Biotransformation of fluoroquinolone antibiotics by ligninolytic fungi – Metabolites, enzymes and residual antibacterial activity
Introduction
Fluoroquinolones represent a group of xenobiotics that are often monitored in the environment. These compounds are important antibacterial agents used in human and veterinary medicine; however, their presence in the environment can lead to the selection of resistant pathogenic bacterial strains (Hayes et al., 2004). These antibiotics enter the environment mainly via wastewater (Nakata et al., 2005, Mitani and Kataoka, 2006, Lee et al., 2007), have been found in surface waters (Speltini et al., 2010) and can also be accumulated in sewage sludge (Lillenberg et al., 2009, Li and Zhang, 2010, Jia et al., 2012), sediments or agricultural soils after application of sewage sludge or manure (Speltini et al., 2011). Sequestration of fluoroquinolones by sorption onto soil particles reduces their bioavailability, retards their abiotic and biotic degradation and therefore increases their persistence in soils and aquatic sediments (Sukul and Spiteller, 2007, Girardi et al., 2011). However, sorption on soil can also significantly decrease the toxicity of pollutants, as was demonstrated for polycyclic aromatic hydrocarbons (Čvančarová et al., 2013).
Photodegradation is the main abiotic process that eliminates antibiotics in aquatic systems such as surface waters (Cardoza et al., 2005, Sturini et al., 2012). Despite the fact that antibiotics are antimicrobial agents, microbial biotransformation represents another important mechanism in the elimination of these drugs from the environment. Microbial transformation of quinolones was reviewed by Parshikov and Sutherland (2012). Norfloxacin was found to be transformed by Mycobacterium gilvum to N-acetylnorfloxacin and N-nitrosonorfloxacin. However; although N-nitrosonorfloxacin has lower antibacterial activity, nitrosamines are potentially carcinogenic (Adjei et al., 2006). Another degradation mechanism of norfloxacin was described by Kim et al. (2011) who carried out the biodegradation using the Microbacterium sp. strain isolated from a wastewater treatment plant. Regarding fungal degradation, the biotransformation of selected fluoroquinolones mainly by a brown rot fungus was described by Wetzstein et al. (1999). Flumequine degradation was studied using the zygomycete Cunninghamella elegans (Williams et al., 2007) and transformation of ciprofloxacin, enrofloxacin and sarafloxacin by the saprobic fungus Mucor ramannianus was investigated by Parshikov et al., 1999, Parshikov et al., 2000, Parshikov et al., 2001b. The ability of the nonpathogenic fungus Pestalotiopsis guepini to metabolize norfloxacin was also studied (Parshikov et al., 2001a, Parshikov et al., 2001b, Williams et al., 2004). Another promising group of fungi that are able to transform recalcitrant compounds and possess a unique set of extracellular ligninolytic enzymes are ligninolytic fungi (Muzikář et al., 2011, Čvančarová et al., 2012, Křesinová et al., 2012). However, little is known about the biotransformation of fluoroquinolones by white rot fungi. Marengo et al. (1997) investigated the biodegradation of 14C-labeled sarafloxacin hydrochloride by the fungus Phanerochaete chrysosporium and Prieto et al. (2011) metabolized norfloxacin and ciprofloxacin by Trametes versicolor, where the latter authors identified several transformation products of the antibiotics. In a recent study, a transformation pathway of flumequine by several white rot fungi was suggested (Čvančarová et al., 2013).
The purpose of this study was first to elaborate knowledge of the degradation potential of white rot fungi for fluoroquinolones and secondly to assess possible environmental risks following from the biodegradation processes. The fungal strains Irpex lacteus, Panus tigrinus, Dichomitus squalens, T. versicolor and Pleurotus ostreatus were selected to biodegrade norfloxacin (NOR), ofloxacin (OF) and ciprofloxacin (CIP) in liquid medium. The bacteria Vibrio fischeri and duckweed Lemna minor were used as test assays to consider possible changes in ecotoxical effects related to the biodegradation. In addition, the residual antibiotic activity of the biodegradation product mixtures was estimated using several Gram-positive and Gram-negative bacteria. Multivariate data analysis was performed to elucidate correlations between identified metabolites and the remaining antibacterial activity measured in the sample solutions. An attempt was also made to estimate possible participation of ligninolytic enzymes in the degradation.
Section snippets
Chemicals
The analytical standards of the individual antibiotics (norfloxacin – NOR, CAS No 70458-96-7, ⩾98%; ofloxacin – OF, CAS No 82419-36-1, ⩾99%; ciprofloxacin – CIP, CAS No 85721-33-1, ⩾98%) were obtained from Sigma Aldrich (Steinheim, Germany). All the solvents were purchased from Merck (Darmstadt, Germany) or Chromservis (Prague, Czech Republic) and were of p.a. quality, trace analysis quality or gradient grade.
