Treatment of mastitis during lactation

The secretomes of bovine mammary epithelial cell subpopulations differentially modulate macrophage function

Bovine mammosphere-derived epithelial cell (MDEC) cultures are heterogeneous and enriched for stem and progenitor cells. We previously reported that the bovine MDEC secretome, comprised of all bioactive factors secreted by the cells, displays regenerative properties, exerts antimicrobial effects, and modulates neutrophil activity, positioning it as a promising non-antibiotic biologic therapy for infectious diseases important to the dairy industry, like mastitis. Mastitis is defined as inflammation of the udder, and it is typically caused by bacterial infection. The effect of the MDEC secretome on macrophages, a first line of defense against bacterial infections in the udder, is unknown and could impact the utility of the secretome as a therapy for mastitis. To address this, we isolated bovine monocytes from peripheral blood and maintained them as an unpolarized (M0) population or polarized them into M1 or M2 phenotypes. Macrophages cultured with the secretome of bovine MDECs were assessed for their ability to phagocytose labeled bacterial particles and accumulate reactive oxygen species (ROS). We used single-cell RNA sequencing (scRNA-seq) and fluorescence-activated cell sorting (FACS) to isolate a subpopulation of MDECs that exert enhanced effects on macrophages. We found that the secretome of MDECs that do not express cluster of differentiation (CD) 73, a cell surface enzyme used as a marker for mesenchymal stromal cells, most strongly increased macrophage phagocytosis and ROS accumulation. These findings will help optimize the generation of the bovine MDEC secretome as a suitable treatment option for mastitis.

Pharmacokinetic/pharmacodynamic modeling in plasma and milk and Monte Carlo simulations of marbofloxacin against Staphylococcus aureus and Mycoplasma agalactiae in lactating sheep

In livestock ruminants such as sheep, different infectious diseases such as mastitis or contagious agalactia are originated from pathogens as Staphylococcus aureus and Mycoplasma agalactiae. Fluoroquinolones are authorized in dairy animals, including their extralabel use, as an alternative when other treatment failed in the European Union (EU), however, in the United States, are prohibited from extralabel drug use in food-producing animals. Marbofloxacin, a well-known fluoroquinolone is commonly used in dairy cattle in the EU at 10 mg/kg. However, their off-label use in sheep also has been described. Nevertheless, the dose extrapolations from dairy cows should include pharmacokinetic (PK) studies because of interspecies differences and the potential risks of antimicrobial resistance or toxicity. In this regard, the aims of this research were to (1) describe the i.v. and i.m. PK analysis of marbofloxacin in plasma and milk of lactating sheep at 10 mg/kg, (2) determine the MIC and calculate the tentative epidemiological cutoff values (TECOFF) for Mycoplasma agalactiae and Staphylococcus aureus wild-type isolates from sheep, and (3) conduct a pharmacokinetic and pharmacodynamic (PK/PD) analysis with the Monte Carlo simulation to obtain the probability of target attainment for different MIC values, known as the PK/PD cutoff values. The results of this study could help to establish the efficacy of a 10 mg/kg dosage regimen of marbofloxacin in lactating sheep. Plasma and milk concentrations were described with a nonlinear mixed effects model. The intramuscular bioavailability was 88%, and the volume of distribution was 1.31 L/kg with a clearance value of 0.38 L/h/kg. Half-lives after i.v. and i.m. dosing were 6.53 and 7.09 h in plasma, and 6.62 and 6.65 h in milk, respectively. High concentrations were determined in milk with area under the curve (AUC) milk/plasma ratios close to 1.28. The MIC values for Staphylococcus aureus and Mycoplasma agalactiae were obtained, and TECOFF values of 1.0 and 2.0 µg/mL, respectively, were determined. The Monte Carlo simulations predicted that the dosage regimen of 10 mg/kg per 24 h in lactating sheep can be adequate for intermediate and high MIC values of 0.5 and 1.0 μg/mL, respectively, and could be useful for populations with a target AUC/MIC ratio ≤48 for Staphylococcus aureus, but not for Mycoplasma agalactiae. Results derived for this study could be taken as previous tentative points for further studies of marbofloxacin in lactating and nonlactating sheep in a clinical context.

Mapping Antimicrobial Resistance in Staphylococcus epidermidis Isolates from Subclinical Mastitis in Danish Dairy Cows

Background/Objectives: Although Staphylococcus epidermidis is a key cause of subclinical mastitis in Danish dairy cows, its sensitivity to antimicrobials remains unexplored. Here, we analyzed sixty S. epidermidis isolates derived from 42 dairy cows across six conventional dairy herds in Denmark. Methods: Phenotypic resistance was measured by antimicrobial susceptibility testing and minimum inhibitory concentration (MIC) analysis, and genotypic resistance was examined through whole-genome sequencing and identification of antimicrobial resistance genes (ARGs). Correspondence between phenotypic and genotypic resistance was then evaluated by Cohen's kappa statistics. Furthermore, the presence of plasmid replicon genes and the strain diversity among the S. epidermidis isolates was investigated to associate these findings with the observed AMR patterns. Results: Results showed that 30/60 isolates (50.0%) were resistant to penicillin phenotypically, while 35/60 (58.3%) were positive for a corresponding blaZ gene (κ = 0.83, p < 0.01). A fosB gene, encoding fosfomycin resistance, was detected in all 60/60 isolates (100.0%), but fosfomycin resistance was not analyzed phenotypically. Based on MIC analysis, 3/60 isolates (5.0%) were multi-drug resistant, showing resistance towards penicillin, erythromycin, and tetracycline. However, in 11/60 genomes (18.3%), ARGs encoding resistance towards ≥3 antimicrobial classes (e.g., beta-lactams, phosphonic acid, tetracyclines, aminoglycosides, macrolides, lincosamides, and fusidane) were detected. Eleven different ARGs were detected among the 60 isolates in total. No methicillin-resistant Staphylococcus epidermidis (MRSE) were recorded. Results further showed that each herd had one primary sequence type (ST) and resistance profile associated with it, and plasmid-mediated horizontal gene transfer of ARGs was indicated This study underscores the importance of routine resistance surveillance and species-specific diagnoses to improve treatment outcomes and ensure prudent use of antimicrobials.

Intractable Recurrent Abscess Around the Nipple Caused by Mastitis Remitted by Kampo Medicine Treatment: A Case Report

We present a case of a 46-year-old woman with recurrent breast abscess resistant to conventional treatments. Initial diagnosis of mastitis led to antibiotic therapy; however, abscess formation recurred. Subsequent interventions, including incision, drainage, and various antibiotics, were insufficient because of recurrent infections. Due to the side effects of long-term antibiotic use, the patient was referred to the Kampo medicine department to address the premenstrual symptoms and recurrent infections. Treatment with Kampo medicines resulted in significant symptom reduction within a month. After treatment, the patient experienced mild symptoms, and breast abscess recurrence was prevented for more than two years. This case highlights the potential role of Kampo medicine in the management of refractory breast abscesses associated with premenstrual symptoms. Further research is required to explore the efficacy and mechanisms of action of Kampo medicines in similar cases.

Immortalized mammosphere-derived epithelial cells retain a bioactive secretome with antimicrobial, regenerative, and immunomodulatory properties

BACKGROUND

The secretome of primary bovine mammosphere-derived epithelial cells (MDECs) has been shown to exert antimicrobial, regenerative, and immunomodulatory properties in vitro, which warrants its study as a potential biologic treatment with the potential to be translated to human medicine. Currently, the use of the MDEC secretome as a therapy is constrained by the limited life span of primary cell cultures and the decrease of secretome potency over cell passages.

METHODS

To address these limitations, early-passage bovine MDECs were immortalized using hTERT, a human telomerase reverse transcriptase. The primary and immortal MDECs were compared morphologically, transcriptomically, and phenotypically. The functional properties and proteomic profiles of the secretome of both cell lines were evaluated and compared. All experiments were performed with both low and high passage cell cultures.

RESULTS

We confirmed through in vitro experiments that the secretome of immortalized MDECs, unlike that of primary cells, maintained antimicrobial and pro-migratory properties over passages, while pro-angiogenic effects of the secretome from both primary and immortalized MDECs were lost when the cells reached high passage. The secretome from primary and immortalized MDECs, at low and high passages exerted immunomodulatory effects on neutrophils in vitro.

CONCLUSIONS

High passage immortalized MDECs retain a bioactive secretome with antimicrobial, regenerative, and immunomodulatory properties, suggesting they may serve as a consistent cell source for therapeutic use.

