University of Hertfordshire


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Original languageEnglish
Pages (from-to)361
Number of pages368
JournalEpidemiology and Infection
Publication statusPublished - 1987


The antibiotic resistance of Mycoplasma mycoides ssp. mycoides strain T1 was investigated. This strain was resistant to high levels ( > 100 ug/ml) of rifampicin and nalidixic acid. It was sensitive to streptomycin, spectinomycin and novobiocin;however, single step mutants with high levels of resistance (>100 ug/ml) were readily isolated. With erythromycin and tylosin for which the minimum inhibitory concentration (MIC) for the parent strain was < 0.1 ug/ml, mutants resistant to > 100 ug/ml were obtained in two and three steps respectively. The MIC of tetracycline in single step resistant mutants (0-6 ug/ml) 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 ug/ml streptomycin compared to that to 20 ug/ml.

ID: 13400978