Antimicrobial Activity against Paenibacillus larvae and Functional Properties of Lactiplantibacillus plantarum Strains: Potential Benefits for Honeybee Health

Contribution of Microbiota to Bioactivity Exerted by Bee Bread

Bee-collected pollen (BCP) and bee bread (BB) are honey bee products known for their beneficial biological properties. The main goal of this study was to investigate BB microbiota and its contribution to bioactivity exerted by BB. The microbiota of BB samples collected at different maturation stages was investigated via culture-independent (Next Generation Sequencing, NGS) and culture-dependent methods. Microbial communities dynamically fluctuate during BB maturation, ending in a stable microbial community structure in mature BB. Bee bread bacterial isolates were tested for phenotypes and genes implicated in the production and secretion of enzymes as well as antibacterial activity. Out of 309 bacterial isolates, 41 secreted hemicellulases, 13 cellulases, 39 amylases, 132 proteinases, 85 Coomassie brilliant blue G or R dye-degrading enzymes and 72 Malachite Green dye-degrading enzymes. Furthermore, out of 309 bacterial isolates, 42 exhibited antibacterial activity against Staphylococcus aureus, 34 against Pseudomonas aeruginosa, 47 against Salmonella enterica ser. Typhimurium and 43 against Klebsiella pneumoniae. Artificially fermented samples exerted higher antibacterial activity compared to fresh BCP, strongly indicating that BB microbiota contribute to BB antibacterial activity. Our findings suggest that BB microbiota is an underexplored source of novel antimicrobial agents and enzymes that could lead to new applications in medicine and the food industry.

Production of Conjugated Linoleic Acid (CLA) by Lactiplantibacillus plantarum: A Review with Emphasis on Fermented Foods

The term Conjugated Linoleic Acid (CLA) refers generically to a class of positional and geometric conjugated dienoic isomers of linoleic acid. Among the isomers of linoleic acid cis9, trans11-CLA (c9, t11-CLA) and trans10, cis12-CLA (t10, c12-CLA) are found to be biologically active isomers, and they occur naturally in milk, dairy products and meat from ruminants. In addition, some vegetables and some seafoods have also been reported to contain CLA. Although the CLA levels in these natural sources are insufficient to confer the essential health benefits, anti-carcinogenic or anti-cancer effects are of current interest. In the rumen, CLA is an intermediate of isomerization and the biohydrogenation process of linoleic acid to stearic acid conducted by ruminal microorganisms. In addition to rumen bacteria, some other bacteria, such as Propionibacterium, Bifidobacterium and some lactic acid bacteria (LAB) are also capable of producing CLA. In this regard, Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) has demonstrated the ability to produce CLA isomers from linoleic acid by multiple enzymatic activities, including hydration, dehydration, and isomerization. L. plantarum is one of the most versatile species of LAB and the bacterium is widely used in the food industry as a microbial food culture. Thus, in this review we critically analyzed the literature produced in the last ten years with the aim to highlight the potentiality as well as the optimal conditions for CLA production by L. plantarum. Evidence was provided suggesting that the use of appropriate strains of L. plantarum, as a starter or additional culture in the production of some fermented foods, can be considered a critical factor in the design of new CLA-enriched functional foods.

Bacterial Strains Isolated from Stingless Bee Workers Inhibit the Growth of Apis mellifera Pathogens

Apis mellifera bees are an important resource for the local economy of various regions in Argentina and the maintenance of natural ecosystems. In recent years, different alternatives have been investigated to avoid the reduction or loss of colonies caused by pathogens and parasites such as Ascosphaera apis, Aspergillus flavus, and Paenibacillus larvae. We focused on bacterial strains isolated from the intestine of native stingless bees, to elucidate their antagonistic effect on diseases of A. mellifera colonies. For this purpose, worker bees of the species Tetragonisca fiebrigi, Plebeia spp., and Scaptotrigona jujuyensis were captured from the entrance to tree hives and transported to the laboratory, where their intestines were extracted. Twenty bacterial colonies were isolated from the intestines, and those capable of inhibiting enterobacteria in vitro and producing organic acids, proteases, and chitinases were selected. Four genera, Levilactobacillus, Acetobacter, Lactiplantibacillus, and Pantoea, were selected and identified by the molecular marker that codes for the 16S rRNA gene. For inhibition assays, cell suspensions and cell-free suspensions were performed. All treatments showed significant antibacterial effects, in comparison with the controls, against P. larvae and antifungal effects against A. apis and A. flavus. However, the mechanisms by which these bacteria inhibit the growth of these pathogens were not studied.

