Varroa bee hive attack is a serious and common problem in bee keeping. In our work, an ectomicroflora of Varroa destructor mites was characterised as a potential source of bacterial bee diseases. Using a cultivation approach, a variable population of bacteria was isolated from the body surface of Varroa mites with frequency of about 150 cfu per mite individual. Nine studied isolates were classified to four genera and six species by a combination of matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF)-and 16S ribosomal RNA (rRNA)-based methods, suggesting relatively low diversity of Varroa mite-associated ecto-microflora. The Varroa mite-associated bacterial population was found to be dominated by Gram-positive bacteria of Bacillus and Microbacterium genera. Gram-negative bacteria were represented by members of Brevundimonas and Rhizobium genera. Most of the identified species are not known to be associated with Varroa mite, either honey bee or honey up until now and some of them are probably representatives of new bacterial taxa. Varroa destructor / ecto-microflora / heterotrophic bacteria / Microbacterium

American foulbrood is a dangerous world-wide spread disease of honey bees caused by the Paenibacillus larvae bacterium. Antibiotic treatments are less effective and leave residues in bee products. It is therefore necessary to find an alternative, especially using natural ingredients such as plant essential oils, probiotics, fatty or organic acids. Two strains of P. larvae were used for this study: CCM 4488, a strain from the Czech collection of micro-organisms and a Slovak field strain which was isolated from infected bee combs and characterized on the basis of biochemical properties. Plant essential oils of sage (Salvia officinalis), anise (Pimpinella anisum), oregano (Origanum vulgare), caraway (Carum carvi), thyme (Thymus vulgaris), rosemary (Rosmarinum officinalis), clove (Syzygium aromaticum), camomile (Chamomilla recutita) and fennel (Foeniculum vulgare) were used for the testing of the inhibitory activity against P. larvae. Essential oils at amounts of 5 µl and 10 µl were applied to sterile discs on MYPGP agar; inhibition zone diameters were measured after 24-h incubation at 37 °C. The strongest inhibitory activity against both P. larvae strains was noted in case of the essential oils from oregano, thyme and clove; essential oils from camomile, rosemary and fennel showed no or weak antibacterial activity. Medium strong inhibition activity was recorded in case of previously untested essential oil from Carum carvi. There was a difference in sensitivity of both tested strains to essential oils. Our study confirmed that some essential oils can be used in the prevention of American foulbrood but further experiments aimed at their influence on physiological intestinal microflora of honey bees must be performed.