Intestinal Yeast flora of honey bee in presence/absence of Nosema spp.: preliminary results

In the last years, several research are aimed at the study of the intestinal microbiota of honey bee and their role in bee health. The literature reports that the flora of healthy bees is dominated by bacteria while only 1% is represented by yeasts and other fungi. Some authors describe that various diseases or stress increase the number of yeasts. Borsuk et al (2013 Med. Weter. 2013, 69, 726-729) studying the yeast microflora in bees experimentally infected by Nosema spp. noted an increase of yeasts in presence of a weak degree of Nosema infection, while heavy infections reduced the number of yeasts. In the present work, we describe preliminary result about the research of yeasts in bee guts in presence/absence of natural infection by Nosema spp. A total of 200 bees were collected from June to October 2015 in apiaries of Bologna province. The bees were euthanasized by placing their 4-5 minutes in freezer, then each single bee was dipped in ethyl alcohol, the gut was aseptically removed and put in 500 microliter of sterile saline in eppendorf and ground with pestle. One hundred microliter of the suspension were used for counting the number of Nosema spp spores per gut in a Burker chamber; other 100 microliters were spread onto the surface of Petri plates containing Sabouraud Dextrose Agar with Chloramphenicol and incubated at 30°C for 7 days to count the number of CFU (Colony Forming Unit)/gut. Nosema spp was found in 25/200 (12.5%) bee, with number of spore/gut ranging from 5000 to 34 million. Yeasts were found in 55/200 (27.5%) bee, with an approximate number of CFUs/gut ranging from 5 to 14000. The yeast CFU was significatively correlated to the number of Nosema spores (Spearman's rho p = 0.016). The species composition of yeast will be further elucidated.