An overview on mastitis-associated Escherichia coli: Pathogenicity, host immunity and the use of alternative therapies

Proteomics and metabolomics reveal the role of miR-320b in regulating inflammation of bovine mammary epithelial cells

MicroRNAs (miRNAs) are a class of endogenous non-coding small RNAs that are widely found in organisms and play an important regulatory role in various biological processes, especially immune and inflammatory responses. However, the function of miR-320b in the inflammatory responses of bovine mammary epithelial cells (bMECs) remains to be elucidated. In this study, we examined the miR-320b mimic transduction group (miR-320b_mimic) and negative control mimic transduction group (NC_mimic) of lipopolysaccharide-treated bMECs using data-independent acquisition (DIA) proteomics and untargeted metabolomics. Subsequently, we performed a joint analysis of the sequencing data. Proteomic analysis identified 330 differentially abundant proteins (DAPs) primarily related to PPAR, ferroptosis, arachidonic acid metabolism, IL-17, and complement and coagulation cascades. Metabolome analysis identified 128 and 66 differentially accumulated metabolites (DAMs) in the positive and negative ion mode primarily involved in linoleic acid metabolism, cholesterol metabolism, AMPK, MAPK, and chemokine. Integrated metabolomics and proteomics analysis revealed the co-enrichment of DAPs and DAMs in choline metabolism in cancer, endocrine resistance, glycerophospholipid metabolism, primary bile acid biosynthesis, and the ferroptosis signaling pathways. The results of quantitative real-time PCR (RT-qPCR) showed that compared with the NC_mimic group, mRNA expression levels of COX-2, IL-12 A, iNOS, MAPK1, and MAPK14 genes were significantly down-regulated, and the mRNA expression levels of PPARγ, CEBPα, CEBPβ, FABP4, and LPL genes were significantly up-regulated in the miR-320b_mimic group. These results provide crucial insights into the molecular regulatory functions of miR-320b and offer valuable data for further research on molecular breeding aimed at enhancing mastitis resistance in bovine animals.

Emergence of highly virulent multidrug and extensively drug resistant Escherichia coli and Klebsiella pneumoniae in buffalo subclinical mastitis cases

This study aimed to characterize virulence and antibiotic resistance genes in multidrug-resistant (MDR) and extensively drug-resistant (XDR) Escherichia coli and Klebsiella pneumoniae isolated from cases of subclinical mastitis (SCM) in buffaloes. A cross-sectional study was conducted on 1540 quarter milk samples collected from 385 buffaloes. Milk samples were screened using the California Mastitis Test and Modified Whiteside Test. Positive samples underwent bacterial culture, biochemical tests, biofilm detection and molecular analysis for pathogen identification and detection of virulence, resistance, and extended-spectrum beta-lactamase (ESBL) genes. The prevalence of SCM was 67.9% (1046/1540) at the quarter level and 80.8% (311/385) at the animal level. E. coli was identified in 9.5% (146/1540) of the samples, while K. pneumoniae was detected in 9.09% (140/1540). Virulence genes, such as stx1 (27.4%), and resistance genes, including aac(3)-iv (77.4%) and tetA (76.7%), exhibited higher prevalence. Additionally, β-lactamase genes, notably blaTEM (67.1%), and ESBL genes, such as blaCTX-M1, were detected. Biofilm formation was detected in 83.6% (122/146) of E. coli isolates and 75.7% (106/140) of K. pneumoniae isolates. Antimicrobial susceptibility testing revealed significant resistance to ampicillin, amoxicillin-clavulanic acid, and aminoglycosides. MDR was observed in 31.5% of E. coli and 39.3% of K. pneumoniae isolates, with XDR rates of 8.9% and 12.9%, respectively. These findings underscore the alarming spread of resistant pathogens in SCM-affected buffaloes, emphasizing the urgent need for ongoing surveillance and targeted intervention strategies.

ALKBH5 Improves the Epithelial Cell Tight Junctions to Inhibit Escherichia coli-Induced Mastitis

Mastitis poses a severe threat to the global cattle industry, causing huge economic losses. Environmental mastitis is mainly induced by Escherichia coli (E. coli), and the current treatment is still using antibiotics, with problems such as drug resistance and food safety. ALKBH5 is an RNA m6A demethylase that plays an important role in various biological processes, while p65 is a key regulator of inflammatory responses. Therefore, studying the interaction between ALKBH5 and p65 in protecting the mammary epithelial barrier provides new insights into the pathogenesis of mastitis. This study revealed that E. coli-induced acute inflammation activated the NF-κB/p65 signaling pathway and disrupted mammary epithelial cell tight junctions. Knockdown of ALKBH5 promoted p65 phosphorylation and inhibited the expressions of the tight junction proteins TJP1, CDH1, and OCLN. Furthermore, motif analysis, CHIP-PCR, and dual luciferase assay confirmed that phosphorylated p65 inhibited TJP1 promoter activity, thereby inhibiting TJP1 expression. In addition, the mouse experiment further demonstrated that knockdown of ALKBH5 aggravated E. coli-induced acute mastitis and epithelial cell tight junction disruption, and promoted E. coli invasion and proliferation. Significantly, this study is the first to demonstrate the details of the interaction between p65 and TJP1 and to declare the molecular mechanism of ALKBH5 in improving the cell tight junction, which lays a potential target and theoretical foundation for the treatment of mastitis and other infectious diseases.

