Biochemical characterization of different genotypes of Paenibacillus larvae subsp. larvae, a honey bee bacterial pathogen

Abstract

Paenibacillus larvaesubsp.larvae(P. l. larvae) is the aetiological agent of American foulbrood (AFB), the most virulent bacterial disease of honey bee brood worldwide. In many countries AFB is a notifiable disease since it is highly contagious, in most cases incurable and able to kill affected colonies. Genotyping of field isolates ofP. l. larvaerevealed at least four genotypes (AB,Ab,abandαB) present in Germany which are genotypically different from the reference strain DSM 7030. Therefore, based on these data, five different genotypes ofP. l. larvaeare now identified with genotypeABstanding out with a characteristic brown-orange and circled two-coloured colony morphology. Analysing the metabolic profiles of three German genotypes (AB,Abandab) as well as of the reference strain using the Biolog system, a characteristic biochemical fingerprint could be obtained for each strain. Cluster analysis showed that while genotypesAb,aband the reference strain DSM 7030 are rather similar, genotypeABis clearly different from the others. Analysis of all isolates for plasmid DNA revealed two different plasmids present only in isolates belonging to genotypeAB. Therefore, genotypeABis remarkable in all aspects analysed so far. Future analysis will show whether or not these differences will expand to differences in virulence.