A fibronectin-binding protein (FbpA) of Weissella cibaria inhibits colonization and infection of Staphylococcus aureus in mammary glands

Weissella paramesenteroides NRIC1542 inhibits dextran sodium sulfate-induced colitis in mice through regulating gut microbiota and SIRT1/NF-κB signaling pathway

Inflammatory bowel disease (IBD) is a kind of recurrent inflammatory disorder of the intestinal tract. The purpose of this study was to investigate the effects of Weissella paramesenteroides NRIC1542 on colitis in mice. A colitis model was induced by adding 1.5% DSS to sterile distilled water for seven consecutive days. During this process, mice were administered different concentrations of W. paramesenteroides NRIC1542. Colitis was assessed by DAI, colon length and hematoxylin-eosin staining of colon sections. The expressions of NF-κB signaling proteins and the tight junction proteins ZO-1 and occludin were detected by western blotting, and the gut microbiota was analyzed by 16S rDNA. The results showed that W. paramesenteroides NRIC1542 significantly reduced the degree of pathological tissue damage and the levels of TNF-α and IL-1β in colonic tissue, inhibiting the NF-κB signaling pathway and increasing the expression of SIRT1, ZO-1 and occludin. In addition, W. paramesenteroides NRIC1542 can modulate the structure of the gut microbiota, characterized by increased relative abundance of Muribaculaceae_unclassified, Paraprevotella, Prevotellaceae_UCG_001 and Roseburia, and decrease the relative abundance of Akkermansia and Alloprevotella induced by DSS. The above results suggested that W. paramesenteroides NRIC1542 can protect against DSS-induced colitis in mice through anti-inflammatory, intestinal barrier maintenance and flora modulation.

Isolation, Characterization, Genome Annotation, and Evaluation of Hyaluronidase Inhibitory Activity in Secondary Metabolites of Brevibacillus sp. JNUCC 41: A Comprehensive Analysis through Molecular Docking and Molecular Dynamics Simulation

Brevibacillus sp. JNUCC 41, characterized as a plant-growth-promoting rhizobacterium (PGPR), actively participates in lipid metabolism and biocontrol based on gene analysis. This study aimed to investigate the crucial secondary metabolites in biological metabolism; fermentation, extraction, and isolation were performed, revealing that methyl indole-3-acetate showed the best hyaluronidase (HAase) inhibitory activity (IC50: 343.9 μM). Molecular docking results further revealed that the compound forms hydrogen bonds with the residues Tyr-75 and Tyr-247 of HAase (binding energy: -6.4 kcal/mol). Molecular dynamics (MD) simulations demonstrated that the compound predominantly binds to HAase via hydrogen bonding (MM-PBSA binding energy: -24.9 kcal/mol) and exhibits good stability. The residues Tyr-247 and Tyr-202, pivotal for binding in docking, were also confirmed via MD simulations. This study suggests that methyl indole-3-acetate holds potential applications in anti-inflammatory and anti-aging treatments.

Elimination of Pathogen Biofilms via Postbiotics from Lactic Acid Bacteria: A Promising Method in Food and Biomedicine

Pathogenic biofilms provide a naturally favorable barrier for microbial growth and are closely related to the virulence of pathogens. Postbiotics from lactic acid bacteria (LAB) are secondary metabolites and cellular components obtained by inactivation of fermentation broth; they have a certain inhibitory effect on all stages of pathogen biofilms. Postbiotics from LAB have drawn attention because of their high stability, safety dose parameters, and long storage period, which give them a broad application prospect in the fields of food and medicine. The mechanisms of eliminating pathogen biofilms via postbiotics from LAB mainly affect the surface adhesion, self-aggregation, virulence, and QS of pathogens influencing interspecific and intraspecific communication. However, there are some factors (preparation process and lack of target) which can limit the antibiofilm impact of postbiotics. Therefore, by using a delivery carrier and optimizing process parameters, the effect of interfering factors can be eliminated. This review summarizes the concept and characteristics of postbiotics from LAB, focusing on their preparation technology and antibiofilm effect, and the applications and limitations of postbiotics in food processing and clinical treatment are also discussed.