Retrospective evaluation of udder recovery of cows with subclinical mastitis following treatment with acoustic pulse technology (APT) on commercial dairy farms and its economic impact

Retrospective evaluation of udder recovery following treatment of the inflamed quarter with acoustic pulse technology (APT) of cows with subclinical mastitis was done on 4 Israeli commercial dairy farms. Here, we evaluated the APT treatment as a tool to manage subclinical mastitis and its economic consequences in commercial farms. Recovery of the infected glands following APT treatment was compared to the customary no-treatment (NT) for cows with subclinical mastitis. Over 2 years, 467 cows with subclinical mastitis were identified. Subclinical mastitis was defined by elevated somatic cell count (SCC; >1 × 106 cells/mL) in the monthly test-day milk sample; 222 cows were treated with APT and 245 cows were not treated and served as control. Differences between treatment groups in culling, milk quality, milk yield and bacterial elimination were analyzed. After treatment, cure from bacteria was calculated only for cows with pre-isolated bacteria. The percentage of sampled cows determined as cured (no bacterial finding) in the NT group was 32.7% (35/107) (30.9% Gram negative; 32.4% Gram positive) and in the APT-treated group, 83.9% (42/55) (89.4% Gram negative; 80.6% Gram positive). Culling rate due to mastitis was significantly lower (>90%) in the APT-treated vs. NT group. Recovery was 66.0% in the APT group compared to 11.5% in the NT group at 90 d post-treatment. Average milk volume per cow in the APT-treated group was 16.1% higher compared to NT cows. Based on the study, savings incurred by using APT to treat only subclinical cows per 100-cow herd can total $15,106/y, or $309 per treated subclinically infected cow.

Extended-Spectrum Beta-Lactamase-Producing Escherichia coli and Other Antimicrobial-Resistant Gram-Negative Pathogens Isolated from Bovine Mastitis: A One Health Perspective

Antimicrobial resistance (AMR) poses an imminent threat to global public health, driven in part by the widespread use of antimicrobials in both humans and animals. Within the dairy cattle industry, Gram-negative coliforms such as Escherichia coli and Klebsiella pneumoniae stand out as major causative agents of clinical mastitis. These same bacterial species are frequently associated with severe infections in humans, including bloodstream and urinary tract infections, and contribute significantly to the alarming surge in antimicrobial-resistant bacterial infections worldwide. Additionally, mastitis-causing coliforms often carry AMR genes akin to those found in hospital-acquired strains, notably the extended-spectrum beta-lactamase genes. This raises concerns regarding the potential transmission of resistant bacteria and AMR from mastitis cases in dairy cattle to humans. In this narrative review, we explore the distinctive characteristics of antimicrobial-resistant E. coli and Klebsiella spp. strains implicated in clinical mastitis and human infections. We focus on the molecular mechanisms underlying AMR in these bacterial populations and critically evaluate the potential for interspecies transmission. Despite some degree of similarity observed in sequence types and mobile genetic elements between strains found in humans and cows, the existing literature does not provide conclusive evidence to assert that coliforms responsible for mastitis in cows pose a direct threat to human health. Finally, we also scrutinize the existing literature, identifying gaps and limitations, and propose avenues for future research to address these pressing challenges comprehensively.

Occurence of antimicrobial residues in milk and labneh consumed in Lebanon

Antimicrobials are administered in livestock for different uses leading to milk contamination and several undesirable effects. Because there is a lack of surveillance of antimicrobial residues (AMRs) in milk and dairy products in Lebanon, this study aims to determine the occurrence of AMRs in 90 Lebanese samples of milk and labneh (concentrated yoghurt). Multi-residue screening methods with suitable sample preparations were applied to detect 71 AMRs in milk and labneh, respectively, using LC-MS/MS. Of the total number of samples, 71% was contaminated with AMRs and (fluoro)quinolones and macrolides were the most detected families. Additional confirmation tests proved that 6.7% of the milk samples were non-compliant for the macrolides tilmicosin, tulathromycin and spiramycin. Moreover, some labneh prepared from contaminated milk samples was analysed to determine the fate of AMRs during the manufacturing process. The results showed that some AMRs could be concentrated, eliminated or degraded, based on their physicochemical characteristics.

Understanding mastitis: Microbiome, control strategies, and prevalence - A comprehensive review

Mastitis significantly affects the udder tissue in dairy cattle, leading to inflammation, discomfort, and a decline in both milk yield and quality. The condition can be attributed to an array of microbial agents that access the mammary gland through multiple pathways. The ramifications of this ailment are not merely confined to animal welfare but extend to the financial viability of the livestock industry. This review offers a historical lens on mastitis, tracing its documentation back to 1851, and examines its global distribution with a focus on regional differences in prevalence and antimicrobial resistance (AMR) patterns. Specific microbial genes and communities implicated in both mastitis and AMR are explored, including Staphylococcus aureus, Streptococcus agalactiae,Streptococcus dysagalactiae, Streptococcus uberis Escherichia coli, Klebsiella pneumoniae, Mycoplasma bovis, Corynebacterium bovis, among others. These microorganisms have evolved diverse strategies to elude host immune responses and neutralize commonly administered antibiotics, complicating management efforts. The review aims a comprehensive overview of the current knowledge and research gaps on mastitis and AMR, and to highlight the need for a One Health approach to address this global health issue. Such an approach entails multi-disciplinary cooperation to foster judicious antibiotic use, enhance preventive measures against mastitis, and bolster surveillance and monitoring of AMR in pathogens responsible for mastitis.

Assessment of antibiotic use patterns in bovine mastitis treatment in the dairy sector in Serbia

The dairy sector is essential for the world's food systems, playing a vital role in agricultural production. Yet, mastitis, an inflammation of the mammary gland, affects a considerable portion of the dairy cow population annually, leading to reduced productivity and sustainability. Insight into therapeutic protocols is essential for a better understanding of the situation on farms with the aim of developing new or harmonizing existing protocols in the mastitis treatment. This study conducted on dairy farm in Serbia aimed to explore the most commonly used antibiotics during bovine mastitis treatment and their association with daily milk yield. Data from 100 lactating cows, including therapeutic protocols, lactation numbers, mastitis episodes, milk yield, and antibiotic usage, were obtained from a computerized database and statistically analysed. The results demonstrated a high prevalence of narrow-spectrum antibiotics usage, with the majority of cows treated with combination therapy. The route of antibiotic application did not significantly impact daily milk yield, while treatment duration had no discernible effect. Nonetheless, specific antibiotics were associated with milk yield variations, suggesting the need for careful antibiotic selection and management in mastitis therapy. These findings emphasize the importance of prudent antibiotic use to safeguard animal health and long-term milk production sustainability.

Bovine milk-derived cells express transcriptome markers of pluripotency and secrete bioactive factors with regenerative and antimicrobial activity

The bovine mammary stem/progenitor cell secretome stimulates regeneration in vitro and contains proteins associated with antimicrobial defense. This has led to the exploration of the secretome as a biologic treatment for mastitis, a costly inflammation of the udder commonly caused by bacteria. This study reports on a population of bovine mammary stem/progenitor cells isolated non-invasively from milk (MiDCs). MiDCs were characterized by immunophenotyping, mammosphere formation assays, and single cell RNA sequencing. They displayed epithelial morphology, exhibited markers of mammary stem/progenitor cells, and formed mammospheres, like mammary gland tissue-isolated stem/progenitor cells. Single cell RNA sequencing revealed two sub-populations of MiDCs: epithelial cells and macrophages. Functionally, the MiDC secretome increased fibroblast migration, promoted angiogenesis of endothelial cells, and inhibited the growth of mastitis-associated bacteria, including antibiotic-resistant strains, in vitro. These qualities of MiDCs render them a source of stem cells and stem cell products that may be used to treat diseases affecting the dairy industry, including mastitis.

