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% of Enterobacteriaceae strains at less than 0.5 microgram/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 against Pseudomonas aeruginosa (MIC90 0.5 micrograms/ml) and inhibited most other strains of Pseudomonas species at less than 1 microgram/ml. It was more active than ciprofloxacin or ofloxacin against hemolytic streptococci and Streptococcus pneumoniae, 90% of strains being inhibited at less than 0.5 micrograms/ml. MICs increased in the presence of 9 mM Mg2+ and at pH 5.5. The frequency of spontaneous mutation was low for Enterobacteriaceae, Pseudomonas aeruginosa and Staphylococcus aureus (10(-10), but repeated exposure to BMY-40062 caused selection of resistant isolates. Clinical isolates of Pseudomonas aeruginosa resistant to ciprofloxacin and ofloxacin were resistant to BMY-40062.