Biosynthesis of Gamma-Aminobutyric Acid (GABA) by Lactiplantibacillus plantarum in Fermented Food Production

In recent decades, given the important role of gamma-aminobutyric acid (GABA) in human health, scientists have paid great attention to the enrichment of this chemical compound in food using various methods, including microbial fermentation. Moreover, GABA or GABA-rich products have been successfully commercialized as food additives or functional dietary supplements. Several microorganisms can produce GABA, including bacteria, fungi, and yeasts. Among GABA-producing microorganisms, lactic acid bacteria (LAB) are commonly used in the production of many fermented foods. Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a LAB species that has a long history of natural occurrence and safe use in a wide variety of fermented foods and beverages. Within this species, some strains possess not only good pro-technological properties but also the ability to produce various bioactive compounds, including GABA. The present review aims, after a preliminary excursus on the function and biosynthesis of GABA, to provide an overview of the current uses of microorganisms and, in particular, of L. plantarum in the production of GABA, with a detailed focus on fermented foods. The results of the studies reported in this review highlight that the selection of new probiotic strains of L. plantarum with the ability to synthesize GABA may offer concrete opportunities for the design of new functional foods.

Probiotics and in-hive fermentation as a source of beneficial microbes to support the gut microbial health of honey bees

Managed populations of honey bees (Apis mellifera Linnaeus; Hymenoptera: Apidae) are regularly exposed to infectious diseases. Good hive management including the occasional application of antibiotics can help mitigate infectious outbreaks, but new beekeeping tools and techniques that bolster immunity and help control disease transmission are welcome. In this review, we focus on the applications of beneficial microbes for disease management as well as to support hive health and sustainability within the apicultural industry. We draw attention to the latest advances in probiotic approaches as well as the integration of fermented foods (such as water kefir) with disease-fighting properties that might ultimately be delivered to hives as an alternative or partial antidote to antibiotics. There is substantial evidence from in vitro laboratory studies that suggest beneficial microbes could be an effective method for improving disease resistance in honey bees. However, colony level evidence is lacking and there is urgent need for further validation via controlled field trials experimentally designed to test defined microbial compositions against specific diseases of interest.

Comparing the biological properties and chemical profiling of chestnut bee pollen and bee bread collected from Anatolia

Bee bread (BB) and bee pollen (BP) are accepted as functional food and considered in medical properties due to its important bioactive components. These bee products show different biological properties, but researches on these aspects have not been clear yet. In present study, Anatolian BB and BP extracts were analyzed for the first time for their pollen type, total phenolic (TPC) and flavonoid content (TFC), and antimicrobial and antioxidant properties. Samples were analyzed for their antimicrobial efficacy by the agar well diffusion and MIC methods. HPLC analysis was used to identify the compounds in the BB and BP samples. Antioxidant activity was measured by the FRAP and DPPH methods. As a result of microscopy for pollen identification, Fagaceae family was dominant. Phenolic compound analysis showed that the amounts of p-coumaric acid and rutin were found to be the highest in BB and BP, respectively. Stronger antioxidant activity was obtained from BP. MIC values of BB were range from 250 to 12.5 μg/mL. The most susceptible bacterium was Mycobacterium smegmatis. The extract of BP was effective on all gram-negative bacteria with doses range from 250 μg/mL to 500 μg/mL. The lowest MIC value was detected with the concentration of 12.5 μg/mL against M. smegmatis. Anatolian BB and BP could be considered as a functional foods due to antioxidant activity and may be beneficial in the management and treatment of pathogenic bacteria because of high antimicrobial activity.

