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The aim of this work was the investigation on the efficacy of pulverised sugar dusting on knocking-down Varroa destructor mites and the influence of the dynamics of the treatment on the degree of infestation in honey bee colonies. Two methods were deployed to measure the degree of infestation of bee colonies with V. destructor mites: the sugar shake method and the technique which involves mesh bottom boards equipped with sticky inserts. The research was carried out on 30 strong honey bee colonies in three successive years. The results proved that dusting with pulverised sugar (particle diameter below 40 μm) influenced the fall of V. destructor in comparison with both their fall off prior to the treatment and the negative control. The most discernible effects on the mite fall and the decline in their population in the hives was obtained with dustings repeated at threeday intervals. To conclude, the dynamics of the treatment affected the degree of infestation in bee colonies. However, the efficacy of sugar dusting was significantly lower in comparison with the one of flumethrin (positive control). Thus, in spite of considerable favourable effects on the decline in the degree of infestation with mites, by no means may dusting with pulverised sugar be advised to beekeepers as the one and only means of bee protection against V. destructor. The use of the technique which involves mesh bottom boards equipped with sticky inserts proved more efficacious and sensitive in the judgment of the degree of infestation of bee colonies in comparison with the sugar shake method, which includes dusting 300 bees with 40 g of pulverised sugar (particle diameter below 40 μm)

Nosema ceranae is the most widespread microsporidian species which infects the honey bees of Apis mellifera by causing the weakening of their colonies and a decline in their productive and reproductive capacities. The only registered product for its control is the antibiotic fumagillin; however, in the European Union, there is no formulation registered for use in beekeeping. Thymol (3-hydroxy-p-cymene) is a natural essential-oil ingredient derived from Thymus vulgaris, which has been used in Varroa control for decades. The aim of this study was to investigate the effect of thymol supplementation on the expression of immune-related genes and the parameters of oxidative stress and bee survival, as well as spore loads in bees infected with the microsporidian parasite N. ceranae. The results reveal mostly positive effects of thymol on health (increasing levels of immune-related genes and values of oxidative stress parameters, and decreasing Nosema spore loads) when applied to Nosema-infected bees. Moreover, supplementation with thymol did not induce negative effects in Nosema-infected bees. However, our results indicate that in Nosema-free bees, thymol itself could cause certain disorders (affecting bee survival, decreasing oxidative capacity, and downregulation of some immune-related gene expressions), showing that one should be careful with preventive, uncontrolled, and excessive use of thymol. Thus, further research is needed to reveal the effect of this phytogenic supplement on the immunity of uninfected bees.

The aim of this study was to assess the expression of a toxic shock syndrome toxin-1 (TSST-1) gene of Staphylococcus aureus in different types of milk, depending on inadequate temperature and storage conditions. Pasteurized and UHT milk were inoculated with monotoxic TSST-1 strain of S. aureus and growth kinetics was determined by the drop plate method using Baird-Parker agar medium in accordance with EN ISO 6888-1. The patterns of gene regulation were detected by quantitative reverse transcriptase PCR. Relative quantification method for statistical significance testing was used to detect significant gene expression responses. The results of experiments showed the dependence of the growth rate and consequent up-regulation of TSST-1 encoding gene on storage time-temperature and type of milk. In contaminated pasteurized and UHT milk kept at both 15 °C and 22 °C S. aureus significantly increased its virulent potential over time. This effect was a bit more emphasized in UHT milk serving as a "proof of concept". Possible explanation could be a presence of lactic acid bacteria in pasteurized milk which is known to have down-regulatory effect on TSST-1 gene. Maintenance of the milk storage temperature below 8 °C and employment of microbiological control measures in hygienic practices, from milk producer through retailer and on to the consumer is of utmost importance to decrease risk of non-emetic staphylococcal poisoning.

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