Detection of ciprofloxacin resistance in gram-negative bacteria due to alterations in gyrA

Two plasmids containing the cloned Escherichia coli wild-type gyrA gene were used to transform ciprofloxacin-resistant Gram-negative clinical isolates to screen for DNA gyrase A-mediated quinolone resistance. The results show that the technique is simple and applicable to a wide range of Gram-negative species including E. coli, Enterobacter cloacae, Klebsiella aerogenes, Morganella morganii, Proteus mirabilis, Pseudomonas aeruginosa, Campylobacter jejuni and Neisseria gonorrhoeae. The use of an arithmetical MIC series of dilutions (as opposed to standard geometrical ones) was found to be essential during screening for the detection of altered gyrase A. The observations were consistent with the suggestion that DNA gyrase is highly conserved among different species of bacteria and that gyrase A-mediated resistance can occur in all.