Chitosan Oligosaccharides Coupling Inhibits Bacterial Biofilm-Related Antibiotic Resistance against Florfenicol

The formation of bacterial biofilms has increased the resistance of bacteria to various environmental factors and is tightly associated with many persistent and chronic bacterial infections. Herein we design a strategy conjugating florfenicol, an antibiotic commonly used in the treatment of streptococcus, with the antimicrobial biomaterial, chitosan oligosaccharides. The results demonstrated that the florfenicol-COS conjugate (F-COS) efficiently eradicated the mature Streptococcus hyovaginalis biofilm, apparently inhibiting drug resistance to florfenicol. A quantity of 250 μg/mL F-COS showed effective inhibitory activity against planktonic cells and biofilm of the bacteria, and a 4-fold improvement of the F-COS compared to unmodified florfenicol was observed. Furthermore, the conjugate showed a broad-spectrum activity against both Gram-positive and Gram-negative bacteria. It suggested that F-COS might have a potential for application in the treatment of biofilm-related infections.

Biochar-mediated sorption of antibiotics in pig manure

Using manure contaminated with antibiotics as fertilizer is a primary source of soil pollution with antibiotics and concomitantly with antibiotic resistance genes (ARG). Bioavailable antibiotics trigger further ARG amplification during manure storage. Consequently it is aimed to facilitate the immobilization of antibiotics in manure. To this end, five biochars derived from pine cone (BCP), rice husk, sewage sludge, digestate and Miscanthus were tested as additional sorbents in liquid pig manure for sulfamethazine, ciprofloxacin, oxytetracycline and florfenicol. Non-linear sorption was best-fit using the Freundlich isotherm (R² > 0.82) and the pseudo-second-order model best described sorption kinetics (R² > 0.94). Antibiotics' sorption onto manure increased in the order sulfamethazine < florfenicol < ciprofloxacin < oxytetracycline. Admixtures of BCP to manure changed the order to sulfamethazine < oxytetracycline < florfenicol = ciprofloxacin. Generally, with the addition of biochar, sorption coefficients of florfenicol increased most (by factors>2.7) followed by sulfamethazine and ciprofloxacin. Yet, oxytetracycline was mostly mobilized probably due to competitive adsorption. Effects depended on the proportion of biochar added and the type of biochar, whereby plant-derived biochar exhibited better immobilization of antibiotics. Depending on the type and portion of biochar, admixtures to manure can be used to lower the mobility and hence bioavailability of fenicols, fluoroquinolones and sulfonamides.

pH-Controlled Drug Release by Diffusion through Silica Nanochannel Membranes

We report in this work the fabrication of a flow-through silica nanochannel membrane (SNM) for controlled drug release applications. The ultrathin SNM consists of parallel nanochannels with a uniform diameter of ∼2.3 nm and a density of 4 × 10¹² cm^-2, which provide simultaneously high permeability and size selectivity toward small molecules. The track-etched porous polyethylene terephthalate film premodified with silane on its surface was used to support the ultrathin SNM via irreversible covalent bond formation, thus offering mechanical strength, flexibility, and stability to the ultrathin SNM for continuous and long-term use. Alkylamines were subsequently grafted onto the SNM surface to modulate the "on" and "off" state of nanochannels by medium pH for controlled drug release. Thiamphenicol glycinate hydrochloride (TPG), an intestinal drug, was studied as a model to permeate through an ultrathin SNM in both simulated gastric fluid (pH = 1.2) and simulated intestinal fluid (pH = 7.5). The release in the latter case was 178 times faster than that in the former. Moreover, a nearly zero-order constant release of TPG via single-file diffusion was achieved up to 24 h, demonstrating the feasibility of sustained and continuous release of small-molecule drugs in a pH-controlled manner.

