Pathogen-specific production losses in bovine mastitis

Frequency of non-aureus staphylococci and mammaliicocci species isolated from quarter clinical mastitis: A 6-year retrospective study

Non-aureus staphylococci and mammaliicocci (NASM) are the most frequently isolated bacterial group from bovine milk samples. Most studies focus on subclinical mastitis caused by NASM; however, NASM can cause clinical mastitis (CM) as well. We evaluated retrospective data from 6 years (2017-2022) to determine the species and frequency of NASM isolated from quarter bovine CM. The data was comprised of microbiological results from quarter CM samples routinely submitted to Quality Milk Production Services at Cornell University for microbial identification by MALDI-TOF mass spectrometry. A total of 9,909 microbiological results from 410 dairy herds were evaluated. Our results showed that 29 distinct NASM species were identified, with the 8 most prevalent NASM species being Staphylococcus chromogenes, Staphylococcus haemolyticus, Staphylococcus simulans, Staphylococcus epidermidis, Staphylococcus sciuri (now Mammaliicoccus sciuri), Staphylococcus agnetis/Staphylococcus hyicus, Staphylococcus borealis, and Staphylococcus xylosus. The NASM distribution remained similar among seasons, but the frequency of NASM CM cases was higher during the summer. Our results showed different patterns of variations in the isolation frequency over time, depending on the bacterial species: increasing or decreasing trends, cyclic fluctuations, and, except for Staphylococcus borealis, a significant seasonality effect for our study's most prevalent NASM. This study showed that Staphylococcus chromogenes remains the most frequent (43%) NASM species identified from bovine CM, followed by Staphylococcus haemolyticus (18%), and Staphylococcus simulans (12%).

Global losses due to dairy cattle diseases: A comorbidity-adjusted economic analysis

An economic simulation was carried out over 183 milk-producing countries to estimate the global economic impacts of 12 dairy cattle diseases and health conditions: mastitis (subclinical and clinical), lameness, paratuberculosis (Johne's disease), displaced abomasum, dystocia, metritis, milk fever, ovarian cysts, retained placenta, and ketosis (subclinical and clinical). Estimates of disease impacts on milk yield, fertility, and culling were collected from the literature, standardized, meta-analyzed using a variety of methods ranging from simple averaging to random-effects models, and adjusted for comorbidities to prevent overestimation. These comorbidity-adjusted disease impacts were then combined with a set of country-level lactational incidence and/or prevalence estimates, herd characteristics, and price estimates within a series of Monte Carlo simulations that estimated and valued the economic losses due to these diseases. It was estimated that total annual global losses are USD 65 billion (B). Subclinical ketosis, clinical mastitis, and subclinical mastitis were the costliest diseases modeled, resulting in mean annual global losses of approximately USD 18B, USD 13B, and USD 9B, respectively. Estimated global annual losses due to clinical ketosis, displaced abomasum, dystocia, lameness, metritis, milk fever, ovarian cysts, paratuberculosis, and retained placenta were estimated to be USD 0.2B, 0.6B, 0.6B, 6B, 5B, 0.6B, 4B, 4B, and 3B, respectively. Without adjustment for comorbidities, when statistical associations between diseases were disregarded, mean aggregate global losses would have been overestimated by 45%. Although annual losses were greatest in India (USD 12B), the USA (USD 8B), and China (USD 5B), depending on the measure of losses used (losses as a percent of GDP, losses per capita, losses as a percent of gross milk revenue), the relative economic burden of these dairy cattle diseases across countries varied markedly.

Intramammary infections in lactating Jersey cows: Prevalence of microbial organisms and association with milk somatic cell count and persistence of infection

There are limited data available regarding pathogens causing intramammary infections (IMI) in Jersey cows. The objectives of this study were to characterize the prevalence of IMI caused by different microorganisms in lactating Jersey cattle and evaluate the associations among microbes and somatic cell count (SCC) and persistence of IMI. This prospective, observational, longitudinal study included lactating Jersey cows (n = 753) from 4 farms within a 415 km radius of Columbia, Missouri. Quarter foremilk samples were aseptically collected monthly for 3 consecutive months. Microorganisms were identified using aerobic milk culture and MALDI-TOF mass spectrometry. A commercial laboratory measured SCC using flow cytometry. Milk culture results were used to classify single microorganism infections as persistent (same microorganism species identified at first sampling and one other sampling) or nonpersistent infection. Mixed models were built to evaluate the associations between IMI status and SCC natural logarithm (lnSCC), as well as persistence and lnSCC. Overall, staphylococci were the most commonly isolated microorganisms among the 7,370 quarter-level milk samples collected. Median prevalence (using all 3 samplings) of specific microbes varied among farms; however, Staphylococcus chromogenes was a common species found at all farms. The most common microbial species that persisted were Staph. chromogenes, Staphylococcus aureus, Staphylococcus simulans, and Streptococcus uberis. Streptococcus dysgalactiae and Staph. aureus were the IMI associated with the most inflammation based on lnSCC. The small number of herds included in this study with the large variation in herd type limits the generalizability of the data. However, results of this study seem to be similar to those of previous studies in other breeds, suggesting management factors are more important than breed-specific differences when evaluating causes of IMI and associated subclinical mastitis.

Biofilm Formation and Antimicrobial Resistance of Staphylococcus aureus and Streptococcus uberis Isolates from Bovine Mastitis

This study aimed to assess (a) the biofilm producer ability and antimicrobial resistance profiles of Staphylococcus (Staph.) aureus and Streptococcus (Strep.) uberis isolated from cows with clinical mastitis (CM) and subclinical mastitis (SCM), and (b) the association between biofilm producer ability and antimicrobial resistance. We isolated a total of 197 Staph. aureus strains (SCM = 111, CM = 86) and 119 Strep. uberis strains (SCM = 15, CM = 104) from milk samples obtained from 316 cows distributed in 24 dairy herds. Biofilm-forming ability was assessed using the microplate method, while antimicrobial susceptibility was determined using the disk diffusion method against 13 antimicrobials. Among the isolates examined, 57.3% of Staph. aureus and 53.8% of Strep. uberis exhibited the ability to produce biofilm, which was categorized as strong, moderate, or weak. In terms of antimicrobial susceptibility, Staph. aureus isolates displayed resistance to penicillin (92.9%), ampicillin (50.8%), and tetracycline (52.7%). Conversely, Strep. uberis isolates exhibited resistance to penicillin (80.6%), oxacillin (80.6%), and tetracycline (37.8%). However, no significant correlation was found between antimicrobial resistance patterns and biofilm formation ability among the isolates.

Antibacterial efficacy of novel bismuth-silver nanoparticles synthesis on Staphylococcus aureus and Escherichia coli infection models

Introduction

The emergence of multi-drug-resistant bacteria is one of the main concerns in the health sector worldwide. The conventional strategies for treatment and prophylaxis against microbial infections include the use of antibiotics. However, these drugs are failing due to the increasing antimicrobial resistance. The unavailability of effective antibiotics highlights the need to discover effective alternatives to combat bacterial infections. One option is the use of metallic nanoparticles, which are toxic to some microorganisms due to their nanometric size.

Methods

In this study we (1) synthesize and characterize bismuth and silver nanoparticles, (2) evaluate the antibacterial activity of NPs against Staphylococcus aureus and Escherichia coli in several infection models (in vivo models: infected wound and sepsis and in vitro model: mastitis), and we (3) determine the cytotoxic effect on several cell lines representative of the skin tissue.

Results and discussion

We obtained bimetallic nanoparticles of bismuth and silver in a stable aqueous solution from a single reaction by chemical synthesis. These nanoparticles show antibacterial activity on S. aureus and E. coli in vitro without cytotoxic effects on fibroblast, endothelial vascular, and mammary epithelium cell lines. In an infected-wound mice model, antibacterial effect was observed, without effect on in vitro mastitis and sepsis models.

