Distribution and genetic diversity among Aspergillus flavus isolates across three agro-ecologies essential for maize cultivation in Ghana

Fungal mycotoxins are important contaminants of agricultural commodities that pose serious concerns to producers, consumers and exporters. Aflatoxin is a carcinogenic metabolite produced by the fungi Aspergillus flavus and A. parasiticus. These fungi and other mould species living in the soil contaminate several crops including maize. This study was undertaken with the following objectives: (i) to assess the presence of A. flavus and other moulds in Ghanaian soil; (ii) to determine the distribution and density of A. flavus under three agro-ecologies noted for major maize production; and (iii) to assess the effect of percentage of carbon (C) and nitrogen (N) and soil pH on A. flavus population densities and diversity in the isolates found across the agro-ecologies. The data showed seven moulds that were common across the agro-ecologies. Significant differences (P < 0.05) were observed in the A. flavus density and distribution within and across these agro-ecologies. Fumesua soils recorded the highest levels of A. flavus (1.185 × 10³ cfu g⁻¹) while Akomadan recorded the least (9.76 × 10² cfu g⁻¹). Percentage available C, N and soil pH did not significantly influence A. flavus density. The A. flavus isolates identified in this study varied in genetic sequence within the aflatoxin gene cluster, but these differences were not distinguishable by origin.     

Comparative performance of the highly invasive Mimosa invisa and its less invasive subspecies under different nutrient and light conditions

Invasive plants may be more plastic than non‐invasive plants and maintain high fitness under various environmental conditions. Previous studies mainly focused on the comparisons between invasive and native plants, and comparisons between highly invasive and less invasive exotic species are still relatively rare, especially for comparisons at the subspecies level. This study examined the effects of nutrient addition and shading on the performance of the highly invasive Mimosa invisa and its less invasive subspecies M. invisa var. inermis under either isolated or competitive conditions. Nutrient addition increased biomass and plant height and decreased root‐to‐shoot ratio (R/S). Shading decreased biomass and R/S and increased plant height. Under isolated conditions, the two invaders did not differ in R/S, plant height and plasticity of these traits in response to nutrient addition or shading, and the two invaders also did not differ in biomass production under each of the nutrient and light treatments. When the two invaders competed with each other, M. invisa outcompeted M. invisa var. inermis under high soil nutrient conditions, and the two invaders did not differ in performance under other growth conditions. Thus, only considering competition may we find out the difference between highly invasive species and their closely related, less invasive subspecies. Management of M. invisa should focus on habitats with high soil nutrient availability, in which M. invisa is more likely to dominate.     

Potassium fertilization improves apple fruit (Malus domestica Borkh. Cv. Fuji) development by regulating trehalose metabolism

Potassium (K) fertilization and antioxidant enzymes both positively influence plant growth and development. However, it is not known whether K treatment improves fruit development via increasing soluble sugar. In this study, K-treated apple (Malus domestica Borkh.) fruit was harvested from 60 to 150 days after full bloom and was analyzed for ROS production and trehalose metabolism. The results show that K fertilization improved fruit firmness, increased growth according to several parameters, increased soluble sugar content, and decreased ROS production. The ascorbate metabolic pathway more effectively reduced ROS production than catalase and peroxidase (POD) did under K treatment. Trehalose-treated fruit also showed higher activity of ascorbate-related enzymes (DHAR, GR, and APX) compared with non-treated fruit. The changes of antioxidant enzyme activity in trehalose-treated fruit corresponded to those in K-treated fruit. Moreover, trehalase (TREH) activity in fruit was notably reduced by K treatment. This demonstrates that K influences ROS production via regulating trehalose content and TREH activity in fruit. This study provides new insight into the K mechanism which improves fruit development, including fruit firmness and size.     

Isolation of Mycoplasma salivarium from swine

Mycoplasma salivarium, a common human oropharyngeal mycoplasma, was isolated from nasal and pharyngeal secretions of 14 of 284 swine in a barrier-maintained, disease-free herd. M. salivarium was recovered from one boar 6 times over a 26-month period and one time only from 13 other swine. Human isolates of M. salivarium were compared with the swine isolates by DNA-DNA hybridization and SDS-PAGE of the cell proteins and the strains were shown to be closely related. One of eight of the swine from which M. salivarium was isolated had complement-fixing antibodies and another culture-positive animal had metabolic-inhibiting antibodies to M. salivarium. Overt disease was not associated with the organism. These results support previous findings that mycoplasmas closely related to M. salivarium may be isolated from the nasopharynges of swine and they further indicate that the organism can establish persistently in swine without evidence of overt disease.     

