Antibacterial therapeutics for the treatment of chytrid infection in amphibians: Columbus's egg?

BACKGROUND: The establishment of safe and effective protocols to treat chytridiomycosis in amphibians is urgently required. In this study, the usefulness of antibacterial agents to clear chytridiomycosis from infected amphibians was evaluated. RESULTS: Florfenicol, sulfamethoxazole, sulfadiazine and the combination of trimethoprim and sulfonamides were active in vitro against cultures of five Batrachochytrium dendrobatidis strains containing sporangia and zoospores, with minimum inhibitory concentrations (MIC) of 0.5-1.0 µg/ml for florfenicol and 8.0 µg/ml for the sulfonamides. Trimethoprim was not capable of inhibiting growth but, combined with sulfonamides, reduced the time to visible growth inhibition by the sulfonamides. Growth inhibition of B. dendrobatidis was not observed after exposure to clindamycin, doxycycline, enrofloxacin, paromomycin, polymyxin E and tylosin. Cultures of sporangia and zoospores of B. dendrobatidis strains JEL423 and IA042 were killed completely after 14 days of exposure to 100 µg/ml florfenicol or 16 µg/ml trimethoprim combined with 80 µg/ml sulfadiazine. These concentrations were, however, not capable of efficiently killing zoospores within 4 days after exposure as assessed using flow cytometry. Florfenicol concentrations remained stable in a bathing solution during a ten day period. Exposure of Discoglossus scovazzi tadpoles for ten days to 100 µg/ml but not to 10 µg florfenicol /ml water resulted in toxicity. In an in vivo trial, post metamorphic Alytes muletensis, experimentally inoculated with B. dendrobatidis, were treated topically with a solution containing 10 µg/ml of florfenicol during 14 days. Although a significant reduction of the B. dendrobatidis load was obtained, none of the treated animals cleared the infection. CONCLUSIONS: We thus conclude that, despite marked anti B. dendrobatidis activity in vitro, the florfenicol treatment used is not capable of eliminating B. dendrobatidis infections from amphibians.

Cutaneous hyalohyphomycosis in a girdled lizard (Cordylus giganteus) caused by the Chrysosporium anamorph of Nannizziopsis vriesii and successful treatment with voriconazole.

The Chrysosporium anamorph of Nannizziopsis vriesii was associated with dermatomycosis and high mortality in a group of captive giant girdled lizards (Cordylus giganteus). Treatment of one of the infected girdled lizards with voriconazole, which was selected on the basis of in vitro sensitivity testing of the isolate, resulted in resolution of lesions and negative fungal cultures from the skin. Three hours after oral administration of 10 mg/kg, the plasma level of voriconazole exceeded the 0.25-µg/mL minimal inhibitory concentration tenfold. In conclusion, administration of voriconazole at 10 mg/kg of body weight once daily for 10 weeks resulted in clinical cure and was well tolerated. A longer follow-up time and larger studies will be necessary to determine the long-term efficacy and safety of this treatment in giant girdled lizards.

Combined pharmacokinetic and urodynamic study of the effects of oral administration of phenylpropanolamine in female Beagle dogs.

This study investigated the differences in pharmacokinetic, urodynamic and haemodynamic parameters after administration of two dosages of phenylpropanolamine (PPA) in female Beagle dogs. Blood was collected and urethral pressure profiles were performed over 24 h periods following single or three times daily (T(0),T(6h),T(12h)) administration of PPA. The maximal concentration (C(max)) was reached 2 h after PPA administration (T(max)) and the half-life (T((1/2))) was 4 h. Three times daily administration induced an increase in C(max) due to bioaccumulation. A significant increase in urethral resistance, compared to the control group, was observed at T(max) after 1 week of once daily administrations, but not when PPA was administered every 6 h during the day, despite higher plasma concentrations following more frequent dosing. An increase in mean arterial pressure was compensated by a decreased heart rate. Clinical efficacy with the temporary increase in urethral resistance following single daily administration of PPA in dogs suffering from urethral sphincter mechanism incompetence (USMI) needs to be further investigated in a randomised clinical trial.

Designing a treatment protocol with voriconazole to eliminate Aspergillus fumigatus from experimentally inoculated pigeons.

