An important criterion to consider in the selection of strains for dietary adjuncts is the ability of the microorganisms to survive the severe conditions of acidity and bile concentrations usually found in the gastrointestinal tract. In the present work, we report the effects of digestions by artificial gastric and intestinal fluids on beta-galactosidase activity and survival of four strains of dairy propionibacteria previously selected by their bile tolerance and beta-galactosidase activity. The strains were exposed to artificial gastric juice at pH values between 2 and 7 and then subjected to artificial intestinal digestion. Both viability and beta-galactosidase activity were seriously affected at pH 2. Skim milk and Emmental cheese juice exerted a protective effect on the parameters tested. The trypsin present in the intestinal fluid inactivated the enzyme beta-galactosidase in strains of Propionibacterium freudenreichii but not in Propionibacterium acidipropionici. Moreover, the presence of bile salts enhanced the beta-galactosidase activity of these strains by permeabilization of the cells during the first hour of exposure. The intestinal transit rate confirmed the permanence of the bacteria in the intestine for long enough to be permeabilized. These results suggest that P. acidipropionici would be a good source of beta-galactosidase activity in the intestine. We also propose a practical and effective in vitro method as a tool of screening and selection of potential probiotic bacteria.

An important lesson from the war on pathogenic bacteria has been the need to understand the physiological responses and evolution of natural microbial communities. Bacterial populations in the environment are generally forming biofilms subject to some level of phage predation. These multicellular communities are notoriously resistant to antimicrobials and, consequently, very difficult to eradicate. This has sparked the search for new therapeutic alternatives, including phage therapy. This study demonstrates that S. aureus biofilms formed in the presence of a non-lethal dose of phage phiIPLA-RODI exhibit a unique physiological state that could potentially benefit both the host and the predator. Thus, biofilms formed under phage pressure are thicker and have a greater DNA content. Also, the virus-infected biofilm displayed major transcriptional differences compared to an untreated control. Significantly, RNA-seq data revealed activation of the stringent response, which could slow down the advance of the bacteriophage within the biofilm. The end result would be an equilibrium that would help bacterial cells to withstand environmental challenges, while maintaining a reservoir of sensitive bacterial cells available to the phage upon reactivation of the dormant carrier population.

We studied the effect of the angiotensin converting enzyme (ACE) inhibitor, quinapril, on the clinical and morphological lesions of a normotensive model of immune complex nephritis. Untreated rats developed massive nephrotic syndrome, intense cell proliferation and glomerular and tubulointerstitial lesions. In the renal cortex of nephritic rats there was a significant increase in gene expression of TGF-beta 1, fibronectin and collagens, and ACE activity. Systolic blood pressure remained normal with progression of the disease. Administration of quinapril for three weeks to animals with glomerular lesions (proteinuria 20 to 50 mg/day) avoided the development of intense proteinuria (79 +/- 28 vs. 589 +/- 73 mg/day, P < 0.001) and decreased cell proliferation, glomerulosclerosis, tubulointerstitial lesions, and inflammatory infiltrates. Cortical gene expression of TGF-beta 1 and matrix proteins was also diminished. ACE activity was inhibited by 68% in renal cortex. These results show that quinapril administration to normotensive rats with immune complex nephritis decreases proteinuria and glomerular and tubulointerstitial lesions, probably modulating the local angiotensin II generation and its effects on cell growth, TGF beta and matrix protein synthesis.

Aims:  To evaluate strains of Lactobacilli, Bifidobacteria and Streptococci for their ability to produce conjugated linoleic acid (CLA) from free linoleic acid (LA). Methods and Results:  Eight dairy bacteria tolerant to LA were grown in MRS broth containing LA (200 μg ml−1) and CLA was assessed. Seven bacteria were able to form CLA after 24 h of incubation, varying percentage conversion between 17% and 36%. Lactobacillus casei, Lactobacillus rhamnosus, Bifidobacterium bifidum and Streptococcus thermophilus showed the highest LA conversion and were inoculated into buffalo milk supplemented with different concentration of LA. The production of CLA at 200 μg ml−1 of LA was two‐ or threefold in milk than MRS broth. All evaluated strains were able to produce CLA from high LA levels (1000 μg ml−1). Conclusions:  The most tolerant strain to LA was Lact. casei. Lacttobacillus rhamnosus produced the maximum level of CLA at high LA concentrations (800 μg ml−1). The selected bacteria may be considered as adjunct cultures to be included on dairy fermented products manufacture. Low concentration of LA must be added to the medium to enhance CLA formation. Significance and Impact of the Study:  The production of CLA by strains using milks from regional farms as medium offer a possible mechanism to enhance this beneficial compound in dairy products and those the possibility to develop functional foods.