Medicinal Plants Based Products Tested on Pathogens Isolated from Mastitis Milk

Bovine mastitis a major disease that is commonly associated with bacterial infection. The common treatment is with antibiotics administered intramammary into infected quarters of the udder. The excessive use of antibiotics leads to multidrug resistance and associated risks for human health. In this context, the search for alternative drugs based on plants has become a priority in livestock medicine. These products have a low manufacturing cost and no reports of antimicrobial resistance to these have been documented. In this context, the main objective of this study was to determine the antimicrobial effect of extracts and products of several indigenous, or acclimatized plants on pathogens isolated from bovine mastitis. A total of eleven plant alcoholic extracts and eight plant-derived products were tested against 32 microorganisms isolated from milk. The obtained results have shown an inhibition of bacterial growth for all tested plants, with better results for Evernia prunastri, Artemisia absinthium, and Lavandula angustifolia. Moreover, E. prunastri, Populus nigra, and L. angustifolia presented small averages of minimum inhibitory and bactericidal concentrations. Among the plant-derived products, three out of eight have shown a strong anti-microbial effect comparable with the effect of florfenicol and enrofloxacin, and better than individual plant extracts possibly due to synergism. These results suggest an important anti-microbial effect of these products on pathogens isolated from bovine mastitis with a possible applicability in this disease.

Preparation and Performance of Poly(D,L-lactic acid)–Polyethylene Glycol–Poly(D,L-lactic acid) Electrospun Fibrous Membranes for Drug Release

In this study, poly(D,L-lactic acid)–polyethylene glycol–poly(D,L-lactic acid), hereafter referred to as PDLLA–PEG–PDLLA, triblock copolymer membranes were prepared by electrospinning. Scanning electron microscopy images revealed the morphology of the microfibers, which had a diameter ranging from 300 to 900 nm. Fourier transform infrared spectroscopy was employed for structural analysis of the PDLLA–PEG–PDLLA/florfenicol (FF) membranes, which exhibited three absorption peaks at 3455, 1684, and 1533 cm−1, respectively, indicating that the triblock copolymer and FF are very well blended in the composite membranes. Differential scanning calorimetry revealed that weak interaction possibly decreased the activity of the segment and elevated the T g from 43 °C to 46 °C. From the in vitro dissolution tests, PDLLA as a biodegradable and biocompatible polymer can improve the solubility of FF. The rate of drug release increased with increasing PEG proportion. Furthermore, tensile and nanoindentation tests demonstrated that nanofibers exhibit mechanical properties such as tensile stress (700–2800 KPa), strain (40–120%), and good toughness (0.28–0.98 GPa). In conclusion, PDLLA–PEG–PDLLA nanofibers as a carrier improve the solubility of FF and control drug release.

Effects of thiamphenicol on nitrate reduction and N2O release in estuarine and coastal sediments

Nitrate overload is an important driver of water pollution in most estuarine and coastal ecosystems, and thus nitrate reduction processes have attracted considerable attention. Antibiotics contamination is also an emerging environmental problem in estuarine and coastal regions as a result of growing production and usage of antibiotics. However, the effects of antibiotics on nitrate reduction remain unclear in these aquatic ecosystems. In this study, continuous-flow experiments were conducted to examine the effects of thiamphenicol (TAP, a common chloramphenicol antibiotic) on nitrate reduction and greenhouse gas N2O release. Functional genes involved in nitrogen transformation were also quantified to explore the microbial mechanisms of the TAP influence. Production of N2 were observed to be inhibited by TAP treatment, which implied the inhibition effect of TAP on nitrate reduction processes. As intermediate products of nitrogen transformation processes, nitrite and N2O were observed to accumulate during the incubation. Different TAP inhibition effects on related functional genes may be the microbial mechanism for the changes of nutrient fluxes, N2 fluxes and N2O release rates. These results indicate that the antibiotics residues in estuarine and coastal ecosystems may contribute to nitrate retention and N2O release, which could be a major factor responsible for eutrophication and greenhouse effects.

