Immune response of Staphylococcus aureus strains in a mouse mastitis model is linked to adaptive capacity and genotypic profiles

Biological characterization of the phage lysin AVPL and its efficiency against Aerococcus viridans-induced mastitis in a murine model

Aerococcus viridans (A. viridans) is an important opportunistic zoonotic pathogen that poses a potential threat to the animal husbandry industry, such as cow mastitis, due to the widespread development of multidrug-resistant strains. Phage lysins have emerged as a promising alternative antibiotic treatment strategy. However, no lysins have been reported to treat A. viridans infections. In this study, the critical active domain and key active sites of the first A. viridans phage lysin AVPL were revealed. AVPL consists of an N-terminal N-acetylmuramoyl-L-alanine amidase catalytic domain and a C-terminal binding domain comprising two conserved LysM. H40, N44, E52, W68, H147, T157, F60, F64, I77, N92, Q97, H159, V160, D161, and S42 were identified as key sites for maintaining the activity of the catalytic domain. The LysM motif plays a crucial role in binding AVPL to bacterial cell wall peptidoglycan. AVPL maintains stable activity in the temperature range of 4-45°C and pH range of 4-10, and its activity is independent of the presence of metal ions. In vitro, the bactericidal effect of AVPL showed efficient bactericidal activity in milk samples, with 2 µg/mL of AVPL reducing A. viridans by approximately 2 Log10 in 1 h. Furthermore, a single dose (25 µg) of lysin AVPL significantly reduces bacterial load (approximately 2 Log10) in the mammary gland of mice, improves mastitis pathology, and reduces the concentration of inflammatory cytokines (TNF-α, IL-1β, and IL-6) in mammary tissue. Overall, this work provides a novel alternative therapeutic drug for mastitis induced by multidrug-resistant A. viridans.

IMPORTANCE

A. viridans is a zoonotic pathogen known to cause various diseases, including mastitis in dairy cows. In recent years, there has been an increase in antibiotic-resistant or multidrug-resistant strains of this pathogen. Phage lysins are an effective approach to treating infections caused by multidrug-resistant strains. This study revealed the biological properties and key active sites of the first A. viridans phage lysin named AVPL. AVPL can effectively kill multidrug-resistant A. viridans in pasteurized whole milk. Importantly, 25 μg AVPL significantly alleviates the symptoms of mouse mastitis induced by A. viridans. Overall, our results demonstrate the potential of lysin AVPL as an antimicrobial agent for the treatment of mastitis caused by A. viridans.

Characterization and antioxidant activity of nano-formulated berberine and cyperus rotundus extracts with anti-inflammatory effects in mastitis-induced rats

Bovine mastitis caused by infectious pathogens, mainly Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), constitutes a major destructive challenge for the dairy industry and public health. Berberine chloride (BER) and Cyperus rotundus possess a broad spectrum of anti-inflammatory, antioxidant, antibacterial, and antiproliferative activities; however, their bioavailability is low. This research aimed first to prepare an ethanolic extract of Cyperus rotundus rhizomes (CRE) followed by screening its phytochemical contents, then synthesis of BER and CRE loaded chitosan nanoparticles (NPs) (BER/CH-NPs and CRE/CH-NPs), afterward, the analysis of their loading efficiency in addition to the morphological and physicochemical characterization of the formulated NPs employing Scanning Electron Microscopy (SEM), Zeta Potential (ZP), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) assessments compared to their crude forms to evaluate the enhancement of bioavailability and stability. Isolation of bacterial strains from the milk of mastitic cows, used for induction of mammary gland (MG) inflammation in female albino rats, and a preliminary investigation of the prophylactic oral doses of the prepared NPs against S. aureus-induced mastitis in female rats. The minimal inhibitory concentration (MIC) of BER/CH-NPs and CRE/CH-NPs is 1 mg/kg b.w. BER/CH-NPs and CRE/CH-NPs alone or in combination show significant (P ≤ 0.05) DPPH radical scavenging activity (69.2, 88.5, and 98.2%, respectively) in vitro. Oral administration of BER/CH-NPs and CRE/CH-NPs to mastitis rats significantly (P ≤ 0.05) attenuated TNF-α (22.1, 28.6 pg/ml), IL-6 (33.4, 42.9 pg/ml), IL-18 (21.7, 34.7 pg/ml), IL-4 (432.9, 421.6 pg/ml), and MPO (87.1, 89.3 pg/ml) compared to mastitis group alongside the improvement of MG histopathological findings without any side effect on renal and hepatic functions. Despite promising results with BER and CRE nanoparticles, the study is limited by small-scale trials, a focus on acute administration, and partially explored nanoparticle-biological interactions, with no economic or scalability assessments. Future research should address these limitations by expanding trial scopes, exploring interactions further, extending study durations, and assessing economic and practical scalability. Field trials and regulatory compliance are also necessary to ensure practical application and safety in the dairy industry. In conclusion, the in vitro and in vivo results proved the antioxidant and anti-inflammatory efficacy of BER/CH-NPs and CRE/CH-NPs in low doses with minimal damage to the liver and kidney functions, supposing their promising uses in mastitis treatment.