Non-aureus staphylococci and mammaliicocci (NASM): their role in bovine mastitis and One Health

Non-aureus staphylococci (NAS) are gaining importance in mastitis and public health, and some NAS have been reclassified as mammaliicocci (NASM). Bovine milk production has a major influence on the world economy, being an essential source of income for small, medium and large producers, and bovine mastitis caused by NASM can cause an economic impact. Mastitis generates financial losses due to reduced revenue, increased veterinary costs and expenses associated with animal slaughter. However, it is also a public health issue involving animal health and welfare, human health and the ecosystem. Furthermore, it is an increasingly common infection caused by NASM, including antimicrobial-resistant strains. Despite all these adverse effects that NASM can cause, some studies also point to its protective role against mastitis. Therefore, this review article addresses the negative and positive aspects that NASM can cause in bovine mastitis, the virulence of the disease and resistance factors that make it difficult to treat and, through the One Health approach, presents a holistic view of how mastitis caused by NASM can affect both animal and human health at one and the same time.

Outcomes after treatment of nonsevere gram-negative clinical mastitis with ceftiofur hydrochloride for 2 or 5 days compared with negative control

A study was conducted at 3 commercial dairies in California to compare outcomes of treating nonsevere (mild and moderate) gram-negative (GN) clinical mastitis (CM) with intramammary (IMM) ceftiofur HCl (125 mg of ceftiofur HCl per tube) in either 2-d (SP2) or 5-d (SP5) treatment programs compared with nontreatment (CON). In addition, we contrasted results from cases classified as mild and moderate. Four hundred fifteen cases were included in the final dataset, including 135 CON, 133 SP2, and 147 SP5. Milk from quarters with CM was sampled for on-farm culture (OFC) to differentiate gram-positive (GP) and GN bacteria, with results known within 24 h. Those with GN infections were randomly assigned to experimental groups, while those with GP, mixed infections, and contaminated samples did not continue in the study and received standard farm therapy. For cows with GN infections, a sample was submitted for MALDI-TOF assay. Only nonsevere cases were enrolled, and all quarters yielded monocultures of GN species. Clinical scores were obtained 0, 1, 2, 3, 4, 5, 14, 21, and 28 ± 3 d relative to enrollment. Milk samples were collected from quarters 14, 21, and 28 ± 3 d after enrollment, and submitted for routine culture and, when appropriate, submitted to MALDI-TOF evaluation. For many response criteria, there were significant interactions between treatments and CM severity scores at the time of enrollment, with effectiveness of ceftiofur HCl treatment being more beneficial compared with CON as mastitis clinical severity increased. While most treatment responses were significant for animals with mild or moderate GN mastitis, the largest responses were noted among cows with moderate CM cases.

Estimation of epidemiological cut-off values for eight antibiotics used for treatment of bovine mastitis caused by Streptococcus uberis and Streptococcus dysgalactiae subsp. dysgalactiae

Interpretive criteria for antimicrobial susceptibility testing are lacking for most antimicrobials used for bovine streptococcal mastitis. The objectives of this study were to determine (tentative) epidemiological cut-off ((T)ECOFF) values for clinically relevant antibiotics used for treatment of bovine mastitis, and to estimate the proportion of acquired resistance (non-wild-types) in Streptococcus dysgalactiae subsp. dysgalactiae and Streptococcus uberis. A total of 255 S. uberis and 231 S. dysgalactiae subsp. dysgalactiae isolates were obtained in Denmark and Norway from bovine mastitis. The isolates were tested for susceptibility to 10 antibiotics using broth microdilution. In accordance with the European Committee on Antimicrobial Susceptibility Testing (EUCAST) standard operating procedure, additional published MIC distributions were included for the estimation of ECOFFs for cloxacillin, cephapirin, lincomycin and tylosin, and TECOFFs for amoxicillin, benzylpenicillin, cephapirin and oxytetracycline. The proportion of non-wild-type (NWT) isolates for the beta-lactams was significantly higher in the Danish S. uberis (45-55%) compared to the Norwegian isolates (10-13%). For oxytetracycline, the proportion of NWT was significantly higher in the Danish isolates, both for S. uberis (28% vs. 3%) and S. dysgalactiae (22% vs. 0%). A bridging study testing in parallel MICs in a subset of isolates (n = 83) with the CLSI-specified and the EUCAST-specified broths showed excellent correlation between the MICs obtained with the two methods. The new ECOFFs and TECOFFs proposed in this study can be used for surveillance of antimicrobial resistance, and - for antimicrobials licensed for streptococcal bovine mastitis - as surrogate clinical breakpoints for predicting their clinical efficacy for this indication.

Investigating the relationship between fluctuations in daily milk yield as resilience indicators and health traits in Holstein cattle

Disease-related milk losses directly affect dairy herds' profitability and the production efficiency of the dairy industry. Therefore, this study aimed to quantify phenotypic variability in milk fluctuation periods related to diseases and to explore milk fluctuation traits as indicators of disease resilience. By combining high-frequency daily milk yield data with disease records of cows that were treated and recovered from the disease, we estimated milk variability trends within a fixed period around the treatment day of each record for 5 diseases: udder health, reproductive disorders, metabolic disorders, digestive disorders, and hoof health. The average milk yield decreased rapidly from 6 to 8 d before the treatment day for all diseases, with the largest milk reduction observed on the treatment day. Additionally, we assessed the significance of milk fluctuation periods highly related to diseases by defining milk fluctuations as a period of at least 10 consecutive days in which milk yield fell below 90% of the expected milk production values at least once. We defined the development and recovery phases of milk fluctuations using 3,847 milk fluctuation periods related to disease incidences, and estimated genetic parameters of milk fluctuation traits, including milk losses, duration of the fluctuation, variation rate in daily milk yield, and standard deviation of milk deviations for each phase and their genetic correlation with several important traits. In general, the disease-related milk fluctuation periods lasted 21.19 ± 10.36 d with a milk loss of 115.54 ± 92.49 kg per lactation. Compared with the development phase, the recovery phase lasted an average of 3.3 d longer, in which cows produced 11.04 kg less milk and exhibited a slower variation rate in daily milk yield of 0.35 kg/d. There were notable differences in milk fluctuation traits depending on the disease, and greater milk losses were observed when multiple diseases occurred simultaneously. All milk fluctuation traits evaluated were heritable with heritability estimates ranging from 0.01 to 0.10, and moderate to high genetic correlations with milk yield (0.34 to 0.64), milk loss throughout the lactation (0.22 to 0.97), and resilience indicator (0.39 to 0.95). These results indicate that cows with lower milk losses and higher resilience tend to have more stable milk fluctuations, which supports the potential for breeding for more disease-resilient cows based on milk fluctuation traits. Overall, this study confirms the high effect of diseases on milk yield variability and provides insightful information about their relationship with relevant traits in Holstein cattle. Furthermore, this study shows the potential of using high-frequency automatic monitoring of milk yield to assist on breeding practices and health management in dairy cows.

Genetic association between fat-to-protein ratio and traits of economic interest in early lactation Holstein cows in Brazil

The aims of this study were to estimate the genetic parameters for fat-to-protein ratio (F:P) within the first 90 days of lactation and to examine their genetic associations with daily milk yield (MY), somatic cell score (SCS), and calving interval between the first and second calving (IFSC) and between the second and third calving (ISTC) during the first three lactations of Holstein cows. We utilized 200,626 production-related data officially recorded from 77,436 cows milked two or three times a day from 2012 to 2022, sourced from the Holstein Cattle Breeders Association of Paraná State, Brazil. The (co)variance components were estimated using animal models, adopting the restricted maximum likelihood (REML) method with single-trait analysis (for heritability and repeatability) and two-trait analysis (for genetic and phenotypic correlations), per lactation. Regardless of lactation number, heritability estimates were relatively low, ranging from 0.08 ± 0.005 to 0.10 ± 0.003 for F:P; 0.08 ± 0.01 to 0.18 ± 0.005 for MY; 0.04 ± 0.01 to 0.07 ± 0.004 for SCS; and 0.03 ± 0.01 for both IFSC and ISTC. Repeatability estimates within the same lactation were low for F:P (ranging from 0.17 ± 0.002 to 0.19 ± 0.03), high for MY (between 0.50 ± 0.003 and 0.53 ± 0.002), and moderate to high for SCS (between 0.39 ± 0.003 and 0.44 ± 0.004). Genetic correlations between F:P and MY ranged from -0.26 ± 0.03 to -0.15 ± 0.02; F:P and SCS, from -0.06 ± 0.03 to -0.03 ± 0.08; F:P and IFSC, 0.31 ± 0.01; F:P and ISTC, 0.20 ± 0.01; MY and IFSC, 0.24 ± 0.05; and MY and ISTC, 0.13 ± 0.08. The fat-to-protein ratio during early lactation showed low genetic variability, regardless of lactation number. Furthermore, it was genetically correlated with MY, IFSC, and ISTC, although there is an antagonistic and unfavorable correlation between traits that can limit genetic progress.

