The Synthetic Peptide LyeTx I mn∆K, Derived from Lycosa erythrognatha Spider Toxin, Is Active against Methicillin-Resistant Staphylococcus aureus (MRSA) In Vitro and In Vivo.

The urgent global health challenge posed by methicillin-resistant Staphylococcus aureus (MRSA) infections demands effective solutions. Antimicrobial peptides (AMPs) represent promising tools of research of new antibacterial agents and LyeTx I mn∆K, a short synthetic peptide based on the Lycosa erythrognatha spider venom, is a good representative. This study focused on analyzing the antimicrobial activities of LyeTx I mn∆K, including minimum inhibitory and bactericidal concentrations, synergy and resensitization assays, lysis activity, the effect on biofilm, and the bacterial death curve in MRSA. Additionally, its characterization was conducted through isothermal titration calorimetry, dynamic light scattering, calcein release, and finally, efficacy in a mice wound model. The peptide demonstrates remarkable efficacy against planktonic cells (MIC 8-16 µM) and biofilms (>30% of inhibition) of MRSA, and outperforms vancomycin in terms of rapid bactericidal action and anti-biofilm effects. The mechanism involves significant membrane damage. Interactions with bacterial model membranes, including those with lysylphosphatidylglycerol (LysylPOPG) modifications, highlight the versatility and selectivity of this compound. Also, the peptide has the ability to sensitize resistant bacteria to conventional antibiotics, showing potential for combinatory therapy. Furthermore, using an in vivo model, this study showed that a formulated gel containing the peptide proved superior to vancomycin in treating MRSA-induced wounds in mice. Together, the results highlight LyeTx I mnΔK as a promising prototype for the development of effective therapeutic strategies against superficial MRSA infections.

Microbial communities associated with honey bees in Brazil and in the United States.

Honey bee colony losses worldwide call for a more in-depth understanding of the pathogenic and mutualistic components of the honey bee microbiota and their relation with the environment. In this descriptive study, we characterized the yeast and bacterial communities that arise from six substrates associated with honey bees: corbicular pollen, beebread, hive debris, intestinal contents, body surface of nurses and forager bees, comparing two different landscapes, Minas Gerais, Brazil and Maryland, United States. The sampling of five hives in Brazil and four in the USA yielded 217 yeast and 284 bacterial isolates. Whereas the yeast community, accounted for 47 species from 29 genera, was dominated in Brazil by Aureobasidium sp. and Candida orthopsilosis, the major yeast recovered from the USA was Debaryomyces hansenii. The bacterial community was more diverse, encompassing 65 species distributed across 31 genera. Overall, most isolates belonged to Firmicutes, genus Bacillus. Among LAB, species from Lactobacillus were the most prevalent. Cluster analysis evidenced high structuration of the microbial communities, with two distinguished microbial groups between Brazil and the United States. In general, the higher difference among sites and substrates were dependents on the turnover effect (~ 93% of the beta diversity), with a more pronounced effect of nestedness (~ 28%) observed from Brazil microbiota change. The relative abundance of yeasts and bacteria also showed the dissimilarity of the microbial communities between both environments. These results provide a comprehensive view of microorganisms associated with A. mellifera, highlighting the importance of the environment in the establishment of the microbiota associated with honey bees.

Biological activities of extracts from Aspidosperma subincanum Mart. and in silico prediction for inhibition of acetylcholinesterase.

Species of Aspidosperma are traditionally used to treat malaria, leishmaniasis, microbial, and inflammatory diseases. Aspidosperma subincanum Mart. known as "guatambu" is used in Brazilian traditional medicine to treat diabetes, hypercholesterolemia, and digestive diseases. Its tonic properties have been employed by the indigenous populations to stimulate the circulatory and genitourinary tracts and to improve respiratory function as well as to relieve spasms and to reduce fever. The species is known to contain antitumoural and antimalarial indole alkaloids. In the present study, various less explored biological activities of extracts from leaves and branches of A. subincanum were investigated, that is, inhibition of acetylcholinesterase as well as antioxidant and antibacterial activity. Twenty-one known indole alkaloids from this species were targeted for predicting the inhibition of acetylcholinesterase, and their biological activities were collected from the literature. Through in silico the prediction, the indole alkaloids uleine and derivatives demonstrated a strong probability of being able to inhibit the acetylcholinesterase enzyme, as well as the olivacine derivatives 3,4-dihydroolivacine and N-methyl-tetrahydro-olivacine (guatambuine), and the subincanadines C and E. Indeed, the extracts of A. subincanum showed acetylcholinesterase inhibitory activity, antioxidant activity in the lipid peroxidation assay, and antimicrobial activity against Staphylococcus aureus ATCC 25923, and their pharmacological properties should be explored further.