The use of bacteriophages as antimicrobials against pathogenic bacteria offers a promising alternative to traditional antibiotics and disinfectants. Significantly, phages may help to remove biofilms, which are notoriously resistant to commonly used eradication methods. However, the successful development of novel antibiofilm strategies must take into account that real-life biofilms usually consist of mixed-species populations. Within this context, this study aimed to explore the effectiveness of bacteriophage-based sanitation procedures for removing polymicrobial biofilms from food industry surfaces. We treated dual-species biofilms formed by the food pathogenic bacterium Staphylococcus aureus in combination with Lactobacillus plantarum, Enterococcus faecium, or Lactobacillus pentosus with the staphylococcal phage phiIPLA-RODI. Our results suggest that the impact of bacteriophage treatment on S. aureus mixed-species biofilms varies depending on the accompanying species and the infection conditions. For instance, short treatments (4 h) with a phage suspension under nutrient-limiting conditions reduced the number of S. aureus cells in 5-h biofilms by ϳ1 log unit without releasing the nonsusceptible species. In contrast, longer infection periods (18 h) with no nutrient limitation increased the killing of S. aureus cells by the phage (decrease of up to 2.9 log units). However, in some cases, these conditions promoted the growth of the accompanying species. For example, the L. plantarum cell count in the treated sample was up to 2.3 log units higher than that in the untreated control. Furthermore, phage propagation inside dual-species biofilms also depended greatly on the accompanying species, with the highest rate detected in biofilms formed by S. aureus-L. pentosus. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) also showed changes in the three-dimensional structures of the mixed-species biofilms after phage treatment. Altogether, the results presented here highlight the need to study the impact of phage therapy on microbial communities that reflect a more realistic setting.IMPORTANCE Biofilms represent a major source of contamination in industrial and hospital settings. Therefore, developing efficient strategies to combat bacterial biofilms is of the utmost importance from medical and economic perspectives. Bacteriophages have shown potential as novel antibiofilm agents, but further research is still required to fully understand the interactions between phages and biofilm-embedded bacteria. The results presented in this study contribute to achieving a better understanding of such interactions in a more realistic context, considering that most biofilms in the environment consist of mixed-species populations. KEYWORDS Staphylococcus aureus, biofilms, phage

Obesity induces local/systemic inflammation accompanied by increases in macrophage infiltration into adipose tissue and production of inflammatory cytokines, chemokines, and hormones. Previous studies have shown that probiotics could improve the intestinal dysbiosis induced by metabolic diseases such as obesity, diabetes, and metabolic syndrome. Microorganisms could (directly or indirectly) affect adipokine levels due to their capacity to induce translocation of several intestinal microbial antigens into systemic circulation, which could lead to metabolic endotoxemia or produce immunomodulation in different organs. The aim of the present study was to select non-inflammatory lactic acid bacteria (LAB) strains with the capacity to modulate adipokine secretion by the adipose tissue. We wish to elucidate the role of potential probiotic strains in the regulation of the cross talking between immune cells such as macrophages and adipose cells. Mouse macrophage cell line RAW 264.7 was used for evaluating the ability of 14 LAB strains to induce cytokine production. The LAB strains were chosen based on their previously studied beneficial properties in health. Then, in murine adipocyte culture and macrophage–adipocyte coculture, we determined the ability of these strains to induce cytokines and leptin secretion. Tumor necrosis factor alpha, interleukin 6 (IL-6), IL-10, monocyte chemoattractant protein-1, and leptin levels were measured in cell supernatants. We also performed the detection and quantification of leptin receptor (Ob-Rb) expression in macrophage cell lines stimulated by these LAB strains. Differential secretion profile of cytokines in macrophage cells induced by LAB strains was observed. Also, the levels of Ob-Rb expression diverged among different LAB strains. In LAB-stimulated coculture cells (adipocytes and macrophages), we observed differential production of leptin and cytokines. Furthermore, we detected lower production levels in single culture than cocultured cells. The principal component analysis showed an association between the four clusters of strains established according to their inflammatory profiles and leptin adipocyte production and leptin receptor expression in macrophages. We conclude that coculture is the most appropriate system for selecting strains with the ability to modulate adipokine secretion. The use of microorganisms with low and medium inflammatory properties and ability to modulate leptin levels could be a strategy for the treatment of some metabolic diseases associated with dysregulation of immune response.

Adhesion to the intestinal mucosa is a desirable property for probiotic microorganisms and has been related to many of their health benefits. In the present study, 24 dairy Propionibacterium strains were assessed with regard to their hydrophobic characteristics and their autoaggregation and hemagglutination abilities, since these traits have been shown to be indicative of adherence in other microorganisms. Six strains were further tested for their capacity to adhere to ileal epithelial cells in vitro and in vivo. The results of the study showed that propionibacteria were highly hydrophilic, and hemagglutination and autoaggregation were properties not commonly found among these microorganisms. No relationship was found between surface characteristics and adhesion ability, since hemagglutinating, autoaggregating, and nonautoaggregating bacteria were able to adhere to intestinal cells both in vitro and in vivo. Microscopic examination revealed that autoaggregating cells adhered in clusters, with adhesion being mediated by only a few bacteria, whereas the hemagglutinating and nonautoaggregating strains adhered individually or in small groups making contact with each epithelial cell with the entire bacterial surface. The in vitro assessment of adhesion was a good indication of the in vivo association of propionibacteria with the intestinal epithelium. Therefore, the in vitro method presented here should be valuable in screening routinely adhesive properties of propionibacteria for probiotic purposes. The adhesion ability of dairy propionibacteria would prolong their maintenance in the gut and increase the duration of their provision of beneficial effects in the host, supporting the potential of Propionibacterium in the development of new probiotic products.

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