Comparative evaluation of the antibacterial effects of royal jelly extract and oxytetracycline ۲۰% and their combination on penibacillus larvae to control American Foulbrood disease in laboratory conditions

American foulbrood (AFB) is a serious bacterial disease that threatens honeybee populations, caused by Paenibacillus larvae. Beekeepers have traditionally relied on oxytetracycline ۲۰%, a widely used antibiotic, to control its spread. However, the increasing risk of antibiotic resistance and the presence of antibiotic residues in honey have raised concerns about its long-term use. This has driven the search for natural alternatives, with royal jelly emerging as a promising candidate due to its bioactive antibacterial properties. This study examines and compares the antibacterial effects of royal jelly extract and oxytetracycline ۲۰%, both individually and in combination, to determine their effectiveness against P. larvae. The inhibitory properties were evaluated using the Kirby-Bauer disk diffusion method, optical density (OD ۶۰۰) measurement, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). Various concentrations of oxytetracycline ۲۰% (۵, ۱۰, and ۲۰ µg/mL) and royal jelly extract (۱۰%, ۲۰%, and ۳۰% w/v) were tested separately and together. Results showed that oxytetracycline ۲۰% had a stronger inhibitory effect at all tested concentrations (MIC = ۰.۷۱ µg/mL, MBC = ۹.۱۰ µg/mL), while royal jelly required higher concentrations to show significant antibacterial activity (MIC = ۱۱۰.۷۰ µg/mL, MBC = ۱۹۶.۳۸ µg/mL). Interestingly, combining royal jelly with oxytetracycline reduced the MBC to ۷.۲۶ µg/mL, indicating a synergistic effect. This suggests that while royal jelly alone is less effective than oxytetracycline, it can enhance the antibiotic’s efficacy, potentially reducing the required dosage. Such a reduction could help combat bacterial resistance and minimize antibiotic residues in honeybee products. These findings highlight the potential role of royal jelly as a natural supplement in AFB management. However, further studies are needed to assess its practical applications and safety under real beekeeping conditions.

کلیدواژه ها:

American Foulbrood ، Paenibacillus larvae ، oxytetracycline ، royal jelly extract ، antibacterial effects