A New Benzaldehyde Derivative Exhibits Antiaflatoxigenic Activity against Aspergillus flavus

Aflatoxin B1 (AFB1) is the most potent naturally occurring carcinogen for humans and animals produced by the common fungus Aspergillus flavus (A. flavus). Aflatoxin (AF) contamination in commodities is a global concern related to the safety of food and feed, and it also impacts the agricultural economy. In this study, we investigated the AFB1-inhibiting activity of a new benzaldehyde derivative, 2-[(2-methylpyridin-3-yl)oxy]benzaldehyde (MPOBA), on A. flavus. It was found that MPOBA inhibited the production of AFB1 by A. flavus, with an IC50 value of 0.55 mM. Moreover, the inhibition of conidiation was also observed at the same concentration. The addition of MPOBA resulted in decreased transcript levels of the aflR gene, which encodes a key regulatory protein for the biosynthesis of AF, and also decreased transcript levels of the global regulator genes veA and laeA. These results suggested that MPOBA has an effect on the regulatory mechanism of the development and differentiation of conidia, leading to the inhibition of AFB1 production. In addition, the cytotoxicity study showed that MPOBA had a very low cytotoxic effect on the Madin-Darby canine kidney (MDCK) cell line. Therefore, MPOBA may be a potential compound for developing practically effective agents to control AF contamination.

Elution profiles of metronidazole from calcium sulfate beads

BACKGROUND

Antibiotic beads are used to treat local bacterial infections by delivering high drug concentrations to infected tissue.

OBJECTIVES

This study examined the elution characteristics of metronidazole from metronidazole-calcium sulfate (MCa) and metronidazole-calcium-potassium sulfate (MCaK) beads over 20 days and the antibacterial efficacy of the beads after storage.

METHODS

The MCa and MCaK beads were prepared by mixing 250 mg of metronidazole and 10 g of calcium sulfate hemihydrate with water and a 3% potassium sulfate solution, respectively. The beads were placed in phosphate-buffered saline for the elution study. The metronidazole eluents were determined using high-performance liquid chromatography. The microstructures were examined by scanning electron microscopy (SEM), and the antimicrobial activity was evaluated by a microbioassay.

RESULTS

For the 20-day study, the total amount of metronidazole released was greater in the MCa beads than in the MCaK beads by 6.61 ± 0.48 mg (89.11% ± 3.04%) and 4.65 ± 0.36 mg (73.11% ± 4.38%), respectively. The amounts of eluted drugs from the MCa and MCaK beads were higher than the minimum inhibitory concentration at 0.5 µg/mL against anaerobic bacteria at both 20 days and 14 days. SEM showed that calcium crystals on the outer surface had dissolved after elution, and thinner calcium crystals were prominent in the MCaK beads. The MCa and MCaK beads exhibited antibacterial activity after setting, followed by storage at room temperature or 4°C for 21 days.

CONCLUSIONS

The MCa beads could release more drug than the MCaK beads, but all eluted metronidazole amounts were effective in controlling bacterial infections. Both metronidazole beads could be stored at ambient temperature or in a refrigerator.

Pharmacokinetic characteristics of azithromycin in freshwater crocodiles (Crocodylus siamensis) after intramuscular administration at three different dosages

The study evaluated the pharmacokinetic features of azithromycin (AZM) in 15 freshwater crocodiles (Crocodylus siamensis) in Thailand. The crocodiles were administered a single intramuscular (i.m.) injection of AZM at three different dosages of 2.5, 5, and 10 mg/kg body weight (b.w.). Blood samples were collected at pre-assigned times up to 168 h. The plasma concentrations of AZM were measured using a validated liquid chromatography-tandem mass spectrometry method. The plasma concentration of AZM were quantifiable for up to 168 h after i.m. administration at the three different dosages. A non-compartmental model was used to fit the plasma concentration of AZM versus the time curve for each crocodile. The elimination half-life values of AZM were 33.70, 38.11, and 34.80 h following i.m. injection after dosages of 2.5, 5, and 10 mg/kg b.w., respectively. There were no significant differences among groups. The results indicated that the overall rate of elimination of AZM in freshwater crocodiles was relatively slow. The maximum concentration and area under the curve from zero to the last values of AZM increased in a dose-dependent fashion. The average binding percentage of AZM to plasma protein was 48.66%. Based on the pharmacokinetic data, the susceptibility break-point and the surrogate PK-PD index (T > MIC), the intramuscular administration of AZM at a dose of 10 mg/kg b.w. might be appropriate for the treatment of susceptible bacterial infections (MIC < 4 μg/ml) in freshwater crocodiles.