Impact of persulfate and ultraviolet light activated persulfate pre-oxidation on the formation of trihalomethanes, haloacetonitriles and halonitromethanes from the chlor(am)ination of three antibiotic chloramphenicols

Persulfate oxidation processes, with and without activation using ultraviolet light (respectively UV/PS and PS) have the potential to degrade anthropogenic chemicals in water. However, little is known about the impact of PS or UV/PS pre-oxidation on downstream formation of disinfection by-products (DBPs). In this study the three antibiotic chloramphenicols (chloramphenicol and two of its analogues [thiamphenicol and florfenicol], referred to collectively as CAPs), which frequently occur in wastewater-impacted source waters used by drinking water treatment plants, were selected as model antibiotic compounds. The formation of carbonaceous and nitrogenous disinfection by-products, including halomethanes, haloacetonitriles and halonitromethanes, during chlorination and chloramination preceded by PS and UV/PS was investigated. No significant concentrations of haloacetonitriles and halonitromethanes were detected during chlorination. During chloramination chloramphenicol formed a considerable amount of dichloronitromethane (e.g., 3.44 ± 0.33% mol/mol at NH2Cl dose = 1 mM) and trichloronitromethane (e.g., 0.79 ± 0.07% mol/mol at NH2Cl dose = 1 mM), compared with THM and HAN formation. PS pre-oxidation achieved a statistically significant reduction in trichloromethane formation from chlorination, and in HAN and HNM formation from chloramination. Although UV/PS slightly increased dichloroacetonitrile formation during chloramination, it significantly decreased dichloronitromethane and trichloronitromethane formation during chloramination. Overall, the use of PS and UV/PS has the potential to have contrasting impacts on DBP formation in heavily wastewater-impacted waters, depending on the disinfection method. Hence, their application needs to be carefully balanced against the downstream effect on DBP formation.

Aqueous photodegradation of antibiotic florfenicol: kinetics and degradation pathway studies

The occurrence of antibacterial agents in natural environment was of scientific concern in recent years. As endocrine disrupting chemicals, they had potential risk on ecology system and human beings. In the present study, the photodegradation kinetics and pathways of florfenicol were investigated under solar and xenon lamp irradiation in aquatic systems. Direct photolysis half-lives of florfenicol were determined as 187.29 h under solar irradiation and 22.43 h under xenon lamp irradiation, respectively. Reactive oxygen species (ROS), such as hydroxyl radical (·OH) and singlet oxygen ((1)O2) were found to play an important role in indirect photolysis process. The presence of nitrate and dissolved organic matters (DOMs) could affect photolysis of florfenicol in solutions through light screening effect, quenching effect, and photoinduced oxidization process. Photoproducts of florfenicol in DOMs solutions were identified by solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) analysis techniques, and degradation pathways were proposed, including photoinduced hydrolysis, oxidation by (1)O2 and ·OH, dechlorination, and cleavage of the side chain.

Degradation of florfenicol in water by UV/Na2S 2O 8 process

UV irradiation-activated sodium persulfate (UV/PS) was studied to degrade florfenicol (FLO), a phenicol antibiotic commonly used in aquaculture, in water. Compared with UV/H2O2 process, UV/PS process achieves a higher FLO degradation efficiency, greater mineralization, and less cost. The quantum yield for direct photolysis of FLO and the second-order rate constant of FLO with sulfate radicals were determined. The effects of various factors, namely PS concentration, anions (NO3 (-), Cl(-), and HCO3 (-)), ferrous ion, and humic acid (HA), on FLO degradation were investigated. The results showed that the pseudo-first-order rate constant increased linearly with increased PS concentration. The tested anions all adversely affected FLO degradation performance with the order of HCO3 (-) > Cl(-) > NO3 (-). Coexisting ferrous ions enhanced FLO degradation at a Fe(2+)/PS molar ratio under 1:1. HA significantly inhibited FLO degradation due to radical scavenging and light-screening effect. Toxicity assessment showed that it is capable of controlling the toxicity for FLO degradation. These findings indicated that UV/PS is a promising technology for water polluted by antibiotics, and the treatment is optimized only after the impacts of water characteristics are carefully considered.