Characterization of Lactic Acid Bacteria Strains Isolated from Algerian Honeybee and Honey and Exploration of Their Potential Probiotic and Functional Features for Human Use

Using culture enrichment methods, 100 strains of bacilli of lactic acid bacteria (LAB) were isolated from honeybee Apis mellifera intermissa and fresh honey, collected from apiaries located in the north-east of Algeria. Amongst all of the isolated LAB, 19 selected strains were closely affiliated to four species-Fructobacillus fructosus (10), Apilactobacillus kunkeei (5), Lactobacillus kimbladii and/or Lactobacillus kullabergensis (4)-using phylogenetic and phenotypic approaches. The in vitro probiotic characteristics (simulated gastrointestinal fluids tolerance, autoaggregation and hydrophobicity abilities, antimicrobial activity and cholesterol reduction) and safety properties (hemolytic activity, antibiotic resistance and absence of biogenic amines) were evaluated. The results indicated that some strains showed promising potential probiotic properties. In addition, neither hemolytic activity nor biogenic amines were produced. The carbohydrate fermentation test (API 50 CHL) revealed that the strains could efficiently use a broad range of carbohydrates; additionally, four strains belonging to Apilactobacillus kunkeei and Fructobacillus fructosus were found to be exopolysaccharides (EPS) producers. This study demonstrates the honeybee Apis mellifera intermissa and one of her products as a reservoir for novel LAB with potential probiotic features, suggesting suitability for promoting host health.

Probiotic candidates for controlling Paenibacillus larvae, a causative agent of American foulbrood disease in honey bee

BACKGROUND

American foulbrood (AFB) disease caused by Paenibacillus larvae is dangerous, and threatens beekeeping. The eco-friendly treatment method using probiotics is expected to be the prospective method for controlling this pathogen in honey bees. Therefore, this study investigated the bacterial species that have antimicrobial activity against P. larvae.

RESULTS

Overall, 67 strains of the gut microbiome were isolated and identified in three phyla; the isolates had the following prevalence rates: Firmicutes 41/67 (61.19%), Actinobacteria 24/67 (35.82%), and Proteobacteria 2/67 (2.99%). Antimicrobial properties against P. larvae on agar plates were seen in 20 isolates of the genus Lactobacillus, Firmicutes phylum. Six representative strains from each species (L. apis HSY8_B25, L. panisapium PKH2_L3, L. melliventris HSY3_B5, L. kimbladii AHS3_B36, L. kullabergensis OMG2_B25, and L. mellis OMG2_B33) with the largest inhibition zones on agar plates were selected for in vitro larvae rearing challenges. The results showed that three isolates (L. apis HSY8_B25, L. panisapium PKH2_L3, and L. melliventris HSY3_B5) had the potential to be probiotic candidates with the properties of safety to larvae, inhibition against P. larvae in infected larvae, and high adhesion ability.

CONCLUSIONS

Overall, 20 strains of the genus Lactobacillus with antimicrobial properties against P. larvae were identified in this study. Three representative strains from different species (L. apis HSY8_B25, L. panisapium PKH2_L3, and L. melliventris HSY3_B5) were evaluated to be potential probiotic candidates and were selected for probiotic development for the prevention of AFB. Importantly, the species L. panisapium isolated from larvae was identified with antimicrobial activity for the first time in this study.

Probiotic Properties, Safety Assessment, and Aroma-Generating Attributes of Some Lactic Acid Bacteria Isolated from Iranian Traditional Cheese

Artisanal cheeses are known as the source of beneficial lactic acid bacteria (LAB). Therefore, this study aimed to isolate and characterize LAB with different proteolytic activities from Iranian artisanal white cheeses. The isolates were classified into low, medium, and high proteolytic activity clusters via K-means clustering and identified as Lactiplantibacillus (Lpb.) pentosus L11, Lpb. plantarum L33, and Enterococcus faecium L13, respectively. Some safety tests (such as resistance to antibiotics, hemolytic activity, and biogenic amine production), probiotic properties (including cell surface hydrophobicity, auto/co-aggregation, and antibacterial activity), and production of volatile compounds were evaluated. These were non-hemolytic and non-biogenic amine producers, and showed no irregular antibiotic resistance. Lpb. plantarum L33 had the highest hydrophobicity (30.55%) and auto-aggregation (49.56%), and the highest co-aggregation was observed for Lpb. pentosus L11 with Staphylococcus aureus (61.51%). The isolates also showed a remarkable antibacterial effect against pathogenic bacteria. Moreover, Lpb. pentosus L11 and Lpb. plantarum L33 with low and medium proteolytic activity produced a wider range of volatile compounds in milk compared to the strain with a high proteolytic effect. The results showed that a probiotic strain with low or medium proteolytic activity could improve the flavor characteristics of fermented milk.

