Abstract
The honey bee microbiota is involved in several important functions, and alterations in the composition could have a severe effect on honey bee health. Among the bacteria identified in the honey bee microbiome are a group of non-pathogenic honey bee-specific lactic acid bacteria (hbs-LAB) that have been shown to inhibit the growth of bacterial pathogens such as Paenibacillus larvae, the causative agent of American foulbrood (AFB). While P. larvae only causes disease in larvae and not in adult honey bees, there are reports of the pathogen causing changes in the microbiota composition of the adults. The aim of this study was to investigate how AFB in the colony affect the hbs-LAB composition in adult honey bees. Adult bees were collected from colonies with and without AFB during three outbreaks of AFB in Sweden. The hbs-LAB was analyzed using qPCR to detect and quantify the number of ten hbs-LAB (five Lactobacilli, two Apilactobacilli, one Bombilactobacilli, and two Bifidobacterium). The hbs-LAB composition was compared between AFB outbreaks and depending on the AFB status of the honeybee colony at the time of sampling. The data analyses revealed differences in the abundance of individual hbs-LAB between outbreaks and an overall difference in bacterial community composition depending on AFB status. Also, a higher hbs-LAB diversity was observed in samples that were P. larvae culture positive.