Cathodic degradation of antibiotics: characterization and pathway analysis

Antibiotics in wastewaters must be degraded to eliminate their antibacterial activity before discharging into the environment. A cathode can provide continuous electrons for the degradation of refractory pollutants, however the cathodic degradation feasibility, efficiency and pathway for different kinds of antibiotics is poorly understood. Here, we investigated the degradation of four antibiotics, namely nitrofurazone (NFZ), metronidazole (MNZ), chloramphenicol (CAP), and florfenicol (FLO) by a poised cathode in a dual chamber electrochemical reactor. The cyclic voltammetry preliminarily proved the feasibility of the cathodic degradation of these antibiotics. The cathodic reducibility of these antibiotics followed the order of NFZ > MNZ > CAP > FLO. A decreased phosphate buffered solution (PBS) concentration as low as 2 mM or utilization of NaCl buffer solution as catholyte had significant influence on antibiotics degradation rate and efficiency for CAP and FLO but not for NFZ and MNZ. PBS could be replaced by Na2CO3-NaHCO3 buffer solution as catholyte for the degradation of these antibiotics. Reductive dechlorination of CAP proceeded only after the reduction of the nitro group to aromatic amine. The composition of the degradation products depended on the cathode potential except for MNZ. The cathodic degradation process could eliminate the antibacterial activity of these antibiotics. The current study suggests that the electrochemical reduction could serve as a potential pretreatment or advanced treatment unit for the treatment of antibiotics containing wastewaters.

Florfenicol residues in rainbow trout after oral dosing in recirculating and flow-through culture systems

Aquaflor is a feed premix for fish containing the broad spectrum antibacterial agent florfenicol (FFC) incorporated at a ratio of 50% (w/w). To enhance the effectiveness of FFC for salmonids infected with certain isolates of Flavobacterium psychrophilum causing cold water disease, the FFC dose must be increased from the standard 10 mg·kg⁻¹ body weight (BW)·d⁻¹ for 10 consecutive days. A residue depletion study was conducted to determine whether FFC residues remaining in the fillet tissue after treating fish at an increased dose would be safe for human consumption. Groups of Rainbow Trout Oncorhynchus mykiss (total n = 144; weight range, 126-617 g) were treated with FFC at 20 mg·kg⁻¹ BW·d⁻¹ for 10 d in a flow-through system (FTS) and a recirculating aquaculture system (RAS) each with a water temperature of ∼13°C. The two-tank RAS included a nontreated tank containing 77 fish. Fish were taken from each tank (treated tank, n = 16; nontreated tank, n = 8) at 6, 12, 24, 48, 72, 120, 240, 360, and 480 h posttreatment. Florfenicol amine (FFA) concentrations (the FFC marker residue) in skin-on fillets from treated fish were greatest at 12 h posttreatment (11.58 μg/g) in the RAS and were greatest at 6 h posttreatment (11.09 μg/g) in the FTS. The half-lives for FFA in skin-on fillets from the RAS and FTS were 20.3 and 19.7 h, respectively. Assimilation of FFC residues in the fillets of nontreated fish sharing the RAS with FFC-treated fish was minimal. Florfenicol water concentrations peaked in the RAS-treated tank and nontreated tanks at 10 h (453 μg/L) and 11 h (442 μg/L) posttreatment, respectively. Monitoring of nitrite concentrations throughout the study indicated the nitrogen oxidation efficiency of the RAS biofilter was minimally impacted by the FFC treatment.

Concentration-dependent photodegradation kinetics and hydroxyl-radical oxidation of phenicol antibiotics

Thiamphenicol and florfenicol are two phenicol antibiotics widely used in aquaculture and are ubiquitous as micropollutants in surface waters. The present study investigated their photodegradation kinetics, hydroxyl-radical (OH) oxidation reactivities and products. Firstly, the photolytic kinetics of the phenicols in pure water was studied as a function of initial concentrations (C0) under UV-vis irradiation (λ>200nm). It was found that the kinetics was influenced by C0. A linear plot of the pseudo-first-order rate constant vs C0 was observed with a negative slope. Secondly, the reaction between the phenicol antibiotics and OH was examined with a competition kinetic method under simulated solar irradiation (λ>290nm), which quantified their bimolecular reaction rate constants of (2.13±0.02)×10(9)M(-1)s(-1) and (1.82±0.10)×10(9)M(-1)s(-1) for thiamphenicol and florfenicol, respectively. Then the corresponding OH oxidated half-lives in sunlit surface waters were calculated to be 90.5-106.1h. Some main intermediates were formed from the reaction, which suggested that the two phenicols underwent hydroxylation, oxygenation and dehydrogenation when OH existed. These results are of importance to assess the phenicol persistence in wastewater treatment and sunlit surface waters.

