Host-pathogen interactions in bovine mammary epithelial cells and HeLa cells by Staphylococcus aureus isolated from subclinical bovine mastitis

Probio-M9, a breast milk-originated probiotic, alleviates mastitis and enhances antibiotic efficacy: Insights into the gut-mammary axis

Breast milk naturally contains lactic acid bacteria, but their precise origin remains a subject of debate. In this study, we utilized a rat mastitis animal model to investigate the potential of a breast milk-derived probiotic strain, Lacticaseibacillus rhamnosus Probio-M9, in alleviating mastitis and enhancing the efficacy of antibiotic treatment. Through histopathological analysis of mammary tissue, we observed that Probio-M9 effectively relieved mastitis, mitigated inflammation, and improved the response to antibiotic treatment. Metagenomic analysis further revealed that Probio-M9 enhanced interactions among gut microbes, accompanied by an increase in the relative abundance of Ruminococcaceae and the regulation of specific genes and carbohydrate-active enzymes, subsequently impacting host immunity. Additionally, an intriguing finding was the translocation of live Probio-M9 from the gut to the mammary tissue only during bacterial mastitis and lactation, likely facilitated through lymphatic circulation. These findings advance our understanding of the intricate gut-mammary axis and provide valuable insights into the potential health benefits of probiotic interventions.

The prevalence of adhesion and biofilm genes in Staphylococcus aureus isolates from bovine mastitis: A comprehensive meta-analysis

BACKGROUND

Mastitis poses significant challenges to the dairy industry, resulting in economic losses and increased veterinary expenses. Staphylococcus aureus is a common cause of bovine mastitis, relying on efficient adhesion and biofilm formation for infection.

OBJECTIVES

This study aimed to employ meta-analysis to investigate the occurrence of adhesion and biofilm genes in S. aureus associated with bovine mastitis, as documented in previous studies.

METHODS

This meta-analysis was done according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses, examined 22 eligible articles and revealed varying prevalence rates of adhesion and biofilm genes in S. aureus isolates from bovine mastitis.

RESULTS

Among the genes, clfB showed the highest prevalence (p-estimate = 0.905), followed by fnbA (p-estimate = 0.689) and fnbB (p-estimate = 0.502). The icaA and icaD genes also showed a relatively high prevalence (p-estimate = 0.694 and 0.814, respectively). Conversely, the biofilm-associated proteins gene had the lowest prevalence (p-estimate = 0.043). Subgroup analyses based on mastitis types and publication years revealed no significant differences in gene prevalence. Insufficient data hindered the analysis of fib, sasG , eno and bbp genes.

CONCLUSION

This study provides valuable insights for managing S. aureus-induced bovine mastitis. Additionally, larger-scale research, particularly on less-studied genes, is necessary to comprehend the molecular roles of adhesion and biofilm genes in S. aureus-induced bovine mastitis.

Proteomics and Genetic Approaches Elucidate the Circulation of Low Variability Staphylococcus aureus Strains on Colombian Dairy Farms

Staphylococcus aureus is one of the most prevalent pathogens causing bovine mastitis in the world, in part because of its ease of adaptation to various hosts and the environment. This study aimed to determine the prevalence of S. aureus in Colombian dairy farms and its relationship with the causal network of subclinical mastitis. From thirteen dairy farms enrolled, 1288 quarter milk samples (QMS) and 330 teat samples were taken from cows with positive (70.1%) and negative California Mastitis Test (CMT). In addition, 126 samples from the milking parlor environment and 40 from workers (nasal) were collected. On each dairy farm, a survey was conducted, and the milking process was monitored on the day of sampling. S. aureus was identified in 176 samples, i.e., 138 QMS, 20 from teats, 8 from the milking parlor environment, and 10 from workers' nasal swabs. Isolates identified as S. aureus underwent proteomics (clustering of mass spectrum) and molecular (tuf, coa, spa Ig, clfA, and eno genes) analysis. Regarding proteomics results, isolates were distributed into three clusters, each with members from all sources and all farms. Concerning molecular analysis, the virulence-related genes clfA and eno were identified in 41.3% and 37.8% of S. aureus isolates, respectively. We provide evidence on the circulation of S. aureus strains with limited variability among animals, humans, and the environment. The parameters with the lowest compliance in the farms which may be implicated in the transmission of S. aureus are the lack of handwashing and abnormal milk handling.