The Weissella and Periweissella genera: up-to-date taxonomy, ecology, safety, biotechnological, and probiotic potential

Bacteria belonging to the genera Weissella and Periweissella are lactic acid bacteria, which emerged in the last decades for their probiotic and biotechnological potential. In 2015, an article reviewing the scientific literature till that date on the taxonomy, ecology, and biotechnological potential of the Weissella genus was published. Since then, the number of studies on this genus has increased enormously, several novel species have been discovered, the taxonomy of the genus underwent changes and new insights into the safety, and biotechnological and probiotic potential of weissellas and periweissellas could be gained. Here, we provide an updated overview (from 2015 until today) of the taxonomy, ecology, safety, biotechnological, and probiotic potential of these lactic acid bacteria.

The Controversial Nature of Some Non-Starter Lactic Acid Bacteria Actively Participating in Cheese Ripening

This mini review deals with some controversial non-starter lactic acid bacteria (NSLAB) species known to be both human and animal pathogens but also health-promoting and probiotic. The focus is on Lactococcus garvieae, two Streptococcus species (S. uberis and S. parauberis), four Weissella species (W. hellenica, W. confusa, W. paramesenteroides, and W. cibaria), and Mammalicoccus sciuri, which worldwide, are often found within the microbiotas of different kinds of cheese, mainly traditional artisanal cheeses made from raw milk and/or relying on environmental bacteria for their ripening. Based on literature data, the virulence and health-promoting effects of these bacteria are examined, and some of the mechanisms of these actions are reviewed. Additionally, their possible roles in cheese ripening are also discussed. The analysis of the literature data available so far showed that, in general, the pathogenic and the beneficial strains, despite belonging to the same species, show somewhat different genetic constitutions. Yet, when the safety of a given strain is assessed, genomic analysis on its own is not enough, and a polyphasic approach including additional physiological and functional tests is needed.

The Weissella Genus: Clinically Treatable Bacteria with Antimicrobial/Probiotic Effects on Inflammation and Cancer

Weissella is a genus earlier considered a member of the family Leuconostocaceae, which was reclassified into the family Lactobacillaceae in 1993. Recently, there have been studies emphasizing the probiotic and anti-inflammatory potential of various species of Weissella, of which W. confusa and W. cibaria are the most representative. Other species within this genus include: W. paramesenteroides, W. viridescens, W. halotolerans, W. minor, W. kandleri, W. soli, W. ghanensis, W. hellenica, W. thailandensis, W. fabalis, W. cryptocerci, W. koreensis, W. beninensis, W. fabaria, W. oryzae, W. ceti, W. uvarum, W. bombi, W. sagaensis, W. kimchi, W. muntiaci, W. jogaejeotgali, W. coleopterorum, W. hanii, W. salipiscis, and W. diestrammenae. Weissella confusa, W. paramesenteroides, W. koreensis, and W. cibaria are among the few species that have been isolated from human samples, although the identification of these and other species is possible using metagenomics, as we have shown for inflammatory bowel disease (IBD) and healthy controls. We were able to isolate Weissella in gut-associated bacteria (post 24 h food deprivation and laxatives). Other sources of isolation include fermented food, soil, and skin/gut/saliva of insects/animals. With the potential for hospital and industrial applications, there is a concern about possible infections. Herein, we present the current applications of Weissella on its antimicrobial and anti-inflammatory mechanistic effects, the predisposing factors (e.g., vancomycin) for pathogenicity in humans, and the antimicrobials used in patients. To address the medical concerns, we examined 28 case reports focused on W. confusa and found that 78.5% of infections were bacteremia (of which 7 were fatal; 1 for lack of treatment), 8 were associated with underlying malignancies, and 8 with gastrointestinal procedures/diseases of which 2 were Crohn’s disease patients. In cases of a successful resolution, commonly administered antibiotics included: cephalosporin, ampicillin, piperacillin-tazobactam, and daptomycin. Despite reports of Weissella-related infections, the evolving mechanistic findings suggest that Weissella are clinically treatable bacteria with emerging antimicrobial and probiotic benefits ranging from oral health, skin care, obesity, and inflammatory diseases to cancer.

