THE EFFECT OF PROBIOTICS CELL FREE SUPERNATANT ON GROWTH AND VIABILITY OF IRANIAN ISOLATE OF PAENIBACILLUS LARVAE, THE ETIOLOGICAL AGENT OF AMERICA FOULBROOD DISEASE

Background and Aim:American Foulbrood (AFB) caused by Paenibacillus larvae is the most devastating bacterial disease in honey bee (Apia mellifera) larvae. The aim of the present work was to study the effect of cell free supernatant of probiotics on the growth and viability of an Iranian strain, P.larvaeKB10.Methods:The strain was isolated from a comb with signs of AFB and identified on the basis of culture, biochemical characteristics and partial 16srRNA sequencing. Antibacterial effect of Lactobacilli strains was determined by drop plate method using cell free supernatant(CFS) of overnight cultured Lactobacilli in MRS broth. The minimal inhibitory(MIC) and bactericidal(MBC) concentrations were studied by microplate technique. The effect of CFS on viability of the isolate was investigated in 2 to 6 hour of exposure.Results:P.larvaeKB10 was identified on the basis of colony morphology on CSA and MYPGP media, long gram-positive bacilli appeared single or arranged chains in gram staining. Catalase negative, gelatinase and Methyl Red positive, unable to use starch and unable to grow in Nutrient broth colonies were selected for molecular identification. The alignment of partial 16srRNA of P.larvaeKB10, with database revealed 97% identity with P.larvae subspecies larvae and 98% identity with P.larvae subspecies pulvifacience. The most antibacterial effect was observed in L.reuteriATCC23272. The MIC and MBC of the CFS were 1/1 v/v CFS/MRS. Viability test of 1.5×108 cfu/ml P.larvaeKB10 revealed that two hours of exposure with CFS in MIC concentration was enough to completely eliminate the pathogen.Conclusion:The obtained results indicate bactericidal effect of L.reuteriATCC23272 CFS on P.larvaeKB10 growth and viability.

کلیدواژه ها:

beekeeping ، American Foulbrood disease ، probiotics ، cell free supernatant ، antimicrobial activity