Biodegradation experiment, microorganisms and measurement of enzyme activities
The selected antibiotics were degraded separately by the white rot fungi I. lacteus
Degradation in liquid media
The residual concentrations of the selected fluoroquinolones were determined directly in the medium by HPLC/UV after 3, 6, 10 and 14 d of cultivation. The results are presented in Fig. 1. NOR, OF and CIP were eluted from the column at 8.4, 8.0 and 8.8 min, respectively. Abiotic degradation and adsorption onto the mycelium were not observed in the respective heat-killed controls.
I. lacteus was the most efficient strain and transformed NOR, OF and CIP completely after 10 d. T. versicolor reduced the
Conclusions
The results showed that fluoroquinolone antibiotics are easily degradable by ligninolytic fungi. Especially I. lacteus and T. versicolor have high degradation potential toward CIP, OF and NOR where they completely transformed the antibiotics in 10 and 14 d of cultivation. However, the results of the residual antibiotic activity test revealed that only I. lacteus has the potential to also remove this activity during the course of degradation in the case of OF and NOR. In contrast, even though CIP
Acknowledgements
We wish to thank Mrs. Hana Mikesková for providing us with the bacterial strains which were used to determine of the residual antibacterial activity. This work was supported by Competence Center TE01020218 of the Technology Agency of the Czech Republic and by the Grant No. 13-28283S of the Czech Science Foundation.
References (44)
- et al.
Breakdown products on metabolic pathway of degradation of benz[a]anthracene by a ligninolytic fungus
Chemosphere
(2006) - et al.
In vivo and in vitro polycyclic aromatic hydrocarbons degradation by Lentinus (Panus) tigrinus CBS 577.79
Bioresour. Technol.
(2010) - et al.
Biodegradation of PCBs by ligninolytic fungi and characterization of the degradation products
Chemosphere
(2012) - et al.
Influence of the bioaccessible fraction of polycyclic aromatic hydrocarbons on the ecotoxicity of historically contaminated soils
J. Hazard. Mater.
(2013) - et al.
Biodegradation of ciprofloxacin in water and soil and its effects on the microbial communities
J. Hazard. Mater.
(2011) - et al.
Toxicity evaluation with Vibrio fischeri test of organic chemicals used in aquaculture
Chemosphere
(2007) - et al.
Occurrence and fate of quinolone and fluoroquinolone antibiotics in a municipal sewage treatment plant
Water Res.
(2012) - et al.
Determination of ofloxacin, norfloxacin, and ciprofloxacin in sewage by selective solid-phase extraction, liquid chromatography with fluorescence detection, and liquid chromatography–tandem mass spectrometry
J. Chromatogr. A
(2007) - et al.
Simultaneous determination of fluoroquinolones, sulfonamides and tetracyclines in sewage sludge by pressurized liquid extraction and liquid chromatography electrospray ionization-mass spectrometry
J. Chromatogr. A
(2009) - et al.
Determination of fluoroquinolones in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography–tandem mass spectrometry
Anal. Chim. Acta
(2006)
Biodegradation of chlorobenzoic acids by ligninolytic fungi
J. Hazard. Mater.
Determination of fluoroquinolone antibiotics in wastewater effluents by liquid chromatography–mass spectrometry and fluorescence detection
Chemosphere
Regioselective transformation of ciprofloxacin to N-acetylciprofloxacin by the fungus Mucor ramannianus
FEMS Microbiol. Lett.
Degradation of the antibiotics norfloxacin and ciprofloxacin by a white-rot fungus and identification of degradation products
Bioresour. Technol.
Analytical methods for the determination of fluoroquinolones in solid environmental matrices
TrAC-Trends Anal. Chem.
Photodegradation of fluoroquinolones in surface water and antimicrobial activity of the photoproducts
Water Res.
Fungal transformation of an antimicrobial fluoroquinolone drug during growth on poultry litter materials
J. Appl. Poult. Res.
Biotransformation of flumequine by the fungus Cunninghamella elegans
Chemosphere
Transformation of the antibacterial agent norfloxacin by environmental mycobacteria
Appl. Environ. Microbiol.
Antibiotic susceptibility testing by a standardized single disk method
Am. J. Clin. Pathol.
Biodegradation of endocrine-disrupting compounds by ligninolytic fungi: mechanisms involved in the degradation
Environ. Microbiol.
Degradation of PAHs by ligninolytic enzymes of Irpex lacteus
Folia Microbiol.
Cited by (103)
Mycoremediation of different wastewater toxicants and its prospects in developing value-added products: A review
2024, Journal of Water Process Engineering