Effect of NZ2114 against Streptococcus dysgalactiae biofilms and its application in murine mastitis model

Bovine mastitis caused by Streptococcus dysgalactiae (S. dysgalactiae) is usually treated with antibiotics, which may potentially increase drug resistance as the abuse. NZ2114, a variant of fungal defensin plectasin, displayed a potent antibacterial activity against S. dysgalactiae. The inhibition/eradication effect of the antimicrobial peptide NZ2114 on the early/mature biofilm of S. dysgalactiae CVCC 3938 was evaluated, as well as the elimination of bacteria in mature biofilms. In this study, NZ2114 displayed potent antibacterial activity against S. dysgalactiae CVCC 3938 and three clinical isolated S. dysgalactiae strains (0.11-0.45 μM). The early biofilm inhibition of S. dysgalactiae CVCC 3938 was 55.5–85.9% after treatment with NZ2114 at concentrations of 1–16 × MIC, which was better than that of vancomycin at the same concentration. The mature biofilm eradication rate was up to 92.7–97.6% with the increasing concentration (2–16 × MIC) of NZ2114, and the eradication rate did not change significantly with further increase of NZ2114 concentration, while the biofilm eradication rate of vancomycin-treated group at the same concentration remained at 92.5%. NZ2114 reduced the number of persister bacteria in biofilm. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) further demonstrated that NZ2114 could effectively reduce the biofilm thickness and bacterial number of S. dysgalactiae CVCC 3938. In vivo therapeutic effect of NZ2114 on murine mastitis model showed that NZ2114 was better than vancomycin in alleviating mammary gland inflammation by regulating cytokines production, inhibiting bacterial proliferation, and reducing the number of mammary gland bacteria. These data suggested that NZ2114 is a potential peptide candidate for the treatment of mastitis.

Assessment of the safety and probiotic properties of Roseburia intestinalis: A potential “Next Generation Probiotic”

Roseburia intestinalis is an anaerobic bacterium that produces butyric acid and belongs to the phylum Firmicutes. There is increasing evidence that this bacterium has positive effects on several diseases, including inflammatory bowel disease, atherosclerosis, alcoholic fatty liver, colorectal cancer, and metabolic syndrome, making it a potential “Next Generation Probiotic.” We investigated the genomic characteristics, probiotic properties, cytotoxicity, oral toxicity, colonization characteristics of the bacterium, and its effect on the gut microbiota. The genome contains few genes encoding virulence factors, three clustered regularly interspaced short palindromic repeat (CRISPR) sequences, two Cas genes, no toxic biogenic amine synthesis genes, and several essential amino acid and vitamin synthesis genes. Seven prophages and 41 genomic islands were predicted. In addition to a bacteriocin (Zoocin A), the bacterium encodes four metabolic gene clusters that synthesize short-chain fatty acids and 222 carbohydrate-active enzyme modules. This bacterium is sensitive to antibiotics specified by the European Food Safety Authority, does not exhibit hemolytic or gelatinase activity, and exhibits some acid resistance. R. intestinalis adheres to intestinal epithelial cells and inhibits the invasion of certain pathogens. In vitro experiments showed that the bacterium was not cytotoxic. R. intestinalis did not affect the diversity or abundance of the gut flora. Using the fluorescent labelling method, we discovered that R. intestinalis colonizes the cecum and mucus of the colon. An oral toxicity study did not reveal any obvious adverse effects. The lethal dose (LD)50 of R. intestinalis exceeded 1.9 × 10⁹ colony forming units (CFU)/kg, whereas the no observed adverse effect level (NOAEL) derived from this study was 1.32 × 10⁹ CFU/kg/day for 28 days. The current research shows that, R. intestinalis is a suitable next-generation probiotic considering its probiotic properties and safety.

Factors Affecting Spontaneous Endocytosis and Survival of Probiotic Lactobacilli in Human Intestinal Epithelial Cells