Treatment of mild to moderate clinical bovine mastitis caused by gram-positive bacteria: A noninferiority randomized trial of local penicillin treatment alone or combined with systemic treatment

Bovine mastitis is one of the most important diseases in modern dairy farming, as it leads to reduced welfare and milk production and increased need for antibiotic use. Clinical mastitis in Denmark is most often treated with a combination of local and systemic treatment with penicillin. The objective of this randomized clinical trial was to assess whether worse results could be expected with local intramammary treatment with penicillin compared with a combination of local and systemic treatment with penicillin in terms of the bacteriological cure of mild and moderate clinical mastitis cases caused by gram-positive bacteria. We carried out a noninferiority trial with a noninferiority margin set to a relative reduction in bacteriological cure of 15% between these 2 treatment groups to assess the effect of reducing the total antibiotic use by a factor of 16 for each treated case. Clinical mastitis cases from 12 Danish dairy farms were considered for enrollment. On-farm selection of gram-positive cases was carried out by the farm personnel within the first 24 h after a clinical mastitis case was detected. A single farm used bacterial culture results from the on-farm veterinarian, whereas the other 11 farms were provided with an on-farm test to distinguish gram-positive bacteria from gram-negative or samples without bacterial growth. Cases with suspected gram-positive bacteria were allocated to a treatment group: either local or combination. Bacteriological cure was assessed based on the bacterial species identified in the milk sample from the clinical mastitis case and 2 follow-up samples collected approximately 2 and 3 wk after ended treatment. Identification of bacteria was carried out using MALDI-TOF on bacterial culture growth. Noninferiority was assessed using unadjusted cure rates and adjusted cure rates from a multivariable mixed logistic regression model. Of the 1,972 clinical mastitis cases registered, 345 (18%) met all criteria for inclusion (full data). The data set was further reduced to 265 cases for the multivariable analysis to include only complete registrations. Streptococcus uberis was the most commonly isolated pathogen. Noninferiority was demonstrated for both unadjusted and adjusted cure rates. The unadjusted cure rates were 76.8% and 83.1% for the local and combined treatments, respectively (full data). The pathogen and somatic cell count before the clinical case had an effect on the efficacy of treatment; thus efficient treatment protocols should be herd- and case-specific. The effect of pathogen and somatic cell count on treatment efficacy was similar irrespective of the treatment protocol. We conclude that bacteriological cure of local penicillin treatment for mild and moderate clinical mastitis cases was noninferior to the combination of local and systemic treatment using a 15% noninferiority margin. This suggests that a potential 16-fold reduction in antimicrobial use per mastitis treatment can be achieved with no adverse effect on cure rate.

Invited review: Selective treatment of clinical mastitis in dairy cattle

Treatment of clinical mastitis (CM) and use of antimicrobials for dry cow therapy are responsible for the majority of animal-defined daily doses of antimicrobial use (AMU) on dairy farms. However, advancements made in the last decade have enabled excluding nonsevere CM cases from antimicrobial treatment that have a high probability of cure without antimicrobials (no bacterial causes or gram-negative, excluding Klebsiella spp.) and cases with a low bacteriological cure rate (chronic cases). These advancements include availability of rapid diagnostic tests and improved udder health management practices, which reduced the incidence and infection pressure of contagious CM pathogens. This review informed an evidence-based protocol for selective CM treatment decisions based on a combination of rapid diagnostic test results, review of somatic cell count and CM records, and elucidated consequences in terms of udder health, AMU, and farm economics. Relatively fast identification of the causative agent is the most important factor in selective CM treatment protocols. Many reported studies did not indicate detrimental udder health consequences (e.g., reduced clinical or bacteriological cures, increased somatic cell count, increased culling rate, or increased recurrence of CM later in lactation) after initiating selective CM treatment protocols using on-farm testing. The magnitude of AMU reduction following a selective CM treatment protocol implementation depended on the causal pathogen distribution and protocol characteristics. Uptake of selective treatment of nonsevere CM cases differs across regions and is dependent on management systems and adoption of udder health programs. No economic losses or animal welfare issues are expected when adopting a selective versus blanket CM treatment protocol. Therefore, selective CM treatment of nonsevere cases can be a practical tool to aid AMU reduction on dairy farms.

Clinical field trial of parenteral amoxicillin for the treatment of clinical and subclinical mastitis in smallholder dairy farms in the upper region of Northern Thailand

Background and Aim

Mastitis, primarily caused by intramammary bacterial infection, is the most expensive disease in the global dairy industry due to its negative impact on milk composition and manufacturing properties. This study aimed to evaluate the efficacy of parenteral amoxicillin in the treatment of clinical and subclinical mastitis in smallholder dairy farms in Northern Thailand.

Materials and Methods

A total of 51 cows with clinical and subclinical mastitis from dairy cooperatives in Lamphun and Chiang Mai provinces, Northern Thailand, were enrolled in this study. Conventional bacteriological procedures were applied to identify the causative bacteria in milk samples from these cows before and 7 days after treatment, and antibiotic susceptibility tests were conducted using the disk diffusion method for all bacteria isolated before treatment. All cows with mastitis were administered 15 mg/kg of amoxicillin (LONGAMOX^®, Syva Laboratories SA, Spain) intramuscularly every other day for 3 days.

Results

Environmental streptococcal bacteria (Streptococcus uberis and Streptococcus spp.) were commonly isolated from infected quarters and were highly susceptible to amoxicillin (100%). The clinical efficacy of amoxicillin treatment for clinical mastitis cases was 80.43%, and the bacteriological efficacy was 47.82%, with opportunistic staphylococcal bacteria (coagulase-negative staphylococci) and contagious streptococcal bacteria (Streptococcus agalactiae) being the most sensitive microorganisms (100%). In subclinical mastitis cases, the bacteriological efficacy of parenteral amoxicillin was 70.45%, with environmental streptococcal bacteria (S. uberis) being the most (100%) sensitive microorganisms.

Conclusion

Amoxicillin is highly efficacious and can be used to treat clinical and subclinical mastitis in dairy cows, particularly mastitis caused by environmental Streptococcus spp. These findings could be used to guide treatment regimens in veterinary practice in smallholder dairy farms in Thailand.

Evaluation of acoustic pulse technology as a non-antibiotic therapy for bovine intramammary infections: Assessing bacterial cure vs. recovery from inflammation

Introduction

The spread of antimicrobial resistance (AMR) is a major threat to human and animal health. Therefore, new solutions are needed to prevent returning to a world without effective antibiotics. Mastitis in dairy cows is a major reason for antimicrobial use in food animal production, and mastitis-causing bacteria have the potential to develop AMR. In this study, acoustic pulse technology (APT) was explored as an alternative to antimicrobials for the treatment of mastitis in dairy cows. APT involves the local transmission of mechanical energy through soundwaves which stimulate anti-inflammatory and angiogenic responses in the udder. These responses promote udder recovery and enhance resistance to bacterial infections.

Methods

We examined 129 Israeli dairy cows with mastitis in this prospective, controlled study to assess the efficiency of APT treatment on cure and recovery rates. An accurate diagnosis of suspected or confirmed infectious mastitis was made from cows having clinical signs of mastitis and/or somatic cell count (SCC) of above 400,000 cells/mL. The cows were divided into three groups: Group 1 (n = 29), cows with no bacterial findings (NBF); Group 2 (n = 82), cows with clinical signs of mastitis or SCC &gt;400,000 cells/mL in the most recent test; and Group 3 (n = 18), cows with chronic mastitis (two or more tests with SCC &gt;400,000 cells/mL within 3 months). All the cows received APT treatment, which involved 400 pulses on two sides of the infected quarter, delivered in three phases over 3 days. The cure for the mammary gland was indicated by the absence of bacterial growth in post-treatment cultures and recovery by a decrease in SCC to &lt; 250,000 cells/mL in two of three post-treatment tests.

Results and discussion

In Group 2, cure and recovery rates were 67.1 and 64.6%, respectively, and were not significantly different between Gram-negative and Gram-positive infections. A similar recovery rate was found in NBF cows. However, in cows with chronic mastitis, both the cure and recovery rates were significantly lower (22.2 and 27.8%, respectively). These results have important implications for dairy farmers, as APT treatment could lead to substantial savings of up to $15,106/year in a 100-cow herd, considering the national estimated prevalence of mastitis and the cost of individual treatment. APT should be further investigated as a viable and sustainable alternative to antimicrobial therapy for mastitis, offering economic benefits to dairy producers and the possibility of preventing AMR.

Intramammary Ethno-Veterinary Formulation in Bovine Mastitis Treatment for Optimization of Antibiotic Use

Increasing pressure on animal and human health as well as food security, due to antimicrobial resistance, is leading to increased demand for natural-product-derived antibiotics worldwide. Considering the importance of bovine mastitis as well as the huge challenge posed by mastitis therapy in cattle production, the main goal of this research was to evaluate the effectiveness of the essential oil-based pharmaceutical (Phyto-Bomat), as an alternative to the existing treatment with antibiotics. The therapeutic response of the cows was monitored using clinical and bacteriological cure of the proposed formulation. Among 550 dairy cows, 75 were diagnosed with a clinical or subclinical form of mastitis and divided into three experimental groups: treated with antibiotic; Phyto-Bomat; antibiotic and Phyto-Bomat. Indicators of bacteriological cure were somatic cell count (SCC), total bacterial count, and causative agent isolation, while the clinical cure was accessed by observing physical udder conditions. All mentioned indicators were assessed before and after the treatment (1st and 7th day post-treatment), with all of the three therapeutic protocols. After Phyto-Bomat treatment, no visible signs of irritation were noticed, while no significant effect in reducing SCC and total bacterial count was observed. Phyto-Bomat has shown promising results in the treatment of mastitis, without the risk of udder irritation, alone or in combination with antibiotics as part of a mastitis control program during lactation.