Investigating the Anna Karenina principle of the breast microbiome

The relationship between the microbiome and disease has long been a central focus of research in human microbiome. Inspired by Leo Tolstoy's dictum, the Anna Karenina Principle (AKP) offers a framework for understanding the complex dynamics of microbial communities in response to perturbations, suggesting that dysbiotic individuals exhibit greater variability/heterogeneity in their microbiome compared to healthy counterparts. While some studies have proved the alignment of microbiome responses to disease with the AKP effect, it remains uncertain whether the human breast microbiome responds similarly to breast disease. This study used beta-diversity and similarity in Hill numbers, along with shared species analysis (SSA), to explore this issue. We observed that during mastitis, changes in both the taxa richness and composition in the breast milk microbiome align with the AKP effect, while alterations in abundant taxa exhibit an anti-AKP effect. The response of breast tissue microbiome to breast cancer differs from that of milk microbiome to mastitis. Breast cancer induce anti-AKP effects in taxa richness, and non-AKP effects in common taxa and taxa composition. Overall, our findings identified different responses to breast diseases across taxa abundance in the breast microbiome. Mastitis primarily involves increasing the heterogeneity of rare taxa in the breast milk microbiome, while breast cancer associates with decreased dispersion of rare taxa in the tissue microbiome.

Difference Analysis on Virulence Genes, Biofilms and Antimicrobial Susceptibility of Escherichia coli from Clinical and Subclinical Bovine Mastitis

Escherichia coli (E. coli) has the ability to induce clinical and subclinical mastitis in dairy cows, causing a huge loss for the dairy industry. In this study, 51 subclinical mastitis isolates and 36 clinical mastitis isolates from eight provinces of China between 2019 and 2021 were used to investigate the differences in their biological characteristics. The results showed that B1 (52.9%) and A (39.1%) were the predominant phylogroups; R1 (50.6%) was the predominant lipopolysaccharide (LPS) core type; and 44 STs (ST10 and ST58 were the most sequence-prevalent STs) and 2 new STs (ST14828 and ST14829) were identified; however, no significant difference was observed between the clinical and subclinical group strains. To compare the virulence gene differences between the clinical and subclinical mastitis-related isolates, 18 common virulence genes (including afaE, eaeA, papC, saa, sfa, ompA, aer, irp2, iucD, escV, sepD, east1, estB, stx2e, CNF1, cba, hlyA and traT) were determined using the PCR method. The results showed that the detection rates of traT, irp2 and iucD in clinical mastitis isolates were significantly higher than those in subclinical mastitis isolates (p ˂ 0.05). Meanwhile, subclinical-group E. coli had stronger biofilm formation abilities than the clinical group (p < 0.05) in 78 (89.7%) mastitis-related E. coli that could form biofilms. Furthermore, 87 mastitis-related E. coli showed severe resistance against tetracycline (37.9%), ampicillin (36.8%), streptomycin (34.5%) and cotrimoxazole (28.7%); their most prevalent resistance genes were blaCTX-M (33.3%), tetA (27.6%), sul2 (18.4%) and strB (28.7%). It was noteworthy that the clinical-group strains had a higher resistance against ampicillin and possessed higher amounts of the resistance gene blaCTX-M (p < 0.05) compared to the subclinical group. This study aims to provide references for preventing the E. coli isolates from inducing different types of mastitis.

Prevalence and Antibiotic Resistance of Escherichia coli Isolated from Raw Cow's Milk

Escherichia coli (E. coli) is one of the most common pathogens in both humans and livestock. This study aimed to investigate the prevalence of E. coli isolated from raw cow milk and evaluate its antimicrobial resistance rates. A total of 1696 milk samples were collected from Romanian dairy farms from 2018 to 2022. E. coli was isolated on various selective agar media, such as Cled agar and Columbia Agar with 5% Sheep Blood. The identification of E. coli was performed by MALDI-TOF MS. E. coli isolates were tested for their susceptibility against 18 commonly used antibiotics in a disk diffusion method. The overall prevalence of E. coli was 22.45% of all isolated pathogens. Antibiogram analysis revealed that 27.51% of E. coli isolates from milk were multidrug-resistant. Resistance was highest for penicillin-novobiocin (87.78%), followed by streptomycin (53.7%). Resistance to six drugs (amoxicillin, streptomycin, kanamycin-cephalexin, marbofloxacin, ampicillin) showed a significant increasing trend over time, while for two drugs (penicillin G-framycetin, doxycycline), a significant decrease was observed. Our results suggest that milk can be a reservoir of bacteria with the potential for infection in humans via the food chain. Furthermore, there is a need for surveillance and monitoring to control the increase in resistance to currently used antimicrobials in dairy farms because the occurrence of multidrug-resistant E. coli isolated from milk poses a health hazard to consumers.

Involvement of adhesins (EcpD, FdeC, FimH) expressed in mammary pathogenic Escherichia coli on adhesion to bovine mammary epithelial cells

Mammary pathogenic Escherichia coli (MPEC) causes mastitis, which results in substantial economic losses to the dairy industry. A high percentage of Escherichia coli isolated from cows with clinical mastitis harbor adhesin genes, such as fimH. However, it is unclear whether these adhesins are important in the adhesion of MPEC to bovine mammary epithelial cells (BMECs). Therefore, we investigated the effect of adhesins (EcpD, FdeC, and FimH) in MPEC on adherence to the bovine mammary epithelium using cultured BMECs. For this purpose, we used wild-type MPEC as well as single- and double-mutants of fimH, ecpD, and fdeC, and performed adhesion assays with BMECs. First, BMECs were cultured in the presence of lactogenic hormones to induce milk component production and tight junction formation. The bacterial count of the wild-type strain that adhered to the BMECs increased in a dose-dependent manner. In deletion mutant strains, the ΔfimH strain showed lower adhesion (P < 0.05), whereas the adhesion ratio of the ΔecpD and ΔfdeC strains was not statistically different compared with that of the wild-type strain (P > 0.05). Additionally, the fimH/fdeC double-deletion mutants showed the lowest adhesion to BMECs. In conclusion, FimH is crucial in the adhesion of MPEC to BMECs. Overall, our work identifies FimH or FimH/FdeC as interesting targets for future drugs or vaccines to improve the treatment, prevention or chronicity of mastitis induced by MPEC.

