Putative determinants of virulence in Melissococcus plutonius, the bacterial agent causing European foulbrood in honey bees (original) (raw)
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Scientific reports, 2016
European foulbrood (EFB) caused by Melissococcus plutonius is an important bacterial disease of honeybee larvae. M. plutonius strains can be grouped into three genetically distinct groups (CC3, CC12 and CC13). Because EFB could not be reproduced in artificially reared honeybee larvae by fastidious strains of CC3 and CC13 previously, we investigated a method to improve experimental conditions using a CC3 strain and found that infection with a potassium-rich diet enhanced proliferation of the fastidious strain in larvae at the early stage of infection, leading to the appearance of clear clinical symptoms. Further comparison of M. plutonius virulence under the conditions revealed that the representative strain of CC12 was extremely virulent and killed all tested bees before pupation, whereas the CC3 strain was less virulent than the CC12 strain, and a part of the infected larvae pupated. In contrast, the tested CC13 strain was avirulent, and as with the non-infected control group, most...
Genes, 2018
In Europe, approximately 84% of cultivated crop species depend on insect pollinators, mainly bees. (the Western honey bee) is the most important commercial pollinator worldwide. The Gram-positive bacterium is the causative agent of European foulbrood (EFB), a global honey bee brood disease. In order to detect putative virulence factors, we sequenced and analyzed the genomes of 14 strains, including two reference isolates. The isolates do not show a high diversity in genome size or number of predicted protein-encoding genes, ranging from 2.021 to 2.101 Mbp and 1589 to 1686, respectively. Comparative genomics detected genes that might play a role in EFB pathogenesis and ultimately in the death of the honey bee larvae. These include bacteriocins, bacteria cell surface- and host cell adhesion-associated proteins, an enterococcal polysaccharide antigen, an epsilon toxin, proteolytic enzymes, and capsule-associated proteins. In vivo expression of three putative virulence factors (endo-alp...
Journal of Apicultural Science, 2020
The bacterium Melissococcus plutonius is the etiologic agent of the European foulbrood (EFB), one of the most harmful bacterial diseases that causes the larvae of bees to have an intestinal infection. Although EFB has been known for more than a century and is practically present in all countries where beekeeping is practiced, the disease has been little studied compared to American foulbrood. Recently, great advances have been made to understand the disease and the interaction between the pathogen and its host. This review summarizes the research and advances to understand the disease. First, the morphological characteristics of M. plutonius, the infection process and bacterial development in the gut of the larva are described. Also, the epidemiological distribution of EFB and factors that favor the development of the disease as well as the classification of M. plutonius according its genomic and phenotype characteristics are reported. Finally, the new molecular tools for the study of M. plutonius, possible virulence factors in its genome, the issue of current EFB control measures and possible alternatives to the use of antibiotics are addressed.
Journal of Apicultural Science, 2020
The bacterium Melissococcus plutonius is the etiologic agent of the European foulbrood (EFB), one of the most harmful bacterial diseases that causes the larvae of bees to have an intestinal infection. Although EFB has been known for more than a century and is practically present in all countries where beekeeping is practiced, the disease has been little studied compared to American foulbrood. Recently, great advances have been made to understand the disease and the interaction between the pathogen and its host. This review summarizes the research and advances to understand the disease. First, the morphological characteristics of M. plutonius, the infection process and bacterial development in the gut of the larva are described. Also, the epidemiological distribution of EFB and factors that favor the development of the disease as well as the classification of M. plutonius according its genomic and phenotype characteristics are reported. Finally, the new molecular tools for the study ...
The ISME Journal
Melissococcus plutonius is the causative agent of European foulbrood (EFB), which is a serious brood disease of the European honey bee (Apis mellifera). EFB remains a threat because of a poor understanding of disease epidemiology. We used a recently published multi-locus sequence typing method to characterise 206 M. plutonius isolates recovered from outbreaks in England and Wales over the course of 2 years. We detected 15 different sequence types (STs), which were resolved by eBURST and phylogenetic analysis into three clonal complexes (CCs) 3, 12 and 13. Single and double locus variants within CC3 were the most abundant and widespread genotypes, accounting for 85% of the cases. In contrast, CCs 12 and 13 were rarer and predominantly found in geographical regions of high sampling intensity, consistent with a more recent introduction and localised spread. K-function analysis and interpoint distance tests revealed significant geographical clustering in five common STs, but pointed to different dispersal patterns between STs. We noted that CCs appeared to vary in pathogenicity and that infection caused by the more pathogenic variants is more likely to lead to honey bee colony destruction, as opposed to treatment. The importance of these findings for improving our understanding of disease aetiology and control are discussed.
