A NEW MUTATION IN 16S RIBOSOMAL-RNA OF ESCHERICHIA-COLI CONFERRING SPECTINOMYCIN RESISTANCE

We report a novel mutation, C1066U in 16S rRNA which was selected for resistance to spectinomycin, an antibiotic which inhibits ribosomal tr anslocation. The minimal inhibitory concentration (MIC) of spectinomyc in determined for this mutant (15 mu g/ml) is greater than with the wi ld-type plasmid (5 mu g/ml) but lower than with the well known C1192U mutation (>80 mu g/ml). The C1066U mutation also increases the cells s ensitivity to fusidic acid, another antibiotic which inhibits translat ion at the translocation stage, whereas C1192U is unchanged relative t o the wild type. We discuss why the acquisition of resistance to one o f these drugs is often associated with hypersensitivity to the other.