Bovine neutrophils stimulated with Streptococcus uberis induce neutrophil extracellular traps, and cause cytotoxicity and transcriptional upregulation of inflammatory cytokine genes in bovine mammary epithelial cells

This study aimed to understand the response of neutrophils stimulated by Streptococcus uberis, a major cause of mastitis. It was found that the production of neutrophil extracellular traps (NETs) was induced in milk clots from mastitic milk produced by S. uberis-infected bovine udders. The release of NETs from neutrophils stimulated by S. uberis was investigated. Bovine neutrophils cocultured with S. uberis in vitro released the components of NETs, which contained extracellular DNA and elastase. Bovine mammary epithelial cells (BMECs) incubated in coculture supernatants containing components of NETs, caused cytotoxicity and transcriptional upregulation of inflammatory cytokines, including of interleukin (IL) -1β, tumor necrosis factor (TNF)-α, IL-6, and IL-8, in BMECs. These findings suggest that bovine neutrophils stimulated by S. uberis induce responses that cause exacerbated inflammation, such as NET formation, cytotoxicity against BMECs, and increased production of inflammatory cytokines. Bovine neutrophil responses stimulated by S. uberis could be involved in the progression of S. uberis-induced mastitis.

Antimicrobial activities of Agave fructans against multi-resistant and biofilm-producing Staphylococcus aureus isolated from bovine mastitis

Bovine mastitis is an emerging disease that causes large economic losses. Staphylococcus aureus its main etiological agent, is multi-resistant to antimicrobials and produces biofilm. The objective of this study was to investigate the effect of Agave fructans (AF), a type of prebiotic, on multi-resistant and biofilm-forming isolates of S. aureus. Ten isolates of S. aureus from bovine subclinical mastitis previously characterized as highly resistant to antimicrobials and biofilm formers were used in this study. The growth kinetics of S. aureus in the presence of AF was evaluated by the Baranyi and Roberts microbial growth model using the DMFit program. The antibacterial activity of AF against S. aureus was studied by the well-diffusion method and the effect on biofilm formation by the crystal violet method. All assays were performed in triplicate for each isolate and an ANOVA with Tukey's post hoc was performed considering p < 0.05 as significant. The AF showed a decrease in maximum growth rate (µmax) and OD max levels (Ymax) in all isolates with all concentrations. Also, zones of inhibition were observed due to the effect of all AF concentrations in all isolates in a dose-dependent manner. Interestingly, S. aureus biofilm formation was inhibited by all AF concentrations assessed in this study. More investigations are required to elucidate the mechanisms of action of AF on S. aureus as well as in vivo studies to evaluate its therapeutic efficacy for bovine mastitis.

Antioxidative Sirt1 and the Keap1-Nrf2 Signaling Pathway Impair Inflammation and Positively Regulate Autophagy in Murine Mammary Epithelial Cells or Mammary Glands Infected with Streptococcus uberis

Streptococcus uberis mastitis in cattle infects mammary epithelial cells. Although oxidative responses often remove intracellular microbes, S. uberis survives, but the mechanisms are not well understood. Herein, we aimed to elucidate antioxidative mechanisms during pathogenesis of S. uberis after isolation from clinical bovine mastitis milk samples. S. uberis's in vitro pathomorphology, oxidative stress biological activities, transcription of antioxidative factors, inflammatory response cytokines, autophagosome and autophagy functions were evaluated, and in vivo S. uberis was injected into the fourth mammary gland nipple of each mouse to assess the infectiousness of S. uberis potential molecular mechanisms. The results showed that infection with S. uberis induced early oxidative stress and increased reactive oxygen species (ROS). However, over time, ROS concentrations decreased due to increased antioxidative activity, including total superoxide dismutase (T-SOD) and malondialdehyde (MDA) enzymes, plus transcription of antioxidative factors (Sirt1, Keap1, Nrf2, HO-1). Treatment with a ROS scavenger (N-acetyl cysteine, NAC) before infection with S. uberis reduced antioxidative responses and the inflammatory response, including the cytokines IL-6 and TNF-α, and the formation of the Atg5-LC3II/LC3I autophagosome. Synthesis of antioxidants determined autophagy functions, with Sirt1/Nrf2 activating autophagy in the presence of S. uberis. This study demonstrated the evasive mechanisms of S. uberis in mastitis, including suppressing inflammatory and ROS defenses by stimulating antioxidative pathways.

Novel lncRNA regulatory elements in milk somatic cells of Holstein dairy cows associated with mastitis

Despite regulatory elements such as long non - coding RNAs representing most of the transcriptome, the functional understanding of long non - coding RNAs in relation to major health conditions including bovine mastitis is limited. This study examined the milk somatic cell transcriptome from udder quarters of 6 Holstein dairy cows to identify differentially expressed long non - coding RNAs using RNA - Sequencing. Ninety - four differentially expressed long non - coding RNAs are identified, 5 of which are previously annotated for gene name and length, 11 are annotated for gene name and 78 are novel, having no gene name or length previously annotated. Significant inflammatory response and regulation of immune response pathways (false discovery rate < 0.05) are associated with the differentially expressed long non - coding RNAs. QTL annotation analysis revealed 31 QTL previously annotated in the genomic regions of the 94 differentially expressed long non - coding RNAs, and the majority are associated with milk traits. This research provides a better understanding of long non - coding RNAs regulatory elements in milk somatic cells, which may enhance current breeding strategies for more adaptable or high mastitis resistant cattle.

Pathogen and severity-dependent immune responses in bovine mastitis: highlight the dynamics of differential somatic cell count

Immune responses in bovine clinical mastitis (CM) probably differ depending on the causative pathogen and disease severity. The observational study aimed to investigate whether both factors are associated with the dynamics of immune indicators, including somatic cell score (SCS), white blood cell count (WBC), serum albumin/globulin (A/G) ratio, and differential somatic cell count (DSCC). We collected blood and milk samples 0, 3, 5, 7, 14, and 21 days after CM occurred in 38 cows, and grouped the cases (n=49) by disease severity and pathogen. We analyzed data using a linear mixed model considering the effects of pathogens and severity, calculated estimated-marginal means for indicators at each time point, and compared the means between groups. The dynamics of WBC varied depending on both pathogen and severity. WBC changed drastically in either severe or coliform-caused CM, slightly elevated in streptococcal mastitis, but unchanged in staphylococcal mastitis. This possibly relates to the deficiency in innate immune response toward staphylococci. The A/G ratio also changed depending on severity, as it dropped sharply only in severe CM. We observed a non-linear relationship between DSCC and SCS, possibly due to mammary epithelial cells shedding in milk when CM occurred. When cows recovering from Streptococcus dysgalatiae mastitis, DSCC decreased while SCS remained high, suggesting a healing process requiring more macrophages. Our results demonstrate that both the severity and pathogen are associated with immune responses in CM, providing insights into mastitis pathogenesis.

The current state of phage therapy in livestock and companion animals

In a global context, bacterial diseases caused by pathogenic bacteria have inflicted sustained damage on both humans and animals. Although antibiotics initially appeared to offer an easy treatment for most bacterial infections, the recent rise of multidrug-resistant bacteria, stemming from antibiotic misuse, has prompted regulatory measures to control antibiotic usage. Consequently, various alternatives to antibiotics are being explored, with a particular focus on bacteriophage (phage) therapy for treating bacterial diseases in animals. Animals are broadly categorized into livestock, closely associated with human dietary habits, and companion animals, which have attracted increasing attention. This study highlights phage therapy cases targeting prominent bacterial strains in various animals. In recent years, research on bacteriophages has gained considerable attention, suggesting a promising avenue for developing alternative substances to antibiotics, particularly crucial for addressing challenging bacterial diseases in the future.