The effects of the antibiotics ampicillin, florfenicol, sulfamethazine, and tylosin on biogas production and their degradation efficiency during anaerobic digestion

The impacts of four common animal husbandry antibiotics (ampicillin, florfenicol, sulfamethazine, and tylosin) on anaerobic digestion (AD) treatment efficiency and the potential for antibiotic degradation during digestion were evaluated. Sulfamethazine and ampicillin exhibited no impact on total biogas production up to 280 and 350 mg/L, respectively, although ampicillin inhibited biogas production rates during early stages of AD. Tylosin reduced biogas production by 10-38% between 130 and 913 mg/L. Florfenicol reduced biogas by ≈ 5%, 40% and 75% at 6.4, 36 and 210 mg/L, respectively. These antibiotic concentrations are higher than commonly seen for mixed feedlot manure, so impacts on full scale AD should be minimal. Antibiotic degradation products were found, confirming AD effectively degraded ampicillin, florfenicol, and tylosin, although some products were persistent throughout the process. Contamination of AD solid and liquid effluents with sulfamethazine and antibiotic transformation products from florfenicol and tylosin could present an environmental concern.

Atmospheric pressure ionization-tandem mass spectrometry of the phenicol drug family

In this work, the mass spectrometry behaviour of the veterinary drug family of phenicols, including chloramphenicol (CAP) and its related compounds thiamphenicol (TAP), florfenicol (FF) and FF amine (FFA), was studied. Several atmospheric pressure ionization sources, electrospray (ESI), atmospheric pressure chemical ionization and atmospheric pressure photoionization were compared. In all atmospheric pressure ionization sources, CAP, TAP and FF were ionized in both positive and negative modes; while for the metabolite FFA, only positive ionization was possible. In general, in positive mode, [M + H](+) dominated the mass spectrum for FFA, while the other compounds, CAP, TAP and FF, with lower proton affinity showed intense adducts with species present in the mobile phase. In negative mode, ESI and atmospheric pressure photoionization showed the deprotonated molecule [M-H](-), while atmospheric pressure chemical ionization provided the radical molecular ion by electron capture. All these ions were characterized by tandem mass spectrometry using the combined information obtained by multistage mass spectrometry and high-resolution mass spectrometry in a quadrupole-Orbitrap instrument. In general, the fragmentation occurred via cyclization and losses or fragmentation of the N-(alkyl)acetamide group, and common fragmentation pathways were established for this family of compounds. A new chemical structure for the product ion at m/z 257 for CAP, on the basis of the MS(3) and MS(4) spectra is proposed. Thermally assisted ESI and selected reaction monitoring are proposed for the determination of these compounds by ultra high-performance liquid chromatography coupled to tandem mass spectrometry, achieving instrumental detection limits down to 0.1 pg.

Aquatic toxicity of four veterinary drugs commonly applied in fish farming and animal husbandry

Doramectin (DOR), metronidazole (MET), florfenicol (FLO), and oxytetracycline (OXT) are among the most widely used veterinary drugs in animal husbandry or in aquaculture. Contamination of the environment by these pharmaceuticals has given cause for concern in recent years. Even though their toxicity has been thoroughly analyzed, knowledge of their ecotoxicity is still limited. We investigated their aquatic toxicity using tests with marine bacteria (Vibrio fischeri), green algae (Scenedesmus vacuolatus), duckweed (Lemna minor) and crustaceans (Daphnia magna). All the ecotoxicological tests were supported by chemical analyses to confirm the exposure concentrations of the pharmaceuticals used in the toxicity experiments, since deviations from the nominal concentration can result in underestimation of biological effects. It was found that OXT and FLO have a stronger adverse effect on duckweed (EC50=3.26 and 2.96mgL(-1) respectively) and green algae (EC50=40.4 and 18.0mgL(-1)) than on bacteria (EC50=108 and 29.4mgL(-1)) and crustaceans (EC50=114 and 337mgL(-1)), whereas MET did not exhibit any adverse effect in the tested concentration range. For DOR a very low EC50 of 6.37×10(-5)mgL(-1) towards D. magna was determined, which is five orders of magnitude lower than values known for the toxic reference compound K2Cr2O7. Our data show the strong influence of certain veterinary drugs on aquatic organisms and contribute to a sound assessment of the environmental hazards posed by commonly used pharmaceuticals.

