The combination of colistin and enrofloxacin provides an additive effect. Enrofloxacin, a synthetic,
broad-spectrum antimicrobial compound, is part of the fluoroquinoline group of antibiotics.
It is active against both Gram-negative and Gram-positive bacteria as well as mycoplasmas.
Enrofloxacin is well-absorbed after oral administration, and it is rapidly excreted in the bile and
urine, primarily as enrofloxacin and its metabolite ciprofloxacin. Colistin, an antibiotic from
the polymyxin group, exhibits bactericidal action against Gram-negative bacteria like E. coli,
Haemophilus, and Salmonella spp. It is poorly absorbed after oral administration, and serum
concentrations are generally not detectable in target species. Orally administered colistin is almost
entirely eliminated in feces.