Etiology of severe mastitis in French dairy herds

Severe clinical mastitis is not so frequent in dairy cows, but it can have a significant economic impact due to its high mortality rate and adverse effects on milk production. Surveys about the cause of mastitis typically provide overall findings without connecting them to a specific medical condition. There are few studies on the specific etiology of severe mastitis. Only etiological results obtained during field studies are available in France, and the number of mastitic milk samples analyzed is always low. In recent years, veterinary clinics have improved their ability to identify bacteria causing bovine mastitis using a widely used method. This in-clinic milk culture made it possible to better understand the etiology of mastitis according to the symptoms observed. Regarding clinical mastitis, veterinarians treat severe cases differently than less severe ones. Based on data from nineteen veterinary clinics in France and over 2000 severe mastitis cases, the current study revealed that Enterobacteriaceae, particularly Escherichia coli, is the most common cause, isolated on average from 53.9% of milk samples. This information is highly reliable for practitioners to quickly and effectively treat the condition, because early and targeted treatment is crucial to avoid the complication of endotoxic shock.

Association of milk microbiome with bovine mastitis before and after antibiotic therapy

Background and Aim

Mastitis is recognized as the most common disease in cattle and causes economic losses in the dairy industry. A number of opportunistic bacterial taxa have been identified as causative agents for this disease. Conventionally, antibiotics are used to treat mastitis; however, most bacteria are resistant to the majority of antibiotics. This study aimed to use molecular methods to identify milk microbiome patterns characteristic of mastitis that can help in the early diagnosis of this disease and in the development of new treatment strategies.

Materials and Methods

To evaluate the microbiome composition, we performed NGS sequencing of the 16S rRNA gene of the V3 region.

Results

An increase in the abundance of the bacterial genera Hymenobacter and Lachnospiraceae NK4A136 group is associated with the development of subclinical and clinical mastitis in dairy cows. These bacteria can be added to the list of markers used to detect mastitis in cows. Furthermore, a decrease in the abundance of Ralstonia, Lachnospiraceae NK3A20 group, Acetitomaculum, Massilia, and Atopostipes in cows with mastitis may indicate their role in maintaining a healthy milk microbiome. Antibiotics reduced the levels of Streptococcus in milk compared to those in the healthy group and cows before antibiotic treatment. Antibiotic therapy also contributed to an increase in the abundance of beneficial bacteria of the genus Asticcacaulis.

Conclusion

This study expands our understanding of the association between milk microbiota and mastitis.

Metataxonomic analysis of milk microbiota in the bovine subclinical mastitis

Subclinical mastitis is one of the most widespread diseases affecting dairy herds with detrimental effects on animal health, milk productivity, and quality. Despite its multifactorial nature, the presence of pathogenic bacteria is regarded one of the main drivers of subclinical mastitis, causing a disruption of the homeostasis of the bovine milk microbial community. However, bovine milk microbiota alterations associated with subclinical mastitis still represents a largely unexplored research area. Therefore, the species-level milk microbiota of a total of 75 milk samples, collected from both healthy and subclinical mastitis-affected cows from two different stables, was deeply profiled through an ITS, rather than a traditional, and less informative, 16S rRNA gene microbial profiling. Surprisingly, the present pilot study not only revealed that subclinical mastitis is characterized by a reduced biodiversity of the bovine milk microbiota, but also that this disease does not induce standard alterations of the milk microbial community across stables. In addition, a flow cytometry-based total bacterial cell enumeration highlighted that subclinical mastitis is accompanied by a significant increment in the number of milk microbial cells. Furthermore, the combination of the metagenomic and flow cytometry approaches allowed to identify different potential microbial marker strictly correlated with subclinical mastitis across stables.

Indirect Sensing of Subclinical Intramammary Infections in Dairy Herds with a Milking Robot

This study determined the impact of subclinical intramammary infections (IMIs), such as the major and minor udder pathogens (MaPs and MiPs), on the somatic cell count (SCC) in cow milk and investigated the possibilities of indirect sensing of the udder pathogens using the mastitis detection index (MDi) (DeLaval, Tumba, Sweden). The MDi incorporates quarter-level milk electrical conductivity, blood in milk, and milking interval. The case group (n = 21; MDi ≥ 1.4) was compared with the control group (n = 24; MDi < 1.4) for the presence of IMIs. The microbiological investigation of udder quarter foremilk samples was performed two times with an interval of 10 to 14 days. The case and control groups differed in terms of the occurrence of MaPs and MiPs in milk. During the continuous subclinical IMI and the episodic MaP infection, a higher SCC was detected compared with the episodic MiP infection or quarters without IMI. The novel finding of this study was that by using the milk quality sensor for the sensing of subclinical IMIs, there was an indication for the successful detection of episodic MaPs. However, the sensing of the continuous subclinical IMIs was not possible in the current study and still needs to be investigated.

Effects of oral administration of lipopolysaccharide derived from Pantoea agglomerans on innate immunity of mammary glands in dairy goats

This study aimed to evaluate the effect of orally administered lipopolysaccharide (LPS) derived from Pantoea agglomerans (LPSpa) on innate immune functions, including the concentrations of antimicrobial components and interleukin (IL)-10 in goat milk, for the prevention of goat mastitis. Twelve Tokara goats were divided into two groups of six goats. Goats in the LPSpa and control groups were orally administrated with 0.4 g/kg dextrin with or without 0.02 mg/kg LPSpa for 7 days (day 0-6), respectively. After treatment (i.e., day 7), 1 μg LPS from Escherichia coli O111 (LPSec) was infused into one side of the udder in both groups to induce mastitis. Milk from all sides of the udder, saliva, and feces were collected on days 0 and 7. After LPSec infusion into the udders, milk was collected from the infused side of the udder on days 8, 10, and 12. Milk yields and somatic cell counts were recorded during the examination period. The concentrations of immunoglobulin (Ig) A in saliva, feces, and milk and the concentrations of lactoferrin, goat β defensin-1 (GBD1), S100A7, and IL-10 in milk were measured. After LPSpa oral administration, the concentrations of GBD-1 and IL-10 in the milk of the LPSpa group were significantly higher on day 7 than those in the control group, and the concentration of IgA in the feces tended to be higher than that in the control group. After LPSec intramammary infusion, S100A7 concentration on day 12 was significantly lower in the LPSpa group than in the control group. These findings suggest that the oral administration of LPSpa may prevent mastitis by increasing the concentration of GBD1 in milk.

The combination of vaccines and adjuvants to prevent the occurrence of high incidence of infectious diseases in bovine

As the global population grows, the demand for beef and dairy products is also increasing. The cattle industry is facing tremendous pressures and challenges. The expanding cattle industry has led to an increased risk of disease in cattle. These diseases not only cause economic losses but also pose threats to public health and safety. Hence, ensuring the health of cattle is crucial. Vaccination is one of the most economical and effective methods of preventing bovine infectious diseases. However, there are fewer comprehensive reviews of bovine vaccines available. In addition, the variable nature of bovine infectious diseases will result in weakened or even ineffective immune protection from existing vaccines. This shows that it is crucial to improve overall awareness of bovine vaccines. Adjuvants, which are crucial constituents of vaccines, have a significant role in enhancing vaccine response. This review aims to present the latest advances in bovine vaccines mainly including types of bovine vaccines, current status of development of commonly used vaccines, and vaccine adjuvants. In addition, this review highlights the main challenges and outstanding problems of bovine vaccines and adjuvants in the field of research and applications. This review provides a theoretical and practical basis for the eradication of global bovine infectious diseases.