Generation of Anti-Mastitis Gene-Edited Dairy Goats with Enhancing Lysozyme Expression by Inflammatory Regulatory Sequence using ISDra2-TnpB System

Gene-editing technology has become a transformative tool for the precise manipulation of biological genomes and holds great significance in the field of animal disease-resistant breeding. Mastitis, a prevalent disease in animal husbandry, imposes a substantial economic burden on the global dairy industry. In this study, a regulatory sequence gene editing breeding strategy for the successful creation of a gene-edited dairy (GED) goats with enhanced mastitis resistance using the ISDra2-TnpB system and dairy goats as the model animal is proposed. This included the targeted integration of an innate inflammatory regulatory sequence (IRS) into the promoter region of the lysozyme (LYZ) gene. Upon Escherichia Coli (E. coli) mammary gland infection, GED goats exhibited increased LYZ expression, showing robust anti-mastitis capabilities, mitigating PANoptosis activation, and alleviating blood-milk-barrier (BMB) damage. Notably, LYZ is highly expressed only in E. coli infection. This study marks the advent of anti-mastitis gene-edited animals with exogenous-free gene expression and demonstrates the feasibility of the gene-editing strategy proposed in this study. In addition, it provides a novel gene-editing blueprint for developing disease-resistant strains, focusing on disease specificity and biosafety while providing a research basis for the widespread application of the ISDra2-TnpB system.

Selective IgG binding to the LPS glycolipid core found in bovine colostrum, or milk, during Escherichia coli mastitis influences endotoxin function

The dynamic interplay between intramammary IgG, formation of antigen-IgG complexes and effector immune cell function is essential for immune homeostasis within the bovine mammary gland. We explore how changes in the recognition and binding of anti-LPS IgG to the glycolipid "functional" core in milk from healthy or clinically diagnosed Escherichia coli (E. coli) mastitis cows' controls endotoxin function. In colostrum, we found a varied anti-LPS IgG repertoire and novel soluble LPS/IgG complexes with direct IgG binding to the LPS glycolipid core. These soluble complexes, absent in milk from healthy lactating cows, were evident in cows diagnosed with E. coli mastitis and correlated with endotoxin-driven inflammation. E. coli mastitis milk displayed a proportional reduction in anti-LPS glycolipid core IgG compared to colostrum. Milk IgG extracts showed that only colostrum IgG attenuated LPS induced endotoxin activity. Furthermore, LPS-stimulated reactive oxygen species (ROS) in milk granulocytes was only suppressed by colostrum IgG, while IgG extracts of neither colostrum nor E. coli mastitis milk influenced N-formylmethionine-leucyl-phenylalanine (fMLP)-stimulated ROS in LPS primed granulocytes. Our findings support bovine intramammary IgG diversity in health and in response to E. coli infection generate milk anti-LPS IgG repertoires that coordinate appropriate LPS innate-adaptive immune responses essential for animal health.

A novel vaccine strategy using quick and easy conversion of bacterial pathogens to unnatural amino acid-auxotrophic suicide derivatives

We propose a novel strategy for quick and easy preparation of suicide live vaccine candidates against bacterial pathogens. This method requires only the transformation of one or more plasmids carrying genes encoding for two types of biological devices, an unnatural amino acid (uAA) incorporation system and toxin-antitoxin systems in which translation of the antitoxins requires the uAA incorporation. Escherichia coli BL21-AI laboratory strains carrying the plasmids were viable in the presence of the uAA, whereas the free toxins killed these strains after the removal of the uAA. The survival time after uAA removal could be controlled by the choice of the uAA incorporation system and toxin-antitoxin systems. Multilayered toxin-antitoxin systems suppressed escape frequency to less than 1 escape per 109 generations in the best case. This conditional suicide system also worked in Salmonella enterica and E. coli clinical isolates. The S. enterica vaccine strains were attenuated with a >105 fold lethal dose. Serum IgG response and protection against the parental pathogenic strain were confirmed. In addition, the live E. coli vaccine strain was significantly more immunogenic and provided greater protection than a formalin-inactivated vaccine. The live E. coli vaccine was not detected after inoculation, presumably because the uAA is not present in the host animals or the natural environment. These results suggest that this strategy provides a novel way to rapidly produce safe and highly immunogenic live bacterial vaccine candidates.

IMPORTANCE

Live vaccines are the oldest vaccines with a history of more than 200 years. Due to their strong immunogenicity, live vaccines are still an important category of vaccines today. However, the development of live vaccines has been challenging due to the difficulties in achieving a balance between safety and immunogenicity. In recent decades, the frequent emergence of various new and old pathogens at risk of causing pandemics has highlighted the need for rapid vaccine development processes. We have pioneered the use of uAAs to control gene expression and to conditionally kill host bacteria as a biological containment system. This report proposes a quick and easy conversion of bacterial pathogens into live vaccine candidates using this containment system. The balance between safety and immunogenicity can be modulated by the selection of the genetic devices used. Moreover, the uAA-auxotrophy can prevent the vaccine from infecting other individuals or establishing the environment.

