Molecular Basis of Antibiotic Self-Resistance in a Bee Larvae Pathogen

Paenibacillus larvae, the causative agent of the devastating honey-bee disease American Foulbrood, produces the cationic polyketide-peptide hybrid paenilamicin that displays high antibacterial and antifungal activity. Its biosynthetic gene cluster contains a gene coding for the N-acetyltransferase PamZ. We show that PamZ acts as self-resistance factor in P. larvae by deactivation of paenilamicin. Using tandem MS, NMR spectroscopy and synthetic diastereomers, we identified the N-terminal amino group of the agmatinamic acid as the N-acetylation site. These findings highlight the pharmacophore region of paenilamicin, which we very recently identified as a new ribosome inhibitor. Here, we further elucidated the crystal structure of PamZ:acetyl-CoA complex at 1.34 Å resolution. An unusual tandem-domain architecture provides a well-defined substrate-binding groove decorated with negatively-charged residues to specifically attract the cationic paenilamicin. Our results will help to understand the mode of action of paenilamicin and its role in pathogenicity of P. larvae to fight American Foulbrood.

Impacts of Diverse Natural Products on Honey Bee Viral Loads and Health

Western honey bees (Apis mellifera), a cornerstone to crop pollination in the U.S., are faced with an onslaught of challenges from diseases caused by parasites, pathogens, and pests that affect this economically valuable pollinator. Natural products (NPs), produced by living organisms, including plants and microorganisms, can support health and combat disease in animals. NPs include both native extracts and individual compounds that can reduce disease impacts by supporting immunity or directly inhibiting pathogens, pests, and parasites. Herein, we describe the screening of NPs in laboratory cage studies for their effects on honey bee disease prevention and control. Depending on the expected activity of compounds, we measured varied responses, including viral levels, honey bee immune responses, and symbiotic bacteria loads. Of the NPs screened, several compounds demonstrated beneficial activities in honey bees by reducing levels of the critical honey bee virus deformed wing virus (DWV-A and-B), positively impacting the gut microbiome or stimulating honey bee immune responses. Investigations of the medicinal properties of NPs in honey bees will contribute to a better understanding of their potential to support honey bee immunity to fight off pests and pathogens and promote increased overall honey bee health. These investigations will also shed light on the ecological interactions between pollinators and specific floral food sources.

Identifying the climatic drivers of honey bee disease in England and Wales

Honey bee colony health has received considerable attention in recent years, with many studies highlighting multifactorial issues contributing to colony losses. Disease and weather are consistently highlighted as primary drivers of colony loss, yet little is understood about how they interact. Here, we combined disease records from government honey bee health inspections with meteorological data from the CEDA to identify how weather impacts EFB, AFB, CBP, varroosis, chalkbrood and sacbrood. Using R-INLA, we determined how different meteorological variables influenced disease prevalence and disease risk. Temperature caused an increase in the risk of both varroosis and sacbrood, but overall, the weather had a varying effect on the six honey bee diseases. The risk of disease was also spatially varied and was impacted by the meteorological variables. These results are an important step in identifying the impacts of climate change on honey bees and honey bee diseases.

Nosema Disease of European Honey Bees

Nosematosis is currently a frequently discussed honey bee disease caused by two types of Microsporidia: Nosema apis and Nosema ceranae. Nosematosis as an intestinal disease caused by these species is one of the main factors associated with the weakening and loss of hives, with none of the stressors acting in isolation and all having an important synergistic or additive effect on the occurrence of parasitic infection. The most important factors are exposure to pesticides and nutritional stress, both worsening the immune response. Honey bees Apis mellifera become more susceptible to parasites and subsequently the disease manifests itself. Choosing the right laboratory diagnostics is important to determine the prevalence of both species. Our review summarizes the most commonly used methodologies, especially polymerase chain reaction (PCR), which is a reliable method for detecting nosematosis, as well as for distinguishing between the two species causing the disease.

Conducting an International, Exploratory Survey to Collect Data on Honey Bee Disease Management and Control

The Istituto Zooprofilattico Sperimentale del Lazio e della Toscana (IZSLT) and the International Federation of Beekeepers’ Associations (Apimondia) set up a worldwide survey in 2015–2017 to gather information on beekeepers’ perceptions concerning good beekeeping practices, the main honey bee diseases, and the technical assistance they receive. The on-line dissemination of the survey was facilitated by the “Technologies and Practices for Small Agricultural Producers” platform (TECA) of the Food and Agriculture Organization of the United Nations (FAO). In total, 248 questionnaires were received from the European region and the results are reported here. Varroosis remains the biggest concern and is the most important reason for beekeepers’ use of veterinary medicines. However, a sustainable approach to managing Varroa was detected. American foulbrood (AFB) and European foulbrood (EFB) infections are mainly managed through the shook swarm technique or burning the hives. Concerning technical assistance for disease management, beekeepers were mainly supported by their associations or expert beekeepers. Relevant data were collected and analyzed but information from many low-income countries in Africa or Asia is still missing, and more efforts are needed to fill the knowledge gaps.

