Search Results (105)

Bovine mastitis, particularly that caused by Staphylococcus aureus, presents a major challenge to dairy production worldwide due to its economic impact, animal welfare concerns, and zoonotic potential. This narrative review synthesizes current literature on the epidemiology, pathogenesis, resistance patterns, and control strategies related to S. aureus-associated mastitis in dairy cattle. It highlights the pathogen’s virulence mechanisms, such as biofilm formation, immune evasion, and toxin production, that facilitate persistent infections. The review compiles global prevalence data, revealing significant geographic variation and disparities between clinical and subclinical cases. Antimicrobial resistance, especially the emergence of methicillin-resistant S. aureus (MRSA), is extensively examined alongside resistance gene profiles. Diagnostic approaches, including culture, PCR, MALDI-TOF MS, and AI-based systems, are evaluated for their sensitivity and field applicability. Additionally, the review addresses public health implications, zoonotic risks, and One Health perspectives, culminating in an exploration of prevention strategies, including improved hygiene, vaccination, dry cow therapy, and AI-driven herd management. The findings emphasize the urgent need for integrated surveillance, precision diagnostics, and targeted interventions to mitigate the burden of S. aureus mastitis. Full article

Water buffalo (Bubalus bubalis) are a primary source of milk in Pakistan, where bovine mastitis is a significant health issue among cattle, leading to substantial economic losses. Staphylococcus aureus is a predominant pathogen associated with mastitis; however, a detailed molecular characterization of the strains in the country remains limited. We previously characterized mastitis strains from the Hazara division of Khyber Pakhtunkhwa, Pakistan. In this study, we investigated mastitis cases in the Peshawar division, including samples from both animals and human farm workers for comparison. Higher rates of mastitis (67.27% of animals) and sub-clinical mastitis (91.03% of positive animals) were identified in Peshawar than for those (34.55% and 75.31%, respectively) previously observed in Hazara. Methicillin-susceptible S. aureus (MSSA) belonging to clonal complex 9 (ST2454) were predominant. Methicillin-resistant S. aureus (MRSA) belonging to ST22 and ST8 were also detected in the Nowshera district. While no S. aureus colonization was observed among animal handlers, evidence of hand contamination suggests a potential route for pathogen spread. Low levels of antibiotic resistance were noted amongst isolates, but higher rates were seen in MRSA. This study presents only the second comprehensive molecular investigation of S. aureus isolated from buffalo mastitis in Pakistan and indicates a concerning rise in mastitis within the province. Full article

Subclinical mastitis causes economic losses due to reduced milk yield and elevated somatic cell counts (SCCs), despite no visible clinical signs. A higher incidence of subclinical mastitis has been reported in cattle infected with bovine leukemia virus (BLV). Levamisole (LMS), known for its immunomodulatory properties, has been suggested as a potential alternative to antibiotics for mastitis treatment; however, its efficacy in BLV-infected cows, particularly in relation to proviral load (PVL), remains unclear. This study aimed to evaluate the therapeutic effect of LMS on subclinical mastitis and its impact on milk immune responses by classifying BLV-infected cows based on PVL. A total of 42 dairy cows with subclinical mastitis (48 quarters) were grouped as BLV-negative, low-PVL, or high-PVL using a PVL cut-off value of 17.8 copies/10 ng DNA, and were administered LMS orally. Changes in viable bacterial counts, SCCs, and milk leukocyte populations were compared. LMS administration significantly reduced the SCC and milk macrophage numbers, especially in BLV-negative and low-PVL cows. These results suggest that LMS may improve subclinical mastitis in certain BLV-infected cows and that PVL may serve as a useful indicator for treatment responsiveness. However, the limited effect in high-PVL cows and the small sample size have limitations, warranting further investigation. Full article

Lactococcus lactis (L. lactis) is a pathogenic Gram-positive, catalase-negative coccobacillus (GPCN) associated with bovine mastitis. In this study, nine strains of L. lactis were successfully isolated and characterized from 457 milk samples from cows with clinical mastitis in China. All isolates exhibited a high degree of susceptibility to marbofloxacin and vancomycin. A series of molecular and cell biological techniques were used to explore the biological characteristics and pathogenicity of these isolates. The virulence gene profiles of the isolates were analyzed using whole genome resequencing combined with polymerase chain reaction (PCR) to elucidate the differences in virulence gene expression between isolates. To provide a more visual demonstration of the pathogenic effect of L. lactis on bovine mammary epithelial cells, an in vitro infection model was established using MAC-T cells. The results showed that L. lactis rapidly adhered to the surface of bovine mammary epithelial cells and significantly induced the release of lactate dehydrogenase, suggesting that the cell membranes might be damaged. Ultrastructural observations showed that L. lactis not only adhered to MAC-T cells, but also invaded the cells through a perforation mechanism, leading to a cascade of organelle damage, including mitochondrial swelling and ribosome detachment from the endoplasmic reticulum. The objective of this study was to provide strong evidence for the cytotoxic effects of L. lactis on bovine mammary epithelial cells. Based on this research, a prevention and treatment strategy for L. lactis as well as major pathogenic mastitis bacteria should be established, and there is a need for continuous monitoring. Full article