LncRNA CA12-AS1 targets miR-133a to promote LPS-induced inflammatory response in bovine mammary epithelial cells

Bovine mastitis seriously affects milk production and quality and causes huge economic losses in the dairy industry. Recent studies have shown that long non-coding RNAs (lncRNAs) may regulate bovine mastitis. In this study, the expression of lncRNA CA12-AS1 was significantly upregulated in LPS-induced bovine mammary epithelial cells (bMECs) but negatively correlated with the expression of miR-133a, suggesting that it may be related to the inflammatory response in bMECs. Dual luciferase reporter gene assay revealed that miR-133a is a downstream target gene of lncRNA CA12-AS1. Furthermore, lncRNA CA12-AS1 silencing negatively regulated the expression of miR-133a inhibited the secretion of inflammatory factors (IL-6, IL-8 and IL-1β) and decreased the mRNA expression levels of nuclear factor kappa B (NF-κB) (p65/p50) and apoptosis-related genes (BAX, caspase3 and caspase9). LncRNA CA12-AS1 silencing also promoted the mRNA expression levels of the Tight junction (TJ) signaling pathway-related genes (Claudin-1, Occludin and ZO-1), apoptotic gene BCL2, proliferation-related genes (CDK2, CDK4 and PCNA) and the viability of bMECs. However, overexpression of lncRNA CA12-AS1 reversed the above effects. These results revealed that lncRNA CA12-AS1 is a pro-inflammatory regulator, and its silencing can alleviate bovine mastitis by targeting miR-133a, providing a novel strategy for molecular therapy of cow mastitis.

Genes and pathways revealed by whole transcriptome analysis of milk derived bovine mammary epithelial cells after Escherichia coli challenge

Mastitis, inflammation of the mammary gland, is the costliest disease in dairy cattle and a major animal welfare concern. Mastitis is usually caused by bacteria, of which staphylococci, streptococci and Escherichia coli are most frequently isolated from bovine mastitis. Bacteria activate the mammary immune system in variable ways, thereby influencing the severity of the disease. Escherichia coli is a common cause of mastitis in cattle causing both subclinical and clinical mastitis. Understanding of the molecular mechanisms that activate and regulate the host response would be central to effective prevention of mastitis and breeding of cows more resistant to mastitis. We used primary bovine mammary epithelial cell cultures extracted noninvasively from bovine milk samples to monitor the cellular responses to Escherichia coli challenge. Differences in gene expression between control and challenged cells were studied by total RNA-sequencing at two time points post-challenge. In total, 150 and 440 (Padj < 0.05) differentially expressed genes were identified at 3 h and 24 h post-challenge, respectively. The differentially expressed genes were mostly upregulated at 3 h (141/150) and 24 h (424/440) post-challenge. Our results are in line with known effects of E. coli infection, with a strong early inflammatory response mediated by pathogen receptor families. Among the most significantly enriched early KEGG pathways were the TNF signalling pathway, the cytokine-cytokine receptor interaction, and the NF-kappa B signalling pathway. At 24 h post-challenge, most significantly enriched were the Influenza A, the NOD-like receptor signalling, and the IL-17 signaling pathway.

The inhibition effect of caffeic acid on NOX/ROS-dependent macrophages M1-like polarization contributes to relieve the LPS-induced mice mastitis

The mammary gland is an adipose tissue containing not only adipocytes but also epithelial, endothelial, and immune cells. Epithelial cells and macrophages, as the integral components of the immune system, are on the front line of defense against infection. Our preliminary work proved that caffeic acid (CA) can effectively inhibit the inflammatory cascade of bovine mammary epithelial cells (BMEC) induced by lipopolysaccharide (LPS) and maintain cellular integrity and viability. Here, we investigated the therapeutic effect of CA on LPS-induced mice mastitis and explored its regulatory mechanism on macrophage inflammatory response induced by LPS in vitro. Firstly, the mice mastitis model was established by intramammary injection with 10 μg LPS, after which different CA doses (5, 10, 15 mg/kg) were administered. Then, the pathological section, myeloperoxidase (MPO) activity, proinflammatory factors and chemokines releasement, and redox state of mammary tissues were assessed, confirming CA's effectiveness on mice mastitis. In vitro, we validated the therapeutic relevance of CA in relieving LPS-induced RAW264.7 inflammatory and oxidative stress responses. Moreover, we further provided evidence that CA significantly reduced LPS-induced reactive oxygen species (ROS) generation via NADPH oxidase (NOX), which improved the imbalance relationship between nuclear factor kappa-B (NF-κB) and NF-E2 p45-related factor 2 (Nrf2) and led to a marked weakening of M1 polarization. The NOX-ROS signal inhibited by CA weakened the oxidative burst and neutrophil chemotaxis of macrophages, thus alleviating the immune cascade in mammary gland tissue and reducing the LPS-induced inflammatory damage. Collectively, CA would be a potential candidate or antibacterial synergist for curbing mastitis.

