title: Antibiotic sensitivity and mutation rates to antibiotic resistance in Mycoplasma mycoides ssp. mycoides.
abstract: The antibiotic resistance of Mycoplasma mycoides ssp. mycoides strain T1 was investigated. This strain was resistant to high levels (greater than 100 micrograms ml-1) of rifampicin and nalidixic acid. It was sensitive to streptomycin, spectinomycin and novobiocin; however, single step mutants with high levels of resistance (greater than 100 micrograms ml-1) were readily isolated. With erythromycin and tylosin for which the minimum inhibitory concentration (MIC) for the parent strain was less than 0.1 microgram ml-1, mutants resistant to greater than 100 micrograms ml-1 were obtained in two and three steps respectively. The MIC of tetracycline in single step resistant mutants (0.6 microgram ml-1) was tenfold higher than the parent strain, but could not be increased further. There was only a twofold increase in resistance to chloramphenicol in single step mutants. The frequency of resistant mutants varied with the antibiotic and was between 4 X 10(-6) and 2 X 10(-8). The mutation rate to antibiotic resistance to streptomycin, spectinomycin, novobiocin, erythromycin and tylosin was between 3 X 10(-8) and 5 X 10(-9) per cell per generation. There was a fivefold decrease in mutation rate to resistance to 60 micrograms ml-1 streptomycin compared to that to 20 micrograms ml-1.
authors.forename: D H
authors.initials: DH
authors.lastname: Lee
authors.forename: R J
authors.initials: RJ
authors.lastname: Miles
authors.forename: J R
authors.initials: JR
authors.lastname: Inal
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial / Q000235:genetics; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009176:Mycoplasma mycoides / Q000187:drug effects* / Q000235:genetics; D013307:Streptomycin / Q000494:pharmacology; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D013752:Tetracycline; D013307:Streptomycin