Modeling manure colloid-facilitated transport of the weakly hydrophobic antibiotic florfenicol in saturated soil columns

Field application of livestock manure introduces animal hormones and veterinary antibiotics into the environment. Colloids present in manure may potentially intensify the environmental risk of groundwater pollution by colloid-facilitated contaminant transport. The transport behavior of the veterinary antibiotic florfenicol in saturated homogeneously packed soil columns has been investigated in both the presence and absence of manure colloids. Results show that facilitated transport of florfenicol is significant in the presence of manure colloids. Multiple chemical and physical processes caused by the presence of manure colloids were considered to contribute to facilitated transport. Florfenicol breakthrough curves (BTCs) were fit well by two models. The two-site nonequilibrium adsorption contaminant transport model suggested the mechanisms for facilitated florfenicol transport are as follows: manure colloids decrease the sorption capacity of florfenicol to soil, enhance the instantaneous equilibrium adsorption, and suppress the time-dependent kinetic adsorption processes. The colloid-facilitated model further evaluated the partition coefficient of florfenicol to colloids and indicated that cotransport has little contribution. A stepwise inverse model fitting approach resulted in robust parameter estimation. The adoption of the nonlinear Freundlich adsorption equation in the two-site nonequilibrium model significantly increased the fit of the model to the breakthrough curves.

Light-source-dependent effects of main water constituents on photodegradation of phenicol antibiotics: mechanism and kinetics

Thiamphenicol and florfenicol are two phenicol antibiotics commonly used in aquaculture. Photodegradation experiments on these phenicols were performed in aqueous solutions under irradiation of different light sources. We found under UV-vis irradiation (lamda >200 nm) they photodegraded the fastest in seawater, followed by pure water and freshwater, whereas under solar or simulated sunlight (lamda >290 nm), they photodegraded in freshwater only. The effects of Cl- (the dominant seawater constituent), humic acids (HA, main constituents in freshwater) and other water constituents on the photodegradation of the antibiotics as a function of different light sources were studied so as to interpret the light-source-dependent effects of different waters. Under UV-vis irradiation, Cl- was found to promote singlet oxygen ((1)O2) formation and accelerated the photodegradation of phenicols, whereas the phenicols did not photolyze under simulated solar irradiation, irrespective of Cl-. In contrast, the presence of HA inhibited phenicol photolysis under UV-vis irradiation through competitive photoabsorption, but HA photosensitized degradation under simulated solar irradiation. Under UV-vis irradiation, the wavelength-averaged (200-290 nm) quantum yields for thiamphenicol and florfenicol in pure water were 0.022 +/- 0.001 and 0.029 +/- 0.001, respectively. Their solar photolytic half-lives in freshwater were 186 +/- 17 h and 99 +/- 16 h, respectively. UV-vis photodegradation intermediates were identified by HPLC-MS/MS, and degradation pathways were proposed. These involve photoinduced hydrolysis, dechlorination, self-sensitized photo-oxidation processvia (1)O2, and chlorination. These results are of importance toward the goal of assessing the persistence of phenicols in wastewater treatment and the environment.

