Daily Intake of Household-Produced Milk Kefir on Salmonella Typhimurium Infection in C57BL/6 Mice: Mortality, Microbiota Modulation and Immunological Implications.

AIMS: Salmonellosis, a major global cause of diarrheal diseases, significantly impacts the intestinal microbiome. Probiotic-rich beverages, such as kefir, are increasingly utilized as alternative health-promoting beverages associated with various microbiota benefits. This study investigated the repercussions of daily consumption of household-produced milk kefir on Salmonella enterica serovar Typhimurium infection in C57BL-6 mice. METHODS AND RESULTS: Kefir consumption pre infection reduced the presence of inflammatory cells in the colon and altered the cytokine profile by reducing IL-10 and increasing IFN-γ. Despite reducing intestinal inflammation, kefir intake did not yield a prompt response to an acute infection caused by the aggressive pathogen Salmonella. This contributed to increased mortality in the mice, evidenced by higher fecal Salmonella counts post-infection. Metabarcoding analysis demonstrated that the use of kefir before infection increases butyric acid by the higher abundance of Lachnospiraceae and Prevotellaceae families and genus in feces, coupled with an increase in Muribaculaceae family and Bacteroides genus among infected kefir-treated mice. While kefir hinted at microbiota alterations reducing enterobacteria (Helicobacter), decrease IL-10, and increased IFN-γ, butyric acid on pre-infection, the beverage potentially facilitated the systemic translocation of pathogens, intensifying the infection's severity by altering the immune response. CONCLUSIONS: The use of kefir in the dosage of 10% w/v (109 CFU), for acute infections with Salmonella Typhimurium, may not be enough to combat the infection and worsen the prognosis, leaving the intestine less inflamed, favoring the replication and translocation of the pathogen. These findings underscore the importance of prudently evaluating the widespread use of probiotics and probiotic-rich beverages, especially during acute infections, given their potential association with adverse effects during these diseases.

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.

Proteomic Profiles of Staphylococcus aureus Strains Associated with Subclinical Bovine Mastitis.

Staphylococcus aureus is the main pathogen associated with bovine mastitis, an intramammary inflammation that leads to significant economic losses in dairy herds. Efforts have been made to identify the bacterial determinants important to the infective process but most of the studies are focused on surface and secreted proteins. Considering that virulence is affected by metabolism, in this study we contrasted the proteome of strains of S. aureus causing persistent subclinical (Sau302 and Sau340) and clinical bovine mastitis (RF122). Protein expressions from cytosolic fractions of bacteria grown under conditions mimicking the mastitic mammary glands are reported. A total of 342 proteins was identified, 52 of which were differentially expressed. Among those down-regulated in the subclinical strains were the two-component sensor histidine kinase SaeS and PurH, both involved in bacterial virulence. The ribosome hibernation promotion factor and the 50S ribosomal protein L13 were up-regulated suggesting that Sau302 and Sau340 modulate protein translation, a condition that may contribute to bacterial survival under stressful conditions. TRAP, a regulator possibly involved in pathogenesis, was expressed only in RF122 while proteins from the Isd system, involved in heme acquisition, were exclusive to Sau302 and Sau340. In summary, the metabolic differences suggest a reduced virulence of the strains causing subclinical mastitis which may contribute to the persistent infection seen in the animals.

Carbohydrate-independent antibiofilm effect of Bothrops jararacussu lectin BJcuL on Staphylococcus aureus.

The antivirulence approach to fighting biofilm-based infections caused by Staphylococcus aureus is a promising therapy that has been studied extensively. Here, we compare the antibiofilm activity of a purified lectin from Bothrops jararacussu venom (BJcuL) and commercial lectins obtained from Triticum vulgaris (Wheat Germ Agglutinin, WGA), Bandeiraea simplicifolia BS-II, and Maclura pomifera. Only WGA had antibiofilm activity, although no effect was seen on pre-formed biofilms. The pre-incubation of WGA and BJcuL with their preferential sugars inhibited the biological activity of WGA, but not that of BJcuL, suggesting that biofilm disruption does not involve carbohydrate-recognition domains (CRDs). Quantitative real-time PCR showed that BJcuL promotes modulation of expression of S. aureus genes involved in biofilm formation. Light microscopy revealed cocci and small cell clusters after biofilm formation in the presence of BJcuL, showing that the lectin treatment was unable to completely disrupt biofilm structure. Exposing the free cells to 50 times the minimum inhibitory concentration of gentamicin or ciprofloxacin did not prevent biofilm reestablishment, although inhibition was stronger than in the control (no lectin). This disruption of the biofilm architecture can expose the bacterial cell and may facilitate clearance by the immune system.

Draft Genome Sequences of Staphylococcus aureus Strains Isolated from Subclinical Bovine Mastitis in Brazil.

Here, we present the draft genome sequences of four Staphylococcus aureus strains isolated from mastitic milk collected from animals with subclinical manifestations. Three of them were typed as sequence type 126 (ST126), a genotype with no genome sequence available. ST126 is found in several herds of southern Brazil and is described as a bovine pathogen strongly associated with milk around the world.