The secretome of Staphylococcus aureus strains with opposite within-herd epidemiological behavior affects bovine mononuclear cell response

Staphylococcus aureus modulates the host immune response directly by interacting with the immune cells or indirectly by secreting molecules (secretome). Relevant differences in virulence mechanisms have been reported for the secretome produced by different S. aureus strains. The present study investigated the S. aureus secretome impact on peripheral bovine mononuclear cells (PBMCs) by comparing two S. aureus strains with opposite epidemiological behavior, the genotype B (GTB)/sequence type (ST) 8, associated with a high within-herd prevalence, and GTS/ST398, associated with a low within-herd prevalence. PBMCs were incubated with different concentrations (0%, 0.5%, 1%, and 2.5%) of GTB/ST8 and GTS/ST398 secretome for 18 and 48 h, and the viability was assessed. The mRNA levels of pro- (IL1-β and STAT1) and anti-inflammatory (IL-10, STAT6, and TGF-β) genes, and the amount of pro- (miR-155-5p and miR-125b-5p) and anti-inflammatory (miR-146a and miR-145) miRNAs were quantified by RT-qPCR. Results showed that incubation with 2.5% of GTB/ST8 secretome increased the viability of cells. In contrast, incubation with the GTS/ST398 secretome strongly decreased cell viability, preventing any further assays. The GTB/ST8 secretome promoted PBMC polarization towards the pro-inflammatory phenotype inducing the overexpression of IL1-β, STAT1 and miR-155-5p, while the expression of genes involved in the anti-inflammatory response was not affected. In conclusion, the challenge of PBMC to the GTS/ST398 secretome strongly impaired cell viability, while exposure to the GTB/ST8 secretome increased cell viability and enhanced a pro-inflammatory response, further highlighting the different effects exerted on host cells by S. aureus strains with epidemiologically divergent behaviors.

Potential of phage EF-N13 as an alternative treatment strategy for mastitis infections caused by multidrug-resistant Enterococcus faecalis