Investigation of the pathophysiology of bacterial mastitis using precision-cut bovine udder slices

Mastitis in cattle is a major health problem as well as incurring high costs for the dairy industry. To assess the suitability of precision-cut bovine udder slices (PCBUS) for bovine mastitis studies, we infected PCBUS with 2 different Staphylococcus aureus strains. Accordingly, we investigated both the tissue response to infection based on immune mediators at the mRNA and protein levels and the invasion of bacteria within the tissue. The studied proteins represent immune mediators of early inflammation [IL-1β, tumor necrosis factor-α (TNF-α), prostaglandin E₂ (PGE₂)] and showed a time-dependent increase in concentration. Infection of PCBUS with S. aureus resulted in increased expression of proinflammatory cytokines and chemokines such as TNF-α, C-C motif chemokine ligand 20 (CCL20), IL-1β, IL-6, and IL-10, but not C-X-C motif chemokine ligand 8 (CXCL8), lingual antimicrobial peptide (LAP), or S100 calcium binding protein A9 (S100A9) at the mRNA level. To compare the data acquired with this model, we carried out investigations on primary bovine mammary epithelial cells. Our results showed that the immune responses of both models-PCBUS and primary bovine mammary epithelial cells-were similar. In addition, investigations using PCBUS enabled us to demonstrate adherence of bacteria in the physiological cell network. These findings support the use of PCBUS in studies designed to further understand the complex pathophysiological processes of infection and inflammation in bovine mastitis and to investigate alternative therapies for mastitis.

Effect of Two Different Drug-Resistant Staphylococcus aureus Strains on the Physiological Properties of MAC-T Cells and Their Transcriptome Analysis

Staphylococcus aureus (S. aureus) is one of the main pathogens causing mastitis in dairy cows. The current work mainly focuses on the pathway of apoptosis induction in MAC-T cells caused by S. aureus infection or other factors. However, the physiological characteristics of S. aureus infected MAC-T cells and the resulting mRNA expression profile remain unknown particularly in the case of diverse drug resistant strains. Methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) strains were used to infect MAC-T cells to investigate this issue. The adhesion, invasion and apoptosis ability of MRSA-infected group and MSSA-infected group was assessed over time (2, 4, 6, 8, and 12 h). After 8 h, the RNA sequencing was conducted on the MRSA-infected and the MSSA-infected with uninfected MAC-T cells as controls. The results showed that the adhesion and invasion ability of MRSA-infected and MSSA-infected to MAC-T cells increased and then decreased with infection time, peaking at 8 h. The adhesion and invasion rates of the MSSA-infected were substantially lower than those of the MRSA-infected, and the invasion rate of the MSSA-infected group was nearly non-existent. Then the apoptosis rate of MAC-T cells increased as the infection time increased. The transcriptome analysis revealed 549 differentially expressed mRNAs and 390 differentially expressed mRNAs in MRSA-infected and MSSA-infected MAC-T cells, respectively, compared to the uninfected MAC-T cells. According to GO analysis, these differentially expressed genes were involved in immune response, inflammation, apoptosis, and other processes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated the following pathways were linked to adhesion, invasion inflammation and apoptosis, including AMPK, FOXO, HIF-1, IL-17, JAK-STAT, MAPK, mTOR, NF-κB, p53, PI3K-Akt, TNF, Toll-like receptor, Rap1, RAS, prion disease, the bacterial invasion of epithelial cells pathway. We found 86 DEGs from 41 KEGG-enriched pathways associated with adhesion, invasion, apoptosis, and inflammation, all of which were implicated in MAC-T cells resistance to MRSA and MSSA infection. This study offers helpful data toward understanding the effect of different drug-resistant S. aureus on dairy cow mammary epithelial cells and aid in the prevention of mastitis in the dairy industry.