Background/Objectives: This review aimed to compare the efficacy of antibiotic treatment vs. non-antibiotic treatment in mild and moderate clinical mastitis in lactating dairy cows, categorized by the causative pathogen. Methods: The initial systematic review plan, which resulted in only four relevant articles, was altered due to limited available studies and significant heterogeneity among them. Consequently, five additional articles, closely meeting our criteria with minor differences, were included to ensure comprehensive analysis, resulting in nine included articles. Due to these pragmatic constraints, this review represents a hybrid between a systematic and a narrative review. The outcome of interest was the bacteriological cure (BC). Results: The findings revealed that antibiotic treatment resulted in improved BC rates for cases caused by Streptococci. For cases caused by Escherichia (E.) coli, antibiotic therapy showed no significant improvement in BC rates compared to non-antibiotic treatment, suggesting that antibiotics may be often unnecessary for these cases due to self-limiting tendencies. However, severe E. coli mastitis warrants systemic antibiotic treatment due to potentially life-threatening complications. Klebsiella spp. mastitis showed better cure rates with antibiotic therapy. Conclusions: This study underscores the importance of regular pathogen diagnostics to guide appropriate treatment, advocating for the use of on-farm rapid tests to reduce unnecessary antibiotic use while ensuring effective treatment outcomes. Full article

The 2024 outbreak of highly pathogenic avian influenza virus (HPAIV) H5N1 in U.S. dairy cattle presented an unprecedented scenario where the virus infected bovine mammary glands and was detected in milk, raising serious concerns for public health and the dairy industry. Unlike previously described subclinical influenza A virus (IAV) infections in cattle, H5N1 infection induced severe clinical symptoms, including respiratory distress, mastitis, and abnormal milk production. To understand the host immune responses and changes, particularly in the mammary gland, we performed single-cell RNA sequencing analysis on bovine milk somatic cells (bMSCs) in vitro exposed to an H5N1 isolate from an infected dairy farm. We identified ten distinct cell clusters and observed a shift toward type-2 immune responses, characterized by T cells expressing IL13 and GATA3, and three different subtypes of epithelial cells based on the expression of genes associated with milk production. Our study revealed temporal dynamics in cytokine expression, with a rapid decline in luminal epithelial cells and an increase in macrophages and dendritic cells, suggesting a role in increased antigen presentation. While viral RNA was detected in bulk-exposed bMSC samples via qRT-PCR, no viral reads were observed in the scRNA-seq data, indicating that the immune responses captured may be due to exposure to viral components rather than productive infection. This research fills a critical gap in understanding the immune responses of bovine mammary glands to H5N1 exposure and highlights the need for further investigation into therapeutic strategies for managing such outbreaks. Full article

Mesenchymal stem cells (MSCs) hold significant therapeutic potential in veterinary medicine due to their regenerative and immunomodulatory properties. This review examines the clinical applications of MSCs across multiple animal species, including equine, canine, feline, and bovine medicine. MSC therapies have demonstrated promising outcomes in treating musculoskeletal disorders, osteoarthritis, inflammatory diseases, and tissue injuries, particularly in horses and dogs. In cats, MSCs show potential for managing chronic kidney disease, inflammatory bowel disease, and asthma, while in bovine medicine, they offer alternative treatment approaches for mastitis and orthopedic injuries. Despite these advancements, challenges such as treatment standardization, cell sourcing, and potential adverse effects, including tumorigenicity, remain under investigation. The emerging field of MSC-based veterinary medicine highlights its capacity to enhance healing, reduce inflammation, and improve clinical outcomes. However, further research is necessary to optimize treatment protocols and address safety concerns, ensuring the widespread adoption of MSC therapies in veterinary practice. Full article

