Inhibitory action of essential oils against proteases activity of Paenibacillus larvae, the etiological agent of American Foulbrood disease

American foulbrood (AFB) is a disease affecting the larva of Apis mellifera. The etiological agent is Paenibacillus larvae, which releases metalloproteases involved in the degradation of larval tissues. Through quorum sensing (QS) mechanism, bacteria are able to activate specific genes such as virulence factors. The exoproteases regulation of P. larvae could be associated with QS. A promising mechanism of AFB control is to block QS mechanism with essential oils (EO). The aim of this study was to investigate the potential presence of QS signals in the regulation of P. larvae proteases and the effect of seven EOs on the exoproteases activity of P. larvae. From growth curves and evaluation of the presence of proteases by milk agar plates assay, it was observed protease activity during the late exponential phase of growth. Early production of protease activity (15 hours earlier than control) was observed when a low density culture was incubated with late exponential spent medium (SM) suggesting the presence of factor(s) inducing this activity. SM was obtained by the ultrafiltration of P. larvae cultures on late growth phase and was free of proteases. Proteolytic activity was quantified on P. larvae cultures in presence of sublethal concentration of EO by azocasein method. The EOs, except S. chilensis EO, reduced significantly protease activity (more than 50%). We report for the first time evidence on the possible role of QS on P. larvae and the antiproteolytic activity of EOs (except for S. chilensis) on exoproteases, an interesting therapeutic strategy to control AFB

Short communication: A potential role of tannins in the control of American foulbrood

Aim of study: To evaluate the use of tannins extracts in the control of the American foulbrood pathology and to investigate if these extracts present levels of toxicity on Apis mellifera.Area of study: Paenibacillus larvae strains C1 and C2 were from Balcarce, province of Buenos Aires, strain C6 from Rio Cuarto, in Cordoba province and strain C9 from Concordia in Entre Rios province. Bees larvae used for toxicological assays were collected in Santa Paula experimental apiary, Mar del Plata (belonging to the Centro de Investigación en Abejas Sociales (CIAS-IIPROSAM) from UNMdP.Material and methods: The minimal inhibitory concentration (MIC) of five different tannin extracts were obtained by agar diffusion method on four P. larvae strains; using the MIC value, the toxicity test on A. mellifera larvae was performed afterwards.Main results: The MIC value was in the range of 6.9 to 898.6 µg/mL. Three tannin extracts did not show toxicity against bee larvae; however, those that were fed with the latter showed a significant increase in weight.Research highlights: Three tanninS extracts showed a good antimicrobial activity against P. larvae and they did not show toxicity against bee larvae

Short communication: Natural molecules for the control of Paenibacillus larvae, causal agent of American foulbrood in honey bees (Apis mellifera L.)

Aim of study: To evaluate the potential bactericidal activity of natural molecules against Paenibacillus larvae. Moreover, we investigated if molecules that exhibit antimicrobial activity were able to inhibit the proteolytic activity of the bacterium.Area of study: Isolates S1 and S2 were from Balcarce, Buenos Aires province, strain S3 from Rio Cuarto, Cordoba province, strain S4 from Concordia, Entre Rios province, strain S5 and S8 from Necochea, Buenos Aires, strain S6 and S7 from Mar del Plata, Buenos Aires, strain S9 from Modena, Italy and strain S10 from Emilia Reggio, Italy.Material and methods: Bacterial isolates identification was carried out by amplification of a specific 16S rRNA gene fragment of P. larvae using primers PL5 and PL4. Screening of the antimicrobial activity of thirteen molecules against four P. larvae isolates was conducted by the agar diffusion technique. The antimicrobial activity of selected molecules was evaluated by broth microdilution method.Main results: Menadione, lauric acid, monoglyceride of lauric acid and naringenin showed antimicrobial activity against ten P. larvae isolates. Menadione and lauric acid showed the strongest activities, with minimum inhibitory concentration mean values ranging 0.78-3.125 µg/mLand 25-50 µg/mL, respectively.Research highlights: Those concentrations are feasible to be applied at field level, and constitute promissory candidates to be evaluated using in vivo larval models

Comportamiento Higiénico de Las Abejas Africanizadas ( Apis Mellífera Scutellata Lepeletier) en Apiarios Del Estado Lara, Venezuela

