Asia Life Sciences

Abstract : Honeybees are vulnerable to many diseases, such as European foulbrood, chalkbrood, sacbrood, and American foulbrood (AFB). Caused by Paenibacillus larvae, AFB can cause immense damage to the bee industry. Chemicals and antibiotics have long been used to treat these diseases, resulting in pathogen resistance. As an alternative, antagonistic effect of gut bacteria has been focused on. The culture supernatant (CS) from recently isolated gut bacteria from Thai Apis cerena indica (Bacillus sp., Pantoea sp., Azotobacter sp., Klebsiella sp., and Lactobacillus sp.) were screened for their growth inhibitory activity against P. larvae strains 01 and 02 in an agar well diffusion assay. The CS from Azotobacter sp. had the highest growth inhibition against P. larvae strain 02, while the CS from Bacillus sp., Lactobacillus sp., Klebsiella sp., Azotobacter sp. were all active against both strains. This activity was thermotolerant to 90 ºC for 1 h, but 121 ºC nor to proteinase K and RNase A treatment. Furthermore, the CSs from Bacillus sp. and Klebsiella sp. at pH 3, Pantoea sp. at pH 5, Lactobacillus sp. at pH 8 and 10, and Klebsiella sp. at pH 10 showed the highest inhibitory effect against P. larvae strains 01 and 02. However, the CS inhibitory activity at pH 8–10 was less than that at pH 5 (the pH in the bee stomach). Hence, gut bacteria that can potentially inhibit P. larvae growth were obtained from healthy honeybees.

Abstract : Apis dorsata are important pollinators, while their honey is the most popular for consumption in Asia. Although they have an aggressive and very thorough grooming behavior, ectoparasitic mites that can act as disease vectors have been reported. Here, the presence of mites on different developmental stages of A. dorsata was investigated in three hives in Samutsongkram province in February, 2021 to reveal the health status of A. dorsata in Thailand. No ectoparasitic mites were observed under stereo and compound light microscopy based examination of 150 adult bees (50 bees/hive). In contrast, phoretic mites were found on the bee’s thorax, principally the legs of pair no. 3. Morphological analyses, including scanning electron microscopy, placed the mites in the order Oribatida, and possibly Forcellinia faini, but this awaits molecular confirmation. Prevalence of adult bees with phoretic mites from hive no. 1, 2, and 3 was 32%, 20%, and 30%, respectively, with a range of 0–10 mites per bee. No mites were observed on non-adult stadia. No Paenibacillus larvae, which causes American foulbrood disease, was detected in the mites by multiplex PCR using specific primers for 16S rRNA of bacteria and cytochrome b (cytb) for Apis spp. under an optimized PCR condition. Rather the bacterial amplicon showed a 91.5% nucleotide sequence identity to Lactobacillus fermentum (probiotic bacteria). The ecologic impact of this relationship between phoretic mites, probiotic bacteria, and honeybees, as well as the effect of mites on pollination by A. dorsata, needs to be determined.