The influence of radiation sterilization on thiamphenicol

The effect of ionising radiation, applied in the form of an electron beam, in the doses of 25, 100 and 400 kGy on the physical and chemical properties of thiamphenicol in solid phase has been studied by organoleptic analysis (form, colour, smell, solubility, clarity) and spectroscopic methods (UV, IR, EPR), chromatography (TLC), SEM observations, X-ray diffraction, polarimetry and thermal method (DSC). The above-discussed results have proved that on irradiation with a dose of 25 kGy no significant changes appear in thiamphenicol, apart from the formation of free radicals of the lifetime of over 352 days. On irradiation with much higher doses (100 and 400 kGy) no changes were observed in the IR spectra but the UV line intensities slightly increased at lambda(max)=266 and 273 nm, the colour of the powder changed, the radiolysis products appeared as detected by TLC, changes were also observed in the XRD, SEM pictures, the melting point values (DSC) and optical rotation. On the basis of DSC results a linear relation was found between the irradiation dose and the decrease in the melting point and increase in the enthalpy of melting, characterised by high correlation coefficients of r=0.9839 and 0.9622, respectively. Moreover, a linear relation was established between the optical rotation angle and the irradiation dose, alpha(D) ( degrees )=f(dose), characterised by the correlation coefficient r=0.9874. The results obtained indicate that thiamphenicol can be safely subjected to radiation sterilization by the standard dose of 25 kGy.

Pharmacokinetics of florfenicol and its metabolite, florfenicol amine, in dogs

A study on the bioavailability and pharmacokinetics of florfenicol was conducted in six healthy dogs following a single intravenous (i.v.) or oral (p.o.) dose of 20 mg kg(-1) body weight (b.w.). Florfenicol concentrations in serum were determined by a high-performance liquid chromatography/mass spectrometry. Plasma concentration-time data after p.o. or i.v. administration were analyzed by a non-compartmental analysis. Following i.v. injection, the total body clearance was 1.03 (0.49) L kg(-1)h(-1) and the volume of distribution at steady-state was 1.45 (0.82) L kg(-1). Florfenicol was rapidly distributed and eliminated following i.v. injection with 1.11 (0.94)h of the elimination half-life. After oral administration, the calculated mean C(max) values (6.18 microg ml(-1)) were reached at 0.94 h in dogs. The elimination half-life of florfenicol was 1.24 (0.64) h and the absolute bioavailability (F) was achieved 95.43 (11.60)% after oral administration of florfenicol. Florfenicol amine, the major metabolite of florfenicol, was detected in all dogs after i.v. and p.o. administrations.

Old dogs that learn new tricks: Modified antimicrobial agents that escape pre-existing resistance mechanisms

Increasing numbers of resistant bacteria and decreasing numbers of efficient antimicrobial agents demand for the development of new highly potent antimicrobial agents. The two main directions for the development of new antimicrobial agents are either the development of completely novel antimicrobial agents, or the modification of already existing antimicrobial molecules. The second direction proved to be a more successful and cost-efficient way of generating new antimicrobial agents. For this, chemical modifications have been included which render the antimicrobial agents insensitive to prevalent bacterial resistance mechanisms. However, detailed knowledge of the resistance mechanisms is indispensable. Molecular analysis of resistance mechanisms provides the required data to identify critical target structures. Furthermore, modification of antimicrobial agents makes it possible to escape known resistance mechanisms. In this report, two examples for such successful developments, one from human medicine (telithromycin) and the other from veterinary medicine (florfenicol), are presented.

Optimization and validation of a micellar electrokinetic chromatographic method for the analysis of florfenicol

We have optimized a micellar electrokinetic capillary chromatographic method for the separation of florfenicol and florfenicol amine, its degradation product. The separation was carried out using a 50mM sodium borate buffer (pH 9.0) containing 25mM of sodium dodecyl sulphate. The method selectivity was proven by the simultaneous separation of florfenicol and two structural antibiotics, chloramphenicol and thiamphenicol. The same system can also be applied for the quantitative determination of these antibiotics. The method was then validated regarding linearity, precision and accuracy.

