A substance in honey bee larvae inhibits the growth of Paenibacillus larvae larvae

Abstract

-Paenibacillus larvae larvae, a Gram-positive and spore-forming bacterium, is the cause of American foulbrood. We investigated the resistance of larvae of different ages from different colonies against P. larvae larvae. We prepared ethanol-water-extracts from two, three, four and five day old larvae and also larvae in two capped stages to test the ability of the homogenates to inhibit the growth of P. larvae larvae in vitro. There were age and colony dependent differences in the inhibiting potentials of larvae. The results suggest that the concentration of the inhibiting substance(s) in the extract might be responsible for the known different degree of resistance against P. larvae larvae in vivo. Our results further show that the extracts of the two-, three-and four-day-old larvae have the ability to inhibit the growth of P. larvae larvae very well, while starting around day five the inhibiting effect is gradually reduced.Apis mellifera carnica / Paenibacillus larvae larvae / honeybee larvae / age-related resistance /

American Foulbrood in honeybees and its causative agent, Paenibacillus larvae

“…Hence, there is an urge to develop alternative treatment strategies, which so far follow three different directions: (i) Breeding for honeybee genetic stock showing an increased individual or social immune response against AFB (Evans, 2004;Spivak and Reuter, 2001;Wedenig et al, 2003); (ii) biocontrol through antagonistic bacteria (Alippi and Reynaldi, 2006;Evans and Armstrong, 2005;Evans and Armstrong, 2006;Evans and Lopez, 2004;Olofsson and Vasquez, 2008); and (iii) treatment with natural antibacterial substances like essential oils of various plants (Eguaras et al, 2005;Fuselli et al, 2008aFuselli et al, ,b, 2006Fuselli et al, , 2007Fuselli et al, , 2009Gende et al, 2008;Gende et al, 2009) or propolis (Antunez et al, 2008;Bastos et al, 2008).…”

Lysophosphatidylcholine acts in the constitutive immune defence against American foulbrood in adult honeybees

“…In histological examinations, antimicrobial activity was demonstrated in the peritrophic membrane and isolated midgut tissue 26 . Moreover, tests of homogenized larvae (day 3 and older) revealed a positive correlation between larval age and antibacterial activity 25 . This antimicrobial activity was retained even after heat treatment, ethanolic precipitation, and the application of proteases, prompting us to focus our attention on a non-proteinogenic source of P. larvae resistance.…”

“…We previously reported on the detection of a non-induced heat-stable substance present in the midgut of adult bees that shows strong antibacterial activity against the vegetative stage of different P. larvae isolates occurring in Central Europe 23 24 25 . We demonstrated that about one tenth of a preparation of a single homogenized midgut of an adult honeybee – equaling approximately 50 μg of dry weight tissue – inhibited the growth of vegetative forms of P. larvae in an overnight culturing experiment.…”

American foulbrood in a honeybee colony: spore-symptom relationship and feedbacks between disease and colony development

“…While we could describe the relationship between spore levels and symptom independent of the effects of time of the season and the amount of brood (by keeping these at their mean value), questions remain about the generality of the results. Other possible factors that may change the spore-symptom relationship are variability in bacterial virulence (an innate genetic property of different P. larvae strains [54]), colony genetics [46], resistance against P. larvae [55], and hygienic behaviour [23]. All colonies in the study were placed in the same isolated apiary and were experimentally infected with sufficient Paenibacillus larvae spores to precipitate AFB disease.…”