Search Results (19)

Staphylococcus aureus is a mastitis pathogen that compromises cow health and causes significant economic losses in the dairy industry. High antimicrobial resistance and biofilm formation by S. aureus limit the efficacy of conventional treatments. This study evaluated the potential of polyhexamethylene biguanide nanoparticles (PHMB NPs) against mastitis-causing S. aureus. PHMB NPs showed low toxicity to bovine mammary epithelial cells (MAC-T cells) at concentrations up to four times higher than the minimum inhibitory concentration (1 µg/mL) against S. aureus. In Experiment 1, PHMB NPs significantly reduced biofilm formation by S. aureus by 50% at concentrations ≥1 µg/mL, though they showed limited efficacy against preformed biofilms. In Experiment 2, using an excised teat model, PHMB NPs reduced S. aureus concentrations by 37.57% compared to conventional disinfectants (chlorhexidine gluconate, povidone–iodine, and sodium dichloroisocyanurate), though limited by short contact time. These findings highlight the potential of PHMB NPs for the control of S. aureus growth and biofilm formation. 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

Antimicrobial resistance poses a significant challenge in human and veterinary medicine, primarily due to the overuse and misuse of antimicrobial agents. This issue is especially problematic when treating bovine mastitis, a prevalent infection in dairy cattle often caused by Staphylococcus aureus. We developed a sterile emulsion incorporating essential oils (EOs) of Origanum vulgare and Thymus vulgaris, known for their antimicrobial properties. The formulation based on poloxamer 407 was designed for intramammary or topical application on bovine teats. The most promising emulsion was subjected to preliminary stability testing at various temperature conditions over a 35-day period, during which its physicochemical characteristics, texture profile, and film-forming capacity were assessed. In vitro assays were used to evaluate its efficacy against both antimicrobial-sensitive and -resistant S. aureus strains. Thymol was identified as the predominant bioactive compound in the EOs. The formulation, containing 10% (w/w) EOs, exhibited antimicrobial activity against all tested strains and remained stable without phase separation. The emulsion demonstrated film-forming properties along with a satisfactory texture profile. These findings suggest that the emulsion has potential as an alternative therapeutic approach for the treatment of antimicrobial-resistant S. aureus infections in bovine mastitis, highlighting the potential of natural compounds in combating AMR. Further clinical studies are necessary to confirm the safety and therapeutic efficacy of the emulsion in vivo. Full article

Optimising antimicrobial usage (AMU) in livestock is pivotal to counteract the emergence of antimicrobial resistance. We analysed AMU in more than 1000 cattle herds over 11 years (2008–2018) in the Aosta Valley (Italy), a region where 80% of farms house less than 50 cattle. Dairy cows accounted for over 95% of AMU. AMU was estimated using the defined daily dose animal for Italy (DDDAit) per biomass for the whole herd and a treatment incidence 100 (TI₁₀₀) for cows. Average annual herd-level AMU was low, with 3.6 DDDAit/biomass (range: 3.2–4.0) and 1.2 TI₁₀₀ in cows (range: 1.1–1.3). Third and fourth generation cephalosporins, which are critical for human medicine, represented almost 10% of usage, and intramammary antimicrobials accounted for over 60%. We detected significant downward temporal trends in total AMU, as well as a positive relationship with herd size. The magnitude of such effects was small, leaving scant room for further reduction. However, the frequent use of critical antimicrobials and intramammary products should be addressed, following the principles of prudent AMU. Our findings highlight the importance of monitoring AMU even in low-production, smallholding contexts where a low usage is expected, to identify any deficiencies and implement interventions for further AMU optimisation. Full article

Contagious pathogens are very costly to dairy herds, and they may have zoonotic and reverse-zoonotic potentials and may contribute to the spread of antimicrobial resistance. One of the most important risk factors for spreading these infections is milking, when liner contamination may transfer the pathogens from infected to healthy cows. There is no effective protocol to prevent the transmission of infection without the segregation of infected cows. Recently, the availability of elastomers with patented antimicrobial components in their formulations has allowed the exploration of alternative methods to reduce the risk of infection. Two different types of elastomers (rubber and silicone) and nine different formulations were challenged with three major mastitis pathogens (S. aureus, S. agalactiae, and E. coli). The results that were obtained in this study were interesting and unexpected. Indeed, to our knowledge, this is the first study to show that basic rubber materials have intrinsic antimicrobial activity. Silicone elastomers did not exhibit the same levels of bactericidal activity, although they did exhibit some antibacterial capacity. A significant decrease in bacterial survival curves was observed for all the formulations tested when antimicrobial components were added. The different results observed for the various products are likely due to the different formulations and diverse manufacturing processes. The availability of these new materials that significantly reduce the bacterial load on the liner surface may reduce the risk of spreading intramammary infections during milking. This would be an important step forward in achieving global sustainability of dairy herds, consistent with the objectives of One Health, by reducing the risks of zoonotic diseases and antimicrobial treatments. Full article