Beneficial bacteria as biocontrol agents for American foulbrood disease in honey bees (Apis mellifera)

American foulbrood (AFB) is a cosmopolitan bacterial disease that affects honey bee (Apis mellifera) larvae and causes great economic losses in apiculture. Currently, no satisfactory methods are available for AFB treatment mainly due to the difficulties to eradicate the tenacious spores produced by the etiological agent of AFB, Paenibacillus larvae (Bacillales, Paenibacillaceae). This present review focused on the beneficial bacteria that displayed antagonistic activities against P. larvae and demonstrated potential in AFB control. Emphases were placed on commensal bacteria (genus Bacillus and lactic acid bacteria in particular) in the alimentary tract of honey bees. The probiotic roles lactic acid bacteria play in combating the pathogenic P. larvae and the limitations referring to the application of these beneficial bacteria were addressed.

Disentangling the microbial ecological factors impacting honey bee susceptibility to Paenibacillus larvae infection

Paenibacillus larvae is a spore-forming bacterial entomopathogen and causal agent of the important honey bee larval disease, American foulbrood (AFB). Active infections by vegetative P. larvae are often deadly, highly transmissible, and incurable for colonies but, when dormant, the spore form of this pathogen can persist asymptomatically for years. Despite intensive investigation over the past century, this process has remained enigmatic. Here, we provide an up-to-date synthesis on the often overlooked microbiota factors involved in the spore-to-vegetative growth transition (corresponding with the onset of AFB disease symptoms) and offer a novel outlook on AFB pathogenesis by focusing on the 'collaborative' and 'competitive' interactions between P. larvae and other honey bee-adapted microorganisms. Furthermore, we discuss the health trade-offs associated with chronic antibiotic exposure and propose new avenues for the sustainable control of AFB via probiotic and microbiota management strategies.

Honeybee-associated lactic acid bacteria and their probiotic potential for human use

This study aims to identify lactic acid bacteria (LAB) isolated from honeybees (Apis mellifera workers and larvae) in detail and to determine their functional probiotic properties. A total of 11 strains were classified based on morphological and biochemical characteristics. Preliminary probiotic properties of strains, that were molecularly identified using 16 S rRNA, such as antimicrobial activity, tolerance to digestive conditions, aggregation ability, were investigated. The antimicrobial properties of strains were tested against a wide range of human pathogens. All strains that showed γ-hemolysis and did not contain bacteriophages were considered safe. The strains' survivability checked for 0.3% bile and 3.0-7.8 pH contents was promising. The highest autoaggregation ranged from 14.7 to 30.76% after 4 h. Tested LAB strains markedly exhibited coaggregation with Listeria monocytogenes and Escherichia coli. According to the results, tested bacteria showed significant antagonistic effects against pathogens, and positive probiotic characteristics compatible with in vitro gastrointestinal tract conditions. The results suggest that Apis mellifera LAB symbionts may have a probiotic potential, and be effective and safe candidates for human use. This study provides an addition to the development of the current knowledge by defining in detail honeybee-associated bacteria and determining their probiotic potential.

In Vitro Assessment of Bio-Functional Properties from Lactiplantibacillus plantarum Strains

In recent years, alongside the conventional screening procedures for the evaluation of probiotics for human usage, the pharmaceutical and food industries have encouraged scientific research towards the selection of new probiotic bacterial strains with particular functional features. Therefore, this study intended to explore novel functional properties of five Lactiplantibacillus plantarum strains isolated from bee bread. Specifically, antioxidant, antimicrobial and β-glucosidase activities, exopolysaccharides (EPS) production and the ability to synthesize γ-aminobutyric acid (GABA) were evaluated. The results demonstrated that the investigated L. plantarum strains were effective in inhibiting the growth of some human opportunistic pathogens in vitro (Pseudomonas aeruginosa, Escherichia coli, Proteus mirabilis, Enterococcus faecalis and Staphylococcus aureus). Moreover, the evaluation of antioxidant and β-glucosidase activity and of EPS and GABA production, revealed a different behavior among the strains, testifying how these properties are strongly strain-dependent. This suggests that a careful selection within a given species is important in order to identify appropriate strains for specific biotechnological applications. The results highlighted that the five strains of L. plantarum are promising candidates for application as dietary supplements in the human diet and as microbial cultures in specific food productions.