The costs of chronic mastitis: A simulation study of an automatic milking system farm

Mastitis is a production disease in dairy farming that causes economic losses. Especially chronic mastitis (i.e., mastitis cases continuing longer than 28 days) can substantially affect the risk of transmission of intramammary infections (IMI) and total milk production losses. Insights into the impact of chronic mastitis on production and farm economics are needed to guide chronic mastitis decision-making. We aimed to estimate the costs of chronic mastitis with a Monte Carlo simulation model in which the costs of chronic mastitis were estimated as part of the total mastitis costs. The model simulated milk yields, IMI dynamics, somatic cell count (SCC), and pregnancy status on an average Dutch dairy farm with 100 cow places over 9 years. The model was parameterized using information from the literature and actual sensor data from automatic milking system (AMS) farms. The daily subclinical milk production losses were modeled using a generalized additive model and sensor data. Transmission of IMI was modeled as well. The model results indicated median total costs of mastitis of € 230 per generic IMI case (i.e., a weighted average of all pathogens). The most substantial cost factors were the extra mastitis cases due to transmission, culling, and milk production losses. Other significant costs originated from dry cow treatments and diverted milk. The model also indicated median total costs due to chronic mastitis of € 118 (51 % of the total mastitis costs). The share of chronic mastitis relative to the total mastitis costs was substantial. Transmission of contagious bacteria had the largest share among the chronic mastitis costs (51 % of the costs of chronic cases). The large share of chronic mastitis costs in the total mastitis costs indicates the economic importance of these mastitis cases. The results of the study point to the need for future research to focus on chronic mastitis and reducing its presence on the AMS dairy farm.

Antibiotic residues in milk and milk products: A momentous challenge for the pharmaceutical industry and medicine

Dairy products are nutritious food items that contain various essential nutrients, however, it has been proven that residual antibiotics have contaminated such products. These residues can cause several side effects on human health. They increase antimicrobial resistance against several threatening microorganisms, as well as significant growth in allergenic reactions. Various methods, including heat treatments, have been applied to alleviate and reduce the effect of antibiotic residue level in milk and milk products. Changes in drug levels were not significantly remarkable, obliging researchers to find new approaches to prevent or reduce their risk and limit their complications on human health.

Pharmacoeconomic Analysis of the Different Therapeutic Approaches in Control of Bovine Mastitis: Phytotherapy and Antimicrobial Treatment

Mastitis in dairy cows is responsible for major economic losses on dairy farms worldwide as the most expensive and prevalent disease in dairy cattle. In spite of the fact that antibiotic therapy still remains the main treatment strategy for bovine mastitis, concerns about the shortcomings of this treatment approach are continuously raised. Hence, research on alternative treatments with increased effectiveness and reduced costs is needed. Therefore, we conducted a pharmacoeconomic analysis of conventional antibiotic vs. a proposed Phyto-Bomat treatment based on essential oils in bovine mastitis therapy. Treatments were compared from the farmer's perspective in the domain of costs (expressed in total, direct and indirect, cost differences) and effectiveness (expressed in daily milk yield differences). Economic calculations were based on data from a dairy farm in Serbia. The average cost of conventional antibiotic treatment was estimated at EUR 80.32 consisting of therapy costs, veterinary services and milk rejection costs at EUR 16.54, EUR 17.68 and EUR 46.10, respectively. The average cost of Phyto-Bomat treatment was estimated at EUR 76.34 with therapy costs of EUR 34.34, veterinary costs of EUR 32.00 and rejection of milk costs of only EUR 10.00. Therefore, Phyto-Bomat results in cost savings approximating EUR 4 per each mastitis episode with the highest cost reductions obtained in milk rejection costs. This estimation of Phyto-Bomat's economic benefits could be used as a starting point for the inclusion of this formulation as an alternative treatment approach with a focus on subclinical mastitis since it contributes to most of the financial losses.

Chemical Composition, Antimicrobial Activity, and Withdrawal Period of Essential Oil-Based Pharmaceutical Formulation in Bovine Mastitis Treatment

Due to the emergence of antibiotic-resistant bacteria, the risk it represents to public health, and the possible consequences for animal health and welfare, there is an increasing focus on reducing antimicrobial usage (AMU) in animal husbandry. Therefore, a great interest in developing alternatives to AMU in livestock production is present worldwide. Recently, essential oils (EOs) have gained great attention as promising possibilities for the replacement of antibiotics. The current study aimed to test the potential of using a novel EO-based pharmaceutical formulation (Phyto-Bomat) in bovine mastitis treatment. The antibacterial activity was performed using the microdilution technique. Lactating dairy cows were treated with 15 mL of Phyto-Bomat in the inflamed quarter for 5 consecutive days in order to analyze blood and milk samples for thymol and carvacrol residues using gas chromatography and mass spectrometry (GC-MS). Antimicrobial activity expressed as the minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) indicates that this formulation has the highest activity against Gram-positive strains. The dominant compounds in Phyto-Bomat were thymol and carvacrol, at 12.58 ± 1.23 mg/mL and 23.11 ± 2.31 mg/mL, respectively. The quantification of these two compounds in evaluated biological samples showed that 24 h after administration the concentration of thymol and carvacrol in milk samples was at the same level as before application. On the other hand, thymol and carvacrol were detectable in plasma samples even after 24 h post-treatment, with values ranging from 0.15-0.38 and 0.21-0.66 µg/mL, respectively. The tested formulation showed encouraging results of antibacterial activity against bovine mastitis pathogens, as well as the withdrawal period of dominant compounds, which implies that further testing regarding the bacteriological and clinical cure rates in clinical settings is needed.

Antimicrobial use and its association with the presence of methicillin-resistant staphylococci (MRS) and extended-spectrum beta-lactamases (ESBL)-producing coliforms in mastitic milk on dairy farms in the Chiba Prefecture, Japan

Food-producing animals, including dairy cattle, are potential reservoirs of antimicrobial resistance. However, there is limited data on antimicrobial use and the selection of resistant bacteria. Therefore, we investigated the association between antimicrobial use and resistance to mastitis pathogens using 2016 data from milk samples collected from cows with mastitis in 134 dairy farms in Chiba Prefecture, one of the principal dairy production prefectures in Japan. We recorded the antimicrobial use and isolation of methicillin-resistant staphylococci (MRS) and extended-spectrum beta-lactamase (ESBL)-producing coliforms (E. coli and Klebsiella spp.), and used the antimicrobial treatment incidence (ATI; the theoretical number of animals per 1000 animal-days subjected to antimicrobial treatment) to indicate antimicrobial use on each farm. The farms in which MRS or ESBL-producing coliforms were isolated from at least one mastitic milk sample were classified as antimicrobial resistance (AMR)-positive, and those in which neither MRS nor ESBL-producing coliforms were isolated were classified as AMR-negative. The AMR-positive farms showed a significantly higher ATI (median 45.17) than AMR-negative farms (median 38.40). The results indicate that high antimicrobial usage is associated with AMR in staphylococci and coliforms isolated from mastitic milk on dairy farms in Chiba Prefecture.

Optimal reduced-mixing for an SIS infectious-disease model

Which reduced-mixing strategy maximizes economic output during a disease outbreak? To answer this question, we formulate an optimal-control problem that maximizes the difference between revenue, due to healthy individuals, and medical costs, associated with infective individuals, for SIS disease dynamics. The control variable is the level of mixing in the population, which influences both revenue and the spread of the disease. Using Pontryagin's maximum principle, we find a closed-form solution for our problem. We explore an example of our problem with parameters for the transmission of Staphylococcus aureus in dairy cows, and we perform sensitivity analyses to determine how model parameters affect optimal strategies. We find that less mixing is preferable when the transmission rate is high, the per-capita recovery rate is low, or when the revenue parameter is much smaller than the cost parameter.