Mastitis is one of the most important diseases in dairy cattle farms, and it can affect the health status of the udder and the quantity and quality of milk yielded. The correct management of mastitis is based both on preventive and treatment action. With the increasing concern for antimicrobial resistance, it is strongly recommended to treat only the mammary quarters presenting intramammary infection. For this reason, a timely and accurate diagnosis is fundamental. The possibility to detect and characterize mastitis directly on farm would be very useful to choose the correct management protocol. Some on-field diagnostic tools are already routinely applied to detect mastitis, such as the California Mastitis Test and on-farm culture. Other instruments are emerging to perform a timely diagnosis and to characterize mastitis, such as Infra-Red Thermography, mammary ultrasound evaluation and blood gas analysis, even if their application still needs to be improved. The main purpose of this article is to present an overview of the methods currently used to control, detect, and characterize mastitis in dairy cows, in order to perform a timely diagnosis and to choose the most appropriate management protocol, with a specific focus on on-farm diagnostic tools. Full article

Recently, the use of antimicrobials on dairy farms has been significantly limited from both the legislative and consumer points of view. This study aims to check the efficacy of selective dry cow therapy (SDCT) versus blanket dry cow therapy (BDCT) on bovine udder in healthy animals. SDTC is when an antibiotic is administered only to infected cows, compared with BDCT, where all cows receive an antimicrobial, regardless of their infection status. The milk samples were collected from enrolled Holstein Friesian cows 7 days before dry-off (T0) and 10 days after calving (T1) to assess somatic cell count (SCC), intramammary infections (IMIs), and milk microbiota variation. After pre-drying sampling, cows are randomly assigned to the following treatments: internal teat sealant alone (ITS; 24 cows), which is a treatment in a cow that does not receive antibiotics in SDTC, or in combination with intramammary antibiotic treatment (A+ITS; 22 cows). Non-statistically significant results are found between the two treatment groups at T1 for SCC, milk yield, and alpha diversity in milk microbiota. A statistically (p < 0.033) T1 IMI decrease is reported in the A+ITS group, and a significant beta diversity analysis is shown between the two timepoints (p = 0.009). This study confirms the possibility of selective drying without new IMI risk or increased SCC at calving, considering healthy cows without contagious infections and SCC values >200,000 cells/mL in the previous lactation. Full article

Staphylococcus caprae is a Gram-positive, coagulase-negative staphylococci (CoNS), which appears as commensal in the skin, as well as a prevalent mastitis pathogen of goats. Occasionally, it is also associated with infections in humans. Biofilm formation has been identified as a putative virulence factor in S. caprae. Biofilms are multicellular communities protected by a self-produced extracellular matrix (ECM), which facilitates the resistance of bacterial cells to antimicrobial treatments. The ECM is constructed by exopolysaccharides, including the major exopolysaccharide—polysaccharide intercellular adhesion (PIA), regulated by the ica operon in Staphylococcus species. The aim of this study was to characterize the expression of the ica operon in relation to biofilm formation in S. caprae. Results showed that within a few hours of growth, S. caprae could adhere to polystyrene surfaces, start to accumulate, and form biofilm. Peak biofilm biomass and maturation were reached after 48 h, followed by a reduction in biomass after 72 h. Confocal laser scanning microscopy showed the expression of matrix-associated proteins and polysaccharides at various time points. The expression dynamics of the ica operon were investigated using real-time reverse transcriptase PCR (RT)-qPCR, which showed elevated expression during the early stages of biofilm formation and subsequent downregulation throughout the biofilm aging process. In conclusion, our results show that the ica operon is essential in regulating biofilm formation in S. caprae, similar to other Staphylococcus species. Furthermore, the robustness of the observed biofilm phenotype could account for the successful intramammary colonization and may explain disease persistence caused by this pathogenic bacterium. Full article