Mutualistic bacteria have different forms of interaction with the host. In contrast to the invasion of pathogenic bacteria, naturally occurring internalization of commensal bacteria has not been studied in depth. Three in vitro methods, gentamicin protection, flow cytometry and confocal laser scanning microscopy, have been implemented to accurately assess the internalization of two lactobacillus strains—Lacticaseibacillus paracasei BL23 and Lacticaseibacillus rhamnosus GG—in Caco-2 and T84 intestinal epithelial cells (IECs) under a variety of physiological conditions and with specific inhibitors. First and most interesting, internalization occurred at a variable rate that depends on the bacterial strain and IEC line, and the most efficient was BL23 internalization by T84 and, second, efficient internalization required active IEC proliferation, as it improved naturally at the early confluence stages and by stimulation with epidermal growth factor (EGF). IFN-γ is bound to innate immune responses and autolysis; this cytokine had a significant effect on internalization, as shown by flow cytometry, but increased internalization was not perceived in all conditions, possibly because it was also stimulating autolysis and, as a consequence, the viability of bacteria after uptake could be affected. Bacterial uptake required actin polymerization, as shown by cytochalasin D inhibition, and it was partially bound to clathrin and caveolin dependent endocytosis. It also showed partial inhibition by ML7 indicating the involvement of cholesterol lipid rafts and myosin light chain kinase (MLCK) activation, at least in the LGG uptake by Caco-2. Most interestingly, bacteria remained viable inside the IEC for as long as 72 h without damaging the epithelial cells, and paracellular transcytosis was observed. These results stressed the fact that internalization of commensal and mutualistic bacteria is a natural, nonpathogenic process that may be relevant in crosstalk processes between the intestinal populations and the host, and future studies could determine its connection to processes such as commensal tolerance, resilience of microbial populations or transorganic bacterial migration.

Evaluation of Probiotic Properties and Prebiotic Utilization Potential of Weissella paramesenteroides Isolated From Fruits

Weissella paramesenteroides has gained a considerable attention as bacteriocin and exopolysaccharide producers. However, potential of W. paramesenteroides to utilize different prebiotics is unexplored area of research. Fruits being vectors of various probiotics, five W. paramesenteroides strains, namely, FX1, FX2, FX5, FX9, and FX12, were isolated from different fruits. They were screened and selected based on their ability to survive at pH 2.5 and in 1.0% sodium taurocholate, high cell surface hydrophobicity, mucin adhesion, bile-induced biofilm formation, antimicrobial activity (AMA) against selected enteropathogens, and prebiotic utilization ability, implicating the functional properties of these strains. In vitro safety evaluation showed that strains were susceptible to antibiotics except vancomycin and did not harbor any virulent traits such as biogenic amine production, hemolysis, and DNase production. Based on their functionality, two strains FX5 and FX9 were selected for prebiotic utilization studies by thin layer chromatography (TLC) and short-chain fatty acids (SCFAs) production by high performance liquid chromatography. TLC profile evinced the ability of these two strains to utilize low molecular weight galactooligosaccharides (GOS) and fructooligosaccharides (FOS), as only the upper low molecular weight fractions were disappeared from cell-free-supernatants (CFS). Enhanced β-galactosidase activity correlated with galactose accumulation in residual CFS of GOS displayed GOS utilization ability. Both the strains exhibited AMA against E. coli and Staph. aureus and high SCFAs production in the presence of prebiotic, suggesting their synbiotic potential. Thus, W. paramesenteroides strains FX5 and FX9 exhibit potential probiotic properties with prebiotic utilization and can be taken forward to evaluate synergistic synbiotic potential in detail.

Horizontally Acquired Polysaccharide-Synthetic Gene Cluster From Weissella cibaria Boosts the Probiotic Property of Lactiplantibacillus plantarum

Lactiplantibacillus plantarum are probiotic bacteria, maintaining the integrity of the gastrointestinal epithelial barrier, and preventing the infection of pathogenic bacteria. Exopolysaccharides (EPSs) are often involved in the probiotic property of L. plantarum. Here, we identified a new EPS-synthetic gene cluster, cpsWc, carrying 13 genes, laid on a large plasmid in a well-characterized probiotic L. plantarum strain LTC-113. The cpsWc gene cluster was horizontally acquired from Weissella cibaria, enhancing the biofilm formation ability of the host strain and its tolerance to harsh environmental stresses, including heat, acid, and bile. Transfer of cpsWc also conferred the probiotic properties to other L. plantarum strains. Moreover, cpsWc strengthened the adhesion of LTC-113 to intestinal epithelial cells. Both the cpsWc-carrying LTC-113 and its EPSs per se effectively attenuated the LPS-induced pro-inflammatory effect of intestinal epithelial cells, and inhibited the adhesion of pathogenic bacteria, such as S. typhimurium and E. coli by exclusion and competition. The newly identified cpsWc gene cluster emphasized the contribution of mobile EPS-synthetic element on the probiotic activity of L. plantarum, and shed a light on the engineering of probiotic bacteria.