Association of pre-treatment somatic cell counts with bacteriological cure following diagnosis of intramammary infection

Antibiotic administration is crucial to ensure the health and productivity of dairy cattle. Mastitis is a disease that is typically a result of an intramammary infection (IMI), and antibiotic regimens are implemented to aid in curing IMI. Diagnosis is usually by detection of elevated milk somatic cell counts (SCC) and/or presence of culturable pathogens in the milk. Antibiotic treatment success is associated with the SCC at the time of treatment, though this correlation is still poorly understood. The objective of this project was to evaluate pre-treatment SCC and its association with IMI cure incidence following a standard antibiotic treatment. We hypothesized that pre-treatment SCC would be significantly lower in cases where the IMI ultimately cured compared to cases where the IMI failed to cure. Milk samples were collected aseptically from lactating cow quarters experiencing clinical or subclinical mastitis (n = 52). Clinical mastitis was diagnosed by a trained milking technician and subclinical mastitis was diagnosed at the quarter level as a SCC > 200,000 cells/mL and presence of bacterical growth in milk at time of treatment. After collection of the day 0 (D0) milk samples, the SCC was enumerated, and the milk sample cultured. Intramammary antibiotic therapy Cetftiofur hydrochloride (Spectramast® LC) was administered once/day for 5 days. Post-treatment samples were collected 14 d (D14) and 28 d (D28) later. A bacteriological cure was confirmed when both the D14 and D28 samples were free of culturable pathogens. The overall cure rate was 46.2%. Interestingly, the cure rates of antibiotic therapy decreased as pre-treatment SCC increased. Quarters that experienced bacteriological cure demonstrated a lower pre-treatment SCC (507,041 cells/mL ± 127.86 SEM, P = 0.01) compared to cows that did not cure, which had high pre-treatment SCC (1,640,392 cells/mL ± 333.28 SEM). Quarters that failed to cure had higher SCC values 28 days post-treatment in comparison to quarters that cured (P < 0.001). Future studies should investigate whether we can develop unique SCC-dependent mastitis treatment protocols which increase mastitis cure rates and enhance overall mammary health.

Environmental Bovine Mastitis Pathogens: Prevalence, Antimicrobial Susceptibility, and Sensitivity to Thymus vulgaris L., Thymus serpyllum L., and Origanum vulgare L. Essential Oils

Mastitis is considered to be one of the most important diseases of dairy cows in terms of health, production, and economy. Being the most common cause of antibiotic consumption in dairy cows, treatment of this disease is one of the biggest challenges in the veterinary profession as an increasing number of pathogens develop resistance to antibiotics used in the treatment. Therefore, new alternative approaches for limiting the use of antibiotics in livestock are required. For this reason, our study aimed to investigate prevalence of environmental mastitis associated bacterial strains, as well as the sensitivity of isolated strains to different antibiotics. Additionally, the therapeutic potential of three essential oils (EOs) was tested against bovine Serratia spp. and Proteus spp. mastitis pathogens, based on their chemical composition, as well as antibacterial potential. The study was carried out on 81 milk samples collected from dairy cows with mastitis. In order to determine prevalence of S. marcescens and P. mirabilis, microbiological isolation and identification were performed. Antimicrobial susceptibility testing was performed by disk diffusion method and the microdilution method was used to determine the antibacterial activity of selected EOs. In the oregano EO, a total of 23 compounds were detected, with carvacrol as a dominant component (78.94%). A total of 26 components were present in the EO of common thyme, where thymol was the most abundant compound (46.37%). Thymol also dominated (55.11%) the wild thyme EO. All tested EOs displayed antibacterial activity against all strains to different extents, while wild and common thyme EOs were the most effective. It could be concluded that the tested EOs represent promising therapeutic candidates for effective non-antibiotic treatment of mastitis.

Antibiotics in Dairy Production: Where Is the Problem?

Antibiotics have long been used for the prevention and treatment of common diseases and for prophylactic purposes in dairy animals. However, in recent decades it has become a matter of concern due to the widespread belief that there has been an abuse or misuse of these drugs in animals and that this misuse has led to the presence of residues in derived foods, such as milk and dairy products. Therefore, this review aims to compile the scientific literature published to date on the presence of antibiotic residues in these products worldwide. The focus is on the reasons that lead to their presence in food, on the potential problems caused by residues in the characteristics of dairy products and in their manufacturing process, on the development and spread of antibiotic-resistant bacteria, and on the effects that both residues and resistant bacteria can cause on human and environmental health.

Antimicrobials use and their indications in dairy farm and individual farmer production conditions in southern India

Antimicrobials use (AMU) is the key driver for development of antimicrobials resistant (AMR) pathogen in human and veterinary medicines. Therefore, understanding AMU pattern is prerequisite for focused intervention on AMR. The aim of this study was to understand the AMU pattern and their indications in dairy farm and individual farmer production conditions in southern India. Treatment registers of 6 years (2012 to 2017) containing 3178 cases from dairy farm and 12,057 cases during 2017-2019 under individual farmer production conditions were collected and analyzed by log-linear model. Seasons were classified as rainy (Jul-Oct), winter (Nov-Feb), and summer (Mar-June) as per climatic conditions in the study area. It is observed that mastitis, lameness, and reproductive problems were major health disorders among treated animals in farm and individual farmer production conditions. Season had significant influence on proportional rates of various health disorders in crossbred cows under both the production conditions. AMU pattern was different between the breeds and production conditions. Antibiotics were the most commonly used group of drugs (23-28%) than non-steroidal anti-inflammatory drugs (20%), antihistamine (17%), and nutrient supplements (14-16%). Antibiotics were mostly used for mastitis (47-67%) than other conditions like fever (18%), reproductive problems (15%), and lameness (16%). For treating mastitis, cephalosporins and gentamicin were most commonly used under individual farmer production condition, while penicillin group was frequently used in farm. It is concluded that mastitis is the most common indication for AMU in dairy animals and thus developing appropriate guidelines for mastitis treatment and control is necessary to reduce overall AMU.

Bacteria Isolated From Milk of Dairy Cows With and Without Clinical Mastitis in Different Regions of Australia and Their AMR Profiles

Mastitis is the most common disease in dairy cattle worldwide. The objectives of this study were to estimate the prevalence of different bacterial species associated with mastitis from dairy herds located in geographically and climatically distinct zones in Australia, and to evaluate the antimicrobial susceptibility of the isolated bacteria. Quarter-level milk samples (n = 419) were collected from 151 mastitis cases and 268 healthy controls originating from 18 dairy herds located in tropical (Northern Queensland), subtropical (Southeast Queensland) and temperate zones (Victoria) between March and June 2019. Milk samples were cultured, and the isolated bacteria were grouped into six groups: Enterobacteriaceae spp.; Streptococcus spp.; Staphylococcus aureus, non-aureus staphylococci (NAS); Bacillus spp.; and Others. Mixed effects conditional logistic regression models were applied to quantify the association between the prevalence of each bacterial group and the herd zone and bulk milk tank somatic cell counts (BMTSCC). Of the 205 isolates, 102 (50%) originated from mastitis cases, and 103 (50%) from controls. Staphylococci were the most prevalent (NAS 32% and S. aureus 11%). Contagious mastitis bacteria were more prevalent in Victoria compared to Queensland dairy herds. NAS species (P < 0.001) were less prevalent in herds with BMTSCC >300,000 cells/mL compared with herds with low BMTSCC ≤150,000 cells/mL. Enterobacteriaceae and Streptococcus spp. groups showed high resistance rates to 1 (51 and 47%, respectively), and 2 (11 and 23%, respectively), antimicrobials. More than one third of the Enterobacteriaceae (48%) and Others (43%) groups spp. were resistant to at least three antimicrobials. This study provided a unique opportunity to investigate the prevalence of mastitis-associated bacteria in clinical cases and in apparently healthy controls. The findings of this study help inform mastitis control and antimicrobial stewardship programs aimed to reduce the prevalence of mastitis and antimicrobial resistance in dairy herds.