Fighting antibiotic resistance in the local management of bovine mastitis

Bovine mastitis is a widespread infectious disease with a significant economic burden, accounting for 80 % of the antibiotic usage in dairy animals. In recent years, extensive research has focused on using biomimetic approaches such as probiotics, bacteriocins, bacteriophages, or phytochemicals as potential alternatives to antibiotics. The local administration of therapeutic molecules through the intramammary route is one of the most commonly strategies to manage bovine mastitis. This review highlights the most important findings in this field and discusses their local application in mastitis therapy. In contrast to antibiotics, the proposed alternatives are not limited to promote bacterial death but consider other factors associated to the host microenvironments. To this end, the proposed biomimetic strategies can modulate different stages of infection by modifying the local microbiota, preventing oxidative stress, reducing bacterial adhesion to epithelial cells, modulating the immune response, or mediating the inflammatory process. Numerous in vitro studies support the antimicrobial, antibiofilm or antioxidant properties of these alternatives. However, in vivo studies incorporating these components within pharmaceutical formulations with potential clinical application are limited. The development of secure, stable, and effective drug delivery systems based on the proposed options is necessary to achieve real alternatives to antibiotics in the clinic.

Carbon sphere doped CdS quantum dots served as a dye degrader and their bactericidal behavior analysed with in silico molecular docking analysis

We have employed a co-precipitation method to synthesize different concentrations of carbon spheres (CSs) doped with cadmium sulfide (CdS) quantum dots (QDs) for catalytic reduction and antibacterial applications. Various morphological and structural characterization techniques were used to comprehensively analyze the CS effect on CdS QDs. The catalytic reduction efficiency of CS-doped CdS QDs was evaluated using rhodamine B dye. The antibacterial efficacy was also assessed against the pathogenic microorganism Escherichia coli (E. coli), and substantial destruction in the inhibitory zone was measured. Finally, the synthesized CS-doped CdS QDs demonstrated favorable results for catalytic reduction and antibacterial applications. Computational studies verified the suppressive impact of these formed QDs on DNA gyrase and β-lactamase of E. coli.

Wogonin attenuates inflammation and oxidative stress in lipopolysaccharide-induced mastitis by inhibiting Akt/NF-κB pathway and activating the Nrf2/HO-1 signaling

Mastitis is a disease involved in inflammation of breast which affects human and animals. Wogonin is one bioactive compound from many Chinese herbal medicines, which have multiple properties, including anti-inflammatory activity. However, the roles of wogonin in mastitis progression are largely undefined. Mastitis models were established using LPS-treated mice and mammary epithelial cells (MECs). Infiltration of inflammatory cells was analyzed by hematoxylin-eosin staining and myeloperoxidase (MPO) activity. Inflammatory cytokine (TNF-α and IL-1β) levels were detected via ELISA. The phosphorylation and total of Akt and NF-κB levels and content of Nrf2 and HO-1 were measured via western blot. Cell viability was examined by CCK-8 assay. Oxidative stress was assessed by ROS generation and levels of MDA, GSH, and SOD. Wogonin attenuated LPS-induced infiltration of inflammatory cells, increase of MPO activity and levels of TNF-α and IL-1β, and activation of the Akt/NF-κB pathway in murine mammary gland tissues, and promoted activation of Nrf2/HO-1 signaling. Wogonin did not affect MEC viability, but mitigated LPS-induced inflammation in MECs by reducing TNF-α and IL-1β levels. Wogonin relieved LPS-induced oxidative stress in MECs through decreasing ROS generation and MDA level and increasing GSH and SOD levels. Wogonin repressed LPS-induced activation of the Akt/NF-κB pathway in MECs and increased Nrf2/HO-1 signaling activation. Activated Akt/NF-κB signaling or Nrf2/HO-1 signaling inactivation reversed the suppressive effects of wogonin on LPS-induced inflammation and oxidative stress in MECs. Wogonin mitigates LPS-induced inflammation and oxidative stress of MECs via suppressing activation of the Akt/NF-κB signaling and activating Nrf2/HO-1 pathway, indicating the therapeutic potential of wogonin in mastitis.

Coexpression analysis of lncRNAs and mRNAs identifies potential regulatory long noncoding RNAs involved in the inflammatory effects of lipopolysaccharide on bovine mammary epithelial cells

BACKGROUND

The infection of bovine mammary glands by pathogenic microorganisms not only causes animal distress but also greatly limits the development of the dairy industry and animal husbandry. A deeper understanding of the host's initial response to infection may increase the accuracy of selecting drug-resistant animals or facilitate the development of new preventive or therapeutic intervention strategies. In addition to their functions of milk synthesis and secretion, bovine mammary epithelial cells (BMECs) play an irreplaceable role in the innate immune response. To better understand this process, the current study identified differentially expressed long noncoding lncRNAs (DE lncRNAs) and mRNAs (DE mRNAs) in BMECs exposed to Escherichia coli lipopolysaccharide (LPS) and further explored the functions and interactions of these lncRNAs and mRNAs.

RESULTS

In this study, transcriptome analysis was performed by RNA sequencing (RNA-seq), and the functions of the DE mRNAs and DE lncRNAs were predicted by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Next, we constructed a modulation network to gain a deeper understanding of the interactions and roles of these lncRNAs and mRNAs in the context of LPS-induced inflammation. A total of 231 DE lncRNAs and 892 DE mRNAs were identified. Functional enrichment analysis revealed that pathways related to inflammation and the immune response were markedly enriched in the DE genes. In addition, research results have shown that cell death mechanisms, such as necroptosis and pyroptosis, may play key roles in LPS-induced inflammation.

CONCLUSIONS

In summary, the current study identified DE lncRNAs and mRNAs and predicted the signaling pathways and biological processes involved in the inflammatory response of BMECs that might become candidate therapeutic and prognostic targets for mastitis. This study also revealed several possible pathogenic mechanisms of mastitis.

