Activity of levofloxacin and ciprofloxacin against urinary pathogens

This study compares the antibacterial activities of levofloxacin and ciprof loxacin against recently isolated urinary tract pathogens, by evaluating th eir MICs and MBCs in accordance with NCCLS susceptibility tests, time-kill curves and interference with bacterial adhesion to uroepithelial cells. A t otal of 200 clinical isolates was tested, including the species Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, Providen cia rettgeri, Pseudomonas aeruginosa, Enterococcus faecalis; Staphylococcus aureus and Staphylococcus epidermidis. All E. coli isolates were susceptib le to levofloxacin and only one was resistant to ciprofloxacin, and there w ere no differences between l-lactamase-positive and -negative strains. K. p neumoniae strains resistant to ciprofloxacin were also resistant to levoflo xacin. Methicillin-resistant S. aureus seemed to be less susceptible than m ethicillin-susceptible strains to these quinolones. S. epidermidis strains were susceptible to levofloxacin and ciprofloxacin, with the exception of t wo isolates. Incubation of S. aureus and E. coli with subinhibitory antimic robial concentrations reduced their capacity to adhere to uroepithelial cel ls; this was statistically significant at 0.25 x MIC with respect to contro ls (P < 0.05). Inhibition of adhesion ranged from 36 to 43% when bacteria w ere incubated in the presence of 0.25 x MIC of levofloxacin and ciprofloxac in, and from 10 to 27% at 0.125 x MIC. These findings suggest that levoflox acin is an effective alternative to ciprofloxacin in the treatment of urina ry tract infections and that sub-inhibitory concentrations may contribute t o efficacy.