Next-Generation Sequencing for Whole-Genome Characterization of Weissella cibaria UTNGt21O Strain Originated From Wild Solanum quitoense Lam. Fruits: An Atlas of Metabolites With Biotechnological Significance

The whole genome of Weissella cibaria strain UTNGt21O isolated from wild fruits of Solanum quitoense (naranjilla) shrub was sequenced and annotated. The similarity proportions based on the genus level, as a result of the best hits for the entire contig, were 54.84% with Weissella, 6.45% with Leuconostoc, 3.23% with Lactococcus, and 35.48% no match. The closest genome was W. cibaria SP7 (GCF_004521965.1) with 86.21% average nucleotide identity (ANI) and 3.2% alignment coverage. The genome contains 1,867 protein-coding genes, among which 1,620 were assigned with the EggNOG database. On the basis of the results, 438 proteins were classified with unknown function from which 247 new hypothetical proteins have no match in the nucleotide Basic Local Alignment Search Tool (BLASTN) database. It also contains 78 tRNAs, six copies of 5S rRNA, one copy of 16S rRNA, one copy of 23S rRNA, and one copy of tmRNA. The W. cibaria UTNGt21O strain harbors several genes responsible for carbohydrate metabolism, cellular process, general stress responses, cofactors, and vitamins, conferring probiotic features. A pangenome analysis indicated the presence of various strain-specific genes encoded for proteins responsible for the defense mechanisms as well as gene encoded for enzymes with biotechnological value, such as penicillin acylase and folates; thus, W. cibaria exhibited high genetic diversity. The genome characterization indicated the presence of a putative CRISPR-Cas array and five prophage regions and the absence of acquired antibiotic resistance genes, virulence, and pathogenic factors; thus, UTNGt21O might be considered a safe strain. Besides, the interaction between the peptide extracts from UTNGt21O and Staphylococcus aureus results in cell death caused by the target cell integrity loss and the release of aromatic molecules from the cytoplasm. The results indicated that W. cibaria UTNGt21O can be considered a beneficial strain to be further exploited for developing novel antimicrobials and probiotic products with improved technological characteristics.

Antimicrobial and Antibiofilm Activities of Weissella cibaria against Pathogens of Upper Respiratory Tract Infections

Recently discovered preventive effects of probiotics on oral health have attracted interest to their use for the prevention and treatment of various diseases. This study aimed to evaluate the antimicrobial and antibiofilm properties of Weissella cibaria against Streptococcus pyogenes, Staphylococcus aureus, S. pneumoniae, and Moraxella catarrhalis, the major pathogens of upper respiratory tract infections (URTIs). The antimicrobial activities of W. cibaria were compared with those of other oral probiotics using a competitive inhibition assay and the determination of the minimum inhibitory concentrations (MICs). In addition, a time-kill assay, spectrophotometry, and confocal laser scanning microscopy were used to confirm the antimicrobial and antibiofilm abilities of W. cibaria CMU (oraCMU) and CMS1 (oraCMS1). Both live cells and cell-free supernatants of all tested probiotics, except Streptococcus salivarius, showed excellent antimicrobial activities. All target pathogens were killed within 4 to 24 h at twice the MIC of oraCMU and oraCMS1, which showed the highest antimicrobial activities against M. catarrhalis. The antimicrobial substances that affected different target pathogens were different. Both oraCMU and oraCMS1 showed excellent abilities to inhibit biofilm formation and remove preformed biofilms. Our results suggest that the W. cibaria probiotics offer new possibilities for the prevention and treatment of bacterial URTIs.