Efficient screening of adsorbed receptors for Salmonella phage LP31 and identification of receptor-binding protein

The adsorption process is the first step in the lifecycle of phages and plays a decisive role in the entire infection process. Identifying the adsorption mechanism of phages not only makes phage therapy more precise and efficient but also enables the exploration of other potential applications and modifications of phages. Phage LP31 can lyse multiple Salmonella serotypes, efficiently clearing biofilms formed by Salmonella enterica serovar Enteritidis (S. Enteritidis) and significantly reducing the concentration of S. Enteritidis in chicken feces. Therefore, LP31 has great potential for many practical applications. In this study, we established an efficient screening method for phage infection-related genes and identified a total of 10 genes related to the adsorption process of phage LP31. After the construction of strain C50041ΔrfaL 58-358, it was found that the knockout strain had a rough phenotype as an O-antigen-deficient strain. Adsorption rate and transmission electron microscopy experiments showed that the receptor for phage LP31 was the O9 antigen of S. Enteritidis. Homology comparison and adsorption experiments confirmed that the tail fiber protein Lp35 of phage LP31 participated in the adsorption process as a receptor-binding protein. IMPORTANCE A full understanding of the interaction between phages and their receptors can help with the development of phage-related products. Phages like LP31 with the tail fiber protein Lp35, or a closely related protein, have been reported to effectively recognize and infect multiple Salmonella serotypes. However, the role of these proteins in phage infection has not been previously described. In this study, we established an efficient screening method to detect phage adsorption to host receptors. We found that phage LP31 can utilize its tail fiber protein Lp35 to adsorb to the O9 antigen of S. Enteritidis, initiating the infection process. This study provides a great model system for further studies of how a phage-encoded receptor-binding protein (RBP) interacts with its host's RBP binding target, and this new model offers opportunities for further theoretical and experimental studies to understand the infection mechanism of phages.

MicroRNA miR-223 modulates NLRP3 and Keap1, mitigating lipopolysaccharide-induced inflammation and oxidative stress in bovine mammary epithelial cells and murine mammary glands

Bovine mastitis, the most prevalent and costly disease in dairy cows worldwide, decreases milk quality and quantity, and increases cow culling. However, involvement of microRNAs (miRNAs) in mastitis is not well characterized. The objective was to determine the role of microRNA-223 (miR-223) in regulation of the nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome and kelch like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) oxidative stress pathway in mastitis models induced by lipopolysaccharide (LPS) treatment of immortalized bovine mammary epithelial cells (bMECs) and murine mammary glands. In bMECs cultured in vitro, LPS-induced inflammation downregulated bta-miR-223; the latter interacted directly with the 3' untranslated region (3' UTR) of NLRP3 and Keap1. Overexpression of bta-miR-223 in bMECs decreased LPS and Adenosine 5'-triphosphate (ATP)-induced NLRP3 and its mediation of caspase 1 and IL-1β, and inhibited LPS-induced Keap1 and Nrf2 mediated oxidative stress, whereas inhibition of bta-miR-223 had opposite effects. In an in vivo murine model of LPS-induced mastitis, increased miR-223 mitigated pathology in the murine mammary gland, whereas decreased miR-223 increased inflammatory changes and oxidative stress. In conclusion, bta-miR-223 mitigated inflammation and oxidative injury by downregulating the NLRP3 inflammasome and Keap1/Nrf2 signaling pathway. This study implicated bta-miR-223 in regulation of inflammatory responses, with potential as a novel target for treating bovine mastitis and other diseases.

Advances in Diagnostic Approaches and Therapeutic Management in Bovine Mastitis

Mastitis causes huge economic losses to dairy farmers worldwide, which largely negatively affects the quality and quantity of milk. Mastitis decreases overall milk production, degrades milk quality, increases milk losses because of milk being discarded, and increases overall production costs due to higher treatment and labour costs and premature culling. This review article discusses mastitis with respect to its clinical epidemiology, the pathogens involved, economic losses, and basic and advanced diagnostic tools that have been used in recent times to diagnose mastitis effectively. There is an increasing focus on the application of novel therapeutic approaches as an alternative to conventional antibiotic therapy because of the decreasing effectiveness of antibiotics, emergence of antibiotic-resistant bacteria, issue of antibiotic residues in the food chain, food safety issues, and environmental impacts. This article also discussed nanoparticles'/chitosan's roles in antibiotic-resistant strains and ethno-veterinary practices for mastitis treatment in dairy cattle.

Resveratrol inhibits LPS-induced apoptosis in bovine mammary epithelial cells: the role of PGC1α-SIRT3 axis

Resveratrol (Res) is a bioactive dietary component and alleviates apoptosis in multiple cell types. However, its effect and mechanism on lipopolysaccharide (LPS)-induced bovine mammary epithelial cells (BMEC) apoptosis, which commonly happens in dairy cows with mastitis, is unknown. We hypothesized that Res would inhibit LPS-induced apoptosis in BMEC through SIRT3, a NAD + -dependent deacetylase activated by Res. To test the dose-response effect on apoptosis, 0-50 μM Res were incubated with BMEC for 12 h, followed by 250 μg/mL LPS treatment for 12 h. To investigate the role of SIRT3 in Res-mediated alleviation of apoptosis, BMEC were pretreated with 50 μM Res for 12 h, then incubated with si-SIRT3 for 12 h and were finally treated with 250 μg/mL LPS for 12 h. Res dose-dependently promoted the cell viability and protein levels of Bcl-2 (Linear P < 0.001) but decreased protein levels of Bax, Caspase-3 and Bax/Bcl-2 (Linear P < 0.001). TUNEL assays indicated that cellular fluorescence intensity declined with the rising doses of Res. Res also dose-dependently upregulated SIRT3 expression, but LPS had the opposite effect. SIRT3 silencing abolished these results with Res incubation. Mechanically, Res enhanced the nuclear translocation of PGC1α, the transcriptional cofactor for SIRT3. Further molecular docking analysis revealed that Res could directly bind to PGC1α by forming a hydrogen bond with Tyr-722. Overall, our data suggested that Res relieved LPS-induced BMEC apoptosis through the PGC1α-SIRT3 axis, providing a basis for further in vivo investigations of applying Res to relieve mastitis in dairy cows.

