Microbiological Transformation of Enrofloxacin by the Fungus Mucor ramannianus

Abstract

Enrofloxacin metabolism by Mucor ramannianus was investigated as a model for the biotransformation of veterinary fluoroquinolones. Cultures grown in sucrose-peptone broth were dosed with enrofloxacin. After 21 days, 22% of the enrofloxacin remained. Three metabolites were identified: enrofloxacin N-oxide (62% of the total absorbance), N-acetylciprofloxacin (8.0%), and desethylene-enrofloxacin (3.5%).Fluoroquinolones are synthetic antimicrobial agents that are active against a broad spectrum of pathogenic gram-negative bacteria as well as some gram-positive bacteria and mycoplasmas (10). Several fluoroquinolones are used in clinical medicine, and enrofloxacin and sarafloxacin have been approved in the United States for veterinary use (4). The major metabolite of enrofloxacin in animals is ciprofloxacin, produced by N deethylation of the ethylpiperazine ring (21).The persistence of veterinary fluoroquinolones and the types of metabolites that result from their microbial conversion in the environment have been little known until recent years (6, 12, 22, 23; H. G. Wetzstein, Abstr. 99th Gen. Meet. Am. Soc. Microbiol. abstr. Q-262, p. 583, 1999). Currently, there is a question as to whether the use of fluoroquinolones in poultry causes the replacement of fluoroquinolone-sensitive coliform bacteria by resistant strains (2, 13).Cultures of wood-decaying basidiomycetes, including strains found in manure, have been shown to convert enrofloxacin to CO 2 and at least 11 other metabolites (12,22). Since other pathways are likely to be used by different organisms involved in the bioconversion of fluoroquinolones in the environment, we investigated the transformation of enrofloxacin by a typical zygomycetous soil fungus.Mucor ramannianus strain R-56, which had been isolated from a mushroom collected in a forest in Arkansas (17), was maintained on agar slants (14,18). Triplicate cultures for experiments were grown in sucrose-peptone broth (17) for 2 days. Enrofloxacin [1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid], as the hydrochloride, was a gift from Bayer Corp., Shawnee, Kans. Enrofloxacin hydrochloride was dissolved in 20 mM aqueous KOH and filter sterilized; 1.0 ml was added to each flask to make a final concentration of 253 M enrofloxacin. The cultures were then incubated for an additional 21 days. Cultures without enrofloxacin and dosed, noninoculated controls were also incubated.Methylene chloride extracts of cultures and controls were analyzed by high-performance liquid chromatography (HPLC) (17), using a Phenomenex (Torrance, Calif.) Prodigy 5-m ODS-3 column (10 by 250 mm) with a water-acetic acid-methanol gradient (17). The flow rate was 2.5 ml min Ϫ1 ; metabolites were quantified by the peak areas at 280 nm.For direct exposure probe-electron ionization (DEP/EI) mass spectrometry (17), the quadrupole was scanned from m/z 50 to 650. For liquid chromatography-electrospray ionization (LC/ESI) mass spectrometry (17), a Vydac RP-18 pharmaceutical (5-m) microbore column (...

Modification of Norfloxacin by a Microbacterium sp. Strain Isolated from a Wastewater Treatment Plant

“…In contrast, the nonoxidative 8-defluorination of sparfloxacin and lomefloxacin, which have two F atoms each, is photochemical (17,19). 6-Defluoro-6-hydroxy and desethylene fluoroquinolones may be produced abiotically by photochemical reactions (10,19,46) as well as by fungal biodegradation (40,(51)(52)(53). The labile piperazine rings of fluoroquinolones can be desethylated by both abiotic and biotic processes (10,46,51).…”

“…The metabolism of fluoroquinolones by environmental brown rot fungi is well understood (51)(52)(53), and some metabolic pathways for fluoroquinolones have also been determined for other fungi (40)(41)(42). Ring oxidation or hydroxylation is generally the first step in fungal degradation of fluoroquinolones (51,53).…”

Chemical and toxicological evaluation of an emerging pollutant (enrofloxacin) by catalytic wet air oxidation and ozonation in aqueous solution

“…As described above, LC-MS/MS in ESI (+) mode was used to monitor and identify the composition of reaction mixture at different treatment time intervals. Eleven primary degradation products (Scheme 1) were proposed on the basis of their mass spectra and comparison of their fragmentation patterns by means of related studies (Parshikov et al, 2000;Dewitte et al, 2008). Among the eleven primary degradation products, compounds 1, 2, 3, 4, 7, 8 and 11 were also described in previous reports.…”

Synthesis of ciprofloxacin-conjugated poly (L-lactic acid) polymer for nanofiber fabrication and antibacterial evaluation

“…20 A polyester conjugate of ciprofloxacin has also been prepared through the acid functional group. 21 Ciprofloxacin is reported as a broad spectrum antibiotic used to treat a wide variety of bacterial infections. 22 The mechanism of action of this class of antibiotics is via inhibition of cytoplasmic DNA gyrase or topoisomerase IV, which are required for bacterial DNA replication, 23 and bacterial resistance arises primarily by amino acid substitution within these target enzymes.…”