To investigate the efficacy of voriconazole for the treatment of aspergillosis, three groups of six racing pigeons (Columba livia domestica) were inoculated in the apical part of the right lung with 2x10(7) conidia of an avian derived Aspergillus fumigatus strain. The minimal inhibitory concentration of voriconazole for this strain was 0.25 microg/ml. In two groups, voriconazole treatment was started upon appearance of the first clinical signs and continued for fourteen days. The third group was sham treated. The voriconazole-treated pigeons received voriconazole orally at a dose of 10 mg/kg body weight (BW) q12h (group 1) or 20 mg/kg BW q24h (group 2). Sixteen days post-inoculation all surviving pigeons were euthanized. Weight loss, clinical scores, daily mortality, lesions at necropsy and isolation of A. fumigatus were compared between all groups. In both voriconazole-treated groups, a significant reduction in clinical signs and lesions was observed. Administering voriconazole at 10 mg/kg BW q12h eliminated A. fumigatus and administering voriconazole at 20 mg/kg BW q24h reduced A. fumigatus isolation rates. Mild histological liver abnormalities were found in group 1 (10 mg/kg BW q12h), while mild histological as well as macroscopic liver abnormalities were found in group 2 (20 mg/kg BW q24h). In conclusion, voriconazole at 10 mg/kg BW q12h in pigeons reduces clinical signs and eliminates A. fumigatus in racing pigeons experimentally infected with A. fumigatus.

Induction of the carrier state in pigeons infected with Salmonella enterica subspecies enterica serovar typhimurium PT99 by treatment with florfenicol: a matter of pharmacokinetics.

Paratyphoid caused by Salmonella enterica subsp. enterica serovar Typhimurium is the main bacterial disease in pigeons. The ability of Salmonella serovar Typhimurium to persist intracellularly inside pigeon macrophages results in the development of chronic carriers, which maintain the infection in the flock. In this study, the effect of drinking-water medication with florfenicol on Salmonella infection in pigeons was examined. The pharmacokinetics of florfenicol in pigeons revealed a relatively high volume of distribution of 2.02 liters/kg of body weight and maximum concentrations in plasma higher than the MICs for the Salmonella strain used (4 microg/ml) but quick clearance of florfenicol due to a short half-life of 1.73 h. Together with highly variable bioavailability and erratic drinking-water uptake, these parameters resulted in the inability to reach a steady-state concentration through the continuous administration of florfenicol in the drinking water. Florfenicol was capable of reducing only moderately the number of intracellular salmonellae in infected pigeon macrophages in vitro. Only at high extracellular concentrations (>16 microg/ml) was a more-than-10-fold reduction of the number of intracellular bacteria noticed. Florfenicol treatment of pigeons via the drinking water from 2 days after experimental inoculation with Salmonella serovar Typhimurium until euthanasia at 16 days postinoculation resulted in a reduction of Salmonella shedding and an improvement in the fecal consistency. However, internal organs in florfenicol-treated pigeons were significantly more heavily colonized than those in untreated pigeons. In conclusion, the oral application of florfenicol for the treatment of pigeon paratyphoid contributes to the development of carrier animals through sub-MIC concentrations in plasma that do not inhibit intracellular persistency.

Transvenous electrical cardioversion of atrial fibrillation in six horses using custom made cardioversion catheters.

Pharmacological conversion of atrial fibrillation (AF) to sinus rhythm in horses can be difficult. The objective of this study was to investigate the feasibility of transvenous electrical cardioversion with custom made catheters in eight horses, of which three had failed cardioversion using quinidine sulfate. Two cardioversion catheters and one pacing/sensing electrode were inserted via the right jugular vein and placed using ultrasound guidance into the left pulmonary artery, the right atrium and the right ventricle, respectively. Because immediate recurrence of AF was encountered in the second horse treated, pre-treatment with amiodarone was given to each of the remaining six horses. Induction of general anaesthesia was associated with dislocation of the cardioversion catheter in three horses, requiring a second catheterisation procedure. During general anaesthesia, biphasic R wave synchronised shocks of up to 360 J were delivered between both cardioversion electrodes. In six horses (75%), including two which had failed quinidine sulfate treatment, sinus rhythm was restored with a mean energy level of 295+/-62 J. No side effects were observed. Blood analysis 3 h after cardioversion revealed normal parameters, including cardiac troponin I values. Transvenous electrical cardioversion of atrial fibrillation with custom made cardioversion catheters can be considered as a treatment option for atrial fibrillation in horses, especially when conventional drugs fail.

Evaluation of the pharmacokinetics and bioavailability of intravenously and orally administered amiodarone in horses.