A fiber-enriched diet alleviates Staphylococcus aureus-induced mastitis by activating the HDAC3-mediated antimicrobial program in macrophages via butyrate production in mice

Mounting evidence suggests that the gut microbiota plays an important role in the pathogenesis of mastitis, an important disease affecting the health of lactating women and the development of the dairy industry. However, the effect of the regulation of the gut microbiota by dietary components on mastitis development remains unknown. In this study, we found that a fiber-enriched diet alleviated Staphylococcus aureus (S. au)-induced mastitis in mice, which was dependent on the gut microbiota as depletion of the gut microbiota by antibiotics abolished this protective effect. Likewise, fecal microbiota transplantation (FMT) from high-inulin (HI)-treated mice (HIF) to recipient mice improved S. au-induced mastitis in mice. Consumption of an HI diet and HIF increased fecal short-chain fatty acid (SCFA) levels compared with the control group. Moreover, treatment with SCFAs, especially butyrate, alleviated S. au-induced mastitis in mice. Mechanistically, consumption of an HI diet enhanced the host antimicrobial program in macrophages through inhibiting histone deacetylase 3 by the production of butyrate. Collectively, our results suggest that modulation of the gut microbiota and its metabolism by dietary components is a potential strategy for mastitis intervention and serve as a basis for other infectious diseases.

Assessment of adaptive immune responses of dairy cows with Burkholderia contaminans-induced mastitis

Burkholderia contaminans, an emerging pathogen related to cystic fibrosis, is known to cause potentially fatal infections in humans and ruminants, especially in immunocompromised individuals. However, the immune responses in cows following its infection have not been fully elucidated. In this study, T- and B-lymphocytes-mediated immune responses were evaluated in 15 B. contaminans-induced mastitis cows and 15 healthy cows with multi-parameter flow cytometry. The results showed that infection with B. contaminans was associated with a significant decrease in the number and percentage of B lymphocytes but with a significant increase in the proportion of IgG⁺CD27⁺ B lymphocytes. This indicated that humoral immune response may not be adequate to fight intracellular infection, which could contribute to the persistent bacterial infection. In addition, B. contaminans infection induced significant increase of γδ T cells and double positive (DP) CD4⁺CD8⁺ T cells but not CD4⁺ or CD8⁺ (single positive) T cells in blood. Phenotypic analysis showed that the percentages of activated WC1⁺ γδ T cells in peripheral blood were increased in the B. contaminans infected cows. Interestingly, intracellular cytokine staining showed that cattle naturally infected with B. contaminans exhibited multifunctional TNF-α⁺IFN-γ⁺IL-2⁺ B. contaminans-specific DP T cells. Our results, for the first time, revealed a potential role of IgG⁺CD27⁺ B cells, CD4⁺CD8⁺ T cells and WC1⁺ γδ T cells in the defense of B. contaminans-induced mastitis in cows.

Immune defenses of the mammary gland epithelium of dairy ruminants

The epithelium of the mammary gland (MG) fulfills three major functions: nutrition of progeny, transfer of immunity from mother to newborn, and its own defense against infection. The defense function of the epithelium requires the cooperation of mammary epithelial cells (MECs) with intraepithelial leucocytes, macrophages, DCs, and resident lymphocytes. The MG is characterized by the secretion of a large amount of a nutrient liquid in which certain bacteria can proliferate and reach a considerable bacterial load, which has conditioned how the udder reacts against bacterial invasions. This review presents how the mammary epithelium perceives bacteria, and how it responds to the main bacterial genera associated with mastitis. MECs are able to detect the presence of actively multiplying bacteria in the lumen of the gland: they express pattern recognition receptors (PRRs) that recognize microbe-associated molecular patterns (MAMPs) released by the growing bacteria. Interactions with intraepithelial leucocytes fine-tune MECs responses. Following the onset of inflammation, new interactions are established with lymphocytes and neutrophils recruited from the blood. The mammary epithelium also identifies and responds to antigens, which supposes an antigen-presenting capacity. Its responses can be manipulated with drugs, plant extracts, probiotics, and immune modifiers, in order to increase its defense capacities or reduce the damage related to inflammation. Numerous studies have established that the mammary epithelium is a genuine effector of both innate and adaptive immunity. However, knowledge gaps remain and newly available tools offer the prospect of exciting research to unravel and exploit the multiple capacities of this particular epithelium.

