Fungal Transformation of an Antimicrobial Fluoroquinolone Drug During Growth on Poultry Litter Materials

Abstract

The ability of a nonpathogenic fungus, Pestalotiopsis guepini, to metabolize fluoroquinolone antimicrobial agents during growth on poultry litter materials was investigated. Sterilized rice hulls, ground corncobs, and pine shavings in glass jars covered with foil were moistened with sterile water and inoculated with P. guepini. The litter materials then were dosed with norfloxacin and incubated for 20 d. In rice-hull cultures, P. guepini produced 4 metabolites: 7-amino-1-ethyl- 6-fluoro-4-oxo-1,4-dihydroquinolone-3-carboxylic acid, N-formylnorfloxacin, N-acetylnorfloxacin, and desethylene-N-acetylnorfloxacin. In corncob cultures, the fungus produced N-formylnorfloxacin and N-acetylnorfloxacin. In pine-shavings cultures, there was little growth of the fungus and no metabolism of norfloxacin. The results suggest that fungi that grow on poultry litter may degrade residues of antimicrobial drugs.