Antimicrobial Activity from Putative Probiotic Lactic Acid Bacteria for the Biological Control of American and European Foulbrood Diseases

The balance of the gut microbiome is important for the honey bee’s growth and development, immune function and defense against pathogens. The use of a beneficial bacteria-based strategy for the prevention and biocontrol of American foulbrood (AFB) and European foulbrood (EFB) diseases in honey bees offers interesting prospects. Lactic acid bacteria (LAB) are common inhabitants of the gastrointestinal tract of the honey bee. Among LABs associated with bee gut microbiota, Lactiplantibacillus plantarum (previously Lactobacillus plantarum) and Apilactobacillus kunkeei (formerly classified as Lactobacillus kunkeei) are two of the most abundant species. In this study, four Lactiplantibacillus plantarum strains and four Apilactobacillus kunkeei strains, isolated from the gastrointestinal tract of honey bee (Apis mellifera L.) were selected for their in vitro inhibition ability of Paenibacillus larvae ATCC 9545 and Melissococccus plutonius ATCC 35311. In addition, these LABs have been characterized through some biochemical and functional characteristics: cell surface properties (hydrophobicity and auto-aggregation), carbohydrates assimilation and enzymatic activities. The antimicrobial, biochemical and cell surface properties of these LABs have been functional to their candidature as potential probiotics in beekeeping and for the biocontrol of AFB and EFB diseases.

Functional Properties and Antimicrobial Activity from Lactic Acid Bacteria as Resources to Improve the Health and Welfare of Honey Bees

Simple Summary

Honey bees play a pivotal role in the sustainability of ecosystems and biodiversity. Many factors including parasites, pathogens, pesticide residues, forage losses, and poor nutrition have been proposed to explain honey bee colony losses. Lactic acid bacteria (LAB) are normal inhabitants of the gastrointestinal tract of honey bees and their role has been consistently reported in the literature. In recent years, there have been numerous scientific evidence that the intestinal microbiota plays an essential role in honey bee health. Management strategies, based on supplementation of the gut microbiota with probiotics, may be important to increase stress tolerance and disease resistance. In this review, recent scientific advances on the use of LABs as microbial supplements in the diet of honey bees are summarized and discussed.

Abstract

Honey bees (Apis mellifera) are agriculturally important pollinators. Over the past decades, significant losses of wild and domestic bees have been reported in many parts of the world. Several biotic and abiotic factors, such as change in land use over time, intensive land management, use of pesticides, climate change, beekeeper’s management practices, lack of forage (nectar and pollen), and infection by parasites and pathogens, negatively affect the honey bee’s well-being and survival. The gut microbiota is important for honey bee growth and development, immune function, protection against pathogen invasion; moreover, a well-balanced microbiota is fundamental to support honey bee health and vigor. In fact, the structure of the bee’s intestinal bacterial community can become an indicator of the honey bee’s health status. Lactic acid bacteria are normal inhabitants of the gastrointestinal tract of many insects, and their presence in the honey bee intestinal tract has been consistently reported in the literature. In the first section of this review, recent scientific advances in the use of LABs as probiotic supplements in the diet of honey bees are summarized and discussed. The second section discusses some of the mechanisms by which LABs carry out their antimicrobial activity against pathogens. Afterward, individual paragraphs are dedicated to Chalkbrood, American foulbrood, European foulbrood, Nosemosis, and Varroosis as well as to the potentiality of LABs for their biological control.