Effects of Growth Medium and Inoculum Size on Pharmacodynamics Activity of Marbofloxacin against Staphylococcus aureus Isolated from Caprine Clinical Mastitis

Staphylococcus aureus (S. aureus) is an important pathogen that causes clinical mastitis in goats and produces infections difficult to cure. Different antimicrobials as fluoroquinolones have been used against S. aureus. However, the studies developed to evaluate the bacterial drug interaction only have used the MIC as a single reference point with artificial growth media. The aims of this study were to describe the effect of marbofloxacin on S. aureus isolated from mastitis goats' milk by different approaches as the minimum inhibitory and bactericidal concentrations (MIC and MBC) in cation adjusted Mueller-Hinton broth (CAMHB), serum and milk of goats at two inoculum sizes of 10⁵ and 10⁸ CFU/mL, the determination and analysis of the time kill curves (TKC) by non-linear mixed effect models in each growth medium and inoculum size, as well as the estimation of their pharmacokinetics/pharmacodynamics (PK/PD) cutoff values. The results obtained indicate that MIC values were higher and increases 2,4-fold in serum and 3,6-fold in milk at high inoculum, as well as the EC₅₀ values determined by each pharmacodynamics model. Finally, the PK/PD cutoff values defined as fAUC₂₄/MIC ratios to achieve clinical efficacy were highly dependent on inoculum and growth medium, with median values of 60-180, especially at high inoculum in milk, suggesting that further studies are necessary to evaluate and optimize the best therapeutic strategies for treating S. aureus in lactating goats.

Transfer of certain beta-lactam antibiotics from cow's milk to fresh cheese and whey

The aim of this study was to investigate the transfer of cephalexin, penicillin-G, and ampicillin & cloxacillin from cow's milk to cheese and whey. For this purpose, raw milk was artificially contaminated to different antibiotic levels and then heat-treated to prepare fresh cheese from it. Antibiotic levels of the milk, whey and cheese were measured with LC-MS/MS. The extent of heat degradation was not sufficient to remove the antibiotic residues from milk. Antibiotic concentrations in whey and fresh cheese were in good accordance with the concentration of the same compound in milk suggesting that contamination of the milk will result in contamination of the product. The investigated antibiotics were transferred less into the cheese curd (1.6-12.5% of the original amount), than into the whey (33.2-74.1%). For penicillin-G even 100% (complete removal) was experienced.

A Bioengineered Nisin Derivative To Control Streptococcus uberis Biofilms

Antimicrobial peptides are evolving as novel therapeutic options against the increasing problem of multidrug-resistant microorganisms, and nisin is one such avenue. However, some bacteria possess a specific nisin resistance system (NSR), which cleaves the peptide reducing its bactericidal efficacy. NSR-based resistance was identified in strains of Streptococcus uberis, a ubiquitous pathogen that causes mastitis in dairy cattle. Previous studies have demonstrated that a nisin A derivative termed nisin PV, featuring S29P and I30V, exhibits enhanced resistance to proteolytic cleavage by NSR. Our objective was to investigate the ability of this nisin derivative to eradicate and inhibit biofilms of S. uberis DPC 5344 and S. uberis ATCC 700407 (nsr⁺) using crystal violet (biomass), 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) (viability) assays, and confocal microscopy (viability and architecture). When preestablished biofilms were assessed, both peptides reduced biofilm biomass by over 60% compared to that of the untreated controls. However, a 42% higher reduction in viability was observed following treatment with nisin PV compared to that of nisin A. Accordingly, confocal microscopy analysis revealed significantly more dead cells on the biofilm upper surface and a reduced thickness following treatment with nisin PV. When biofilm inhibition was assessed, nisin PV inhibited biofilm formation and decreased viability up to 56% and 85% more than nisin A, respectively. Confocal microscopy analysis revealed a lack of biofilm for S. uberis ATCC 700407 and only dead cells for S. uberis DPC 5344. These results suggest that nisin PV is a promising alternative to effectively reduce the biofilm formation of S. uberis strains carrying NSR. IMPORTANCE One of the four most prevalent species of bovine mastitis-causing pathogens is S. uberis. Its ability to form biofilms confers on the bacteria greater resistance to antibiotics, requiring higher doses to be more effective. In a bid to limit antibiotic resistance development, the need for alternative antimicrobials is paramount. Bacteriocins such as nisin represent one such alternative that could alleviate the impact of mastitis caused by S. uberis. However, many strains of S. uberis have been shown to possess nisin resistance determinants, such as the nisin resistance protein (NSR). In this study, we demonstrate the ability of nisin and a nisin derivative termed PV that is insensitive to NSR to prevent and remove biofilms of NSR-producing S. uberis strains. These findings will add new information to the antimicrobial bacteriocins and control of S. uberis research fields specifically in relation to biofilms and nsr⁺ mastitis-associated strains.

Advances in therapeutic and managemental approaches of bovine mastitis: a comprehensive review

Mastitis (intramammary inflammation) caused by infectious pathogens is still considered a devastating condition of dairy animals affecting animal welfare as well as economically incurring huge losses to the dairy industry by means of decreased production performance and increased culling rates. Bovine mastitis is the inflammation of the mammary glands/udder of bovines, caused by bacterial pathogens, in most cases. Routine diagnosis is based on clinical and subclinical forms of the disease. This underlines the significance of early and rapid identification/detection of etiological agents at the farm level, for which several diagnostic techniques have been developed. Therapeutic regimens such as antibiotics, immunotherapy, bacteriocins, bacteriophages, antimicrobial peptides, probiotics, stem cell therapy, native secretory factors, nutritional, dry cow and lactation therapy, genetic selection, herbs, and nanoparticle technology-based therapy have been evaluated for their efficacy in the treatment of mastitis. Even though several strategies have been developed over the years for the purpose of managing both clinical and subclinical forms of mastitis, all of them lacked the efficacy to eliminate the associated etiological agent when used as a monotherapy. Further, research has to be directed towards the development of new therapeutic agents/techniques that can both replace conventional techniques and also solve the problem of emerging antibiotic resistance. The objective of the present review is to describe the etiological agents, pathogenesis, and diagnosis in brief along with an extensive discussion on the advances in the treatment and management of mastitis, which would help safeguard the health of dairy animals.

New Treatment Option for Clinical and Subclinical Mastitis in Dairy Cows Using Acoustic Pulse Technology (APT)

The effect of acoustic pulse technology (APT) on recovery, culling, milk yield, and economic benefits for 118 cows with subclinical mastitis was compared with a no-treatment control (59 vs. 59), and another 118 APT-treated cows with clinical mastitis were compared with antibiotic-treated controls (59 vs. 59). Recovery was defined as a decrease in somatic cell count (SCC) to <250 × 103 cells/mL in at least two out of three monthly milk recordings after treatments. For the subclinically infected cows, APT treatment resulted in 65.5% recovery, 0% culling, and additional milk yield of 2.74 L/cow per day compared to 35.6% recovery and 5.1% culling in the no-treatment controls. For the clinically infected cows, APT treatment resulted in 67.8% recovery, 6.8% culling, and additional milk yield of 3.9 L/cow per day compared to 35.6% recovery and 32.2% culling in the antibiotic-treated group. Bacteriological analysis was run for 95 (80%) cows with clinical mastitis (APT-46; AB-49). For cows with Escherichia coli infection, 85.7% (18/21) treated with APT recovered vs. 17.6% (3/17) in the antibiotic-treated group; for cows with streptococcal infection, 66.0% (12/18) in the APT-treated group recovered vs. 44.4% (8/18) in the antibiotic-treated group.

Prevalence of intramammary antibiotic usage in dairy farming

This research communication describes the lactating intramammary (IMM) antibiotic formulation most used by Irish dairy farmers at farm level through interviewing 202 dairy farmers. The IMM antibiotic usage data is not easily available to the researcher and farming community. This study determined that three commercial formulations (Synulox ™, Tetra Delta™ and Terrexine) made up 81% of the products used at farm level. The formulation Synulox™ was the most used at 34% first preference and 32% second preference and contains amoxicillin/clavulanic, a standard broad spectrum antibiotic, for which mastitis pathogen resistance remains low. The aminoglycosides were used in four of the IMM formulations analysed, including Tetra Delta™ and Terrexine. Of the 12 antibiotics identified in the IMM formulations studied, three including cefalexin, benzylpenicillin and penethamate are classified as highly important antibiotics (HIA) by the World Health Organisation (WHO) whilst the other 8 (dihydrostreptomycin, streptomycin, neomycin, framycetin, kanamycin, amoxicillin/clavulanic acid, and cefquinome), are considered critically important (CIA) for use in human health. This study has generated knowledge of the preferences of lactating IMM formulations used at farm level.