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.

Lactobacillus rhamnosus GR-1 Prevents Escherichia coli-Induced Apoptosis Through PINK1/Parkin-Mediated Mitophagy in Bovine Mastitis

Escherichia coli is one of the most important pathogens that cause clinical mastitis in dairy cattle worldwide and lead to severe economic losses. Antibiotics are often used to treat this inflammatory disease; however, antimicrobial resistance and environmental pollution cannot be ignored. Probiotic is the best alternative; however, its mechanisms of action to prevent mastitis remain unclear. Moreover, the role of probiotics in regulating mitophagy, a selective autophagy that maintains mitochondrial quality, needs to be explored. E. coli infection induced NOD-like receptor family member pyrin domain-containing protein 3 (NLRP3) inflammasome assembly, Caspase-1 activation, and apoptosis in MAC-T cells. Infection also resulted in mitochondrial damage and subsequent increase in reactive oxygen species (ROS) production. Moreover, inhibition of ROS release by scavenger N-acetyl-L-cysteine (NAC) abrogated the importance of ROS in NLRP3 assembly and apoptosis in MAC-T cells. Pretreatment with Lactobacillus rhamnosus GR-1 (LGR-1), a probiotic, alleviated E. coli-induced NLRP3 inflammasome activation and apoptosis via ROS inhibition. Besides, E. coli infection inhibited mitophagy while LGR-1 pretreatment augmented PINK1/Parkin–mediated mitophagy activation, which further blocked ROS generation. To explore the effect of LGR-1 in vivo, a mouse mastitis model was established. The results showed that LGR-1 pretreatment had preventive and protective effects on E. coli induced mastitis, and could reduce cytokines levels such as IL-1β and TNF-α. In accordance with the results in vitro, E. coli can inhibit mitophagy and activate NLRP3 inflammasome and apoptosis, while LGR-1 can weaken the effect of E. coli. Taken together, our data indicated that LGR-1 pretreatment induced PINK1/Parkin-mediated mitophagy that eliminated damaged mitochondria and reduced ROS production and NLRP3 inflammasome activation, which subsequently decreased E. coli-induced apoptosis. To conclude, our study suggests that therapeutic strategies aiming at the upregulation of mitophagy under E. coli-induced mastitis may preserve mitochondrial function and provide theoretical support for the application of probiotics in bovine mastitis.

Singularities of Pyogenic Streptococcal Biofilms - From Formation to Health Implication

Biofilms are generally defined as communities of cells involved in a self-produced extracellular matrix adhered to a surface. In biofilms, the bacteria are less sensitive to host defense mechanisms and antimicrobial agents, due to multiple strategies, that involve modulation of gene expression, controlled metabolic rate, intercellular communication, composition, and 3D architecture of the extracellular matrix. These factors play a key role in streptococci pathogenesis, contributing to therapy failure and promoting persistent infections. The species of the pyogenic group together with Streptococcus pneumoniae are the major pathogens belonging the genus Streptococcus, and its biofilm growth has been investigated, but insights in the genetic origin of biofilm formation are limited. This review summarizes pyogenic streptococci biofilms with details on constitution, formation, and virulence factors associated with formation.

Interaction between bovine mammary epithelial cells and planktonic or biofilm Staphylococcus aureus: The bacterial lifestyle determines its internalization ability and the pathogen recognition