Probiotic Potentiality from Versatile Lactiplantibacillus plantarum Strains as Resource to Enhance Freshwater Fish Health

Dietary probiotic supplementation has the potential to enhance the health of fish and their disease resistance. In this study, some properties of ten Lactiplantibacillus plantarum strains have been evaluated, for their potential use as probiotics in freshwater fish diet. In particular, antimicrobial activity, antioxidant activity, the potentiality to survive the gastrointestinal transit and persist in the intestine, were evaluated in vitro. The experimental tests were carried out at 15 °C and 30 °C to determine the suitability of these lactic acid bacteria to be used as probiotics in the diet of fish grown at different temperatures. The results demonstrated that the evaluated Lp. plantarum strains, which often have significant differences among themselves, are characterized by important functional characteristics such as cell surface properties (auto-aggregation and hydrophobicity), ability to produce antioxidant substances, capacity to survive in the presence of 0.3% bile salts and acidic environment (2.5 pH), antagonistic activity against some fish opportunistic pathogens (A. salmonicida, Ps. aeruginosa, E. coli and C. freundii) and other unwanted bacteria present in fish products (S. aureus and L. innocua). The outcomes suggest that these Lp. plantarum strains may be candidates as probiotics in warm- and cold-water aquaculture.

Bee Pollen and Bee Bread as a Source of Bacteria Producing Antimicrobials

The principal objective of the study was the isolation and identification of bacteria that are present in mature bee bread (BB) and dried (ready for selling and consumption) bee pollen (BP). Obtained isolates were screened for their potential to inhibit select human pathogenic bacteria and their ability to produce enzymes of particular industrial importance. Four and five samples of BP and BB, respectively, were used for the study. In total, 81 strains of bacteria were isolated, and 34 (42%) of them exhibited antagonistic interactions with at least one reference strain of pathogenic bacteria, namely Staphylococcus aureus ATCC 25923, Staphylococcus aureus ATCC 29213, Staphylococcus epidermidis 12228, Pseudomonas aeruginosa ATCC 27857, and Escherichia coli ATCC 25922. The sequencing of the 16S rRNA gene revealed that all strains producing antimicrobials belong to the genus Bacillus spp., and among them, five species were identified: B. pumilus (n = 17), B. altitudinis (n = 9), B. licheniformis (n = 4), B. subtilis (n = 2), and B. safensis (n = 1). Furthermore, 69, 54, 39, and 29 of the strains exhibited lipolytic, proteolytic, cellulolytic, and esterolytic activity, respectively. Alpha amylase and beta galactosidase activity were rarely observed, and none of the strains produced laccase. The outcomes of the study revealed that BP and BB can be considered potential sources of bacteria producing antimicrobial agents and/or enzymes of particular industrial importance. Of course, additional research is required to verify this hypothesis, but the results of preliminary studies are promising.

Probiotic Properties and Potentiality of Lactiplantibacillus plantarum Strains for the Biological Control of Chalkbrood Disease

Ascosphaera apis is an entomopathogenic fungus that affects honeybees. In stressful conditions, this fungus (due not only to its presence, but also to the combination of other biotic and abiotic stressors) can cause chalkbrood disease. In recent years, there has been increasing attention paid towards the use of lactic acid bacteria (LAB) in the honeybees' diets to improve their health, productivity and ability to resist infections by pathogenic microorganisms. The screening of 22 strains of Lactiplantibacillus plantarum, isolated from the gastrointestinal tracts of honeybees and beebread, led to the selection of five strains possessing high antagonistic activity against A. apis. This study focused on the antifungal activity of these five strains against A. apis DSM 3116 and DSM 3117 using different matrices: cell lysate, broth culture, cell-free supernatant and cell pellet. In addition, some functional properties and the antioxidant activity of the five L. plantarum strains were evaluated. All five strains exhibited high antagonistic activity against A. apis, good surface cellular properties (extracellular polysaccharide (EPS) production and biofilm formation) and antioxidant activity. Although preliminary, these results are encouraging, and in future investigations, the effectiveness of these bacteria as probiotics in honeybee nutrition will be tested in vivo in the context of an eco-friendly strategy for the biological control of chalkbrood disease.

Editorial for the Special Issue: "Honey Bee Products as an Alternative or Complement to Classical Antibiotics"

Based on World Health Organization reports, the resistance of bacteria to well-known antibiotics is becoming a major global health challenge [...].