Bacterial microflora in the gastrointestinal tract of Nile tilapia, Oreochromis niloticus, cultured in a semi-intensive system- DOI: 10.4025/actascibiolsci.v25i2.2007 / Flora bacteriana de tilápia do Nilo, Oreochromis niloticus, cultivada em sistema semi-intensivo - DOI: 10.4025/actascibiolsci.v25i2.2007

This experiment measured total bacterial numbers in the gastrointestinal regions of semi-intensively cultured tilapia, Oreochromis niloticus L. (Cichlidae). Mean bacterial numbers were higher in both anterior and posterior gut than in stomach. The percentage of isolated species and the percentage of isolates from any particular species varied significantly among gastrointestinal tract regions. Aeromonas hydrophila, Aeromonas veronii, Burkholderia cepacia, Chromobacterium violaceum, Citrobacter freundii, Escherichia coli, Flavimonas oryzihabitans and Plesiomonas shigelloides were the most frequently isolated Gram-negative bacilli. From these samples, only Plesiomonas shigelloides was present in both gastrointestinal regions, with higher number in the posterior gut (76%), when compared to anterior gut (4.8%) and stomach (0.6%). Aeromonas hydrophila (0.6%), Escherichia coli (7.4%), and Flavimonas oryzihabitans were isolated only in the stomach, and Citrobacter freundii and Burkholderia cepacia were found only in the posterior gut. Chromobacterium violaceum was the dominant bacteria isolated from stomach and anterior gut, with 90% and 55%, respectively. Unidentified organisms comprised 0 - 39.3% of the gastrointestinal microflora

A flora bacteriana de diferentes partes do trato gastrintestinal de tilápia Oreochomis niloticus L. (Cichlidae) foi determinada. O número médio de bactérias foi maior no intestino anterior e posterior quando comparado ao estômago. A porcentagem total de espécies bacterianas isoladas e a porcentagem de espécies isoladas em uma espécie particular variaram significativamente entre as regiões do trato gastrintestinal. Aeromonas hydrophila, Aeromonas veronii, Burkholderia cepacia, Chromobacterium violaceum, Citrobacter freundii, Escherichia coli, Flavimonas oryzihabitans e Plesiomonas shigelloides foram os bacilos Gram-negativos encontrados com maior freqüência. Destas espécies, somente Plesiomonas shigelloides esteve presente em cada região do trato gastrintestinal, apresentando maior número no intestino posterior (76%), quando comparado com o intestino anterior (4.8%) e o estômago (0.6%). Aeromonas hydrophila (0.6%), Escherichia coli (7.4%), e Flavimonas oryzihabitans foram isoladas somente do estômago, e Citrobacter freundii e Burkholderia cepacia foram encontradas somente no intestino posterior. Chromobacterium violaceum foi a espécie dominante isolada do estômago e do intestino anterior com 90% e 55%, respectivamente. Organismos não identificados compreendem 0 39.3% da microbiota gastrintestinal

Haematological and biochemical values for Nile tilapia Oreochromis niloticus cultured in semi-intensive system - DOI: 10.4025/actascibiolsci.v25i2.2028 / Valores hematológicos e bioquímicos em tilápia do Nilo Oreochromis niloticus cultivada em sistema semi-intensivo - DOI: 10.4025/actascibiolsci.v25i2.2028

The aim of the present study was to investigate the reference ranges for haematological and biochemical values for Nile tilapia, Oreochromis niloticus (Cichlidae), cultivated in a semi-intensive system. Erythrocytes number was 6.93 ± 8.28 x 106/mm3, hemoglobin 10.52 ± 3.09g/dL of blood and hematocrit 31.85 ± 8.45%, mean corpuscular volume (MVC) 148.80 ±. 153.19µ3, mean corpuscular hemoglobin (MCH) 40.74 ± 34.19 pg and mean corpuscular hemoglobin concentration (MCHC) 35.24 ± 14.92%. Total plasma protein and glucose values obtained were 3.06 ± 0.65g/dl and 60.32 ± 20.22mg/dl, respectively. A correlation matrix was established to compare de degree of association among biometric data and hematological parameters, and among each of them and biochemical values. A positive correlation was observed among weight, length, MCV and MHC, as well as between length and hematocrit. The blood glucose level was positively correlated with weight and length, whereas total protein was positively correlated with hemoglobin. The erythrocytes count was positively correlated with hemoglobin and negatively correlated with MCV and MHC. Microscopy examination of blood smears revealed the presence of erythrocytes, neutrophils, lymphocytes, and monocytes. Under the conditions employed here, no basophils or eosinophils, nor their precursors, could be found in blood smears of Nile tilapia

O objetivo do presente estudo foi investigar os valores de referências hematológicos e bioquímicos para a tilápia do Nilo, Oreochromis niloticus (Cichlidae), cultivada em sistema semi-intensivo. A contagem de eritrócitos foi 6,93 ± 8,28 x 106/mm3, hemoglobina 10,52 ± 3,09g/dL de sangue, hematócrito 31,85 ± 8,45%, volume corpuscular médio (MVC) 148,80 ±.153,19µ3, hemoglobina corpuscular média (MCH) 40,74 ± 34,19pg e concentração de hemoglobina corpuscular média 35,24 ± 14,92%. Os valores de proteína plasmática total e da glicose obtidos foram de 3,06 ± 0,65g/dl e 60,32 ± 20,22mg/dl, respectivamente. Uma matriz de correlação foi estabelecida para comparar o grau de associação entre os dados biométricos e parâmetros hematológicos, e entre estes e os valores bioquímicos. Uma correlação positiva foi observada entre peso, comprimento, MCV e MHC, bem como entre comprimento e hematócrito. O nível de glicose sanguínea foi positivamente correlacionado com o peso e o comprimento, enquanto proteína total foi positivamente correlacionada com a hemoglobina. A contagem de eritrócito foi positivamente correlacionada com a hemoglobina e negativamente correlacionada com MCH e MHC. A observação microscópica do esfregaço sangüíneo revelou a presença de eritrócitos, neutrófilos, linfócitos e monócitos. Sob as condições empregadas no estudo não foram encontrados basófilos, ensinófilos ou seus precur