In vitro and in vivo antibacterial activities of furazolidone

Abstract

The in vitro activity of furazolidone (FZ) was assessed by determination of minimum inhibitory concentration (MIC) and zone diameter breakpoints using the methodology and criteria recommended by the National Committee for Clinical Laboratory Standards and British Society for Antimicrobial Chemotherapy. The results were further analyzed by regression line and error rate-bounded method. For categories of sensitive, intermediate, and resistant, MICs of 5.0.51, >0.51 to <0.67, and ..0.67 ug/ml, respectively, and inhibition zone diameters of .25, <25 to >23, and 55.23 mm, respectively, were obtained based on the pharmacokinetics data of orange-spotted grouper administered with 10 ppm FZ by bath. Based on the computed MIC's and inhibition zone breakpoints for FZ, the control strains of Escherichia coli, Edwardsiella tarda, Listonella anguillarum and Photobacterium damselae subsp. damselae were classified as sensitive, Aeromonas hydrophila was intermediate, and all tested Vibrio species (V. parahaemolyticus, V. alginolyticus, V. harveyi and V. salmonicida) were resistant. For the field isolates, except for all Vibrio species which were still resistant, 15% of Ed. tarda, 33% of L. anguillarum, 70% of A. hydrophila and 100% of P. damselae subsp. damselae were also found resistant to FZ. The in vivo efficacy of FZ after P. damselae subsp. damselae experimental infection of orange-spotted grouper followed by bath treatment of 10 ppm FZ at different exposure periods was also evaluated. The results indicated that FZ in bath for 15-min has no bactericidal effect, while therapeutic effect was observed when treatment time is maintained for longer than 6 h.