrD (40.8%), and DfrK (40.0%) found in Gram-positive bacteria. The gene was integrated within a florfenicol/chloramphenicol-sulfonamide resistance IS element (-IS--) next to a Tn-like transposon that contained genes with resistance to sulfonamides (), streptomycin (), gentamicin/tobramycin/kanamycin (), and quaternary ammonium compounds (Δ). A search of GenBank databases revealed that was present in 26 other strains from different origins as well as in The presence of associated with IS in from animals, as well as its presence in other strains from different sources and countries and in , highlights the global spread of this gene and its potential for further dissemination. The genetic link of IS- with other antibiotic and disinfectant resistance genes showed that multidrug-resistant may be selected and maintained by the use of either one of several antimicrobials.