The main cause of mastitis, one of the most costly diseases in the dairy industry, is bacterial intramammary infection. Many of these bacteria are biofilm formers. Biofilms have been associated with resistance to antibiotics and to the host immune system. Here, we evaluated different experimental models representing bacterial biofilm lifestyle with the aim to study bacterial invasion into bovine mammary epithelial cells and the interaction of these cells with planktonic or biofilm Staphylococcus aureus. Staphylococcus aureus V329, its nonbiofilm-forming mutant and bovine mammary alveolar cells (MAC-T) were used. Bacterial invasion was studied using the gentamicin exclusion test, cell viability by trypan blue exclusion technique, TLR2 expression by flow cytometry, IL1β/IL6 production by ELISA and IL8/TNFα gene expression by real-time polymerase chain reaction. Biofilm and planktonic S. aureus showed differences in their invasion ability, with the biofilm mode showing a lower ability. Planktonic S. aureus reduced MAC-T viability after 6 h of co-culture, while biofilms did so at 24 h. MAC-T infected with planktonic bacteria showed increased TLR2 expression. Both lifestyles increased IL8 expression and IL1β/IL6 production but did not modify TNFα expression. Our results demonstrate that the bacterial lifestyle affects the invasion behavior, suggesting that biofilms reduce the bacteria-epithelial cell interaction. Planktonic cultures seem to induce higher cellular activation than biofilms. Further knowledge about the complex host-biofilm interaction is necessary to design more efficient therapies against bovine mastitis.

Phenotypic Characterization and Whole Genome Analysis of a Strong Biofilm-Forming Staphylococcus aureus Strain Associated With Subclinical Bovine Mastitis in Colombia

Staphylococcus aureus represent a serious threat to public health due to food safety, antibiotic resistance, and the potential zoonotic transmission of strains between dairy cattle and humans. Biofilm formation by S. aureus results in chronicity of the infections which confers protection against the immune response and antibiotics. Likewise, biofilm allows the exchange of mobile genetic material among different strains through microbial interactions inside the matrix. In Colombia, where S. aureus continues to be one of the main pathogens isolated from bovine intramammary infections and where milking by hand is highly frequent, there are knowledge gaps on the zoonotic potential of the strains. Therefore, the aim of this work was to characterize genotypically and phenotypically the S. aureus Sa1FB strain with strong biofilm production and to perform genomic and phenotypic comparisons with other relevant S. aureus strains (native and references strains). These results show a highly productive strain of biofilm and a low ability of cell invasion compared to the other two native strains. In addition, high genomic similarity between S. aureus Sa1FB and the reference strains was observed, despite of the differences reported at the clinical level. However, Sa1FB exhibited special features in terms of mobile genetic elements, highlighting its ability to accept foreign genetic material. Indeed, this could increase mutation, pathogenesis, and adaptability to new hosts, representing a risk for people in contact with the milk obtained from animals infected with these strains. These results present the relevance of surveillance for early detection of emergent clones with zoonotic potential, which reduces the risk of occupational exposure and their spread in the community.

Cell-Free Lactobacillus sp Supernatants Modulate Staphylococcus aureus Growth, Adhesion and Invasion to Human Osteoblast (HOB) Cells

The increase of antibiotic resistance has become a problem. Probiotic bacteria play an important role in preventive/supportive medicine. Therefore, we examined the inhibitory effects of four different Lactobacillus species' (L. acidophilus-La, L. plantarum-Lp, L. fermentum-Lf and L. rhamnosus-Lr) cell-free supernatants (CFSs) on growth, adhesion, invasion, and biofilm formation of Staphylococcus aureus and effects of S. aureus, CFSs, and S. aureus-CFSs co-existence on human osteoblast (HOB) cell viability. Growth alterations were measured spectrophotometrically. Adhesive/invasive bacterial counts were detected by colony counting. Biofilm was evaluated using microtiter plate assay. The MTT assay was used for detection of HOB cell viability. The growth of MSSA significantly (P < 0.01) decreased in the presence of two CFSs (Lf and Lr) (P < 0.01); the growth of MRSA significantly (P < 0.05) reduced in the presence of La CFSs. All tested CFSs were found to reduce adhesion and invasion of MSSA (P < 0.0001). The adhesion of MRSA was enhanced (P < 0.0001) in the presence of all CFSs except La and the invasion of MRSA was decreased (P < 0.01) in the presence of Lr and Lf CFSs. All tested CFSs were shown to inhibit biofilm formation significantly (P < 0.0001). The reduction of S. aureus infected HOB cell viability and exposed to all CFSs except Lr that was found to be significant (P < 0.0001). The viability of HOB cell during co-incubation with MSSA and CFSs was shown to be decreased significantly. However co-existence of MRSA and CFSs did not alter HOB cell viability. These results suggested that lactobacilli as probiotics have low protective effects on MRSA-infected host cells.