Bovine mastitis, a worldwide impact disease: Prevalence, antimicrobial resistance, and viable alternative approaches

Bovine mastitis is globally considered one of the most important diseases within dairy herds, mainly due to the associated economic losses. The most prevalent etiology are bacteria, classified into contagious and environmental, with Staphylococcus aureus, Streptococcus agalactiae, Streptococcus uberis, Escherichia coli and Klebsiella pneumoniae being the most common pathogens associated with mastitis cases. To date these pathogens are resistant to the most common active ingredients used for mastitis treatment. According to recent studies resistance to new antimicrobials has increased, which is why developing of alternative treatments is imperative. Therefore the present review aims to summarize the reports about bovine mastitis along 10 years, emphasizing bacterial etiology, its epidemiology, and the current situation of antimicrobial resistance, as well as the development of alternative treatments for this pathology. Analyzed data showed that the prevalence of major pathogens associated with bovine mastitis varied according to geographical region. Moreover, these pathogens are classified as multidrug-resistant, since the effectiveness of antimicrobials on them has decreased. To date, several studies have focused on the research of alternative treatments, among them vegetal extracts, essential oils, or peptides. Some other works have reported the application of nanotechnology and polymers against bacteria associated with bovine mastitis. Results demonstrated that these alternatives may be effective on bacteria associated with bovine mastitis.

Non-aureus staphylococci and mammaliicocci as a cause of mastitis in domestic ruminants: current knowledge, advances, biomedical applications, and future perspectives - a systematic review

Non-aureus staphylococci and mammaliicocci (NASM) are one of the most common causes of subclinical mastitis in dairy animals and the extent of damage by intramammary infections (IMI) caused by NASM is still under debate. The different effects of NASM on the mammary gland may be associated with differences between bacterial species. NASM are normal and abundant colonizers of humans and animals and become pathogenic only in certain situations. The veterinary interest in NASM has been intense for the last 25 years, due to the strongly increasing rate of opportunistic infections. Therefore, the objective of this review is to provide a general background of the NASM as a cause of mastitis and the most recent advances that exist to prevent and fight the biofilm formation of this group of bacteria, introduce new biomedical applications that could be used in dairy herds to reduce the risk of chronic and recurrent infections, potentially responsible for economic losses due to reduced milk production and quality. Effective treatment of biofilm infection requires a dual approach through a combination of antibiofilm and antimicrobial agents. Even though research on the development of biofilms is mainly focused on human medicine, this technology must be developed at the same time in veterinary medicine, especially in the dairy industry where IMI are extremely common.

The Antimicrobial Applications of Nanoparticles in Veterinary Medicine: A Comprehensive Review

Nanoparticles (NPs) are nanoscaled particles sized from 1-100 nm, which can be composed of inorganic or organic compounds. NPs have distinctive morphology, size, structure, and surface features, which give them specific properties. These particular attributes make them interesting for biological and medical applications. Due to these characteristics, researchers are studying the possible aptness of numerous nanoparticles in veterinary medicine, such as the capacity to act as a drug delivery system. The use of these NPs as a possible bactericidal or bacteriostatic medication has been studied against different bacteria, especially multiresistant strains and the ones that cause mastitis disease. The antibiofilm property of these nanostructures has also already been proved. The antiviral activity has also been shown for some important viral animal diseases; the antifungal activity had been demonstrated against both pathogenic and mycotoxigenic species. Therefore, this review aimed to elucidate the main clinical and preventive veterinary applications of inorganic and organic nanoparticles.

The Economic Evaluation of Mastitis Control Strategies in Holstein-Friesian Dairy Herds

The economic evaluation of mastitis control is challenging. The objective of this study was to perform the economic evaluation of mastitis control, under different intervention scenarios, quantifying the total cost of mastitis caused by S. aureus in Holstein cows in Argentina. A model was set for a dairy herd of Holstein cows endemically infected with S. aureus. A basic mastitis control plan including proper milking procedures, milking machine test, dry cow therapy, and treatment for clinical mastitis, was compared against other more complex and costly interventions, such as segregation and culling of chronically infected cows. Sensitivity analysis was performed by modifying the intramammary infection transition probabilities, economic parameters, and efficacy of treatment strategies. The basic mastitis control plan showed a median total cost of USD88.6/cow per year, which was close to the infected cows culling scenarios outputs. However, the segregation scenario was the most efficient, in which the total cost was reduced by about 50%. Such cost was more sensitive to probabilities and efficacy than the economic parameters. The model is flexible and can be customized by producers and veterinarians according to different control and herd settings.

Reservoirs of Staphylococcus spp. and Streptococcus spp. Associated with Intramammary Infections of Dairy Cows

To design cost-effective prevention strategies against mastitis in dairy cow farms, knowledge about infection pathways of causative pathogens is necessary. Therefore, we investigated the reservoirs of bacterial strains causing intramammary infections in one dairy cow herd. Quarter foremilk samples (n = 8056) and milking- and housing-related samples (n = 251; from drinking troughs, bedding material, walking areas, cow brushes, fly traps, milking liners, and milker gloves), were collected and examined using culture-based methods. Species were identified with MALDI-TOF MS, and selected Staphylococcus and Streptococcus spp. typed with randomly amplified polymorphic DNA-PCR. Staphylococci were isolated from all and streptococci from most investigated locations. However, only for Staphylococcus aureus, matching strain types (n = 2) were isolated from milk and milking-related samples (milking liners and milker gloves). Staphylococcus epidermidis and Staphylococcus haemolyticus showed a large genetic diversity without any matches of strain types from milk and other samples. Streptococcus uberis was the only Streptococcus spp. isolated from milk and milking- or housing-related samples. However, no matching strains were found. This study underlines the importance of measures preventing the spread of Staphylococcus aureus between quarters during milking.

Strain diversity and infection durations of Staphylococcus spp. and Streptococcus spp. causing intramammary infections in dairy cows

To effectively prevent and control bovine mastitis, farmers and their advisors need to take infection pathways and durations into account. Still, studies exploring both aspects through molecular epidemiology with sampling of entire dairy cow herds over longer periods are scarce. Therefore, quarter foremilk samples were collected at 14-d intervals from all lactating dairy cows (n = 263) over 18 wk in one commercial dairy herd. Quarters were considered infected with Staphylococcus aureus, Streptococcus uberis, or Streptococcus dysgalactiae when ≥100 cfu/mL of the respective pathogen was detected, or with Staphylococcus epidermidis or Staphylococcus haemolyticus when ≥500 cfu/mL of the respective pathogen was detected. All isolates of the mentioned species underwent randomly amplified polymorphic DNA (RAPD)-PCR to explore strain diversity and to distinguish ongoing from new infections. Survival analysis was used to estimate infection durations. Five different strains of Staph. aureus were isolated, and the most prevalent strain caused more than 80% of all Staph. aureus infections (n = 46). In contrast, 46 Staph. epidermidis and 69 Staph. haemolyticus strains were isolated, and none of these caused infections in more than 2 different quarters. The 3 most dominant strains of Strep. dysgalactiae (7 strains) and Strep. uberis (18 strains) caused 81% of 33 and 49% of 37 infections in total, respectively. The estimated median infection duration for Staph. aureus was 80 d, and that for Staph. epidermidis and Staph. haemolyticus was 28 and 22 d, respectively. The probability of remaining infected with Strep. dysgalactiae or Strep. uberis for more than 84 and 70 d was 58.7 and 53.5%, respectively. Staphylococcus epidermidis and Staph. haemolyticus were not transmitted contagiously and the average infection durations were short, which brings into question whether antimicrobial treatment of intramammary infections with these organisms is justified. In contrast, infections with the other 3 pathogens lasted longer and largely originated from contagious transmission.