Epidemiology and Genomics of European Foulbrood (Melissococcus plutonius) of Honey Bees
2013
European Foulbrood (EFB) is an important disease of honey bee larvae that has increased in prevalence in recent years, in both the UK and other countries. EFB is caused by the grampositive bacterium Melissococcus plutonius. To date, most molecular epidemiology studies on M. plutonius have concentrated on developing detection methods, and using these to identify the bacteria in honey bees and honey bee hive products, though recently two genomes of M. plutonius have been published. In this thesis a genome sequence for the Type Strain is generated, and used to draw inferences about the accuracy of the published sequences. Genome sequence for other, field-collected isolates were generated and used to identify mobile genetic elements and to elucidate the evolutionary history of M. plutonius. The genome sequences were also used to design the first strain typing scheme for this pathogen, despite this pathogen being previously described as genetically homogenous. Previously undetectable diversity of M. plutonius is explored at a landscape level, showing geographical structuring of populations of the bacterium both within and among countries. The drivers of the observed structure are investigated, with both anthropogenic movements by beekeepers and natural transmission by bees implicated in the maintenance of M. plutonius population structure. This thesis demonstrates the role of the beekeeper in spreading the bacterium through the sale of live bees and through contaminated equipment. Asymptomatic larvae are shown to be carriers of the bacterium (and to go on to develop disease) and a potential role for social wasps as a vector of the pathogen was discovered.
Microbial Ecology, 2005
A sensitive hemi-nested polymerase chain reaction (PCR) was used for detection of Melissococcus plutonius, the causative agent of European foulbrood (EFB). Sampling was made in Switzerland, where EFB is a widespread disease and incidences have increased in recent years. Larvae from brood samples with and without clinical signs of disease (n = 92) and honey (n = 92) from the same colonies were investigated. Individual larvae (n = 60) and pupae (n = 30) from diseased brood in single colonies were also investigated to study the distribution of the bacterium within the brood between larvae. M. plutonius was detected in larvae in all apiaries where symptoms of EFB could be seen, but not in all colonies judged as cases of EFB in the field, when healthy-looking larvae from such colonies were tested. The occurrence of the bacterium within the brood was not limited to larvae with symptoms only, but was mainly found in diseased larvae. The bacterium was also found in pupae. Healthylooking larvae-even from heavily diseased combsfailed, in a number of cases, to amplify product in the PCR. M. plutonius could only be detected in 35% of the brood nest honey from clinically diseased colonies.
A large-scale field survey was conducted to screen major Saudi Arabian beekeeping locations for infection by Melissococcus plutonius. M. plutonius is one of the major bacterial pathogens of honeybee broods and is the causative agent of European Foulbrood disease (EFB). Larvae from samples suspected of infection were collected from different apiaries and homogenized in phosphate buffered saline (PBS). Bacteria were isolated on MYPGP agar medium. Two bacterial isolates, ksuMP7 and ksuMP9 (16S rRNA GenBank accession numbers, KX417565 and KX417566, respectively), were subjected to molecular identification using M. plutonius-specific primers, a BLAST sequence analysis revealed that the two isolates were M. plutonius with more than 98% sequence identity. The molecular detection of M. plutonius from honeybee is the first recorded incidence of this pathogen in Saudi Arabia. This study emphasizes the need for official authorities to take immediate steps toward treating and limiting the spread of this disease throughout the country.
Apidologie, 2007
In Switzerland, the incidence of European foulbrood (EFB), caused by the Gram-positive bacterium Melissococcus plutonius, has increased dramatically between 1997 and 2005 but the epidemiology, including the transmission of M. plutonius, remains poorly understood. In this study, the distribution of M. plutonius among bees originating from apiaries and colonies with and without symptoms of EFB was evaluated using a specific and sensitive hemi-nested PCR. In more than 90% of colonies without EFB symptoms located in apiaries with EFB symptoms, the bees were carriers of M. plutonius. In apiaries without EFB symptoms, but near apiaries with EFB symptoms, bees carrying M. plutonius were detected in about 30% of the colonies. In regions without European foulbrood history, all bee samples were negative. The proportion of adult bees carrying M. plutonius in colonies without symptoms appeared to increase when the distance to apiaries with clinical EFB symptoms decreased.
Journal of Invertebrate Pathology, 2010
European foulbrood (EFB) persists in England and Wales despite current treatment methods, all of which include feeding honey bee colonies with the antibiotic oxytetracycline (OTC). A large-scale field experiment was conducted to monitor a husbandry-based method, using comb replacement (known as Shook swarm), as a drug free EFB control option. The understanding of EFB epidemiology is limited, with little information on the presence of Melissococcus plutonius in disease free colonies. Additional samples were collected from diseased and disease free apiaries to identify symptomless infection. EFB reoccurrence was not significantly different between OTC and husbandry methods and real-time PCR data demonstrated that fewer Shook swarm treated colonies contained M. plutonius carryover to the Spring following treatment. Asymptomatic colonies from diseased apiaries showed an increased risk of testing positive for M. plutonius compared to asymptomatic colonies from disease free apiaries. The probability of a sample being symptomatic increased when a greater quantity of M. plutonius was detected in adult bees and larvae. The possibility of treating EFB as an apiary disease rather than a colony disease and the implications of a control strategy without antibiotics are discussed.