Enzyme-linked immunosorbent assays for detecting antibody to Rickettsia australis in sera of various animal species

New endemic areas of spotted fever-like rickettsial disease have been found in south-eastern Australia (Gippsland, Victoria and Flinders Island, Tasmania). The rickettsia responsible is currently unknown although it may be Rickettsia australis. To investigate serological evidence of rickettsial exposure in various wild animal species, a competitive ELISA was developed which detected antibodies to R. australis. It was based on inhibition of an indirect ELISA detecting antibody to R. australis in guinea pig sera. Pre- and post-infection sera from 2 dogs, 2 rabbits, 5 mice and 6 rats, experimentally infected with R. australis, were tested by competitive ELISA. The results showed that all pre-infection sera were negative and all post-infection sera positive for antibody to R. australis. To test the utility of the competitive ELISA for detecting natural rickettsial infection in non-laboratory animals, 51 dog sera, negative for rickettsial antibody by immunofluorescence (IF) and 20 IF positive dog sera (collected from various locations on the east coast of Australia) were tested. Compared to the IF test the competitive ELISA was 90% sensitive and 96% specific. This new test has potential for detecting antibody to R. australis in the sera of different wild animal species.     

Assessment of diclofenac LC50 reference values in juvenile and embryonic stages of the zebrafish (Danio rerio)

The aim of the study was to compare the acute toxicity of diclofenac to juvenile and embryonic stages of the zebrafish (Danio rerio). Acute toxicity tests were performed on the aquarium fish Danio rerio, which is one of the model organisms most commonly used in toxicity testing. The tests were performed using a semi-static method according to OECD guideline No. 203 (Fish, acute toxicity test). Embryo toxicity tests were performed in zebrafish embryos (Danio rerio) in compliance with OECD No. 212 methodology (Fish, short-term toxicity test on embryo and sac-fry stages). The results were subjected to a probit analysis using the EKO-TOX 5.2 programme to determine 96hLC50 and 144hLC50 (median lethal concentration, 50% mortality after a 96 h or 144 h interval, respectively) values of diclofenac. The statistical significance of the difference between LC50 values in juvenile and embryonic stages of Danio rerio was tested using the Mann-Whitney non-parametric test implemented in the Unistat 5.1 programme. The LC50 mean value of diclofenac was 166.6 +/- 9.8 mg/L in juvenile Danio rerio, and 6.11 +/- 2.48 mg/L in embryonic stages of Danio rerio. The study demonstrated a statistically higher sensitivity to diclofenac (P < 0.05) in embryonic stages compared to the juvenile fish.     

Association of polymorphisms for nuclear receptor coactivator 1 gene with egg production traits in the maternal line of Shaobo hens

1. The objectives of the study were to find polymorphic sites and elucidate the association between SNPs in the nuclear receptor coactivator 1 (NCOA1) gene and reproductive traits. 2. SNPs were detected by PCR-SSCP and DNA sequencing. Four SNPs were detected, including T10155007A, T10125838C, G10118492A and G10109315T. Three polymorphisms were associated with total egg production at the age of 300 d and the G10109315T polymorphism was associated with age at first egg. 3. In conclusion, the NCOA1 gene can be used as a molecular marker for reproductive traits in hens.     

Interindividual variability in plasma concentrations after systemic exposure of swine to dietary doxycycline supplied with and without paracetamol: a population pharmacokinetic approach

Anorexigenic substances released during infection may hinder the therapeutic efficacy of in-feed antibiotics. Paracetamol (acetaminophen; PARA) inhibits the anorexia of infection and seems to improve the clinical efficacy of doxycycline (DOX) against bacterial respiratory disease in swine herds. In order to verify whether PARA selectively stimulates intake of DOX-medicated feed in diseased pigs, we documented the pharmacokinetics (PK) of DOX when coadministered with PARA and examined the effect of in-feed PARA on the interindividual variability in plasma concentrations after systemic exposure to in-feed DOX in swine herds with respiratory disease. Systemic exposure to DOX was measured with the area under the curve (AUC) of its plasma concentrations over time. First, a rich-sampling PK study of in-feed and i.v. DOX (10 mg/kg of BW) and PARA (30 and 10 mg/kg of BW, respectively) was performed on 5 pigs. The PK profiles of in-feed DOX were used in mathematical simulations to determine 5 optimal sampling times for the farm-based population PK study. A randomized, blind, parallel PK study was performed in 2 herds with bacterial respiratory disease, where liquid feed was fortified with DOX alone (5 mg x kg of BW(-1) x meal(-1)) or combined with PARA (15 mg x kg of BW(-1) x meal(-1)). Medicated meals were given twice, 12 h apart, to group-housed growing pigs (n > 50 pigs x treatment(-1) x herd(-1), totaling 215 pigs). Plasma concentrations of DOX and PARA were measured with HPLC. At variance with our expectations, PARA decreased (P = 0.069) mean AUC of in-feed DOX and did not decrease its variability (P > 0.34). Mean AUC of DOX increased with feed intake and with initial exposure to DOX, and was greater in sick animals. Therefore, symptomatic PARA-induced improvement in bacterial respiratory disease control with DOX is more likely caused by its analgesic/antipyretic effects than by its orexigenic effect. Interindividual variation in the AUC of DOX was large in pigs given group medication, even when sufficient feeding space was allowed and the amount of feed offered was greater than their requirements. Therefore, future studies to improve the efficacy of group antibiotic therapy should focus on feeding behavior characteristics as well as biopharmaceutical properties of medicated feeds.