Comparative in vitro activity of the new fluoroquinolone BMY-40062

The results are presented of comparative in vitro susceptibility testing of BMY-40062, a new fluorinated quinolone which contains a tetrabutyl moiety at N-1 and a piperazinyl group at C-7. BMY-40062 inhibited 90 % ofEnterobacteriaceae strains at < 0.5 µg/ml, being either equal in activity to ciprofloxacin or two- to four-fold less active, depending upon the species. BMY-40062 was as active as ciprofloxacin againstPseudomonas aeruginosa (MIC90 0.5 µg/ml) and inhibited most other strains ofPseudomonas species at < 1 µg/ml. It was more active than ciprofloxacin or ofloxacin against hemolytic streptococci andStreptococcus pneumoniae, 90 % of strains being inhibited at < 0.5 µg/ml. MICs increased in the presence of 9 mM Mg²⁺ and at pH 5.5. The frequency of spontaneous mutation was low forEnterobacteriaceae, Pseudomonas aeruginosa andStaphylococcus aureus (10^–10), but repeated exposure to BMY-40062 caused selection of resistant isolates. Clinical isolates ofPseudomonas aeruginosa resistant to ciprofloxacin and ofloxacin were resistant to BMY-40062.