Mastitis is a major infectious disease that causes significant economic losses in the dairy industry. Current control programs primarily rely on antimicrobials, contributing to the growing concerns of the resistance situation and drug residues in milk. This study aimed to identify the bacterial pathogens responsible for subclinical/clinical bovine mastitis, assess their antimicrobial resistance profiles, and evaluate the antimicrobial effects of Caesalpinia sappan in treating mastitis through both in vitro and in vivo studies. A total of 138 bacterial isolates, representing 40 species, were identified from 100 milk samples collected from dairy cows under the Maejo Cooperative Group in Chiang Mai, Thailand, between May 2021 and February 2022. The most prevalent species was Escherichia coli (10.87%), followed by Bacillus cereus (9.42%) and Staphylococcus sciuri (7.97%). The highest resistance rates were observed for penicillin (65.21%), followed by streptomycin and lincomycin (61.59%). Nine isolates resisted all 18 antimicrobials tested. The average minimum inhibitory concentration (MIC) of C. sappan against the identified pathogens ranged from 0.63 to 17.68 mg/mL, with the highest MIC observed against Pseudomonas luteola. In the animal experiment, treatment with a prototype of an intramammary infusion compound primarily formulated from C. sappan significantly reduced the total bacterial count and California Mastitis Test (CMT) scores (p < 0.01). These results suggest that C. sappan exhibits antimicrobial efficacy against various mastitis bacteria and could serve as a potential alternative treatment to control bovine mastitis in dairy cattle within the study region. Full article

Mastitis, an inflammatory condition of the udder, can be caused by the entry of Staphylococcus aureus, whose adhesion to the mammary epithelial cells is influenced by virulence factors such as microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) and the accessory gene regulator (agr) system. Our goal was to determine the adhesion and invasion rates of S. aureus isolates from clinical (mild and moderate) and subclinical mastitis and to assess the impact of MSCRAMM genes and agr types on disease severity. Clinical isolates predominantly carried agrII (p < 0.0083) and multiple MSCRAMM genes, correlating with high adhesion capacity but reduced invasion capacity regardless of clinical severity. Remarkably, subclinical isolates, mainly agr-negative (85.7%), showed increased cellular invasion (p < 0.0001), possibly due to reduced expression of agr-mediated virulence factors. These findings contribute to the understanding of the pathogen–host dynamics in bovine mastitis and highlight the importance of both MSCRAMMs and the agr system in modulating disease severity. These insights can inform targeted interventions for mastitis prevention and treatment. Full article

Staphylococcus aureus-induced mastitis is a significant cause of economic losses in the dairy industry, yet its molecular mechanisms remain poorly defined. Although ferroptosis, a regulated cell death process, is associated with inflammatory diseases, its role in bovine mastitis is unknown. In this study, 11 S. aureus strains were isolated from milk samples obtained from cows with clinical or subclinical mastitis. Transcriptome analysis of Mac-T cells challenged with isolated S. aureus identified differentially expressed genes (DEGs). Enrichment analysis revealed significant associations between DEG clusters and traits related to bovine mastitis. KEGG pathway enrichment revealed ferroptosis, Toll-like receptor, and TNF signaling as significantly enriched pathways. Weighted gene co-expression network analysis (WGCNA) further prioritized ferroptosis-related genes (HMOX1, SLC11A2, STEAP3, SAT1, and VDAC2) involved in iron metabolism. Notably, the expression levels of HMOX1 and SAT1 were significantly increased in S. aureus-challenged Mac-T cells, and this upregulation was consistent with trends observed in transcriptome data from mother–daughter pairs of cows with subclinical mastitis caused by S. aureus infection. Furthermore, Ferrostatin-1 treatment significantly reduced the expression of HMOX1 and SAT1 in S. aureus-challenged cells, confirming the involvement of ferroptosis in this process. This study reveals that ferroptosis plays a key role in S. aureus-induced mastitis and highlights its potential as a target for molecular breeding strategies aimed at improving bovine mastitis resistance. Full article

Staphylococcus aureus is a versatile zoonotic pathogen capable of causing a wide range of infections. Due to the organism’s ability to persist, recalcitrant and recurring infections are a major concern for public and animal health. This study investigated the establishment of persistence using two S. aureus strains—ATCC 29740, a bovine mastitis isolate, and USA300, a human clinical isolate—under substrate depletion. This nutritional stress established a persistence phenotype where the strains remained persistent for >120 days at notable concentrations [>2 log10 CFU/mL] and developed persister-like growth, including small colony variant formations. With RT-qPCR, we found the cell density was higher than represented by the plate count while the intracellular ATP remained constant during the persistence phase. These findings indicate that S. aureus has complex survival strategies to support its persistent state, providing a host-specific perspective when addressing recurrent infections in human and animal infectious diseases. Full article