Infectious mastitis is the most prevalent health problem in dairy cattle that can result in permanent economic losses on dairy farms. The micronised purified flavonoid fraction (MPFF) is a biocompatible active polyphenolic compound derived from flavonoid glycosides which exhibits several antimicrobial, anti-inflammatory, and phlebotonic properties. The goal was to assess the effects of an alternative therapy for mastitis based on MPFF intramammary infusions in late lactation in dairy cows naturally infected by Staphylococcus spp. The California Mastitis Test (CMT scores) was performed to detect mastitis-positive quarters in twelve dairy farms. All cows were screened for immune response by measuring somatic cell counts (SCCs; cells/mL) in milk samples from each quarter. In addition, bacteriological identification, pathogenic bacterial isolates, and total bacterial counts (TBCs; CFU/mL) were assessed before (day 0, last milking day) and after (day 3 post-calving) MPFF application. Antimicrobial sensitivity patterns of the pathogenic isolated bacteria were evaluated. Finally, cure rates (%) were determined for each MPFF treatment. Around 15 mastitis-related genera were isolated. Staphylococcus aureus (25.2%) and coagulase-negative Staphylococci (CNS; 22.4%) were the most prevalent pathogens. No statistical differences were observed in SCCs and TBCs after low, medium, and high MPFF dose administration in S. aureus-positive mastitis cases (p > 0.05). However, differences were observed in SCCs and TBCs after medium and high MPFF dose administration in CNS-positive quarters (p < 0.05). The pathogenic bacteria isolate reduction after MPFF applications showed a dose-response fashion (p < 0.01) while isolates obtained from controls and low MPFF-treated quarters remained similar, irrespective of the pathogen (p > 0.05). Sensitivity patterns were variable, although S. aureus remained resistant, irrespective of the MPFF dose. However, CNS showed a dose-response sensitivity pattern. Finally, the cure rate (%) on day 3 post-partum improved significantly using medium and higher MPFF doses in CNS-positive quarters (p < 0.05). In conclusion, MPFF treatment was found to be more effective for CNS-positive cases in the late lactation due to noticeable dose-specific responses regarding somatic cells, bacterial counts, sensitivity patterns, and cure rates in dairy cattle. Full article

Antimicrobials are widely used to cure intramammary infections (IMI) in dairy cows during the dry period (DP). Nevertheless, the IMI cure is influenced by many factors and not all quarters benefit from antimicrobial dry cow treatment (DCT). To evaluate the true effect of antibiotic DCT compared to self-cure and the role of causative pathogens on the IMI cure, a retrospective cross-sectional study was performed. The analysis included 2987 quarters infected at dry-off (DO). Information on DCT, causative pathogens, somatic cell count, milk yield, amount of lactation, Body Condition Score, and season and year of DO were combined into categorical variables. A generalized linear mixed model with a random cow, farm and year effect and the binary outcome of bacteriological cure of IMI during the DP was conducted. In the final model, a significant effect (p < 0.05) on DP cure was seen for the DO season and the category of causative pathogens (categories being: Staphylococcus aureus, non-aureus staphylococci, streptococci, coliforms, ‘other Gram-negative bacteria’, ‘other Gram positive bacteria’, non-bacterial infections and mixed infections), while antibiotic DCT (vs. non-antibiotic DCT) only showed a significant effect in combination with the pathogen categories streptococci and ‘other Gram-positive bacteria’. Full article

The purpose of this study was to clarify the effects of antimicrobial treatment for mild mastitis caused by Gram-positive bacteria on the milk microbiota in dairy cattle. Sixteen quarters of sixteen cows with mild clinical mastitis from the same herd were included in the study. On the day of onset (day 0), the cows were randomly allocated to a no-treatment (NT; n = 10) group or an intramammary antimicrobial treatment (AMT) group that received AMT starting on day 0 (AMT-AMT group; n = 6). The next day (day 1), the cows in the NT group were randomly allocated into an NT group (NT-NT group; n = 3) that received no treatment or an AMT group that received AMT starting on day 1 (NT-AMT group; n = 7). Milk samples were collected on days 0, 1, 3 and 7, and the milk microbiota of each sample was comprehensively analyzed via 16S rRNA gene amplicon sequencing of the milk DNA. During the treatment period, the milk microbiota of the NT-NT group did not change, but those of the NT-AMT and AMT-AMT groups changed significantly on days three and seven. Thus, the use of antimicrobials for mild mastitis caused by Gram-positive bacteria changes the milk microbiota composition. Full article