Paper-based analytical devices for colorimetric detection of S. aureus and E. coli and their antibiotic resistant strains in milk

Animal derived milk which is an important part of human diet due to its high nutritional value not only supports humans but also presents a growth environment for pathogenic bacteria. Milk may become contaminated with bacteria through udder infections or through contact within the dairy farm environment. Infections are treated with antibiotics, with β-lactams most commonly used in veterinary medicine. However, their frequent use leads to the emergence of β-lactam resistant bacterial strains, which causes difficulties in the treatment of infections in both humans and animals. Detection of pathogens as well as their antibiotic sensitivity is a pre-requisite for successful treatment and this is generally achieved with laboratory-based techniques such as growth inhibition assays, enzyme-linked immunosorbent assays (ELISA) or polymerase chain reactions (PCRs), which are unavailable in resource-limited settings. Here, we investigated paper-based analytical devices (μPADs) for the presumptive detection of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and their antibiotic resistant bacterial strains in milk samples. The μPADs were fabricated on filter paper using wax printing, and then impregnated with chromogenic substrates, which reacted with bacterial enzymes to form coloured products. Limits of detection of S. aureus and E. coli and their antibiotic resistant strains in milk samples were found to be 106 cfu mL-1. Enrichment of milk samples in a selective medium for 12 h enabled detection as low as 10 cfu mL-1. The paper devices tested on a set of 640 milk samples collected from dairy animals in Pakistan demonstrated more than 90% sensitivity and 100% selectivity compared to PCR, showing promise to provide inexpensive and portable diagnostic solutions for the detection of pathogenic bacteria in resource-limited settings.

A Model to Investigate the Impact of Farm Practice on Antimicrobial Resistance in UK Dairy Farms

The ecological and human health impact of antibiotic use and the related antimicrobial resistance (AMR) in animal husbandry is poorly understood. In many countries, there has been considerable pressure to reduce overall antibiotic use in agriculture or to cease or minimise use of human critical antibiotics. However, a more nuanced approach would consider the differential impact of use of different antibiotic classes; for example, it is not known whether reduced use of bacteriostatic or bacteriolytic classes of antibiotics would be of greater value. We have developed an ordinary differential equation model to investigate the effects of farm practice on the spread and persistence of AMR in the dairy slurry tank environment. We model the chemical fate of bacteriolytic and bacteriostatic antibiotics within the slurry and their effect on a population of bacteria, which are capable of resistance to both types of antibiotic. Through our analysis, we find that changing the rate at which a slurry tank is emptied may delay the proliferation of multidrug-resistant bacteria by up to five years depending on conditions. This finding has implications for farming practice and the policies that influence waste management practices. We also find that, within our model, the development of multidrug resistance is particularly sensitive to the use of bacteriolytic antibiotics, rather than bacteriostatic antibiotics, and this may be cause for controlling the usage of bacteriolytic antibiotics in agriculture.

Veterinary Treatment Approach and Antibiotic Usage for Clinical Mastitis in Danish Dairy Herds

Danish veterinarians’ treatment approach and use of antibiotics for clinical mastitis were investigated through a web-based questionnaire. The objective of the study was to describe and evaluate how the clinical mastitis treatment practice in Danish dairy herds corresponds to evidence from the literature and legislative requirements, in order to suggest directions for improvements and approaches encouraging the prudent use of antibiotics. In total, 174 veterinarians working with cattle received the questionnaire and 85 (48.9%) completed it. Their answers suggested that the Danish treatment approach for clinical mastitis generally relies on combined systemic and intramammary antibiotic administration (92% would use this often or always) and almost always includes supportive treatment with nonsteroidal anti-inflammatory drugs (99% would use it often or always in combination with antibiotic therapy). While collecting milk samples in order to target treatment towards pathogens is a priority in the legislation and for veterinarians, the direct application seems hindered due to the waiting time with the currently used analysis practice. Consequently, 91% reported that they would start treatment immediately after clinical examination often or always. The results of this investigation show that there is a potential for improvement in targeting treatments towards the causative pathogen by encouraging methods that allow for a more rapid reliable pathogen determination. When this issue has been addressed, the available evidence on the best treatment practice of Gram-negative-caused mastitis cases can be applied properly, reducing the volume of antibiotic treatments with limited expected effect. Additionally, investigating the potential of reducing combined administration to only intramammary treatment in Gram-positive cases could be a further step towards a more prudent antibiotic strategy.

Epidemiology and Classification of Mastitis

Simple Summary

Farmers should focus on milk quality over quantity. However, in some situations, more attention is focused on the amount of milk produced. In the long term, this approach might represent an important economic cost as it leads to increased incidence of mastitis. Mastitis affects herds in all countries and is the most economically burdensome disease encountered by dairy farmers. The current review focuses on the main pathogens that cause this inflammation and their prevalence as well as strategies to prevent their proliferation. We discuss economic loss, with the goal of demonstrating that prevention is always better than disease management.

Abstract

Farmers should focus on milk quality over quantity because milk that contains unsuitable components and/or antibiotic residues, or has a high somatic cell count, cannot be used in food production and thereby results in reduced milk yield. One of the main problems affecting the ultimate milk yield of dairy cows is mastitis. This disease is the most serious economic and health problem associated with dairy cow herds and is a major reason for excessive culling. Therefore, many studies have addressed this problem to further our understanding of the agents causing mastitis and their classification and virulence factors. This review summarizes the current knowledge regarding mastitis prevalence, the characteristics of its main causative agents, and the effects of mastitis on dairy production. The review also intends to provide guidance for future studies by examining external effects influencing dairy production in cows under field conditions.

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.

Use of plant extracts and essential oils in the control of bovine mastitis

Bovine mastitis is the most important disease affecting dairy herds worldwide, causing direct impacts on farms' profitability and food safety issues. The prevention and treatment of this pathology is especially done through antimicrobials, but the increasing antimicrobial resistance of pathogens to this disease may affect the efficiency of conventional drugs. Besides, antimicrobials residues in milk and the environment are a potential threat to human health. Thereby, the use of plant extracts and essential oils may become promising alternatives for the control of bovine mastitis. Antimicrobial properties present in several plants are well described and plant extracts and essential oils are often considered safe to animals, humans and environment. This review summarizes the current problems encountered in the conventional treatment of mastitis, the possibilities of the use of plant extracts and essential oils as alternative agents for the control of these pathogens and the limitations found in the use of these plant derivatives. Finally, the perspectives to the use of plant extracts and essential oils for the treatment of bovine mastitis are presented.

Multiple Bactericidal Mechanisms of the Zinc Ionophore PBT2

Globally, more antimicrobials are used in food-producing animals than in humans, and the extensive use of medically important human antimicrobials poses a significant public health threat in the face of rising antimicrobial resistance (AMR). The development of novel ionophores, a class of antimicrobials used exclusively in animals, holds promise as a strategy to replace or reduce essential human antimicrobials in veterinary practice. PBT2 is a zinc ionophore with recently demonstrated antibacterial activity against several Gram-positive pathogens, although the underlying mechanism of action is unknown. Here, we investigated the bactericidal mechanism of PBT2 in the bovine mastitis-causing pathogen, Streptococcus uberis In this work, we show that PBT2 functions as a Zn2+/H+ ionophore, exchanging extracellular zinc for intracellular protons in an electroneutral process that leads to cellular zinc accumulation. Zinc accumulation occurs concomitantly with manganese depletion and the production of reactive oxygen species (ROS). PBT2 inhibits the activity of the manganese-dependent superoxide dismutase, SodA, thereby impairing oxidative stress protection. We propose that PBT2-mediated intracellular zinc toxicity in S. uberis leads to lethality through multiple bactericidal mechanisms: the production of toxic ROS and the impairment of manganese-dependent antioxidant functions. Collectively, these data show that PBT2 represents a new class of antibacterial ionophores capable of targeting bacterial metal ion homeostasis and cellular redox balance. We propose that this novel and multitarget mechanism of PBT2 makes the development of cross-resistance to medically important antimicrobials unlikely.IMPORTANCE More antimicrobials are used in food-producing animals than in humans, and the extensive use of medically important human antimicrobials poses a significant public health threat in the face of rising antimicrobial resistance. Therefore, the elimination of antimicrobial crossover between human and veterinary medicine is of great interest. Unfortunately, the development of new antimicrobials is an expensive high-risk process fraught with difficulties. The repurposing of chemical agents provides a solution to this problem, and while many have not been originally developed as antimicrobials, they have been proven safe in clinical trials. PBT2, a zinc ionophore, is an experimental therapeutic that met safety criteria but failed efficacy checkpoints against both Alzheimer's and Huntington's diseases. It was recently found that PBT2 possessed potent antimicrobial activity, although the mechanism of bacterial cell death is unresolved. In this body of work, we show that PBT2 has multiple mechanisms of antimicrobial action, making the development of PBT2 resistance unlikely.

