In vitro antimicrobial activity of generic and brand-name Levofloxacin against clinical and ATCC strains E. coli and S. aureus

In vitro antimicrobial activity between generic and brand-name Levofloxacin was evaluated against isolated strains collected in 3 Colombia hospitals: Staphylococcus aureus and Escherichia coli.  Initially, active substance was quantified using the methodologies identified by the United States Pharmacopeia (USP) 38 NF 32, chromatographic conditions were validated and standardized. The minimum inhibitory concentration (MIC) of Levofloxacin was determined in accordance with the Clinical and Laboratory Standards Institute (CLSI). Growth curves were then performed to determine the maximum growth time of the bacteria in order to determine the MIC at the maximum growth time. Different brands evaluated did not present any difference with MIC of 0.125, 0.062, 0.031, 0.062 and 0.125 µg/ml for  E. Coli ATCC, E. Coli Tropical, S aureus sensible ATCC, S aureus resistant ATCC and S. luteum, respectively. The in vitro antibacterial activity of levofloxacin against E coli Tropically and S luteum are reported for the first time.   Key words: Quinolones, levofloxacin, minimum inhibitory concentration (MIC), Staphylococcus aureus and Escherichia coli (MeSH).