Antibacterial activity of cefquinome against equine bacterial pathogens

Cefquinome is known for its use as an antibacterial drug in cattle and pigs. The objective of this study was to evaluate the antibacterial activity of cefquinome against equine pathogenic bacteria. The minimum inhibitory concentration (MIC) of cefquinome was determined for a total of 205 strains, which had recently been isolated in Europe from diseased horses (respiratory infection, foal septicaemia). The bactericidal activity was tested against 19 strains using the time killing method. The post-antibiotic effect (PAE) and post-antibiotic sub-MIC effect (PA SME) were determined against 12 strains. Cefquinome showed high activity against Actinobacillus equuli and streptococci (MIC90 of 0.016 and 0.032 μg/mL), Enterobacteriaceae (MIC90 = 0.125 μg/mL) and staphylococci (MIC90 = 0.5 μg/mL). The activity was limited against Rhodococcus spp. and Pseudomonas spp. Cefquinome was shown to be a time dependent bactericidal antibiotic against the target pathogens, killing occurring at a concentration close to the MIC. A PAE of 0.5–10 h was calculated against streptococci whereas no PAE was observed for Escherichia coli. A longer PA SME was determined for streptococci (3.3 to >24 h with a killing effect) and E. coli (0.5–13.9 h). Cefquinome was shown to have a broad spectrum of activity which covers many equine pathogens.