Technological interventions and advances in the diagnosis of intramammary infections in animals with emphasis on bovine population-a review

Mastitis, an inflammation of the udder, is a challenging problem in dairy animals accounting for high economic losses. Disease complexity, degree of economic losses and increasing importance of the dairy industries along with public health concerns envisages devising appropriate diagnostics of mastitis, which can offer rapid, accurate and confirmatory diagnosis. The various diagnostic tests of mastitis have been divided into general or phenotypic and specific or genotypic tests. General or phenotypic tests are those that identify general alterations, which are not specific to any pathogen. Genotypic tests are specific, hence confirmatory for diagnosis of mastitis and include specific culture, polymerase chain reaction (PCR) and its various versions (e.g. qRT-PCR), loop-mediated isothermal amplification, lateral flow assays, nucleotide sequencing, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, and other molecular diagnostic methods. However, for highly specific and confirmatory diagnosis, pure cultures still provide raw materials for more sophisticated diagnostic technological interventions like PCR and nucleotide sequencing. Diagnostic ability of like infra-red thermography (IRT) has been shown to be similar to California mastitis test and also differentiates clinical mastitis from subclinical mastitis cases. As such, IRT can become a convenient and portable diagnostic tool. Of note, magnetic nanoparticles-based colorimetric biosensor assay was developed by using for instance proteolytic activity of plasmin or anti-S. aureus antibody. Last but not least, microRNAs have been suggested to be potential biomarkers for diagnosing bovine mastitis. This review summarizes the various diagnostic tests available for detection of mastitis including diagnosis through general and specific technological interventions and advances.

In vitro Antimicrobial Resistance of Causative Agents to Clinical Mastitis in Danish Dairy Cows

This study was undertaken to investigate the antimicrobial resistance patterns of major causative agents to clinical mastitis in Danish dairy cows collected in 2016 to provide data on the current resistance patterns. Such data may subsequently serve as basis for a guideline for prudent use of antimicrobial agents in mastitis treatment. In addition, this study serves as a baseline for future comparison. The minimum inhibitory concentrations in Escherichia coli (n = 62), Klebsiella pneumoniae (n = 18), Staphylococcus aureus (n = 63), coagulase-negative Staphylococci (CNS) (n = 49), Streptococcus uberis (n = 61), Streptococcus dysgalactiae (n = 33), and Streptococcus agalactiae (n = 13) were determined to antimicrobial agents representing most classes relevant for treatment. The occurrence of resistance in the 299 bacterial isolates in total was evaluated using Clinical and Laboratory Standards Institute clinical breakpoints or in-house breakpoint values. For E. coli, low resistance levels were detected, 11.3% being resistant to ampicillin while resistance to other compounds was lower or zero. In contrast, K. pneumoniae revealed frequent ampicillin resistance (83.3%), but was susceptible to most other antimicrobial agents tested. Staphylococci were susceptible to the majority of antimicrobial agents tested, only 17.7% of the S. aureus isolates and 22.4% of the CNS being resistant to penicillin. Species distribution of the CNS isolates revealed that Staphylococcus simulans, Staphylococcus chromogenes, and Staphylococcus epidermidis were the most prevalent species. One S. aureus and one S. chromogenes isolate was found to be cefoxitin resistant and confirmed as methicillin resistant by polymerase chain reaction detection of the mecA gene, showing that methicillin resistance in staphylococci is present. All species of streptococci were susceptible to penicillin. No other critical resistance was found in any species, and resistance was in general low to all clinically relevant compounds. We emphasize the need for continuous surveillance of antibiotic resistance in major mastitis pathogens and the need for harmonization of methods and interpretations.

Influence of oxytetracycline susceptibility as a first-line antibiotic on the clinical outcome in dairy cattle with acute Escherichia coli mastitis

The purpose of this study was to clarify the therapeutic effects of oxytetracycline (OTC) as a first-line antibiotic in cattle with acute Escherichia coli mastitis and systemic signs. Drug susceptibility was determined by the minimum inhibitory concentration (MIC) of E. coli isolated from cows with acute E. coli mastitis (n=38). Cattle were divided into OTC-susceptible (S, n=30) and OTC-resistant (R, n=8) groups. They were further subdivided according to susceptibility to the antibiotic used as a second treatment, into susceptible-susceptible (SS, n=30), resistant-susceptible (RS, n=5), and resistant-resistant (RR, n=3) groups. Clinical signs on the day after initial treatment were compared between S and R groups as short-term indicators of treatment effects. The 28-day survival rate of cattle was then compared among SS, RS, and RR groups as a long-term indicator of treatment effects. There were no differences in clinical signs between S and R groups on the day after the first dose, but the 28-day survival rate was significantly greater in the SS group than in the RR group (P=0.04). The results demonstrated that an effective drug is essential for first-line treatment of acute coliform mastitis. However, anticipating the effectiveness of a first-line antibiotic based on clinical symptoms at the second day of treatment is impossible. It is important to build a picture of drug resistance trends in cattle herds for empirical selection of antibiotics to be administered.

Perfil de imunoglobulinas, cura clínica e bacteriológica após diferentes tratamentos para a mastite clínica bovina

RESUMO O presente estudo objetivou avaliar o perfil das Ig durante os diferentes tratamentos de vacas com mastite clínica. Para isso, 30 vacas com mastite clínica em um quarto mamário foram utilizadas e divididas em três grupos. O primeiro grupo foi composto por 10 animais submetidos ao tratamento combinado com infusão intramamária de 8,5mg de sulfato de cefquinoma após cada ordenha, totalizando três aplicações e administração intramuscular de 2,5mg/kg de enrofloxacina por três dias. O segundo grupo foi composto por 10 animais submetidos ao tratamento intramamário, com infusão intramamária de 8,5mg de sulfato de cefquinoma, após cada ordenha, totalizando três aplicações. O terceiro grupo foi composto por 10 animais submetidos ao tratamento sistêmico, com 2,5mg/kg de enrofloxacina, durante três dias. As amostras de leite foram coletadas de todos os animais antes dos tratamentos (momento 0), no segundo (momento 1), no quinto (momento 2) e no 12º dia (momento 3) após o término dos tratamentos. Estas foram submetidas à contagem de células somáticas, ao California Mastitis Test (CMT), ao exame bacteriológico e à quantificação das IgG1, IgG2, IgA e IgM. O tratamento combinado foi mais eficaz e precoce na taxa de cura clínica, na redução dos escores de CMT e da contagem de células somáticas. Além disso, os resultados do presente estudo demonstraram que as concentrações lácteas das diferentes classes de Ig, apesar de sua importância biológica, não estão relacionadas ao prognóstico da mastite clínica bovina, ou seja, não podem ser consideradas marcadores robustos associados à cura clínica e/ou bacteriológica da infecção intramamária.

Bactericidal Activity and Synergy Studies of Peptide AP-CECT7121 Against Multi-resistant Bacteria Isolated from Human and Animal Soft Tissue Infections

AP-CECT7121 is an antimicrobial peptide, produced by Enterococcus faecalis CECT7121, with bactericidal activity against Gram-positive bacteria. The aim of this study was to evaluate the bactericidal activity of AP-CECT7121, alone and with gentamicin, against multi-resistant bacteria isolated from human and animals with soft tissue infections. During the period 2014-2015, bacterial strains producing human and animal soft tissue infections were studied. Samples from patients attended at a general hospital and cattle from four dairies in the Province of Buenos Aires (Argentina) were included. Twenty-two methicillin-resistant Staphylococcus aureus (11, human blood samples; 11, cow milk) and five vancomycin-resistant Ent. faecium strains isolated from four mastitic dairy cows were tested. AP-CECT7121 (12 mg/L) potency was assessed by time-kill curves alone or with sub-inhibitory concentrations of gentamicin. All staphylococcal strains were susceptible to gentamicin; enterococci did not show high-level gentamicin resistance. Colony counts were carried out at 0, 2, 4, 8, and 24 h of incubation. AP-CECT7121 showed bactericidal activity against all the enterococcal strains. In addition, AP-CECT7121 had a bactericidal effect on most staphylococci (16/22). Early AP-CECT7121/gentamicin synergy (4-8 h) for all staphylococci was detected. At 24 h, synergy (19/22) and indifference (3/22) were observed. Synergy with gentamicin was detected for staphylococci. AP-CECT7121 constitutes an attractive candidate for its use as a natural therapeutic tool for the treatment of infections produced by multi-resistant Staph. aureus and vancomycin-resistant Ent. faecium isolated from humans and animals.