The use of antimicrobials for the treatment of food-producing animals is increasingly scrutinized and regulated based on concerns about maintaining the efficacy of antimicrobials used to treat important human diseases. Consumers are skeptical about the use of antibiotics in dairy cows, while dairy producers and veterinarians demonstrate ambivalence about maintaining animal welfare with reduced antimicrobial usage. Antimicrobial stewardship refers to proactive actions taken to preserve the efficacy of antimicrobials and emphasizes the prevention of bacterial diseases and use of evidence-based treatment protocols. The ability to broadly implement antimicrobial stewardship in the dairy industry is based on the recognition of appropriate antimicrobial usage as well as an understanding of the benefits of participating in such programs. The most common reason for the use of antimicrobials on dairy farms is the intramammary treatment of cows affected with clinical mastitis or at dry off. Based on national sales data, intramammary treatments comprise < 1% of overall antimicrobial use for food-producing animals, but a large proportion of that usage is a third-generation cephalosporin, which is classified as a highest-priority, critically important antimicrobial. Opportunities exist to improve the use of antimicrobials in dairy practice. While there are barriers to the increased adoption of antimicrobial stewardship principles, the structured nature of dairy practice and existing emphasis on disease prevention provides an opportunity to easily integrate principles of antimicrobial stewardship into daily veterinary practice. The purpose of this paper is to define elements of antimicrobial stewardship in dairy practice and discuss the challenges and potential benefits associated with these concepts. Full article

Mastitis is one of the main contributors to antimicrobial resistance in livestock, so alternative therapies are being investigated to address it. The present study assessed the capability of recombinant bovine interleukin-8 (rbIL-8) to improve neutrophil function in the mammary gland and resolve chronic high somatic cell count (SCC) in Holstein cows. Multiparous cows (n = 8) with more than 300,000 SCC per mL were allocated to one of two intramammary infusions: saline (10 mL of saline solution) or rbIL-8 (1.57 mg/mL of recombinant bovine IL-8 diluted in 9 mL of saline). In addition, there was an untreated control group (n = 2, SCC < 300,000 SCC/mL). Milk samples were collected post-treatment at 0, 4, 8, 12, 24, 48, and 144 h to quantify milk SCC, haptoglobin, and IgG concentrations. Neutrophil’s phagocytosis in milk and blood was evaluated via flow cytometry at 0, 24, and 48 h. The log of SCC did not differ between the infused groups (p = 0.369). Neutrophils presented a similar log of cells with high fluorescence for propidium-iodide (PI) and dihydrorhodamine (DHR) in milk (p = 0.412) and blood samples (p = 0.766) in both infused groups. Intramammary infusion of 1.57 mg/mL of rbIL-8 did not improve neutrophils response and failed to resolve chronic high SCC. Full article

This study used 16S rRNA sequencing to evaluate the effects of dry cow antimicrobial therapy on the udder milk microbiota by comparing the microbial populations in milk at dry-off (DRY) (~60 days before calving) and post-partum (FRESH) (4–11 days after calving) from cows receiving an intramammary antibiotic infusion prior to dry-off (IMT) and cows that did not receive treatment (CTL). Milk was collected from 23 cows from the IMT group and 27 cows from the CTL group. IMT and DRY samples had a greater correlation with the genera Brevibacterium and Amaricoccus, and the family Micrococcaceae, when compared to IMT and FRESH samples. CTL group samples collected at DRY had a greater correlation with the genera Akkermansia and Syntrophus, when compared to FRESH samples; no bacterial taxa were observed to have a significant correlation with FRESH samples in the CTL group. DRY samples collected from the CTL group had a greater correlation with the genus Mogibacterium when compared to IMT and CTL samples. For DRY samples collected from the IMT group, a greater correlation with the genus Alkalibacterium when compared to DRY and CTL samples, was observed. The lack of a correlation for FRESH samples between the CTL and IMT treatment groups indicated that intramammary antimicrobial dry cow therapy had no significant effect on the udder milk microbiota post-partum. Full article

The objective of this study was to compare immediate intramammary antimicrobial treatment of mild and moderate cases of clinical mastitis (CM) with a selective treatment protocol based on on-farm culture results using Accumast^®. The study was conducted at a 2600 cow commercial farm in Northeast Germany. Using a randomized design, mild and moderate clinical mastitis cases were assigned to either the blanket therapy (BT) or pathogen-based therapy (SELECT) group. Overall, 468 cases were used for final analyses (BT = 236; SELECT = 232). The percentage of cases assigned to the blanket and pathogen-based groups that received intramammary therapy were 100 and 69.9%, respectively. Implementation of a pathogen-based treatment protocol for mild and moderate CM cases resulted in no significant difference in post-event milk production, somatic cell count, survival to 30 d, and days spent in the hospital compared with a blanket therapy protocol. Cows in the SELECT group had reduced odds of being culled within 60 d post CM (odds ratio = 0.54; 95% CI = 0.31–0.93; p = 0.027). The use of a pathogen-based treatment protocol using an on-farm culture system has the potential to efficiently reduce antimicrobial use without negative effects on health. Full article