Phage Therapy is Effective in Protecting Honeybee Larvae from American Foulbrood Disease

Abstract

American foulbrood disease has a major impact on honeybees (Apis melifera) worldwide. It is caused by a Gram-positive, spore-forming bacterium, Paenibacillus larvae. The disease can only affect larval honeybees, and the bacterial endospores are the infective unit of the disease. Antibiotics are not sufficient to combat the disease due to increasing resistance among P. larvae strains. Because of the durability and virulence of P. larvae endospores, infections spread rapidly, and beekeepers are often forced to burn beehives and equipment. To date, very little information is available on the use of bacteriophage therapy in rescuing and preventing American foulbrood disease, therefore the goal of this study was to test the efficacy of phage therapy against P. larvae infection. Out of 32 previously isolated P. larvae phages, three designated F, WA, and XIII were tested on artificially reared honeybee larvae infected with P. larvae strain NRRL B-3650 spores. The presence of P. larvae DNA in dead larvae was confirmed by 16S rRNA gene-specific polymerase chain reaction amplification. Survival rates for phage-treated larvae were approximately the same as for larvae never infected with spores (84%), i.e., the phages had no deleterious effect on the larvae. Additionally, prophylactic treatment of larvae with phages before spore infection was more effective than administering phages after infection, although survival in both cases was higher than spores alone (45%). Further testing to determine the optimal combination and concentration of phages, and testing in actual hive conditions are needed.

Genomic Analysis of 48 Paenibacillus larvae Bacteriophages

“…P. larvae phages have been isolated and sequenced in Portugal [ 14 ], Germany [ 15 ], and the United States [ 16 , 17 , 18 , 19 , 20 , 21 ], with the latter accounting for the vast majority of published genomes. In addition, six studies have been published within the last two years on treating AFB with P. larvae phages or P. larvae phage endolysins [ 15 , 22 , 23 , 24 , 25 , 26 ].…”

Impacts of Antibiotic and Bacteriophage Treatments on the Gut-Symbiont-Associated Blissus insularis (Hemiptera: Blissidae)

“…Similarly, injection of environmentally derived Pseudomonas aeruginosa phage increased survival time of P. aeruginosa -infected D. melanogaster [61]. In addition to these laboratory-induced infections, oral delivery of a phage preparation has been reported to suppress the impact of American foulbrood disease caused by Paenibacillus larvae in hives of the honeybee, Apis mellifera [62]. …”

Phages in Therapy and Prophylaxis of American Foulbrood – Recent Implications From Practical Applications

“…Temperate phages, especially those capable of transferring antibiotic resistance genes, are not safe and should be excluded from phage therapies. However, there are data suggesting that temperate phages could potentially find use in therapy ( Chung et al, 2012 ; Meader et al, 2013 ), especially in the fight against AFB, as presented by Ghorbani-Nezami et al (2015) . Of course, for safety reasons, their application should be carefully considered.…”

“…Available studies indicated a possible protective effect for bees infected with these extremely resistant forms of bacteria. The aforementioned effect of three P. larvae phages F, WA and XIII was studied in vivo by Ghorbani-Nezami et al (2015) on larvae infected with NRRL B-3650 spores. The authors observed that the survival of larvae treated with phages (phage-treated control) as well as healthy larvae (negative control) was comparable and phages did not cause any deleterious effects.…”