Heat inactivation partially preserved barrier and immunomodulatory effects of Lactobacillus gasseri LA806 in an in vitro model of bovine mastitis

Probiotics could help combat infections and reduce antibiotic use. As use of live bacteria is limited in some cases by safety or regulatory concerns, the potential of inactivated bacteria is worth investigating. We evaluated the potential of live and heat-inactivated Lactobacillus gasseri LA806 to counteract Staphylococcus aureus and Escherichia coli infection cycles in an in vitro model of bovine mastitis. We assessed the ability of live and inactivated LA806 to impair pathogen colonisation of bovine mammary epithelial cells (bMECs) and to modulate cytokine expression by pathogen-stimulated bMECs. Live LA806 induced a five-fold decrease in S. aureus adhesion and internalisation (while not affecting E. coli colonisation) and decreased pro-inflammatory cytokine expression by S. aureus-stimulated bMECs (without interfering with the immune response to E. coli). The ability of inactivated LA806 ability to diminish S. aureus colonisation was two-fold lower than that of the live strain, but its anti-inflammatory properties were barely impacted. Even though LA806 effects were impaired after inactivation, both live and inactivated LA806 have barrier and immunomodulatory properties that could be useful to counteract S. aureus colonisation in the bovine mammary gland. As S. aureus is involved in various types of infection, LA806 potential would worth exploring in other contexts.

Integrated Phenotypic-Genotypic Analysis of Candidate Probiotic Weissella Cibaria Strains Isolated from Dairy Cows in Kuwait

Probiotics represent a possible strategy for controlling intestinal infections in livestock. Members of the Weissella genus are increasingly being studied for health-related applications in animals and humans. Here we investigated the functional properties of two Weissella cibaria strains isolated from cows reared in Kuwait breeding facilities by combining phenotypic with genomic analyses. W. cibaria SP7 and SP19 exhibited good growth in vitro under acidic conditions and in the presence of bile salts compared to the reference probiotic Lacticaseibacillus (formerly Lactobacillus) rhamnosus GG. Both strains were able to adhere to Caco-2 and HT-29 cell lines, as well as to mucin. The cell-free supernatants of the two isolates exhibited inhibitory activity towards Escherichia coli ATCC 25,922 and Salmonella enterica UC3605, which was ultimately due to the low pH of supernatants. W. cibaria SP19 showed a co-aggregation ability similar to that of L. rhamnosus GG when incubated with S. enterica. Whole genome sequencing and analysis revealed that both strains harbored several genes involved in carbohydrate metabolism and general stress responses, indicating bacterial adaptation to the gastrointestinal environment. We also detected genes involved in the adhesion to host epithelial cells or extracellular matrix. No evidence of acquired antibiotic resistance or hemolytic activity was found in either strain. These findings shed light on the potential of W. cibaria for probiotic use in livestock and on the mechanisms underlying host-microbe interaction in the gut. W. cibaria` strain SP19 exhibited the best combination of in vitro probiotic properties and genetic markers, and is a promising candidate for further investigation.

A polyphasic approach to characterize Weissella cibaria and Weissella confusa strains

AIM

To study Weissella cibaria and Weissella confusa strains, lactic acid bacteria (LAB) members naturally present in food products, but not yet included in Qualified Presumption of Safety (QPS) list of European Food Safety Authority (EFSA).

METHODS AND RESULTS

We carried out a comparative genome analysis of 23 sequenced W. cibaria and 7 W. confusa genomes, in parallel with a physiological and functional characterization of several strains previously isolated from sourdough-like maize bran fermentation. The genome analysis revealed the absence of dedicated pathogenicity factors. Some putative virulence genes found in Weissella genomes were also present in other LAB strains, considered safe by EFSA and commonly used as probiotics. The physiological tests carried out on our strains corroborated the genomic results. Moreover, the following functional traits of interest to application in the food sector were identified: the majority of tested strains displayed high acidification rate, high reducing ability, production of exopolysaccharides (EPS), arabinoxylan degradation ability, growth in the presence of fructo-oligosaccharides (FOS), bile and gastric juice tolerance, and antifungal activity.

CONCLUSIONS

These results provide evidence for the possible use of selected strains of W. cibaria and W. confusa in the food sector.

SIGNIFICANCE AND IMPACT OF THE STUDY

This polyphasic study adds to the body of knowledge on the functional and applicable characteristics of these controversial species of LAB. This knowledge contributes to design new selected cultures included in the QPS list required for food applications.

