A Salmonella enterica Serovar Hadar strain resistant to tigecycline (MIC 16 mug/ml) was isolated. Molecular characterization revealed the presence of a plasmid-borne tet(A) variant associated with Tn1721 mediating a rise of the MIC for tigecycline when transferred to Escherichia coli. Additionally, a truncating mutation in ramR was detected. Transformation with wildtype ramR but not with the mutated ramR lowered the MIC for tigecycline. Characterization of this Salmonella isolate thus implicates ramR in resistance to tigecycline.