Bovine mastitis is the most common and costly disease affecting dairy cattle throughout the world. Enterococcus faecalis is one of the environmental origin mastitis-causing pathogens. The treatment of bovine mastitis is primarily based on antibiotics. Due to the negative impact of developing antibiotic resistance and adverse effects on soil and water environments, the trend toward use of nonantibiotic treatments is increasing. Phages may represent a promising alternative treatment strategy. However, it is unknown whether phages have therapeutic effects on E. faecalis-induced mastitis. Thus, the objective of this study was to investigate the degree of protection conferred by a phage during murine mastitis caused by multidrug-resistant E. faecalis. Enterococcus faecalis was isolated from the milk of dairy cows with mastitis, and a phage was isolated using the E. faecalis isolates as hosts. The bactericidal ability of the phage against E. faecalis and the ability to prevent biofilm formation were determined in vitro. The therapeutic potential of the phage on murine mastitis was evaluated in vivo. We isolated 14 strains of E. faecalis from the milk of cows with mastitis, all of which exhibited multidrug resistance, and most (10/14) could form strong biofilms. Subsequently, a new phage (EF-N13) was isolated using the multidrug-resistant E. faecalis N13 (isolated from mastitic milk) as the host. The phage EF-N13 belongs to the family Myoviridae, which has short latent periods (5 min) and high bursts (284 pfu/cell). The genome of EF-N13 lacked bacterial virulence-, antibiotic resistance-, and lysogenesis-related genes. Furthermore, bacterial loading in the raw milk medium was significantly reduced by EF-N13 and was unaffected by potential IgG antibodies. In fact, EF-N13 could effectively prevent the formation of biofilm by multidrug-resistant E. faecalis. All of these characteristics suggest that EF-N13 has potential as mastitis therapy. In vivo, 1 × 105 cfu/gland of multidrug-resistant E. faecalis N13 resulted in mastitis development within 24 h. A single dose of phage EF-N13 (1 × 104, 1 × 105, or 1 × 106 pfu/gland) could significantly decrease bacterial counts in the mammary gland at 24 h postinfection. Histopathological observations demonstrated that treatment with phage EF-N13 effectively alleviated mammary gland inflammation and damage. This effect was confirmed by the lower levels of proinflammatory cytokines IL-6, IL-1β, and tumor necrosis factor-α in the mammary gland treated with phage EF-N13 compared with those treated with phosphate-buffered saline. Overall, the data underscored the potential of phage EF-N13 as an alternative therapy for bovine mastitis caused by multidrug-resistant E. faecalis.

Bovine-associated staphylococci and mammaliicocci trigger T-lymphocyte proliferative response and cytokine production differently

We examined whether distinct staphylococcal and mammaliicoccal species and strains trigger B- and T-lymphocyte proliferation and interleukin (IL)-17A and interferon (IFN)-γ production by peripheral blood mononuclear cells in nulliparous, primiparous, and multiparous dairy cows. Flow cytometry was used to measure lymphocyte proliferation with the Ki67 antibody, and specific monoclonal antibodies were used to identify CD3, CD4, and CD8 T lymphocyte and CD21 B lymphocyte populations. The supernatant of the peripheral blood mononuclear cell culture was used to measure IL-17A and IFN-γ production. Two distinct, inactivated strains of bovine-associated Staphylococcus aureus [one causing a persistent intramammary infection (IMI) and the other from the nose], 2 inactivated Staphylococcus chromogenes strains [one causing an IMI and the other from a teat apex), as well as an inactivated Mammaliicoccus fleurettii strain originating from sawdust from a dairy farm, and the mitogens concanavalin A and phytohemagglutinin M-form (both specifically to measure lymphocyte proliferation) were studied. In contrast to the "commensal" Staph. aureus strain originating from the nose, the Staph. aureus strain causing a persistent IMI triggered proliferation of CD4⁺ and CD8⁺ subpopulations of T lymphocytes. The M. fleurettii strain and the 2 Staph. chromogenes strains had no effect on T- or B-cell proliferation. Furthermore, both Staph. aureus and Staph. chromogenes strains causing persistent IMI significantly increased IL-17A and IFN-γ production by peripheral blood mononuclear cells. Overall, multiparous cows tended to have a higher B-lymphocyte and a lower T-lymphocyte proliferative response than primiparous and nulliparous cows. Peripheral blood mononuclear cells of multiparous cows also produced significantly more IL-17A and IFN-γ. In contrast to concanavalin A, phytohemagglutinin M-form selectively stimulated T-cell proliferation.

