In vitro and in vivo activities of ciprofloxacin and levofloxacin against an SHV-5 extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strain.

Activities of ciprofloxacin and levofloxacin against an SHV-5 extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae strain were studied in vitro and in vivo in septic mice using a high inoculum. Susceptibility to ciprofloxacin and levofloxacin was independent of the inoculum size. In killing curve studies, after 24 hours the initial 7.69 log10 CFU/ml increased in the control to 9.34, while it was reduced to 4.83 by ciprofloxacin and to 4.25 by levofloxacin. Mice were infected with 10(7) CFU/g of K. pneumoniae intraperitoneally. Treatment started 2 hours later, when the mean blood bacterial counts were 7.33 log10 CFU/ml, and lasted for 26 hours from the time of infection. Blood bacterial count was reduced from 7.33 log10 CFU/ml to 4.08 log10 CFU/ml by ciprofloxacin (20 mg/kg/6 hours), and to 3.60 log10 CFU/ml by levofloxacin (50 mg/kg/6 hours) 8 hours after the infection, which differed significantly from the infected untreated group. Ciprofloxacin and levofloxacin prolonged significantly the survival of mice compared with the infected untreated group (p<0.001 for both groups). There were not significant differences either in the survival (p=1.0) or in the blood bacterial counts (p=0.216 after 8 hours) between ciprofloxacin and levofloxacin group. Based on these results both ciprofloxacin and levofloxacin could be alternative therapeutic agents for the infection caused by ESBL-producing Klebsiella strains.