Enrofloxacin and its major metabolite ciprofloxacin in green sea turtles (Chelonia mydas): An explorative pharmacokinetic study

The present study aimed to assess the pharmacokinetic features of enrofloxacin (ENR) and its major metabolite, ciprofloxacin (CIP) in green sea turtles (Chelonia mydas) after single intravenous (i.v.) and intramuscular (i.m.) administration at two dosages of 5 and 7.5 mg/kg body weight (b.w.). The study used 10 animals randomly divided into equal groups. Blood samples were collected at assigned times up to 168 hr. The concentrations of ENR and CIP in turtle plasma were quantified by a validated high-performance liquid chromatography equipped with fluorescence detector (HPLC-FLD). The concentration of ENR in the experimental turtles with respect to time was pharmacokinetically analyzed using a noncompartment model. The concentrations of ENR in the plasma were quantified up to 144 hr after i.v. and i.m. administrations at dosages of 5 and 7.5 mg/kg b.w., whereas CIP was quantified up to 96 and 144 hr, respectively. The elimination half-life values of ENR were 38.7 and 50.4 hr at dose rates of 5 and 7.5 mg/kg b.w. after i.v. administration, whereas CIP was 33.6 and 22.6 hr, respectively. The maximum concentration (C_max ) values of ENR were 2.07 and 2.59 μg/ml at dose rates of 5 and 7.5 mg/kg b.w., respectively. The value of area under the curve from 0 to 24 hr (AUC_0-24 )/minimum inhibitory concentration (MIC) ratio of ENR was >125 for bacteria with MIC of 0.12 and 0.13 μg/ml after the administration of 5 mg/kg by i.m. and i.v. administration, respectively. Based on the pharmacokinetic data, susceptibility break-point and pharmacokinetic (PK)/pharmacodynamic (PD) indices, i.m. single administration of ENR at a dosage of 5 mg/kg b.w. might be clinically appropriate for treatment of susceptible bacteria in green sea turtles (Chelonia mydas).

In vitro studies on gastrointestinal monogastric and avian models to evaluate the binding efficacy of mycotoxin adsorbents by liquid chromatography-tandem mass spectrometry

OBJECTIVE

The objective of this study is evaluating the efficacies of 11 mycotoxin adsorbent products, marketed in South East Asia. Three prominently occurring mycotoxins; aflatoxin B1 (AFB1), deoxynivalenol (DON), and zearalenone (ZEN) were simultaneously spiked into the samples.

MATERIALS AND METHODS

Samples were simultaneously tested in vitro in phosphate buffer and simulated at different pH conditions in the gastrointestinal tracts of the porcine and avian model, analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

All mycotoxin adsorbent products had high efficacy at over 90% for AFB1 adsorption in both GI porcine and avian models. AFB1 could be adsorbed more in acidic condition than the basic condition. ZEN adsorption was determined to be more stable at pH 3 than pH 6.5 or 8.4, in which pH condition might influence on ZEN desorption rate. DON was poorly adsorbed by all tested agents.

CONCLUSIONS

The finding showed that the adsorption rate varied depending on the type of adsorbent. Our results might provide useful information regarding the efficacy of mycotoxin adsorbents commercially marketed in the region.