The gut microbiota contributes to the development of Staphylococcus aureus-induced mastitis in mice

Mastitis is one of the most prevalent diseases in dairy farming worldwide. The gut microbiota plays an important role in the regulation of systemic and local inflammatory diseases, such as mastitis. However, the regulatory mechanism of the gut microbiota on mastitis is still unclear. Thus, the aim of this study was to investigate the function and regulatory mechanisms of the gut microbiota in host defense against mastitis caused by Staphylococcus aureus (S. aureus) infection. Increased blood-milk barrier permeability, and S. aureus-induced mastitis severity were observed gut microbiota-dysbiosis mice compared with those in control mice. Moreover, feces microbiota transplantation (FMT) to microbbiota-dysbiosis mice reversed these effects. Furthermore, established disruption of commensal homeostasis results in significantly increased abundance of pathogenic Enterobacter bacteria, while the relative abundance of short-chain fatty acid (SCFAs)-producing bacterial phyla (Firmicutes and Bacteroidetes) was significantly reduced. However, FMT to gut microbiota-dysbiosis mice reversed these changes. In addition, dysbiosis reduced the levels of SCFAs, and administration of sodium propionate, sodium butyrate, and probiotics (butyrate-producing bacteria) reversed the changes in the blood-milk barrier and reduced the severity of mastitis induced by S. aureus. In conclusion, this new finding demonstrated that the gut microbiota acts as a protective factor in host defense against mastitis and that targeting the gut-mammary gland axis represents a promising therapeutic approach for mastitis treatment.

Identification of a reliable fixative solution to preserve the complex architecture of bacterial biofilms for scanning electron microscopy evaluation

Bacterial biofilms are organized sessile communities of bacteria enclosed in extracellular polymeric substances (EPS). To analyze organization of bacteria and EPS in high resolution and high magnification by scanning electron microscopy (SEM), it is important to preserve the complex architecture of biofilms. Therefore, fixation abilities of formalin, glutaraldehyde, and Methacarn (methanol/chloroform/acetic acid-6:3:1) fixatives were evaluated to identify which fixative would best preserve the complex structure of bacterial biofilms. Economically important Gram-negative Mannheimia haemolytica, the major pathogen associated with bovine respiratory disease complex, and Gram-positive Staphylococcus aureus, the major cause of chronic mastitis in cattle, bacteria were selected since both form biofilms on solid-liquid interface. For SEM analysis, round glass coverslips were placed into the wells of 24-well plates and diluted M. haemolytica or S. aureus cultures were added, and incubated at 37°C for 48–72 h under static growth conditions. Culture media were aspirated and biofilms were fixed with an individual fixative for 48 h. SEM examination revealed that all three fixatives were effective preserving the bacterial cell morphology, however only Methacarn fixative could consistently preserve the complex structure of biofilms. EPS layers were clearly visible on the top, in the middle, and in the bottom of the biofilms with Methacarn fixative. Biomass and three-dimensional structure of the biofilms were further confirmed spectrophotometrically following crystal violet staining and by confocal microscopy after viability staining. These findings demonstrate that Methacarn fixative solution is superior to the other fixatives evaluated to preserve the complex architecture of biofilms grown on glass coverslips for SEM evaluation.

Phenotypic Characterization and Whole Genome Analysis of a Strong Biofilm-Forming Staphylococcus aureus Strain Associated With Subclinical Bovine Mastitis in Colombia