Differential immune response to two Staphylococcus aureus strains with distinct adaptation genotypes after experimental intramammary infection of dairy cows

The aim of this study was to evaluate and compare the ability of two S. aureus strains with different adaptation genotypes (low and high) to the bovine mammary gland (MG) to establish an intramammary infection (IMI) and induce an immune response after an experimental challenge in lactating cows. Two isolates (designated 806 and 5011) from bovine IMI with different genotypic profiles, harboring genes involved in adherence and biofilm production, belonging to different capsular polysaccharide (CP) type, accessory gene regulator (agr) group, pulsotype (PT) and sequence type/clonal complex (ST/CC) were selected. Strains 806 and 5011 were associated with low (nonpersistent-NP) and high (persistent-P) adaptation to the MG, respectively. Strain 806 (NP) was characterized as agr group II, cap5 positive and ST350; strain 5011 (P) agr group I, cap8 positive and CC188. Three groups of clinically healthy cows, 4 cows/treatment group, were inoculated by the intramammary route with strain 806 (NP), strain 5011 (P) and pyrogen-free saline solution. All mammary quarters challenged with strain 806 (NP) developed mild clinical mastitis between 1 and 7 d post inoculation (pi). Quarters challenged with strain 5011 (P) developed a persistent IMI; bacteria were recovered from milk from d 7 pi and up to d 56 pi. In quarters inoculated with strain 806 (NP) the inflammatory response induced was greater and earlier than the one induced by strain 5011 (P), since a somatic cell count (SCC) peak was observed at d 2 pi, while in quarters inoculated with strain 5011 (P) no variations in SCC were observed until d 4 pi reaching the maximum values at d 14 pi; indicating a lower and delayed initial inflammatory response. The highest levels of nitric oxide (NO) and lactoferrin (Lf) detected in milk from quarters inoculated with both S. aureus strains coincided with the highest SCC at the same time periods, indicating an association with the magnitude of inflammation. The high levels of IL-1β induced by strain 806 (NP) were associated with the highest SCC detected (d 2 pi); while quarters inoculated with strain 5011 (P) showed similar IL-1β levels to those found in control quarters. In quarters inoculated with strain 806 (NP) two peaks of IL-6 levels on d 2 and 14 pi were observed; while in quarters inoculated with strain 5011 (P) IL-6 levels were similar to those found in control quarters. The strain 806 (NP) induced a higher total IgG and IgG₁ response; while strain 5011 (P) generated a higher IgG₂ response (even against the heterologous strain). The present study demonstrated that S. aureus strains with different genotype and adaptability to bovine MG influence the local host immune response and the course and severity of the infectious process.

PINK1/parkin-mediated mitophagy alleviates Staphylococcus aureus-induced NLRP3 inflammasome and NF-κB pathway activation in bovine mammary epithelial cells

Staphylococcus aureus (S. aureus) is known to induce chronic and persistent bovine mammary infection, which affects milk quality and leads to premature culling. The ability of S. aureus to invade mammalian cells protects it from clearance by the immune system. Mitophagy is important in cell homeostasis, and can be utilized by pathogens for immune escape. However, mitophagy's role in S. aureus-associated bovine mastitis remains unclear. Here, S. aureus infection induced mitophagy and enhanced mitochondrial translocation of parkin in MAC-T cells. After mitophagy inhibition by Mdivi-1 treatment or PTEN-induced putative kinase 1 (PINK1) silencing in MAC-T cells infected with S. aureus, NOD-like receptor protein 3 (NLRP3) inflammasome activation and p65 and IκBα phosphorylation were increased. Meanwhile, PINK1 overexpression had the opposite effects. In addition, NLRP3 inflammasome overactivation and enhanced p65 and IκBα phosphorylation caused by PINK1 silencing were reversed by MitoTEMPO. Furthermore, PINK1/parkin-mediated mitophagy promoted S. aureus survival and contributed to persistent S. aureus infection. These findings provide new insights into S. aureus invasion in bovine mastitis.