OBJECTIVE: To determine the clinical effects and pharmacokinetics of amiodarone after single doses of 5 mg/kg administered orally or intravenously. ANIMALS: 6 healthy adult horses. PROCEDURE: In a cross over study, clinical signs and electrocardiographic variables were monitored and plasma and urine samples were collected. A liquid chromatography-mass spectrometry method was used to determine the percentage of protein binding and to measure plasma and urine concentrations of amiodarone and the active metabolite desethylamiodarone. RESULTS: No adverse clinical signs were observed. After IV administration, median terminal elimination half-lives of amiodarone and desethylamiodarone were 51.1 and 75.3 hours, respectively. Clearance was 0.35 L/kg x h, and the apparent volume of distribution for amiodarone was 31.1 L/kg. The peak plasma desethylamiodarone concentration of 0.08 microg/mL was attained 2.7 hours after IV administration. Neither parent drug nor metabolite was detected in urine, and protein binding of amiodarone was 96%. After oral administration of amiodarone, absorption of amiodarone was slow and variable; bioavailability ranged from 6.0% to 33.7%. The peak plasma amiodarone concentration of 0.14 microg/mL was attained 7.0 hours after oral administration and the peak plasma desethylamiodarone concentration of 0.03 microg/mL was attained 8.0 hours after administration. Median elimination half-lives of amiodarone and desethylamiodarone were 24.1 and 58.6 hours, respectively. CONCLUSION AND CLINICAL RELEVANCE: Results indicate that the pharmacokinetic distribution of amiodarone is multicompartmental. This information is useful for determining treatment regimens for horses with arrythmias. Amiodarone has low bioavailability after oral administration, does not undergo renal excretion, and is highly protein-bound in horses.

Active electrode arrays by chip embedding in a flexible silicone carrier.

Future cochlear implants demand a higher density of stimulation sites (electrodes) and enhanced functionality (e.g. feedback information). The current generation of implanted cochlear prostheses is making use of a completely "passive scheme" and cannot meet these requirements. An "all-silicon" concept integrating active components with passive electrodes in silicon has been proposed but does not offer the flexibility/stretchability of current silicone-based devices. This paper introduces a novel concept based on silicon chip embedding in a flexible silicone carrier. The process and experimental results will be presented. The concept is also applicable to other types of implanted electrodes, e.g. retinal implants.

2,5-Bis-(2-hydroxybenzoylamino)pentanoic acid, a salicylic acid-metabolite isolated from chicken: characterization and independent synthesis.

From excreta of chickens that had been treated with sodium salicylate, a new compound was detected and identified as a double conjugated ornithine metabolite. The structural assignment of this metabolite was further confirmed by an independent efficient 3-step synthesis from ornithine.

Quantitative analysis of amoxycillin and its major metabolites in animal tissues by liquid chromatography combined with electrospray ionization tandem mass spectrometry.

A sensitive and specific method for the quantitative determination of amoxycillin and its major metabolites (amoxycilloic acid, amoxycillinpiperazine-2',5'-dione) in animal tissue samples using liquid chromatography combined with positive electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) is presented. A liquid extraction using an aqueous 0.01 M potassium dihydrogenphosphate solution as the extraction solvent was performed for a preliminary sample cleanup. The extracts were further purified by a solid-phase extraction using an octadecyl (C18) column. Ampicillin was used as the internal standard. Chromatographic separation of the analytes of interest was achieved on a reversed-phase Hypersil column (100 x 3 mm i.d., dp, 5 microm), using a mixture of 9.6 mM pentafluoropropionic acid in water and acetonitrile as the mobile phase. Gradient elution was performed. To obtain as high sensitivity and selectivity as possible, the mass spectrometer was operated in the multiple reaction monitoring mode. The method was validated for the analysis of amoxycillin and its investigated metabolites in various porcine tissues, kidney, liver, muscle, and fat, according to the requirements defined by the European Community. Calibration graphs were prepared for all tissues, and good linearity was achieved over the concentration range tested (25-500 ng/g, r > or = 0.9974, and goodness of fit < or = 9.6). A limit of quantification of 25 ng/g was obtained for amoxycillin and its metabolites in all tissues, which corresponds to half the maximum residue limit for amoxycillin. Limits of detection ranged from 2.3 to 12.0 ng/g for amoxycillin and from 1.1 to 15.1 ng/g and 0.2 to 2.4 ng/g for amoxycilloic acid and amoxycillinpiperazine-2',5'-dione, respectively. The results for the within-day precision and the trueness fell within the ranges specified. The method has been successfully used for the quantitative determination of amoxycillin and its major metabolites in tissue samples from pigs medicated via the drinking water, proving the usefulness of the developed method for application in the field of residue analysis.