Inhibitive and prophylactic efficacy of lactic acid bacteria from Apis mellifera (Hymenoptera: Apidae) in combating Paenibacillus infections

Abstract

Given the increasing interest in alternative methods of prevention and biological control of bacterial diseases in honey bees, the development of new approaches based on probiotic bacteria for honey bee growth, immune function and defense is important. Honey bees have a rich microbiota that varies with seasonal and geographic changes, developmental stages, diet, and social lifestyle. Nevertheless, lactic acid bacteria are an integral part of the honey bee microbiota. In this study, strains of Apilactobacillus, Leuconostoc and Enterococcus isolated from healthy honey bees were identified and their usefulness as an alternative product to control and prevent American and European foulbrood was investigated. The strains were identified by cultural and molecular analysis. The antimicrobial activities against Paenibacillus larvae and Paenibacillus alvei were tested by agar plug and well diffusion method. The inhibitory effect of the obtained 72-h cell-free supernatants on Paenibacillus larvae spore germination was determined by the Bioscreen C method. It turned out that the strains whose prophylactic effect against Paenibacillus larvae spores in larvae was tested were not largely able to prevent infection. Apilactobacillus and Leuconostoc strains did not affect the health of the larvae, and infection was somewhat clinically eliminated in larvae colonized by Apilactobacillus and Enterococcus. The fact that the strains exhibit potent antimicrobial activity and do not reduce larval viability and live weight is a promising finding with regard to their use for treatment, particularly in the early stages of American foulbrood infection.