Diversity and pathogenesis of Staphylococcus aureus from bovine mastitis: current understanding and future perspectives

Staphylococcus aureus is a leading cause of bovine mastitis worldwide. Despite some improved understanding of disease pathogenesis, progress towards new methods for the control of intramammary infections (IMI) has been limited, particularly in the field of vaccination. Although herd management programs have helped to reduce the number of clinical cases, S. aureus mastitis remains a major disease burden. This review summarizes the past 16 years of research on bovine S. aureus population genetics, and molecular pathogenesis that have been conducted worldwide. We describe the diversity of S. aureus associated with bovine mastitis and the geographical distribution of S. aureus clones in different continents. We also describe studies investigating the evolution of bovine S. aureus and the importance of host-adaptation in its emergence as a mastitis pathogen. The available information on the prevalence of virulence determinants and their functional relevance during the pathogenesis of bovine mastitis are also discussed. Although traits such as biofilm formation and innate immune evasion are critical for the persistence of bacteria, the current understanding of the key host-pathogen interactions that determine the outcome of S. aureus IMI is very limited. We suggest that greater investment in research into the genetic and molecular basis of bovine S. aureus pathogenesis is essential for the identification of novel therapeutic and vaccine targets

Pasta dental com potencial para ser utilizada na hipersensibilidade dentinária

A hipersensibilidade dentinária (HD) é caracterizada por dor de curta duração, bem localizada, exacerbada aos estímulos sensoriais térmicos, químicos, osmóticos e táteis, originada em dentina exposta ao meio bucal, e que não pode ser explicada por nenhuma outra patologia dental. Embora ela seja uma das queixas mais comuns de pacientes em clínicas odontológicas, não existem tratamentos confiáveis para essa condição. O objetivo desse trabalho foi desenvolver uma formulação de creme dental contendo extrato de ginseng brasileiro e de erva doce, e um compósito de vidro bioativo originado da planta Equisetum hyemalle. Esse creme dental, sem flúor, está sendo preparado para ser usado na redução da sensibilidade dentinária. Experimentos iniciais de estabilidade a temperatura ambiente e acelerada (em estufa a 50 ºC) comprovaram a estabilidade físico-química das formulações desenvolvidas. Os extratos de ginseng e erva doce apresentaram atividade antimicrobiana contra o microrganismo S. mutans. Estudo preliminar de eficácia de tratamento da HD utilizando o creme dental preparado nesse trabalho foi feito. Imagens de microscopia eletrônica de varredura feita em dentes incisivos bovinos que apresentavam a dentina aberta, após ser utilizado o creme dental, mostraram resultados satisfatórios no controle fechamento dos túbulos dentinários

Prenylated flavonoid-enriched fraction from maclura tinctoria shows biological activity against Staphylococcus aureus and protects galleria mellonella larvae from bacterial infection.

Background: The Atlantic Forest biome extends along the entire Brazilian coast and is home to approximately 20,000 plant species, many of which are endemic; it is considered one of the hotspot regions of the planet. Several of these species are sources of natural products with biological activities that are still unknown. In this study, we evaluated the antimicrobial activity of 90 extracts derived from native Atlantic Forest tree species against Staphylococcus aureus, an important human and veterinary pathogen. Methods: Extracts from native Atlantic Forest tree species were evaluated for their antimicrobial activity against S. aureus by in vitro standard methods. Phytochemical fractionation of the extract from Maclura tinctoria was performed by liquid-liquid partitioning. LC-DAD-ESI-MS was used for identification of constituents in the most active fraction. Damage of cells and alterations in the permeability of cell membrane were determined by atomic force microscopy (AFM) and crystal violet uptake assay, respectively. In vivo antimicrobial activity was evaluated using Galleria mellonella larvae infected with S. aureus with survival data collected using the Kaplan-Meier method. Results: Among the organic or aqueous extracts tested here, 26 showed biological activity. Eight species showed relevant results, with a minimum inhibitory concentration (MIC) below 1?mg/mL. Antibacterial activity was registered for three species for the first time. An organic extract from Maclura tinctoria leaves showed the lowest MIC (0.08?mg/mL). Fractionation of this extract by liquid-liquid partitioning led to obtaining fraction 11FO d with a MIC of 0.04?mg/mL. This fraction showed strong activity against veterinary S. aureus isolates and contributed to the increased survival of Galleria mellonella larvae infected with S. aureus ATCC 29213. The bacterial surface was not altered by the presence of 11FO d, and no cell membrane damage was detected. The LC-DAD-ESI/MS analyses identified prenylated flavonoids as the major constituents responsible for the antibacterial activity of this active extract. Conclusion: A fraction enriched in prenylated isoflavones and flavanones from M. tinctoria showed in vitro and in vivo efficacy as antistaphylococcal agents. These findings justify the need for further research to elucidate the mechanisms of action of these compounds

Quorum sensing regulated phenotypes in Aeromonas hydrophila ATCC 7966 deficient in AHL production.

The virulence of Aeromonas hydrophila is positively regulated by a quorum sensing (QS) system based on the ahyRI genes. The aim of this study was to evaluate the phenotypic characteristics related to virulence in the A. hydrophila strain ATCC 7966 in order to check if virulence traits are still functioning, despite the absence of a well characterized QS system. As expected, we were not able to detect quorum signaling AHL molecules in A. hydrophila ATCC 7966 by cross-streaking or thin layer chromatography with AHL biosensor strains. Although A. hydrophila ATCC 7966 did not produce AHLs, transcription of the ahyI and ahyR genes was observed by RT-PCR. Phenotypes generally recognized as QS-regulated in A. hydrophila were maintained in ATCC 7966; these phenotypes included proteolytic activity on casein and gelatin and amylolytic, lipolytic, and ?- hemolytic activities, as well as the ability to adhere to surfaces and to form biofilms. Moreover, the addition of exogenous AHLs did not induce changes in the evaluated phenotypes. The results suggest that although this strain does not produce AHL as evaluated in this study, it maintains the phenotypes commonly associated with QS in this species indicating that other regulatory mechanisms independent of ahyRI may be in place