The hygienic behavior of Africanized honeybees (Apis mellifera scutellata Lepeletier) was evaluated in apiaries of three localities of Lara state, Venezuela. Eighty two honeybee colonies in similar management conditions were selected. Hygienic behavior was evaluated using the freezing dead pupae technique with an arbitrary scale specially established for this subspecies. The highest removing of dead pupae was registered in El Corozo locality, with values higher than 95%. The hygienic behavior had a great variation in the Africanized honeybee colonies considered, as 17, 24, and 59% of the honeybee colonies had a low, moderate, and high hygienic behavior, respectively.Se evaluó el comportamiento higiénico de las abejas africanizadas (Apis mellifera scutellata Lepeletier) en apiarios de tres localidades diferentes del estado Lara, Venezuela. Se seleccionaron al azar 82 colonias de abejas en similares condiciones de manejo. Se evaluó el comportamiento higiénico en cada colonia de abejas mediante la técnica de muerte de la cría por congelación utilizando una escala arbitraria especialmente establecida para esta subespecie. La mayor tasa de remoción de pupas muertas fue obtenida en la localidad El Corozo con valores superiores a 95%. La manifestación del comportamiento higiénico presentó una asociación baja con respecto a la localidad y no guarda relación con el grado de africanización de las colonias estudiadas. Se concluye que el comportamiento higiénico presentó gran variación en el grado de manifestación en las colonias de abejas africanizadas, observándose 17, 24 y 59% de colonias con patrón de comportamiento higiénico leve, moderado y alto, respectivamente

Short communication: Antimicrobial activity of indoleacetic, gibberellic and coumaric acids against Paenibacillus larvae and its toxicity against Apis mellifera

Aim of study: To explore three isolated phytomolecules: indoleacetic acid (IAA), gibberellic acid (GA), and the secondary metabolite p-coumaric acid (CUM): (1) evaluating their toxicity against Apis mellifera larvae and adults under controlled conditions in the laboratory; (2) searching for antimicrobial activity against Paenibacillus larvae.Area of study: Honey bee larvae and adults were collected from the experimental apiary of the “Centro de Investigación en Abejas Sociales (CIAS)” (-37.9348798, -57.682817), Institute of the National University of Mar del Plata (UNMdP), Argentina.Material and methods: Paenibacillus larvae strains were isolated from beehives from different provinces of Argentina (Buenos Aires, Córdoba and Entre Ríos) showing clinical symptoms of the American foulbrood. All strains (S1, S2, S3, S4) were genotypically identified using PL5 and PL4 primers and characterized as genotype ERIC1. Then standard essays were performed to determined toxicity of phytomolecules in honey bees and antimicrobial activity through the broth microdilution method.Main results:  The diet with GA, IAA and CUM did not present toxic effects in larvae or adult bees, and only CUM showed antimicrobial activity against P. larvae. In this study, we obtained in vitro values of MNIC (minimum non-inhibitory concentration) of 500 μg mL-1 and a MIC (minimum inhibitory concentration) of 650 μg mL-1 for CUM.Research highlights: The obtained results remark its potential as a natural alternative for the control of P. larvae, avoiding the problems generated by the use of synthetic antibiotics such as the resistance phenomena and the contamination of hive’s products

Prioritizing a research agenda on built environments and physical activity: a twin panel Delphi consensus process with researchers and knowledge users

BACKGROUND: The growth of urban dwelling populations globally has led to rapid increases of research and policy initiatives addressing associations between the built environment and physical activity (PA). Given this rapid proliferation, it is important to identify priority areas and research questions for moving the field forward. The objective of this study was to identify and compare research priorities on the built environment and PA among researchers and knowledge users (e.g., policy makers, practitioners).METHODS: Between September 2022 and April 2023, a three-round, modified Delphi survey was conducted among two independent panels of international researchers (n = 38) and knowledge users (n = 23) to identify similarities and differences in perceived research priorities on the built environment and PA and generate twin 'top 10' lists of the most important research needs.RESULTS: From a broad range of self-identified issues, both panels ranked in common the most pressing research priorities including stronger study designs such as natural experiments, research that examines inequalities and inequities, establishing the cost effectiveness of interventions, safety and injuries related to engagement in active transportation (AT), and considerations for climate change and climate adaptation. Additional priorities identified by researchers included: implementation science, research that incorporates Indigenous perspectives, land-use policies, built environments that support active aging, and participatory research. Additional priorities identified by knowledge users included: built environments and PA among people living with disabilities and a need for national data on trip chaining, multi-modal travel, and non-work or school-related AT.CONCLUSIONS: Five common research priorities between the two groups emerged, including (1) to better understand causality, (2) interactions with the natural environment, (3) economic evaluations, (4) social disparities, and (5) preventable AT-related injuries. The findings may help set directions for future research, interdisciplinary and intersectoral collaborations, and funding opportunities.</p