Association between Mastitis Occurrence in Dairy Cows and Bedding Characteristics of Compost-Bedded Pack Barns

Compost-bedded pack barns (CB) are receiving increasing attention as a housing system that can potentially improve the welfare of dairy cows. This study characterized the frequency and profile of pathogens isolated from clinical (CM) and subclinical (SCM) mastitis in dairy cows housed in CB. It evaluated the association between mastitis occurrence and bedding characteristics in CB systems. Over six months, seven dairy herds were visited monthly for milk and bedding sample collections. Milk samples from mastitis cases were submitted to microbiological identification by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF MS). Bedding samples were submitted to physical-chemical (pH, organic matter, moisture, and carbon to nitrogen ratio) and microbiological counting (total bacterial counts, coliforms, streptococci, and staphylococci) analyses. Regression analysis was used to determine the association between mastitis occurrence and CB characteristics. Our results showed that Escherichia coli and environmental streptococci were the most frequently isolated pathogens from CM cases, while Staphylococcus chromogenes and contagious pathogens (Staphylococcus aureus and Streptococcus agalactiae) were the most commonly isolated from SCM cases. Bedding moisture content was positively associated with the incidence of CM. The bedding carbon to nitrogen ratio was negatively associated with the incidence of SCM, and the bedding total bacteria counts tended to be associated with the incidence of SCM. Bedding counts of coliforms positively associated with the prevalence of SCM. Our results can support decision-makers in the dairy industry seeking strategies for bedding management and mastitis control.

SERS-based immunosensor for E. coli contaminants detection in milk using silver-coated nanoporous silicon substrates

The dairy sector is frequently affected by contagious and environmental factors that spread between animals by numerous means and induce the inflammatory disease of bovine mastitis (BM). Herein, silver decorated porous silicon (Ag-pSi) SERS platform was designed for rapid and reliable Escherichia coli (predominant BM pathogen) detection in various milk origins. The inherent surface void and pore morphology were physically optimized to augment the SERS effect using 4-aminothiphenol (4ATP) while achieving an enhancement factor >4.6 × 10⁷. An indirect immunoassay evaluated the residual unreacted antibodies using an optimized 4ATP/Ag-pSi SERS platform modified with secondary antibodies. Under optimized conditions, the porous substrate offered high sensitivity toward target bacteria detection of 3 CFU mL^-1 and linear response of 10¹-10⁵ CFU mL^-1. Moreover, the selectivity and specificity of the designed sensing platform were cross-validated against other interfering bacteria without compromising its performance efficiencies. Finally, the applicability of the developed system for real-life conditions was elucidated in different milk samples (bovine, goat, sheep) with recovery values of 78-115% compared to the conventional culture technique. Considering the complex media analysis, the miniaturized SERS platform is highly reliable, rapid and accurate that could be applicable for routine on-site analysis of various emerging pathogens relevant to BM management.

Acute Stress-Induced Changes in the Lipid Composition of Cow's Milk in Healthy and Pathological Animals

Producers of milk and dairy products have been faced with the challenge of responding to European society's demand for guaranteed animal welfare production. In recent years, measures have been taken to improve animal welfare conditions on farms and evaluation systems have been developed to certify them, such as the Welfare Quality^® protocol. Among the markers used for this purpose, acute phase proteins stand out, with haptoglobin being one of the most relevant. However, the diagnostic power of these tools is limited and more sensitive and specific technologies are required to monitor animal health status. Different factors such as diet, stress, and diseases modify the metabolism of the animals, altering the composition of the milk in terms of oligosaccharides, proteins, and lipids. Thus, in order to study oxidative-stress-associated lipids, a collection of well-characterized milk samples, both by veterinary diagnosis and by content of the acute stress biomarker haptoglobin, was analyzed by mass spectrometry and artificial intelligence. Two lipid species (sphingomyelin and phosphatidylcholine) were identified as potential biomarkers of health status in dairy cows. Both lipids allow for the discrimination of milk from sick animals and also milk from those with stress. Moreover, lipidomics revealed specific lipid profiles depending on the origin of the samples and the degree of freedom of the animals on the farm. These data provide evidence for specific lipid changes in stressed animals and open up the possibility that haptoglobin could also affect lipid metabolism in cow's milk.

The effect of antibiotic versus no treatment at dry-off on udder health and milk yield in subsequent lactation: A retrospective analysis of Austrian health recording data from dairy herds

Bovine mastitis is the most commonly diagnosed disease of dairy cows worldwide and causes extensive economic losses to milk producers. Intramammary infection status before dry-off plays a decisive role with respect to udder health and milk yield in the subsequent lactation. The aim of this study was to compare the effect of antibiotic dry cow therapy (DCT) versus no treatment at dry-off on milk yield, somatic cell count (SCC), inflammation of the mammary gland (IMG), and the incidence of clinical mastitis in the subsequent lactation. Dairy herd data from 251 Austrian dairy farms were recorded over an observation period of 12 mo and subsequently analyzed. The data set included 5,018 dairy cows: 2,078 were treated with antibiotics (abDCT group) and 2,940 were not treated (noDCT group) at dry-off. The abDCT group was subdivided, based on the antimicrobial active substances used for drying off, into 4 different groups (penicillins, cloxacillin, cephalosporins, and rifaximin). Based on bacteriological culture results, infections were grouped into those caused by major, minor, and other pathogens. Additionally, the IMG was defined via SCC from milk recording data using a cutoff of 200,000 cells/mL before drying off and after calving. The incidence of clinical mastitis cases within 30 and 90 d in milk was calculated using veterinary diagnosis data. To investigate the effect of different dry cow therapies on the following parameters: milk yield, SCC, and diagnosed clinical mastitis cases, different linear mixed models were constructed. Overall, the abDCT group was determined to have a significantly higher milk yield over 305 d in milk in the subsequent lactation (increase of 6.18%), compared with the noDCT group (increase of 4.29%). Both groups (abDCT and noDCT) demonstrated a decrease in the first SCC after calving compared with the SCC before dry-off, although the treated cows had a significantly higher reduction. Regarding the different antibiotic groups, with exception of the rifaximin treated cows, all antibiotic groups showed a significant difference from not treated cows with respect to SCC. Additionally, we were able to demonstrate that cows with IMG before dry-off had a 2.073 times higher chance of an increased SCC (>200,000 cells/mL) after calving. With respect to the veterinary diagnosis data, neither the IMG before drying off nor the type of DCT had a significant influence on the probability of developing clinical mastitis within 30 or 90 d in milk. Only a small number of treatments was accompanied with a bacteriological examination before drying off. However, the existing data in this study indicates that the intramammary infection status before dry-off in combination with different dry cow treatments influences udder health and milk yield after calving. Nevertheless, further studies with larger data sets of bacteriological examinations are necessary to enable a more in-depth investigation into the effects of different antibiotic substances used for DCT.

Anti-inflammatory effects of chlorogenic acid from Taraxacum officinale on LTA-stimulated bovine mammary epithelial cells via the TLR2/NF-κB pathway

Mastitis is an inflammatory disease caused by microbial infection. Chlorogenic acid (CGA), one of the major phenolic acids in Taraxacum officinale, has natural antioxidant and anti-inflammatory properties in various cell types; however, the effects of CGA on Lipoteichoic acid (LTA)-induced bovine mammary epithelial cells (BMECs) have not been investigated. In this study, the CGA content in T. officinale was determined by High-performance liquid chromatography (HPLC). BMECs were infected with LTA to induce the mastitis model. Different concentrations of CGA were administered after establishing the LTA infection. The results showed that the T. officinale contained CGA 1.36 mg/g. CGA significantly reduced the pro-inflammatory gene and protein expression of TNF-α, IL-6, and IL-1β. In addition, CGA downregulated the NO, TLR2, and NF-κB signaling pathways in LTA-infected bovine mammary epithelial cells. Our results indicate that CGA reduced the expression of TNF-α, IL-6, IL-1β, and TLR2 by inhibiting the phosphorylation of proteins in the NF-κB signaling pathways in a dose-dependent manner. This finding suggests that CGA may be a potential agent for the treatment of mastitis in dairy cows.

Evaluation of mammary gland health in dairy cows treated by pegylated granulocyte colony-stimulating factor

The study aimed to determine the effect of the treatment by pegbovigrastim on the health of the mammary gland in dairy cows. Experimental animals were successively treated with 15 mg of pegylated bovine granulocyte colony-stimulating factor (bG-CSF, pegbovigrastim, PEG, Imrestor, Elanco) 10 ± 3 days before expected parturition and 1 day after actual parturition. Cows in the control group remained without treatment. The occurrence of clinical and subclinical mastitis in dairy cows during the first three months postpartum, and bacteriological findings in milk and milk yield were evaluated after preventive pegbovigrastim treatment. The influence of pegbovigrastim, as an additional treatment of mastitis caused by Streptococcus uberis in dairy cows on the standard course of treatment, was evaluated. The average number of antimicrobial (AML) interventions necessary for healing, the proportion of cows with 1, 2, 3 and more AML interventions, milk somatic cell count before treatment, 1 and 2 months after treatment and average milk withdrawal time were evaluated between groups. The results of the study did not find positive effects of pegbovigrastim on any evaluated variables.