Directed Expression of Tracheal Antimicrobial Peptide as a Treatment for Bovine-Associated Staphylococcus Aureus-Induced Mastitis in Mice

Bovine mastitis is perplexing the dairy industry since the initiation of intensive dairy farming, which has caused a reduction in the productivity of cows and an escalation in costs. The use of antibiotics causes a series of problems, especially the formation of bacterial antimicrobial resistance. However, there are limited antibiotic-free therapeutic strategies that can effectively relieve bacterial infection of bovine mammary glands. Hence, in this study, we constructed a mammary gland tissue-specific expression vector carrying the antimicrobial peptide of bovine-derived tracheal antimicrobial peptide (TAP) and evaluated it in both primary bovine mammary epithelial cells (pBMECs) and mice. The results showed that the vector driven by the β-lactoglobulin gene (BLG) promoter could efficiently direct the expression of TAP in pBMECs and the mammary gland tissue of mice. In addition, significant antibacterial effects were observed in both in vitro and in vivo experiments when introducing this vector to bovine-associated Staphylococcus aureus-treated pBMECs and mice, respectively. This study demonstrated that the mammary gland tissue-specific expression vector could be used to introduce antimicrobial peptide both in in vitro and in vivo and will provide a new therapeutic strategy in the treatment of bovine mastitis.

Relative virulence of Staphylococcus aureus bovine mastitis strains representing the main Canadian spa types and clonal complexes as determined using in vitro and in vivo mastitis models

Staphylococcus aureus is one of the main pathogens leading to both clinical and subclinical bovine mastitis in dairy cattle. Prediction of disease evolution based on the characteristics of Staph. aureus isolates that cause intramammary infections and understanding the host-pathogen interactions may improve management of mastitis in dairy herds. For this study, several strains were selected from each of the 6 major Canadian spa types associated with mastitis (t267, t359, t529, t605, t2445, and t13401). Adherence to host cells and intracellular persistence of these strains were studied using a bovine mammary gland epithelial cell line (MAC-T). Additionally, relative virulence and host response (cytokines production) were also studied in vivo using a mouse model of mastitis. Whole-genome sequencing was performed on all strains and associations between clonal complex, sequence type, and presence of certain virulence factors were also investigated. Results show that spa type t2445 was correlated with persistence in MAC-T cells. Strains from spa t359 and t529 showed better ability to colonize mouse mammary glands. The exception was strain sa3154 (spa t529), which showed less colonization of glands compared with other t359 and t529 strains but possessed the highest number of superantigen genes including tst. All strains possessed hemolysins, but spa types t529 and t2445 showed the largest diameter of β-hemolysis on blood agar plates. Although several spa types possessed 2 or 3 serine-aspartate rich proteins (Sdr) believed to be involved in many pathogenic processes, most t529 strains expressed only an allelic variant of sdrE. The spa types t605 (positive for the biofilm associated protein gene; bap+) and t13401 (bap-), that produced the largest amounts of biofilm in vitro, were the least virulent in vivo. Finally, strains from spa type t529 (ST151) elicited a cytokine expression profile (TNF-α, IL-1β and IL-12) that suggests a potential for severe inflammation. This study suggests that determination of the spa type may help predict the severity of the disease and the ability of the immune system to eliminate intramammary infections caused by Staph. aureus.

Infective mastitis due to bovine-associated Streptococcus dysgalactiae contributes to clinical persistent presentation in a murine mastitis model

Background

Mastitis caused by Streptococcus dysgalactiae (GCS) is a major pathology of dairy cows. The mechanisms by which GCS intramammary infection is established and maintained involve not only bacterial adherence and invasion but also modulation of the cytokines and TLR immune response.

Objectives

The study aimed to evaluate characteristics of persistent infection of GCS collected from bovine mastitis milk in a murine mastitis model whose mammary structure is similar to that of dairy cows; dairy cow mastitis can be well simulated by using mice as models. HLJ2019 was tested for its ability to persistently infected mice by intramammary inoculation.

Methods

As antibiotics tested, establish an intramammary infection model in murine, histopathology analyses, relative expression of inflammatory cytokines mRNA and adherence and invasion in mMECs.