Internalization, distribution, and activity of peptide H2 against the intracellular multidrug-resistant bovine mastitis-causing bacterium Staphylococcus aureus

Bovine mastitis is mainly caused by Staphylococcus aureus, which is difficult to eliminate, prone to escape from antibacterial agents, and may cause recurring infections due to the intracellular nature of its infection and multidrug resistance. In this study, the intracellular activities of the NZ2114 derivative peptide H18R (H2) against methicillin-resistant S. aureus (MRSA) and multidrug-resistant bovine S. aureus strains were investigated in bovine mammary epithelial MAC-T cells and mouse mammary glands. The minimum inhibitory concentrations of H2 against S. aureus were 0.5‒1 μg/ml; H2 displayed a lower cytotoxicity than its parental peptide NZ2114 (survival rates of MAC-T cells: 100% [H2 treatment] vs 60.7% [NZ2114 (256 μg/ml) treatment]). H2 was internalized into MAC-T cells mainly via clathrin-mediated endocytosis, and distributed in the cytoplasm. The intracellular inhibition rates against MRSA ATCC43300, the mastitis isolates S. aureus CVCC 3051 and E48 were above 99%, 99%, and 94%, respectively; these were higher than those in case of vancomycin (23-47%). In the mouse model of S. aureus E48-induced mastitis, after treatment with 100 μg of H2 and vancomycin, bacterial numbers in each mammary gland were reduced by 3.96- and 1.59-log CFU, respectively. Additionally, similar to NZ2114 and vancomycin, H2 alleviated the histopathological damage of the mammary tissue and polymorphonuclear neutrophil infiltration in the alveoli. These results suggest that H2 can be used as a safe and effective candidate for treating S. aureus-induced mastitis.

Genome Sequence of Weissella cibaria M2, a Potential Probiotic Strain Isolated from the Feces of a Giant Panda

Here, we report the complete genome sequence of Weissella cibaria M2, a potential probiotic strain isolated from the feces of a giant panda (Ailuropoda melanoleuca). The genome consists of one chromosome of 2.56 Mb and two plasmids. The genome contains 2,420 genes which make up 86.17% of genome.

Lactobacillus casei BL23 modulates the innate immune response in Staphylococcus aureus-stimulated bovine mammary epithelial cells

Probiotics have been adopted to treat and prevent various diseases in humans and animals. They were notably shown to be a promising alternative to prevent mastitis in dairy cattle. This inflammation of the mammary gland is generally of infectious origin and generates extensive economic losses worldwide. In a previous study, we found that Lactobacillus casei BL23 was able to inhibit the internalisation of Staphylococcus aureus, one of the major pathogens involved in mastitis, into bovine mammary epithelial cells (bMEC). In this study, we further explored the capacity of this strain to modulate the innate immune response of bovine mammary epithelial cells during S. aureus infection. L. casei BL23 was able to decrease the expression of several pro-inflammatory cytokines, including interleukins 6, 8, 1α and 1β and tumour necrosis factor alpha, in S. aureus-stimulated bMEC, 8 h post-infection. On the other hand, L. casei did not impair the induction of defensins, such as lingual antimicrobial peptide and defensin β1 in the presence of S. aureus, and even slightly increased the induction of tracheal antimicrobial peptide during S. aureus infection. Finally, this strain did not alter the expression of the pattern recognition receptor nucleotide-binding oligomerisation domain proteins (NOD2). This study demonstrates that L. casei BL23 displayed anti-inflammatory properties on S. aureus-stimulated bMEC. These results open the way to further characterisation of the BL23 probiotic potential in a bovine mammary gland context and to a better understanding of how all these beneficial properties combine in vivo to combat mastitis pathogens.

Surfaceome and Proteosurfaceome in Parietal Monoderm Bacteria: Focus on Protein Cell-Surface Display

