Studies on mutational cross-resistance between ciprofloxacin, novobiocin and coumermycin in Escherichia coli and Staphylococcus warneri.
Nalidixic acid resistant mutants of Escherichia coli KL16 were tested against ciprofloxacin, coumermycin and novobiocin. The mutants gyrA, nalB and nal-24 were more resistant than KL16 to ciprofloxacin, whereas the nal-31 strain was hypersensitive. Only the nalB mutant was more resistant to novobiocin than KL16, but gyrA, nal-31 and nal-24 mutants were more sensitive to coumermycin than KL16. Newly-isolated novobiocin-resistant mutants of KL16 were not cross-resistant to coumermycin or ciprofloxacin. Some coumermycin-resistant mutants were cross-resistant to novobiocin but not ciprofloxacin, whereas mutants resistant to novobiocin and ciprofloxacin were isolated at higher coumermycin concentrations. Two types of Staphylococcus warneri mutant were isolated on media containing novobiocin or coumermycin. Each was resistant to both coumarins, but one was highly resistant to novobiocin and the other to coumermycin. High level resistance to both coumarins was unstable. E. coli mutants differed in susceptibility to bactericidal concentrations of ciprofloxacin, and S. warneri mutants behaved similarly. These results suggest the modes of action of the coumarins are not identical.
Howard
B M
BM
Department of Pharmaceutics, School of Pharmacy, University of London.
Pinney
R J
RJ
Smith
J T
JT
D049933:Aminocoumarins; D002939:Ciprofloxacin / Q000494:pharmacology*; D003374:Coumarins / Q000494:pharmacology; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects*; D009154:Mutation; D009675:Novobiocin / Q000494:pharmacology*; D010641:Phenotype; D013210:Staphylococcus / Q000187:drug effects*
D049933:Aminocoumarins; D003374:Coumarins; D009675:Novobiocin; D002939:Ciprofloxacin; C004628:coumermycin