Evaluation of levofloxacin susceptibility against strains isolated from lower urinary tract infections in the community

The aim of this study was to evaluate the in vitro activity of levofloxacin (LVX) in comparison to nalidixic acid (NAL), ofloxacin (OFX), norfloxacin (NOR), amoxicillin (AMX), cefixime (CFM), cotrimoxazole (SXT) and nitrofurantoin (FT), against 402 strains recently isolated from urine specimens in outpatient women suffering from lower urinary tract infections for which short-term treatment was not indicated. MICs were determined by the agar dilution method on Mueller-Hinton medium (Bio-Rad) according to the recommendations of the Comite de l'Antibiogramme de la Societe Francaise de Microbiologie (CA-SFM). Strains were classified as susceptible (S), intermediate (I) or resistant (R) according to the CA-SFM recommended breakpoints. Quality control was carried out using three reference strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. For E. coli, the most prevalent species (345 isolates: 85.3%), susceptibilities were as follows: AMX: 60.6%, CFM: 99.1%, NAL: 94.8%, NOR: 97.4%, OFX: 97.4%, LVX: 97.4%, SXT: 84.5%, FT: 98%. This study confirms the good in vitro activity of LVX, OFX, and CFM against strains isolated from urinary tract infections in the community and particularly against E. coli, which is by far the most prevalent pathogen, 90% of strains, with more than 97% of strains being susceptible.