Comparative in vitro activity of ciprofloxacin, ofloxacin and pefloxacin against resistant clinical isolates.

The in-vitro antimicrobial activity of three new quinolones, ciprofloxacin, ofloxacin and pefloxacin, was compared against 194 recent clinical isolates, 50 S. aureus, 50 E. coli, 45 E. cloacae and 49 P. aeruginosa. About half of the strains were resistant to a standard reference antibiotic like oxacillin (S. aureus), ampicillin (E. coli), gentamicin (E. cloacae) and amikacin (P. aeruginosa). The resistant selected strains were less susceptible to the three fluoroquinolones tested than the parent isolates, but, except for pefloxacin against E. cloacae and P. aeruginosa, the decrease in susceptibility was relatively low and MICs remained below the resistance break-point.