Acetylation and nitrosation of ciprofloxacin by environmental strains of mycobacteria.

To determine the ability of environmental bacteria to metabolize the frequently prescribed fluoroquinolone drug ciprofloxacin, eight Mycobacterium spp. cultures were grown for 4 days in a medium containing sorbitol and yeast extract with 100 mg x L(-1) ciprofloxacin. After the cultures had been centrifuged and the supernatants extracted with ethyl acetate, two metabolites were purified by using high-performance liquid chromatography. They were identified with liquid chromatography/electrospray ionization mass spectrometry and proton nuclear magnetic resonance spectroscopy. Ciprofloxacin was transformed to both N-acetylciprofloxacin (2.5%-5.5% of the total peak area at 280 nm) and N-nitrosociprofloxacin (6.0%-8.0% of the peak area) by Mycobacterium gilvum PYR-GCK and Mycobacterium sp. PYR100 but it was transformed only to N-acetylciprofloxacin by Mycobacterium frederiksbergense FAn9, M. gilvum ATCC 43909, M. gilvum BB1, Mycobacterium smegmatis mc2155, Mycobacterium sp. 7E1B1W, and Mycobacterium sp. RJGII-135. The results suggest that biotransformation may serve as a ciprofloxacin resistance mechanism for these bacteria.