Bee Bread Exhibits Higher Antimicrobial Potential Compared to Bee Pollen

This study aimed at investigation of the antimicrobial potential of ethanolic extracts of bee bread (BB) and bee pollen (BP) and suspensions of these products in MHB (Mueller Hinton Broth). We covered 30 samples of BP and 19 samples of BB harvested in Polish apiaries. Slightly lower activity was observed against Gram-negative bacteria compared to Gram-positive staphylococci. BB extracts exhibited higher inhibitory potential with minimum inhibitory concentration (MIC) values in the range from 2.5 to 10% (v/v) against Staphylococcus aureus ATCC 25923 and ATCC 29213. Most active BB extracts, namely, BB6, BB11 and BB19, effectively inhibited growth of clinical isolates of S. aureus (n = 9), including MRSA (methicillin resistant Staphylococcus aureus) strains (n = 3) at concentrations ranging from 2.5 to 5.0% (v/v). Minimal bactericidal concentration (MBC) values were in the same range of concentrations; however, a shift from 2.5 to 5.0% (v/v) was observed for some products. The most active BP extracts inhibited the growth of reference strains of S. aureus at a concentration of 5% (v/v). Up to the concentration of 20% (v/v) three and seven BP extracts were not able to inhibit the growth of S. aureus ATCC 29213 and S. aureus ATCC 25923 respectively. The growth of staphylococci was also importantly inhibited in suspensions of the products in MHB. No correlation between phenolic content and antimicrobial activity was observed.

Fructose and Trehalose Selectively Enhance In Vitro Sporulation of Paenibacillus larvae ERIC I and ERIC II Strains

Paenibacillus larvae is a Gram-positive bacterium, the spores of which are the causative agent of the most destructive brood disease of honeybees, American foulbrood (AFB). Obtaining viable spores of pathogen strains is requisite for different studies concerning AFB. The aim of this work was to investigate the effects of five saccharides that may naturally occur in higher amounts in bee larvae on in vitro sporulation of P. larvae. The effect of individual saccharides at different concentrations on spore yields of P. larvae strains of epidemiologically important ERIC genotypes was examined in Columbia sheep blood agar (CSA) and MYPGP agar media. It was found that fructose in ERIC I and trehalose in ERIC II strains at concentrations in the range of 0.5-2% represent new sporulation factors that significantly enhanced the yields of viable spores in both media, mostly in a concentration-dependent manner. The enhancements in spore yield were mainly caused by improvements of the germination ability of the spores produced. Glucose, maltose and sucrose at 1% or 0.5% concentrations also supported sporulation but to a lower extent and not in all strains and media. Based on the knowledge gained, a novel procedure was proposed for the preparation of viable P. larvae spores with supposed improved quality for AFB research.

Inter- and Intra-Species Diversity of Lactic Acid Bacteria in Apis mellifera ligustica Colonies

Lactic acid bacteria could positively affect the health of honey bees, including nutritional supplementation, immune system development and pathogen colonization resistance. Based on these considerations the present study evaluated predominant Lactic Acid Bacteria (LAB) species from beebread as well as from the social stomach and midgut of Apis mellifera ligustica honey bee foragers. In detail, for each compartment, the diversity in species and biotypes was ascertained through multiple culture-dependent approaches, consisting of Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE), 16S rRNA gene sequencing and Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR). The study of a lactic acid bacteria community, performed with PCR-DGGE and sequence analysis targeting the V1-V3 region of the 16S rRNA gene (rDNA), highlighted the presence of a few species, including Apilactobacillus kunkeei, Lactiplantibacillus plantarum, Fructobacillus fructosus, Levilactobacillus brevis and Lactobacillus delbrueckii subsp. lactis. Depending on the different compartments, diverse levels of biodiversity in species were found. Particularly, a very low inter-species biodiversity was detected in the midgut that was prevalently dominated by the presence of Apilactobacillus kunkeei. On the other hand, the beebread was characterized by a reasonable biodiversity showing the presence of five species and the predominance of Apilactobacillus kunkeei, Lactiplantibacillus plantarum and Fructobacillus fructosus. The RAPD-PCR analysis performed on the three predominant species allowed the differentiation into several biotypes for each species. Moreover, a relationship between biotypes and compartments has been detected and each biotype was able to express a specific biochemical profile. The biotypes that populated the social stomach and midgut were able to metabolize sugars considered toxic for bees while those isolated from beebread could contribute to release useful compounds with functional properties. Based on this knowledge, new biotechnological approaches could be developed to improve the health of honey bees and the quality of bee products.