Results

It induced a robust inflammatory reaction in the mammary gland, characterized by histopathological changes, increased myeloperoxidase activity and induced expression of inflammatory cytokines (TNF‐α, IL‐6, IFN‐γ, IL‐10, IL‐1α and IL‐1β) and TLR2/4, the exhibited strong LDH release, adhesion and invasive abilities in contact with mMECs.

Conclusion

These results contribute to increase the available information on host‐pathogen interaction and point out the need for further research to expand the knowledge about these interactions for developing new strategies to intervene in the intramammary persistent infection progress.

Characterization of Streptococcus lutetiensis isolated from clinical mastitis of dairy cows

Streptococcus lutetiensis, previously termed Streptococcus bovis type II/1, has rarely been associated with bovine mastitis. The objectives of this work were to characterize the molecular diversity, antimicrobial resistance profiles, virulence genes of Strep. lutetiensis (n = 37) isolated from bovine clinical mastitis, as well as its pathogenic effects in a murine mastitis model. Genetic relationships of isolates were determined by random amplified polymorphic DNA (RAPD)-PCR, virulence genes were detected by PCR. Antimicrobial susceptibility testing was carried out by broth microdilution technique. The pathogenic effects of Strep. lutetiensis were studied with 2 infection models: bovine mammary epithelial cells cultured in vitro and murine mammary infection in vivo. Streptococcus lutetiensis isolates were clustered into 5 RAPD-types (A-E), with a dominant type A representing 84% of isolates. Eighteen (49%), 16 (43%), and 9 (24%) isolates were resistant to ceftiofur, tetracycline, and erythromycin, respectively. Prevalence of multidrug resistance (resistant to ≥3 classes of antimicrobials) was 24% (9/37). The most prevalent virulence genes were bca (100%), speG (100%), hly (97%), scpB (95%), and ssa (95%). There was no difference between isolates from mild and moderate cases of bovine mastitis in prevalence of virulence genes. Streptococcus lutetiensis rapidly adhered to and subsequently invaded (1 and 3 h after infection, respectively) bovine mammary epithelial cells, resulting in elevated lactate dehydrogenase release (4 h after infection). Edema and hyperemia were observed in challenged mammary glands and bacteria were consistently isolated at 12, 24, and 48 h after infection. In addition, numerous neutrophils migrated into gland alveoli and interstitium of infected mammary tissue. We concluded that Strep. lutetiensis had potential to spread within a dairy herd and good adaptive ability in bovine mammary cells or tissue, which are generally characteristics of a contagious mastitis pathogen.

Bacteriophage Protects Against Aerococcus viridans Infection in a Murine Mastitis Model

Bovine mastitis, an inflammatory disease that occurs frequently in early lactation or the dry period, is primarily caused by bacterial infections. There is growing evidence that Aerococcus viridans (A. viridans) is becoming an important cause of bovine mastitis. The treatment of bovine mastitis is primarily based on antibiotics, which not only leads to a large economic burden but also the development of antibiotic resistance. On the other hand, bacteriophages present a promising alternative treatment strategy. The object of this study was to evaluate the potential of a previously isolated A. viridans phage vB_AviM_AVP (AVP) as an anti-mastitis agent in an experimental A. viridans-induced murine mastitis model. A. viridans N14 was isolated from the milk of clinical bovine mastitis and used to establish a mastitis model in mice. We demonstrated that administration of phage AVP significantly reduced colony formation by A. viridans and alleviated damage to breast tissue. In addition, reduced inflammation was indicated by decreased levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) and myeloperoxidase (MPO) activity in the phage-treated group compared to those in the phosphate buffered saline (PBS)-treated group. To the best of our knowledge, this report is the first to show the potential use of phages as a treatment for A. viridans-induced mastitis.

