Impact of some antimicrobial drugs on the survival and immunity of honey bee workers (Apis mellifera) in relation to the gut microbiota

Beekeepers worldwide use antimicrobial drugs to protect against or treat bacterial infections in honey bee colonies. This study aimed to evaluate three common antimicrobial drugs (Tylan, sodium sulfadimidine, and Septazol) used to control honey bee colony infections and to investigate their effects on honey bee survival, hygienic behavior, immunity, and gut microbiota. Under laboratory conditions, honey bee workers exposed to sulfadimidine had significantly decreased survival compared to the control group. In the field experiments, all antimicrobial drugs render honey bees nonhygienic immediately post-treatment (after 12 days). After 54 days, the colonies recovered and exhibited maximal hygienic behavior. On the other hand, the phenol oxidase activity did not change with all treatments. However, the expression levels of the Apidaecin and Hymenoptaecin genes significantly fluctuated in the treated colonies. These fluctuations may be related to the emergence of pathogenic bacteria in the treated colonies. In general, antimicrobial exposure induced microbial imbalance and perturbed the growth of the gut microbiota. This study revealed adverse effects of the used antimicrobial drugs on honey bee health.