Chitosan can improve antimicrobial treatment independently of bacterial lifestyle, biofilm biomass intensity and antibiotic resistance pattern in non-aureus staphylococci (NAS) isolated from bovine clinical mastitis

Bovine mastitis is the most frequent and costly disease that affects dairy cattle. Non-aureus staphylococci (NAS) are currently one of the main pathogens associated with difficult-to-treat intramammary infections. Biofilm is an important virulence factor that can protect bacteria against antimicrobial treatment and prevent their recognition by the host's immune system. Previously, we found that chronic mastitis isolates which were refractory to antibiotic therapy developed strong biofilm biomass. Now, we evaluated the influence of biofilm biomass intensity on the antibiotic resistance pattern in strong and weak biofilm-forming NAS isolates from clinical mastitis. We also assessed the effect of cloxacillin (Clx) and chitosan (Ch), either alone or in combination, on NAS isolates with different lifestyles and abilities to form biofilm. The antibiotic resistance pattern was not the same in strong and weak biofilm producers, and there was a significant association (p ≤ 0.01) between biofilm biomass intensity and antibiotic resistance. Bacterial viability assays showed that a similar antibiotic concentration was effective at killing both groups when they grew planktonically. In contrast, within biofilm the concentrations needed to eliminate strong producers were 16 to 128 times those needed for weak producers, and more than 1,000 times those required for planktonic cultures. Moreover, Ch alone or combined with Clx had significant antimicrobial activity, and represented an improvement over the activity of the antibiotic on its own, independently of the bacterial lifestyle, the biofilm biomass intensity or the antibiotic resistance pattern. In conclusion, the degree of protection conferred by biofilm against antibiotics appears to be associated with the intensity of its biomass, but treatment with Ch might be able to help counteract it. These findings suggest that bacterial biomass should be considered when designing new antimicrobial therapies aimed at reducing antibiotic concentrations while improving cure rates.

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.

Isolation and evaluation of the efficacy of bacteriophages against multidrug-resistant (MDR), methicillin-resistant (MRSA) and biofilm-producing strains of Staphylococcus aureus recovered from bovine mastitis

Background

Staphylococcus aureus (S. aureus) is one of the major causes of bovine mastitis with significant economic losses around the worldwide. The emergence of multidrug-resistant (MDR), methicillin-resistant (MRSA) and biofilm-producing strains of S. aureus challenges the treatment strategies based on the antibiotic application. Today, alternative or combinational treatment options such as bacteriophage application has received much attention. The goal of the present study was to focus on isolation and evaluation of the efficacy of bacteriophages with specific lytic activity against S. aureus strains with low cure rates (MDR, MRSA and biofilm-producing strains).

Results

In the present study, two phages belonging to the Podoviridae family with specific lytic activity against S. aureus were isolated from the sewage of dairy farms and designated as Staphylococcus phage M8 and Staphylococcus phage B4. Latent period and burst size for Staphylococcus phage M8 (70 min, 72 PFU/cell) and Staphylococcus phage B4 (30 min, 447 PFU/cell) were also defined. Our results revealed the susceptibility of MDR (4/20; 20%), MRSA (4/13; 30.8%) and biofilm-producing (1/10; 10%) strains to Staphylococcus phage M8. Moreover, one biofilm-producing strain (1/10; 10%) was susceptible to Staphylococcus phage B4. Furthermore, both phages kept their lytic activity in milk. They reduced the S. aureus population by about 3 logs in cultured milk after 8 h of incubation.

Conclusion

In conclusion, it seems that both phages had the potential to serve as biological control agents alone or in combination with other agents such as antibiotics against infections induced by S. aureus. However, further studies are needed to investigate the efficacy of these phages in vivo.

Characterization of Staphylococcus aureus Isolates from Bovine Mastitis and Bulk Tank Milk: First Isolation of Methicillin-Susceptible Staphylococcus aureus in Japan

Staphylococcus aureus is one of the most important pathogens in humans as well as in livestock. Particularly, bovine mastitis caused by S. aureus is a serious issue in dairy farms due to disease recurrence. Here, cases of S. aureus-mediated intramammary infection occurring in the Miyagi Prefecture in Japan were monitored from May 2015 to August 2019; a total of 59 strains (49 from bovine milk and 10 from bulk milk) were obtained from 15 dairy farms and analyzed via sequence-based typing methods and antibiotic susceptibility tests. Two pairs of isolates were determined as recurrence cases from the same cows in distinct farms. The sequence type (ST), spa type, and coa type of each pair were the same: one pair showed ST705, t529, and VIb and the other showed ST352, t267, and VIc. In addition, the possession of toxin genes analyzed of each pair was exactly the same. Furthermore, seven oxacillin-sensitive clonal complex 398 isolates were obtained from a single farm. This is the first confirmed case of a Methicillin-Sensitive SA (MSSA) ST398 strain isolated from mastitis-containing cows in Japan. Our findings suggest that nationwide surveillance of the distribution of ST398 strains in dairy farms is important for managing human and animal health.

Mastitis: What It Is, Current Diagnostics, and the Potential of Metabolomics to Identify New Predictive Biomarkers

Periparturient diseases continue to be the greatest challenge to both farmers and dairy cows. They are associated with a decrease in productivity, lower profitability, and a negative impact on cows’ health as well as public health. This review article discusses the pathophysiology and diagnostic opportunities of mastitis, the most common disease of dairy cows. To better understand the disease, we dive deep into the causative agents, traditional paradigms, and the use of new technologies for diagnosis, treatment, and prevention of mastitis. This paper takes a systems biology approach by highlighting the relationship of mastitis with other diseases and introduces the use of omics sciences, specifically metabolomics and its analytical techniques. Concluding, this review is backed up by multiple studies that show how earlier identification of mastitis through predictive biomarkers can benefit the dairy industry and improve the overall animal health.

Bta-miR-223 Targeting the RHOB Gene in Dairy Cows Attenuates LPS-Induced Inflammatory Responses in Mammary Epithelial Cells

Bovine mammary epithelial cells (bMECs) are part of the first line of defense against pathogens. In recent studies, bta-miR-223 has been reported to activate congenital and innate immunity against inflammatory damage during the pathogenesis of mastitis in dairy cows. The purpose of this study was to identify the regulatory mechanism of bta-miR-223 and its downstream target genes in inflammatory bMECs. A double luciferase reporter gene assay demonstrated that ras homolog family member B (RHOB) was the target gene of bta-miR-223. To further elucidate the role of bta-miR-223 in congenital immune responses, bta-miR-223 mimics (mimic/inhibitor) were transfected into bMECs stimulated with lipopolysaccharide (LPS), which activates the Toll-like receptor 4/nuclear factor-κB (TLR4/NF-κB) signaling pathway. Real-time quantitative PCR (qPCR) and Western blot were used to detect the expression of related genes and proteins, and enzyme-linked immunosorbent assay (ELISA) was used to detect secreted inflammatory factors. Results showed that bta-miR-223 expression during inflammation in bMECs reduced the secretion of inflammatory factors by targeting RHOB and deactivation of NF-κB gene activity. Silencing RHOB inhibited LPS-induced inflammatory response in bMECs. Overall, bta-miR-223 attenuated LPS-induced inflammatory response, and acted as a negative feedback regulator via targeting RHOB, providing a novel avenue for mastitis treatment.

Antibacterial effects of oak bark (Quercus robur) and heather herb (Calluna vulgaris L.) extracts against the causative bacteria of bovine mastitis

Background and Aim:

Bovine mastitis has a negative impact on animals, and improper antibiotic use has caused an increase in bacterial resistance. Therefore, medicinal plants could serve as an alternative treatment for this condition. Polyphenols have potential as antibiotic agents. Oak bark has long been used as a medicine and has shown antibacterial effects. Moreover, research on heather plant demonstrated that it has antibacterial properties. This study aimed to assess the antibacterial effects of oak (Quercus robur) bark and heather (Calluna vulgaris L.) herb extracts against common bovine mastitis pathogens.