Application and challenge of bacteriophage in the food protection

In recent years, foodborne diseases caused by pathogens have been increasing. Therefore, it is essential to control the growth and transmission of pathogens. Bacteriophages (phages) have the potential to play an important role in the biological prevention, control, and treatment of these foodborne diseases due to their favorable advantages. Phages not only effectively inhibit pathogenic bacteria and prolong the shelf life of food, but also possess the advantages of specificity and an absence of chemical residues. Currently, there are many cases of phage applications in agriculture, animal disease prevention and control, food safety, and the treatment of drug-resistant disease. In this review, we summarize the recent research progress on phages against foodborne pathogenic bacteria, including Escherichia coli, Salmonella, Campylobacter, Listeria monocytogenes, Shigella, Vibrio parahaemolyticus, and Staphylococcus aureus. We also discuss the main issues and their corresponding solutions in the application of phages in the food industry. In recent years, although researchers have discovered more phages with potential applications in the food industry, most researchers use these phages based on their host spectrum, and the application environment is mostly in the laboratory. Therefore, the practical application of these phages in different aspects of the food industry may be unsatisfactory and even have some negative effects. Thus, we suggest that before using these phages, it is necessary to identify their specific receptors. Using their specific receptors as the selection basis for their application and combining phages with other phages or phages with traditional antibacterial agents may further improve their safety and application efficiency. Collectively, this review provides a theoretical reference for the basic research and application of phages in the food industry.

Escherichia coli Mastitis in Dairy Cattle: Etiology, Diagnosis, and Treatment Challenges

Bovine mastitis is an inflammation of the udder tissue parenchyma that causes pathological changes in the glandular tissue and abnormalities in milk leading to significant economic losses to the dairy industry across the world. Mammary pathogenic Escherichia (E.) coli (MPEC) is one of the main etiologic agents of acute clinical mastitis in dairy cattle. MPEC strains have virulence attributes to resist the host innate defenses and thrive in the mammary gland environment. The association between specific virulence factors of MPEC with the severity of mastitis in cattle is not fully understood. Furthermore, the indiscriminate use of antibiotics to treat mastitis has resulted in antimicrobial resistance to all major antibiotic classes in MPEC. A thorough understanding of MPEC’s pathogenesis and antimicrobial susceptibility pattern is required to develop better interventions to reduce mastitis incidence and prevalence in cattle and the environment. This review compiles important information on mastitis caused by MPEC (e.g., types of mastitis, host immune response, diagnosis, treatment, and control of the disease) as well as the current knowledge on MPEC virulence factors, antimicrobial resistance, and the dilemma of MPEC as a new pathotype. The information provided in this review is critical to identifying gaps in knowledge that will guide future studies to better design diagnostic, prevent, and develop therapeutic interventions for this significant dairy disease.

Integrated Bacteria-Fungi Diversity Analysis Reveals the Gut Microbial Changes in Buffalo With Mastitis

The gut microbial community is closely related to mastitis, but studies regarding the influences of mastitis on gut microbiota in buffalo remain scarce. Herein, we characterized the differences in gut bacterial and fungal communities between mastitis-affected and healthy buffalos. Interestingly, although mastitis had no effect on gut bacterial and fungal diversities in the buffalos, some bacterial and fungal taxa were significantly altered. Bacterial and fungal taxonomic analysis showed that the preponderant bacterial phyla (Firmicutes and Bacteroidetes) and fungal phyla (Ascomycota and Basidiomycota) in buffalo were the same regardless of health status. At the level of genus, the changes in some gut bacterial and fungal abundances between both groups were gradually observed. Compared with healthy buffalos, the proportions of 3 bacterial genera (uncultured_bacterium_f_Muribaculaceae, Eubacterium_nodatum_group, and Lachnoclostridium_10) and 1 fungal genus (Pichia) in the mastitis-affected buffalo were significantly increased, whereas 4 bacterial genera (Ruminococcus_2, Candidatus_Stoquefichus, Turicibacter, and Cellulosilyticum) and 4 fungal genera (Cladosporium, Thermothelomyces, Ganoderma and Aspergillus) were significantly decreased. Taken together, this research revealed that there was significant difference in the compositions of the gut microbial community between the healthy and mastitis-affected buffalos. To our knowledge, this is the first insight into the characteristics of the gut microbiota in buffalos with mastitis, which is beneficial to understand the gut microbial information of buffalo in different health states and elucidate the pathogenesis of mastitis from the gut microbial perspective.

Construction of the waaF Subunit and DNA Vaccine Against Escherichia coli in Cow Mastitis and Preliminary Study on Their Immunogenicity

Escherichia coli (E. coli) is one of the major pathogenic bacteria in bovine mastitis, which usually triggers systemic symptoms by releasing lipopolysaccharide (LPS). waaF is the core in LPS pathogenicity. In this study, a new waaF vaccine candidate was identified, constructed with the pcDNA3.1 (+)HisB-waaF plasmid to create to a DNA vaccine (pcwaaF), and transfected into MCF-7 cells to produce recombinant waaF subunit vaccine (rwaaF). After that, the safety of the two vaccine candidates was evaluated in mouse model. Immunogenicity and mortality of challenged mice were compared in 20 and 40 μg per dose, respectively. The results showed that rwaaF and pcwaaF were successfully constructed and the complete blood count and serum biochemical indicated that both of the vaccine candidates were safe (p &gt; 0.05). In addition, histopathological staining showed no obvious pathological changes. The immune response induced by rwaaF was significantly higher than that of pcwaaF (p &lt; 0.01), indicated by levels of serum concentration of IgG IL-2, IL-4, and IFN-γ, and feces concentration of sIgA. Survival rates of mice in rwaaF groups (both 80%) were also higher than in the pcwaaF groups (40 and 50%, respectively). Comparing the safety, immunogenicity, and E. coli challenge of two vaccine candidates, rwaaF had the better effect and 20 μg rwaaF was more economical. In conclusion, this study demonstrates the utility of a new E. coli vaccine and provides a rationale for further investigation of bovine mastitis therapy and management.