The cell envelope of parietal monoderm bacteria (archetypal Gram-positive bacteria) is formed of a cytoplasmic membrane (CM) and a cell wall (CW). While the CM is composed of phospholipids, the CW is composed at least of peptidoglycan (PG) covalently linked to other biopolymers, such as teichoic acids, polysaccharides, and/or polyglutamate. Considering the CW is a porous structure with low selective permeability contrary to the CM, the bacterial cell surface hugs the molecular figure of the CW components as a well of the external side of the CM. While the surfaceome corresponds to the totality of the molecules found at the bacterial cell surface, the proteinaceous complement of the surfaceome is the proteosurfaceome. Once translocated across the CM, secreted proteins can either be released in the extracellular milieu or exposed at the cell surface by associating to the CM or the CW. Following the gene ontology (GO) for cellular components, cell-surface proteins at the CM can either be integral (GO: 0031226), i.e., the integral membrane proteins, or anchored to the membrane (GO: 0046658), i.e., the lipoproteins. At the CW (GO: 0009275), cell-surface proteins can be covalently bound, i.e., the LPXTG-proteins, or bound through weak interactions to the PG or wall polysaccharides, i.e., the cell wall binding proteins. Besides monopolypeptides, some proteins can associate to each other to form supramolecular protein structures of high molecular weight, namely the S-layer, pili, flagella, and cellulosomes. After reviewing the cell envelope components and the different molecular mechanisms involved in protein attachment to the cell envelope, perspectives in investigating the proteosurfaceome in parietal monoderm bacteria are further discussed.

Effective Antimicrobial Activity of Plectasin-Derived Antimicrobial Peptides against Staphylococcus aureus Infection in Mammary Glands

Staphylococcus aureus (S. aureus) is the causative agent for a wide variety of illnesses ranging from minor skin infections to life-threatening diseases. Development of antibiotic resistance by the bacteria has rendered many antibiotics ineffective. It has been known that plectasin-derived antimicrobial peptides (AMPs; NZ2114 and MP1102) are promising alternatives to antibiotics. However, their activities against S. aureus in mammary glands were unknown. Our objective was to assess the antimicrobial activities of NZ2114 and MP1102 against S. aureus in milk, in cultured mammary epithelial cells, and in a mouse model in order to evaluate their potentials as anti-mastitis agents. NZ2114 and MP1102 showed in vitro bactericidal effects against S. aureus in both the culture medium and the milk. NZ2114 and MP1102 at the concentration of 100 μg/mL reduced the number of S. aureus by almost 100% within 4 h in processed bovine milk. Similarly, both NZ2114 and MP1102 were efficient to reduce the number of internalized S. aureus in cultured mammary epithelial cells. Finally, both AMPs significantly reduced the S. aureus load and concentrations of TNF-α and IL-6 in mammary glands, compared to a buffer control in the mouse model. Our results suggest that NZ2114 and MP1102 may be used to treat S. aureus-induced mastitis.

Contribution of sortase SrtA2 to Lactobacillus casei BL23 inhibition of Staphylococcus aureus internalization into bovine mammary epithelial cells

Probiotics have been considered as a promising strategy to prevent various diseases in both humans and animals. This approach has gained interest in recent years as a potential means to control bovine mastitis. In a previous study, we found that several L. casei strains, including BL23, were able to inhibit the internalization of S. aureus, a major etiologic agent of mastitis, into bovine mammary epithelial cells (bMEC). This antagonism required a direct contact between L. casei and bMEC or S. aureus, suggesting the inhibition relied on interactions between L. casei cell surface components and bMEC. In this study, we have investigated the impact of some candidates which likely influence bacteria host cell interactions. We have shown that L. casei BL23 fbpA retained its inhibitory potential, indicating that L. casei BL23 antagonism did not rely (solely) on competition between S. aureus and L. casei fibronectin-binding proteins for adhesion to bMEC. We have then investigated the impact of four sortase mutants, srtA1, srtA2, srtC1 and srtC2, and a double mutant (srtA1-srtA2) on L. casei BL23 inhibitory potential. Sortases are responsible for the anchoring on the bacterial cell wall of LPXTG-proteins, which reportedly play an important role in bacteria-host cell interaction. All the srt mutants tested presented a reduced inhibition capacity, the most pronounced effect being observed with the srtA2 mutant. A lower internalization capacity of L. casei srtA2 into bMEC was also observed. This was associated with several changes at the surface of L. casei BL23 srtA2 compared to the wild type (wt) strain, including altered abundance of some LPXTG- and moonlighting proteins, and modifications of cell wall structure. These results strongly support the role of sortase A2 in L. casei BL23 inhibition against S. aureus internalization. Deciphering the contribution of the cell surface components altered in srtA2 strain in the inhibition will require further investigation.