Lactobacillus spp. attenuate antibiotic-induced immune and microbiota dysregulation in honey bees

Widespread antibiotic usage in apiculture contributes substantially to the global dissemination of antimicrobial resistance and has the potential to negatively influence bacterial symbionts of honey bees (Apis mellifera). Here, we show that routine antibiotic administration with oxytetracycline selectively increased tetB (efflux pump resistance gene) abundance in the gut microbiota of adult workers while concurrently depleting several key symbionts known to regulate immune function and nutrient metabolism such as Frischella perrera and Lactobacillus Firm-5 strains. These microbial changes were functionally characterized by decreased capped brood counts (marker of hive nutritional status and productivity) and reduced antimicrobial capacity of adult hemolymph (indicator of immune competence). Importantly, combination therapy with three immunostimulatory Lactobacillus strains could mitigate antibiotic-associated microbiota dysbiosis and immune deficits in adult workers, as well as maximize the intended benefit of oxytetracycline by suppressing larval pathogen loads to near-undetectable levels. We conclude that microbial-based therapeutics may offer a simple but effective solution to reduce honey bee disease burden, environmental xenobiotic exposure, and spread of antimicrobial resistance.

Total Brood Removal and Other Biotechniques for the Sustainable Control of Varroa Mites in Honey Bee Colonies: Economic Impact in Beekeeping Farm Case Studies in Northwestern Italy

Honey bee colonies are affected by many threats, and the Varroa mite represents one of the most important causes of honey bee disease. The control of the Varroa population is managed by different methods, and in recent years, biotechnical practices are considered preferable to chemical approaches in order to safeguard honey bee health and avoid residues in bee products as well as the appearance of acaricide resistance. However, little is known about the economic performance of beekeeping exploitations in relation to the methods used for tackling Varroa. This study aims to investigate the economic impact of total brood removal (TBR) as a biotechnique to keep Varroa mites under control, and compare this to other common biotechniques and chemical Varroa control in numerous Italian beekeeping case studies. A pool of economic and technical indexes was proposed. The proposed index pool can be included in the development of an expert system (such as a decision support system) able to address the optimal management of this very complex activity, which requires natural resources, land protection, capital and high technical skills. The result showed that the adoption of the TBR biotechnique vs. other biotechniques led to an increase in terms of total revenue (increase values ranging from 11% to 28%) even though more labor is needed (increase values ranging from 43 to 83 min/hive) and a loss of honey production could be recorded in some cases. Additionally, the total expenses, represented mainly by supplemental nutrition and treatments with oxalic acid, affected the economic results of the biotechnical practices. The use of biotechniques vs. chemical control resulted in decreased treatment costs and increased feeding costs. The advantages resulting from not using synthetic acaricides (which are dangerous for honey bee and human health as well as the environment) as well as the advantages linked to the production of new nuclei (which are involved in the maintenance of bee stock and counteract the decline in honey bee population) and pollination ecosystem services could make beekeeping farms more resilient over time.

Pollen from multiple sunflower cultivars and species reduces a common bumblebee gut pathogen

Pathogens are one of the factors driving pollinator declines. Diet can play an important role in mediating pollinator health and resistance to pathogens. Sunflower pollen (Helianthus annuus) dramatically reduced a gut pathogen (Crithidia bombi) ofBombus impatienspreviously, but the breadth of this effect was unknown. We tested whether pollen from nineH. annuuscultivars, four wildH. annuuspopulations,H. petiolarus, H. argophyllusand twoSolidagospp., reducedCrithidiainB. impatienscompared to mixed wildflower pollen and buckwheat pollen (Fagopyrum esculentum) as controls. We also compared hand- and honeybee-collected pollen (which contains nectar) to assess whether diet effects on pathogens were due to pollen or nectar. AllHelianthusandSolidagopollen reducedCrithidiaby 20–40-fold compared to buckwheat pollen, and all but three taxa reducedCrithidiacompared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduceCrithidiainfection. Our results indicate an important role of pollen diet for bee health and potentially broad options within the Asteraceae for pollinator plantings to manage bee disease.