Epidemic trichodinosis associated with severe epidermal hyperplasia in largemouth bass, Micropterus salmoides, from North Carolina, USA

An epidemic of trichodinosis associated with severe epidermal hyperplasia occurred in adult largemouth bass (Micropterus salmoides) from the Chowan River drainage, North Carolina (USA) in late winter to early spring 2002. Initial reports by anglers of fish with a "jelly-like slime coat" on the skin prompted an electrofishing survey in which about 10% of sampled largemouth bass had a very thick, bluish-white "mucoid layer" on the body and fins. Moderate to heavy infestations of the ciliate Trichodina were detected in wet mounts of skin from five of five fish having the mucoid layer; these fish also had significant gill infestations. An additional two fish with only mild reddening and four asymptomatic fish (no skin lesions) had mild skin infestations but no gill infestations. Two asymptomatic fish had no skin parasites. Four fish with the mucoid layer were necropsied and had extremely severe epidermal hyperplasia on the body and fins. The hyperplasic epidermis had relatively few mucus cells and typically was about 5-10 times thicker than healthy epidermis. The upper four fifths of the epidermis consisted of finely vacuolated, highly flattened, somewhat disorganized epithelial cells. No other significant clinical or histopathologic abnormalities were detected. No systemic infection by pathogenic bacteria was noted. The environmental cause of the epidemic is uncertain but the lesions suggest that some chronic stressor was involved.

Pathogenesis of acute ulceration response (AUR) in hybrid striped bass

In a previous study, we discovered that acute confinement stress causes rapid ulceration of the fins of hybrid striped bass Morone saxatilis female x M. chrysops male (Noga et al. 1998. Vet Pathol 35:102-107). In this paper, we report the development of a reproducible model for studying this phenomenon in juvenile hybrid striped bass. We also determined how quickly ulceration could develop in acutely stressed fish and documented the sequential light microscopic and ultrastructural changes associated with this response. When hybrid striped bass were subjected to a standardized confinement protocol, the pathological response was extremely rapid (fin ulceration began to develop within 15 min of confinement). Grossly, the distal edges of the fins became blanched, and melanophores aggregated near the basement membrane and dermis after 15 min of confinement. Microscopically, the earliest detectable change in the fins, which occurred within 15 min of confinement, was swelling and loss of microridges of the outermost epidermal cells; this was followed by epidermal erosion. After 30 min of stress, epidermal ulceration developed at the distal edges of the fins. At this time, both necrotic and apoptotic epidermal cells were present. The middle and basal epidermal layers were severely spongiotic and the dermis and hypodermis were edematous. Over longer periods (up to 2 h), lesions were similar but increasingly more severe, progressing from the distal edge of the fin towards the base. The response to acute stress showed a significant correlation between confinement period and severity of the pathological changes (epidermal degeneration, epidermal ulceration and leukocyte infiltration). Also, we demonstrated that epidermal damage was not restricted to the fins but also affected the body skin and eyes. The ventral area of the body and the corneal epithelium of stressed fish were ulcerated; however, skin on the head and operculum was not affected, suggesting a site-specific mode of damage. In stressed fish, epidermal ulceration was found in 67 to 97% of all fins, 88% of skin on the ventrum, and 67% of corneas, while control fish had only very mild epidermal ulceration in the few fish in which it was present (on 5 to 10% of the fins, but not on the ventral skin or corneas). Due to the widespread damage to epidermal tissues of the body surface, we have named this the acute ulceration response (AUR). Our study indicates that acute confinement can rapidly cause significant damage to epidermal and ocular epithelium. AUR might be a primary cause of morbidity in acutely stressed fish.

Fluorescein: a rapid, sensitive, nonlethal method for detecting skin ulceration in fish

There is a need to develop simple, rapid, and accurate methods for assessing health in fish populations. In this study we demonstrate that use of fluorescein, a nontoxic fluorescent dye, can rapidly and easily detect the presence of skin ulcers in all fish tested, including rainbow trout (Oncorhynchus mykiss), channel catfish (Ictalurus punctatus), goldfish (Carassius auratus), and hybrid striped bass (Morone saxatilis male X M. chrysops female). Exposure of fish to as little as 0.10 mg fluorescein per milliliter of water for 3 minutes was sufficient to identify experimentally induced lesions, even pinpoint ulcerations. Such lesions were not visible to the naked eye but were clearly demarcated with fluorescein treatment. Examination of fish that appeared clinically normal often revealed the presence of focal ulcerations, which might have been a consequence of damage during capture, but it also might suggest that skin ulceration may be common even in "clinically normal" fish. Exposure of either nonulcerated or experimentally ulcerated hybrid striped bass to an excessively high concentration of fluorescein had no apparent effect on health or survival. Our studies suggest that fluorescein may be a highly useful tool for rapid health screening in fish populations.