Stability of florfenicol in drinking water

Florfenicol, a broad-spectrum antibiotic, is being developed for veterinary application as an oral concentrate intended for dilution with drinking water. When a drug product is dosed via drinking water in a farm setting, a number of variables, including pH, chlorine content, hardness of the water used for dilution, and container material, may affect its stability, leading to a decrease in drug potency. The stability of florfenicol after dilution of Florfenicol Drinking Water Concentrate Oral Solution, 23 mg/mL, with drinking water was studied. A stability-indicating, validated liquid chromatographic method was used to evaluate florfenicol stability at 25 degrees C at 5, 10, and 24 h after dilution. The results indicate that florfenicol is stable under a range of simulated field conditions, including various pipe materials and conditions of hard or soft and chlorinated or nonchlorinated water at low or high pH. Significant degradation (> 10%) was observed only for isolated combinations in galvanized pipes. Analysis indicated that the florfenicol concentration in 8 of the 12 water samples stored in galvanized pipes remained above 90% of the initial concentration (100 mg/L) for 24 h after dilution.

The effects of certain antibiotics on biogas production in the anaerobic digestion of pig waste slurry

Antibiotics commonly used in the treatment of pigs - amoxicillin trihydrate, oxytetracycline hydrochloride and thiamphenicol were added at different concentrations to aliquots of pig waste slurry plus anaerobic sludge in serum bottles. The biogas production and methane concentration in the headspace were monitored to determine the effect of the antibiotics on the anaerobic process. With thiamphenicol significant differences in methane production were found for concentrations of 80 and 160 mg l(-1) slurry. Compared to the control, only minor differences in methane production were noted in the bottles to which amoxicillin (60 and 120 mg l(-1)) had been added. Methane production was about the same for the bottles with different oxytetracycline concentrations (125 and 250 mg l(-1)) and for the control.

Lack of carcinogenicity of thiamphenicol in F344 rats

The carcinogenicity of thiamphenicol (TAP), an antibiotic drug, was examined in Fischer 344 rats of both sexes. TAP was given ad lib. in drinking water at levels of 0 (control), 125 or 250 ppm to groups of 50 male and 50 female rats for 2 yr. The treatment did not affect mortality and no toxic lesions were specifically induced. Furthermore, the incidence of tumours in the treated groups did not show any significant dose-related increase as compared with the control group. The results thus indicate that TAP is neither toxic nor carcinogenic, for any organs or tissues of F344 rats when given continuously at levels of 125 or 250 ppm in drinking water for 2 yr.

Planar chromatographic and liquid chromatographic analysis of thiamphenicol in bovine and human plasma

A planar chromatographic (PC) method was developed to determine thiamphenicol in human and bovine plasma with florphenicol as internal standard. The performance of the method was compared with that of a liquid chromatographic method. Recovery of extraction method developed for plasma was 81.51 +/- 2.85%. Reproducibilities of the PC assay performed with various PC plates were also good.

Effects of florfenicol, chloramphenicol, and thiamphenicol on phagocytosis, chemiluminescence, and morphology of bovine polymorphonuclear neutrophil leukocytes

Florfenicol, chloramphenicol, and thiamphenicol were tested in vitro to determine their potential toxic effects on bovine neutrophils. Antibiotics were tested at 4000, 2000, and 10 micrograms/ml of incubation mixture. Percentage phagocytosis was determined by incubations with neutrophils isolated from milk of five cows and 32P-labeled Staphylococcus aureus and 5% skim milk. The effect of 4000 micrograms of each antibiotic on chemiluminescence was determined on neutrophils isolated from mammary secretions of three nulliparous heifers. Morphological evaluation by transmission and scanning electron microscopy was performed on neutrophils isolated from two heifers at antibiotic concentrations of 4000 and 10 micrograms/ml. Chloramphenicol depressed phagocytosis at the high and medium doses and blocked chemiluminescence activity at the high dose. No effects were observed for florfenicol and thiamphenicol. Transmission electron microscopic examination showed that at the high concentration of drugs, 99, 99, 97, and 76% of the neutrophils treated with florfenicol, chloramphenicol, thiamphenicol, and dimethyl sulfoxide were abnormal. Examination by scanning electron microscopy showed that the percentage of neutrophils without pseudopodia averaged 67, 94, 32, and 16%, respectively. Results indicated that neither florfenicol nor thiamphenicol altered neutrophil function, but they did alter neutrophil morphology, although to a lesser extent than did chloramphenicol.