(1) Background: Bovine mastitis is a lactational disease caused by infection and milk stagnation in the mammary glands. Danggui buxue decoction (DBD), a traditional remedy for blood tonification, anti-inflammation, and antioxidation, has not been used previously to treat mastitis. (2) Methods: In this study, an Escherichia coli mastitis model was established by infecting lactating Kunming mice with clinically isolated bovine mastitis-derived E. coli. Based on this, the effects of DBD on inflammation and oxidative stress in mastitis model mice were evaluated by conducting routine blood tests, H&E staining, qRT-PCR analysis, ELISA, and microcolorimetry. (3) Results: We found that DBD treatment reduced body weight loss, abnormal organ indices, abnormal blood cell counts, pathological damage to breast tissue, and the upregulation of the expression of inflammatory factor in mice caused by E. coli infection. We also found that DBD increased the expression of antioxidants and antioxidant genes and decreased the expression of oxidation products and oxidation-related genes in breast tissue. The therapeutic effect of DBD on inflammation and oxidative stress (OS) in mice occurred through the regulation of the TLR4/NF-κB and Nrf2/HO-1 signaling pathways. (4) Conclusions: DBD imparted its anti-inflammatory and antioxidant effects by inhibiting the TLR4/NF-κB signaling pathway and activating the antioxidant Nrf2/HO-1 signaling pathway Full article

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. Full article

Background/Objectives: Pasteurella multocida commonly colonizes the bovine respiratory tract and can occasionally cause intramammary infections. Here, eight P. multocida isolates from clinical cases of bovine mastitis were investigated for their molecular characteristics as well as phenotypic and genotypic antimicrobial resistance (AMR) properties. Methods: The isolates originated from quarter milk samples obtained in Germany for diagnostic purposes. Antimicrobial susceptibility testing (AST) by broth microdilution was performed according to the Clinical and Laboratory Standards Institute. Closed whole-genome sequences were generated by hybrid assembly of Illumina MiSeq short-reads and Oxford Nanopore MinION long-reads, followed by consecutive sequence analysis. Results: The P. multocida isolates belonged either to capsular:lipopolysaccharide type A:3 (n = 7) or A:6 (n = 1), and multi-locus sequence types 1 (n = 7) or 7 (n = 1). Seven isolates carried AMR genes, such as mef(C), mph(G), strA, strB, aphA1, aadA31, tet(H), tet(Y), floR, catA3, and sul2, as part of an integrative and conjugative element (ICE). These mobile genetic elements, 58,382–78,401 bp in size, were highly similar to the ICEs Tn7406 or Tn7407 that have been previously described in bovine Mannheimia haemolytica and P. multocida, respectively. Moreover, the isolates showed elevated minimal inhibitory concentrations corresponding to the identified AMR determinants. Conclusions: Molecular typing and ICE organization suggest the bovine respiratory tract as reservoir of the investigated mastitis-associated P. multocida. Horizontal cross-genus transfer of multidrug-resistance-mediating ICEs seems to occur under in vivo conditions among different pathogens from cattle in Germany, which underlines the importance of pathogen identification followed by AST for successful bovine mastitis therapy. Full article

Background/Objectives: Bovine mastitis (BM), a prevalent and economically burdensome bacterial infection affecting dairy cattle, poses a significant challenge to the dairy industry. The traditional approach to combating BM, relying heavily on antibiotics, faces growing concerns due to the increasing antibiotic resistance exhibited by pathogens. The objective of this study was to evaluate and determine the antimicrobial and anti-biofilm potential of chitosan nanoparticles (NQo) on S. aureus strains isolated from milk samples obtained from dairy areas in southern Chile from cows diagnosed with BM. Methods: NQo were synthesized using the ionotropic gelation method and thoroughly characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Results: The NQo exhibit a robust positive charge (Z-potential of +55.4 ± 2.5 mV) and an exceptionally small size (20.3 ± 3.2 nm). This unique combination of properties makes NQo particularly well-suited for targeting and interacting with bacterial pathogens. To assess the effectiveness of NQo against BM, we conducted a series of experiments using a Staphylococcus aureus strain isolated from milk samples of cows diagnosed with BM in southern Chile. NQo demonstrated a remarkable ability to inhibit bacterial proliferation and effectively modulate biofilm formation in the S. aureus strains. Furthermore, the performance of NQo in comparison to established antibiotics like ampicillin and gentamicin strongly suggests that these nanoparticles hold immense potential as an attractive alternative for the control, prevention, and/or treatment of BM. Conclusions: NQo exhibit both antimicrobial and antibiofilm activity against a clinically relevant BM pathogen. Further investigations are necessary to develop a hydrogel formulation optimized for effective delivery to the target diseased tissue. Full article