Staphylococcus aureus represent a serious threat to public health due to food safety, antibiotic resistance, and the potential zoonotic transmission of strains between dairy cattle and humans. Biofilm formation by S. aureus results in chronicity of the infections which confers protection against the immune response and antibiotics. Likewise, biofilm allows the exchange of mobile genetic material among different strains through microbial interactions inside the matrix. In Colombia, where S. aureus continues to be one of the main pathogens isolated from bovine intramammary infections and where milking by hand is highly frequent, there are knowledge gaps on the zoonotic potential of the strains. Therefore, the aim of this work was to characterize genotypically and phenotypically the S. aureus Sa1FB strain with strong biofilm production and to perform genomic and phenotypic comparisons with other relevant S. aureus strains (native and references strains). These results show a highly productive strain of biofilm and a low ability of cell invasion compared to the other two native strains. In addition, high genomic similarity between S. aureus Sa1FB and the reference strains was observed, despite of the differences reported at the clinical level. However, Sa1FB exhibited special features in terms of mobile genetic elements, highlighting its ability to accept foreign genetic material. Indeed, this could increase mutation, pathogenesis, and adaptability to new hosts, representing a risk for people in contact with the milk obtained from animals infected with these strains. These results present the relevance of surveillance for early detection of emergent clones with zoonotic potential, which reduces the risk of occupational exposure and their spread in the community.

Epidemiological investigation of subclinical bovine mastitis in Algeria and molecular characterization of biofilm-forming Staphylococcus aureus

Thirty dairy farms were selected for this study; the first objective of our study was to investigate the prevalence of subclinical bovine mastitis (SCM) in Eastern Algeria, from 600 lactating cows, and to identify potential risk factors associated with the occurrence of bovine mastitis and bacteria isolation using logistic regression. The second objective was to evaluate biofilm formation capacity and detect biofilm-associated genes of S. aureus, isolated from SCM cases. Molecular typing was investigated by spa typing. The prevalence of mastitis at cow and quarter level was 37.66% (226/600) and 27.17% (555/2042), respectively. Stage of lactation, cow breed, milk production, and the study area were factors associated with SCM. In addition, the most frequent pathogens isolated from mastitic milk were coagulase-negative staphylococci (CNS), E. coli, and S. aureus. The study area was highly associated with SCM caused by S. aureus; cows from Setif province were 18 times more affected with SCM caused by S. aureus compared to cows from Batna province (OR = 18.6, 95%CI 2.038-171.2), but were less affected with SCM caused by CNS isolates (OR = 0.17, 95%CI 0.033-0.868). Moreover, cows with milk production less than 10 L per day increased (p < 0.05) the prevalence of mastitis caused by E. coli. All the S. aureus isolates had biofilm-forming ability, and 41.66% of isolates were positive for adhesion genes (icaA, icaD, fbnA, and clfA). This study, therefore, warrants the need for improving sanitary measures and strict hygienic measures, and presents the first insight into biofilm-forming ability of S. aureus strains causing mastitis in dairy herds in Algeria, which will help in tracking the evolution of epidemic strains responsible for causing bovine mastitis.

The Role of Functional Amyloids in Bacterial Virulence

Amyloid fibrils are best known as a product of human and animal protein misfolding disorders, where amyloid formation is associated with cytotoxicity and disease. It is now evident that for some proteins, the amyloid state constitutes the native structure and serves a functional role. These functional amyloids are proving widespread in bacteria and fungi, fulfilling diverse functions as structural components in biofilms or spore coats, as toxins and surface-active fibers, as epigenetic material, peptide reservoirs or adhesins mediating binding to and internalization into host cells. In this review, we will focus on the role of functional amyloids in bacterial pathogenesis. The role of functional amyloids as virulence factor is diverse but mostly indirect. Nevertheless, functional amyloid pathways deserve consideration for the acute and long-term effects of the infectious disease process and may form valid antimicrobial targets.

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Functional amyloids are widespread in bacteria, pathogenic and non-pathogenic.

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Bacterial biofilms most commonly function as structural support in the extracellular matrix of biofilms or spore coats, and in cell–cell and cell-surface adherence.

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The amyloid state can be the sole structured and functional state, or can be facultative, as a secondary state to folded monomeric subunits.

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Bacterial amyloids can enhance virulence by increasing persistence, cell adherence and invasion, intracellular survival, and pathogen spread by increased environmental survival.

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Bacterial amyloids may indirectly inflict disease by triggering inflammation, contact phase activation and possibly induce or aggravate human pathological aggregation disorders.