High-performance liquid chromatographic determination of oxolinic acid and flumequine in the live fish feed artemia

Flumequine-loaded titanate nanotubes as antibacterial agents for aquaculture farms

Flumequine (FLUM), a quinolone-derived antibiotic is one of the most prescribed drugs in aquaculture farms. However, its intensive use becomes worrisome because of its environmental risks and the emergence of FLUM-resistant bacteria. To overcome these problems we propose in this study the encapsulation and the delivery of FLUM by titanate nanotubes (TiNTs). Optimal FLUM loading was reached by suspending the dehydrated powder nanomaterials (FLUM : TiNTs ratio = 1 : 5) in ethanol. The drug entrapment efficiency was calculated to be 80% approximately with a sustained release in PBS at 37 °C up to 5 days. Then FLUM@TiNTs was evaluated for both its in vitro drug release and antimicrobial activity against Escherichia coli (E. coli). Spectacularly high antibacterial activity compared to those of free FLUM antibiotic was obtained confirming the efficiency of TiNTs to protect FLUM from rapid degradation and transformation within bacteria improving thereby its antibacterial effect. Indeed FLUM@TiNTs was efficient to decrease gradually the bacterial viability to reach ≈5% after 5 days versus ≈75% with free FLUM. Finally, the ex vivo permeation experiments on sea bass (Dicentrachus labrax) intestine shows that TiNTs act to increase the intestinal permeation of FLUM during the experiment. Indeed the encapsulated FLUM flux increased 12 fold (1.46 μg cm² h⁻¹) compared to the free antibiotic (0.18 μg cm² h⁻¹). Thanks to its physical properties (diameter 10 nm, tubular shape…) and its high stability in the simulated intestinal medium, TiNTs are easy internalized by enterocytes, thus involving an endocytosis mechanism, and then improve intestinal permeation of FLUM. Taken together, FLUM@TiNTs hold potential as an effective approach for enhancing the antimicrobial activity of FLUM and pave the way not only for future pharmacokinetic studies in the treatment and targeting of fish infections but also for instating of novel strategies that overcome the challenges associated with the abusive use of antibiotics in fish farming.

Flumequine (FLUM), a quinolone-derived antibiotic is one of the most prescribed drugs in aquaculture farms.

Determination of flumequine enantiomers and 7-hydroxyflumequine in water and sediment by chiral HPLC coupled with hybrid quadrupole-time-of-flight mass spectrometer

A liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for simultaneous enantiomeric analysis of flumequine and its metabolite 7-hydroxyflumequine in water and sediment had been developed based on the separation method. Sediment samples were extracted with ACN and EDTA-Mcllvaine buffer solution (40:60, v/v) then were enriched and cleaned-up by Cleanert PEP solid-phase extraction cartridges. The extract solvent, solid cartridges, mobile phase ratios, and chiral separation column were all optimized to reach high sensitivity and selectivity, good peak shape, and satisfactory resolution. The results showed that the calibration curves of flumequine enantiomers and 7-hydroxyflumequine were linear in the range of 1.0 to 200.0 µg/L with correlation coefficients of 0.9822–0.9988, the mean recoveries for both the enantiomers ranged from 69.9–84.6% with relative standard deviations (RSDs) being 13.1% or below. The limits of detection (LODs) for both flumequine enantiomers were 2.5 µg/L and 5.0 µg/kg in water and sediment samples, whereas the limits of quantification (LOQs) were 8.0 µg/L and 15.0 µg/kg, respectively. While the LODs for 7-hydroxyflumequine were 3.2 µg/L in water samples and 7.0 µg/kg in sediment samples. The proposed method will be extended for studies on the degradation kinetics and environmental behaviors and providing additional information for reliable risk assessment of these chiral antibiotics.

Monitoring of multiple bacteriocins through a developed dual extraction protocol and comparison of HPLC-DAD with turbidometry as their quantification system

The present study describes the development of a simple and efficient screening system that allows identification and quantification of nine bacteriocins produced by Lactococcus lactis. Cell-free L. lactis extracts presented a broad spectrum of antibacterial activity, including Gram-negative bacteria, Gram-positive bacteria, and fungi. The characterization of their sensitivity to pH, and heat, showed that the extracts retained their antibacterial activity at extreme pH values and in a wide temperature range. The loss of antibacterial activity following treatment of the extracts with lipase or protease suggests a lipoproteinaceous nature of the produced antimicrobials. The extracts were subjected to a purification protocol that employs a two phase extraction using ammonium sulfate precipitation and organic solvent precipitation, followed by ion exchange chromatography, solid phase extraction and HPLC. In the nine fractions that presented antimicrobial activity, bacteriocins were quantified by the turbidometric method using a standard curve of nisin and by the HPLC method with nisin as the external standard, with both methods producing comparable results. Turbidometry appears to be unique in the qualitative determination of bacteriocins but the only method suitable to both separate and quantify the bacteriocins providing increased sensitivity, accuracy, and precision is HPLC.

Treatment of vibriosis in European sea bass larvae, Dicentrarchus labrax L., with oxolinic acid administered by bath or through medicated nauplii of Artemia franciscana (Kellogg): efficacy and residual kinetics

European sea bass larvae were challenged by bath with Listonella anguillarum strain 332A, 2.5×10(7) CFUmL(-1) for 1h. Fish either received no treatment or oral treatment with Artemia franciscana (Kellog) nauplii enriched with oxolinic acid, or bath treatments with oxolinic acid. Medication commenced 1day following challenge and was performed on days 1, 3 and 5 post-challenge at a dosage of 20mgL(-1) for 2h for bath treatments, while two doses each of 750 nauplii per fish were administered daily for five consecutive days in oral treatments. Cumulative mortality reached 96% for the unmedicated challenged group, 32% in the group receiving bath treatments and 17% in the group receiving medicated nauplii. Pharmacokinetic parameters of oxolinic acid were calculated in sea bass larvae, for both treatments. Steady-state concentrations of oxolinic acid of 48.0 and 75.2μgg(-1) were achieved for bath treatment and oral treatment, respectively, while the elimination half-life was calculated to be 25.1h for bath treatment and 21.7h for oral treatment.

Introduction of the HPLC method for the determination of quinolone residues in various muscle tissues

For use in veterinary sanitary control of foodstuffs and raw materials of animal origin in Slovenia, we developed a routine and confirmation analytical method for determining the residues of enrofloxacin, ciprofloxacin and flumequine in the muscle tissue of cattle, pigs and poultry. For the muscle tissue of freshwater fish, the determination of the flumequine residues was introduced. The results obtained through simultaneous determination of the residues of enrofloxacin, ciprofloxacin and flumequine showed that the values for the examined antibiotics were up to 600 times lower than the prescribed maximum residue levels (MRL). Another advantage of this method is that it covers a wide range of different fluoroquinolones.