American foulbrood (AFB) is one of the most deleterious bacterial honey bee diseases though affecting only the larval stages of bees. The causative agent of AFB is the Grampositive bacterium Paenibacillus larvae firstly described in the beginning of the 20th century. Since then AFB has become one of the best-studied honey bee diseases. However many aspects of AFB and the related pathogen P. larvae still remain elusive. This review will focus on three main topics by reviewing both, historical data and new results obtained with modern laboratory techniques: (i) P. larvae and the pathogenesis of AFB, (ii) transmission of P. larvae spores and AFB, and (iii) diagnosis of AFB.

Paenibacillus larvae and American Foulbrood – long since known and still surprising

Paenibacillus larvae is a Gram positive bacterium and the causative agent of the most widespread fatal brood disease of honey bees, American foulbrood (AFB). A total of thirty-three independent Paenibacillus larvae isolates from various geographical origins in North America and five reference strains were investigated for genetic diversity using multilocus sequence typing (MLST). This technique is regarded to be a powerful tool for epidemiological studies of pathogenic bacteria and is widely used in genotyping assays. For MLST, seven housekeeping gene loci, ilvD (dihydroxy-acid dyhydrogenase), tri (triosephosphate isomerase), purH (phospharibosyl-aminoimidazolecarboxamide), recF (DNA replication and repair protein), pyrE (orotate phosphoribosyltransferase), sucC (succinyl coenzyme A synthetase β subunit) and glpF (glycerol uptake facilitator protein) were studied and applied for primer designs. Previously, ERIC type DNA fingerprinting was applied to these same isolates and the data showed that almost all represented the ERIC I type, whereas using BOX-PCR gave an indication of more diversity. All isolates were screened for resistance to four antibiotics used by U.S. beekeepers, showing extensive resistance to tetracycline and the first records of resistance to tylosin and lincomycin. Our data highlight the intraspecies relationships of P. larvae and the potential application of MLST methods in enhancing our understanding of epidemiological relationships among bacterial isolates of different origins.

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Multilocus sequence typing, biochemical and antibiotic resistance characterizations reveal diversity of North American strains of the honey bee pathogen Paenibacillus larvae.

SummaryLytic enzymes are usually reported to have a role in fungal entomopathogenicity. Enzymic profiles produced by Ascosphaera apis, a pathogen causing chalkbrood disease in honey bee larvae were determined by API ZYM kit and standard enzyme assays. Ten isolates of A. apis produced 11 enzymes (i.e. protease, β-N-acetylglucosaminidase, alkaline phosphatase, esterase, esterase lipase, leucine arylamidase, valine arylamidase, acid phosphatase, naphthol-AS-BI-phosphohydrolase, β-glucosidase and α-mannosidase). Two main enzymes (protease and β-N-acetylglucosaminidase), that might play roles in either penetration of the peritrophic membrane in bee larval midgut or breaking down the cuticle of larvae were chosen for further study. All isolates of A. apis gave the highest proteolytic enzymes in sterile germination medium after 11 day-incubation at 30°C. Yeast extract and glucose were the key components for the fungal growth and protease production. The pH optimum for protease production was 8.0. Phenylmethanesu...

Protease and β-N-acetylglucosaminidase of honey bee chalkbrood pathogen Ascosphaera apis

Sustaining apiculture worldwide has been threatened by bee diseases and unexplained colony losses. African honeybee populations seem healthier and no major losses have been reported despite the presence of all the major pests and diseases. The scattered colonies in the large wild population of the continent might ensure slow pathogen spread and thus protect the unmanaged colonies in comparison with the concentration of colonies in managed apiaries. Beekeeping and trade in bee products is responsible for spreading many diseases throughout the world. The recent outbreak of the bacterial disease American foulbrood (AFB) in South Africa is a matter of great concern. Despite a growing number of apiaries testing positive for AFB, no major colony losses have been reported yet. This could be based on higher disease resistance of African honeybees, but such a trait might not persist if pathogens accumulate in the hives. In the first part of this article we review what is known on the history, biology and epidemiology of AFB as well as the control methods available. We then argue that given the particular context of honeybees in Africa, protection policies need to be put in place to ensure that African honeybees remain healthy.

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The Honeybee Disease American Foulbrood — An African Perspective

The detection/quantification in honey of spores of the bacterial pathogen Paenibacillus larvae, etiological agent of the American Foulbrood (AFB) infectious disease of honey bees, represents a usef...

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D. Curcă

Papers

American Foulbrood in honey bees.