Organic Selenium Ameliorates Staphylococcus aureus-Induced Mastitis in Rats by Inhibiting the Activation of NF-κB and MAPK Signaling Pathways

Mastitis is an economically important disease in dairy cows, which is often caused by Staphylococcus aureus (S. aureus). Selenium is an indispensable element for physiological function and contributes to reduce injury of the mammary glands in mastitis. However, adequate sources of selenium have always been an important consideration for livestock. Therefore, the study aimed to explore the protective effect and mechanism of Selenohomolanthionine (SeHLan) on mastitis induced by S. aureus. The S. aureus-induced rat model was established and three doses (0.2, 2, 20 μg/kg body weight/day) of dietary OS were supplemented. The bacterial load, histopathology, and myeloperoxidase (MPO) of the mammary glands were performed and determined. Cytokines, including interleukin (IL)-1β, TNF-α, and IL-6, were detected using qRT-PCR. The key proteins of NF-κB and MAPK signaling pathways were analyzed by Western blot. The results revealed that OS supplementation could reduce the recruitment of neutrophils and macrophages in mammary tissues, but did not decrease S. aureus load in the tissues. The overexpression levels of IL-1β, TNF-α, and IL-6 induced by S. aureus were inhibited after OS treatment. Furthermore, the increased phosphorylation of NF-κB and MAPKs proteins were also suppressed. The results suggest that dietary supplementation with adequate OS during pregnancy contributes to protect the mammary glands from injury caused by S. aureus and alleviate the inflammatory response.

Staphylococcus aureus persistence properties associated with bovine mastitis and alternative therapeutic modalities

Staphylococcus aureus is an important agent of contagious bovine intramammary infections in dairy cattle. Its ability to persist inside the udder is based on the presence of important mechanisms such as its ability to form biofilms, polysaccharide capsules small colony variants, and their ability to invade professional and nonprofessional cells, which will protect S. aureus from the innate and adaptive immune response of the cow, and from antibiotics that are no longer considered to be sufficient against S. aureus bovine mastitis. In this review, we present the recent research outlining S. aureus persistence properties inside the mammary gland, including its regulation mechanisms, and we highlight alternative therapeutic strategies that were tested against S. aureus isolated from bovine mastitis such as the use of probiotic bacteria, bacteriocins and bacteriophages. Overall, the persistence of S. aureus inside the mammary gland remains a pressing veterinary problem. A thorough understanding of staphylococcal persistence mechanisms will elucidate novel ways that can help in the identification of novel treatments.

Receptor and signaling pathway involved in bovine lymphocyte activation by Atractylodis macrocephalae polysaccharides

The present study was to investigate the molecular mechanism underlying lymphocyte activation by total polysaccharides from Atractylodis macrocephalae (RAMPtp). The results showed that RAMPtp significantly promoted the secretions of cytokines (IFN-γ, IL-1α, IL-21, IFN-α, CCL4, CXCL9 and CXCL10), increased the proportions of CD4⁺ and CD8⁺ subpopulations, and enhanced the expressions of c-JUN, NFAT4, STAT1 and STAT3. microRNA sequencing identified 67 differentially expressed miRNAs (DEMs) in RAMPtp-stimulated SMLN lymphocytes, including 55 up-regulated and 12 down-regulated. GO and KEGG enrichment analyses of the predicted DEMs-targeted genes indicated that they were associated with immune system pathways, including PI3K-Akt, MAPKs, Jak-STAT and Calcium signaling pathways, which were confirmed by western blot and pathway inhibition assays. RAMPtp was further observed to favor immunostimulatory effect on both T and B lymphocytes via binding to TCR and membrane Ig individually. These findings might explain the immunomodulatory mechanism of RAMPtp in ameliorating the bovine intramammary infection.

Mammary Defences and Immunity against Mastitis in Sheep

The objectives of this review paper are to present udder defences, including teat of the udder, mammary epithelial cells, leucocytes, immunoglobulins, complement system and chemical antibacterial agents, to describe cooperation and interactions between them and to elaborate on potentials regarding their significance in mammary immunisation strategies. The teat of the udder provides initial protection to the mammary gland. The mammary epithelial cells synthesise antibacterial proteins and the leucocytes produce various inflammation mediators (cytokines or chemokines), phagocytose bacteria and recognise antigenic structures. In the mammary gland, four immunoglobulins (IgG1, IgG2, IgM and IgA) have important roles against bacterial pathogens. The complement system is a collection of proteins, participating in the inflammatory process through various pathways. Other components contributing to humoral mammary defence include lactoferrin, lysozyme and the lactoperoxidase/myeloperoxidase systems, as well as oligosaccharides, gangliosides, reactive oxygen species, acute phase proteins (e.g., haptoglobin and serum amyloid A), ribonucleases and a wide range of antimicrobial peptides. Management practices, genetic variations and nutrition can influence mammary defences and should be taken into account in the formulation of prevention strategies against ovine mastitis.

Antibacterial and antibiotic modifying activity evaluation of ruminants' body fat used as zootherapeutics in ethnoveterinary practices in Northeast Brazil

ETHNOPHARMACOLOGICAL RELEVANCE

Northeast Brazilian ethnoveterinary studies associated with the medicinal use of zootherapies have shown that ruminants' body fat such as sheep (Ovis aries), goats (Capra hircus) and cows (Bos taurus) are used in diseases affecting domestic animals.

AIM OF THE STUDY

The objective of this study was to evaluate the antibacterial activity of the fixed oils from these ruminants in isolation and in association with antibiotics.

RESULTS

Ovis aries (OFOA), Capra hircus (OFCH) and Bos taurus (OFBT) fixed oils were extracted using a Soxhlet apparatus with hexane as the solvent. Through the use of gas chromatography coupled to mass spectrometry (GC-MS) the methyl esters from the ruminants' fixed oils were obtained and the fatty acids present in these oils were indirectly determined. The OFOA, OFCH and OFBT antibacterial and antibiotic modifying activities against standard and multi-resistant bacterial strains were carried out using the broth microdilution test. The fixed oils from these species did not present antibacterial activity when tested in isolation, obtaining Minimal Inhibitory Concentration (MICs) values ≥ 1024 μg/mL. However, when associated with antibiotics, OFBT and OFCH showed a synergistic activity for the Amicacin, Amoxicillin, Norfloxacin and Oxytetracycline antibiotics.

CONCLUSION

The OFOA promoted a synergistic action for the same antibiotics with the exception of Norfloxacin.

Molecular epidemiology of methicillin-susceptible Staphylococcus aureus (MSSA) isolated from milk of cows with subclinical mastitis

Bovine mastitis has been a concern for dairy herd for decades. The adaptation capacity of one of the main species responsible for this disease, Staphylococcus aureus (S. aureus), plays a pivotal role in this issue. The aim of this study was to establish a molecular and phenotypic profile of 285 S. aureus strains isolated from milk of subclinical mastitis cows from 18 different farms in São Paulo State using spa typing, multilocus sequence typing (MLST), pulsed field gel electrophoresis (PFGE), agr cluster (I, II, III and IV) typing, PCR for genes including enterotoxins (sea, seb, sec, sed, see, seg, seh, sei), toxic shock syndrome toxin (tsst-1), and Panton-Valentine leucocidin (pvl), as well as in vitro resistance assays for 12 antibiotics. The results showed a wide variety of strains with a high toxigenic potential; concomitantly, sec, seg and seh were prevalent. In addition, we observed a predominance of the spa types t605 (ST 126, CC126) and t127 (ST1, CC1) and the unusual presence of t321 causing bovine mastitis, which has been previously reported only in swine. The most frequent ST were ST126 (70.5%) and ST1 (10.5%). Regarding PFGE, we observed four major groups and six profile patterns. The highest resistance was observed for streptomycin (9.5%), followed by tetracycline (3.5%), clindamycin (9.3%), and erythromycin (2.8%). The tsst-1 gene was detected in 36.8% of isolates and pvl was not observed. One hundred and thirty-six (47.7%) isolates possessed agr type II, followed by types III (20%) and I (8.1%), with type IV not being detected. We observed that the same spa type could result in different PFGE profiles, so the exclusive use of spa type sequences can lead to incorrect interpretations regarding the spread of clones in an epidemiological context.