Materials and Methods:

Dried oak bark and heather herb were used to prepare extracts using 30%, 50%, and 70% ethanol and acetone as solvents. Their polyphenol content was determined using the Folin–Ciocalteu method. Bovine mastitis-inducing clinical isolates of Escherichia coli, Streptococcus agalactiae, Streptococcus uberis, Serratia liquefaciens, Staphylococcus aureus, and reference cultures of S. aureus and E. coli were used for antibacterial tests. All extracts were screened through a disk diffusion test to ascertain their antibacterial effects, and the minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined for the most effective extracts.

Results:

Oak bark extracts had variable antibacterial effects against S. aureus and Streptococcus strains, but no statistically significant difference was observed in activity against E. coli. The disk diffusion test showed that the oak bark extracts obtained using acetone and ethanol at 30% yielded the best results. However, the 70% acetone oak extract alone affected all types of bacteria. Further antibacterial tests of 70% acetone and 30% ethanol oak extracts revealed that the lowest MIC and MBC scores were against S. aureus strains and E. coli reference cultures. Conversely, the heather herb extracts exhibited broader activity against all types of bacteria, although better results were observed against Gram-positive bacteria. There was also a negative correlation between solvent concentration and antibacterial effect (p < 0.05, r = −0.507). The highest inhibition zone scores and broadest spectrum were observed in samples prepared in 30% ethanol. There was no statistically significant correlation between the phenolic content of plants and their antibacterial effects.

Conclusion:

Oak bark and heather extracts could be used as potential antibacterial agents against bovine mastitis pathogens.

Characterization of rumen, fecal, and milk microbiota in lactating dairy cows

Targeting the gastrointestinal microbiome for improvement of feed efficiency and reduction of production costs is a potential promising strategy. However little progress has been made in manipulation of the gut microbiomes in dairy cattle to improve milk yield and milk quality. Even less understood is the milk microbiome. Understanding the milk microbiome may provide insight into how the microbiota correlate with milk yield and milk quality. The objective of this study was to characterize similarities between rumen, fecal, and milk microbiota simultaneously, and to investigate associations between microbiota, milk somatic cell count (SCC), and milk yield. A total of 51 mid-lactation, multiparous Holstein dairy cattle were chosen for sampling of ruminal, fecal, and milk contents that were processed for microbial DNA extraction and sequencing. Cows were categorized based on low, medium, and high SCC; as well as low, medium, and high milk yield. Beta diversity indicated that ruminal, fecal, and milk populations were distinct (p &lt; 0.001). Additionally, the Shannon index demonstrated that ruminal microbial populations were more diverse (p &lt; 0.05) than were fecal and milk populations, and milk microbiota was the least diverse of all sample types (p &lt; 0.001). While diversity indices were not linked (p &gt; 0.1) with milk yield, milk microbial populations from cows with low SCC demonstrated a more evenly distributed microbiome in comparison to cows with high SCC values (p = 0.053). These data demonstrate the complexity of host microbiomes both in the gut and mammary gland. Further, we conclude that there is a significant relationship between mammary health (i.e., SCC) and the milk microbiome. Whether this microbiome could be utilized in efforts to protect the mammary gland remains unclear, but should be explored in future studies.

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.

Protective effects of chlorogenic acid on inflammatory responses induced by Staphylococcus aureus and milk protein synthesis in bovine mammary epithelial cells

Staphylococcus aureus (S. aureus) is a major mastitis-causing pathogen in dairy cows. Dairy cows with mastitis suffer from a decrease in milk yield and protein content. Chlorogenic acid (CGA) is a natural product with anti-inflammatory effects. In this study, we examined the function and mechanism of CGA with regard to its anti-inflammatory effects and evaluated its protective function in milk protein synthesis in bovine mammary epithelial cells (BMECs). BMECs were cultured with and without infection by S. aureus and CGA, and extracellular inflammatory cytokines and amino acids in the medium and milk proteins were determined by ELISA. The function of IL-10RA in anti-inflammatory processes and of SF-1 in milk protein synthesis was assessed by gene silencing. The activity of mTORC1, NF-κB, and STAT5 was examined by western blot. S. aureus caused intracellular infection and upregulated TNF-α, IL-1β, IL-6, and IL-8, whereas uptake of amino acids and milk protein synthesis were suppressed. CGA mitigated the S. aureus-induced inflammatory response and milk protein synthesis in vitro and in vivo. CGA alleviated S. aureus-induced inhibition of mTORC1 and STAT5 and upregulated IL-10 and IL-10RA. In addition, SF-1 was predicted to be a transcription factor of the milk protein-encoding genes α-LA, β-LG, and CSN2. S. aureus downregulated SF-1 and CGA reversed the decline in milk protein synthesis due to SF-1 knockdown. Thus, CGA mitigates the inflammatory response that is induced by S. aureus and protects the uptake of amino acids and milk protein synthesis in BMECs.

Quantifying current and future raw milk losses due to bovine mastitis on European dairy farms under climate change scenarios

Bovine mastitis is an infectious disease that causes udder inflammation and is responsible for raw milk losses across European dairy farms. It is associated with reduced cow milk yield and contributes to elevated Somatic Cell Count (SCC) in raw milk. Staphylococcus aureus is one of the most prevalent mastitis pathogens that cause subclinical and clinical mastitis and can be present as a coloniser bacterium in cows. Climate change and geographical variability may influence the prevalence of this pathogen. Thus, this research aimed to predict the raw milk losses in three major dairy-producing regions across Europe (i.e. Mediterranean, Atlantic and Continental) under climate change scenarios. An exposure assessment model and a stepwise probabilistic model were developed to predict potential cow milk yield reduction, S. aureus and SCC concentrations in the bulk tank milk at dairy farms. Baseline (i.e. present) and future climate change scenarios were defined, and the resultant concentrations of SCC and S. aureus were compared to the actual European regulatory limits. Across the three regions, raw milk losses ranged from 1.06% to 2.15% in the baseline. However, they increased up to 3.21% in the climate change scenarios when no on-farm improvements were considered. Regarding geographical variation, the highest potential milk losses were reported for the Mediterranean and the lowest for the Continental region. Concerning the fulfilment of the regulatory limits, the mean of S. aureus and SCC levels in milk did not exceed them either in any region or scenario. Nevertheless, when looking at percentiles, the 10th percentile remained above the limits of S. aureus in Atlantic and Mediterranean, but not in the Continental region. The findings provide a snapshot of climate change impacts on raw milk losses due to mastitis. They will allow farmers to detect weaknesses and prepare them to develop adaptation plans to climate change.

Comparison between Some Phenotypic and Genotypic Methods for Assessment of Antimicrobial Resistance Trend of Bovine Mastitis Staphylococcus aureus Isolates from Bulgaria

Simple Summary

The aim of the study was to assess the resistance of bovine mastitis Staphylococcus aureus isolates to antimicrobials by comparison of laboratory methods and statistical analysis. For this, 546 mastitis milk samples at 14 farms from 9 districts in Bulgaria were examined. A total of 92 Staphylococcus aureus strains were isolated and identified. The results showed high resistance to sulfadimethoxine (87%), followed by resistance to penicillin (33.7%), erythromycin (13%), streptomycin (8.7%), tetracycline (6.5%) and gentamicin (1.1%). The comparison of the methods demonstrated more than 90% agreement for 9 tested antimicrobial drugs, hence proving reliability of results from monitoring of resistance. Considering the detected discrepancies for some of isolates, an integral evaluation through standard and modern molecular methods for Staphylococcus aureus is recommended. The results from this study add to the microbiology laboratory experience and strategies for mastitis prevention and control programmes.

Abstract

The aim of this study was to assess the resistance of bovine mastitis S. aureus isolates from farms in Bulgaria to different classes of chemotherapeutic drugs by comparison of some phenotypic and genotypic methods by means of Cohen’s kappa statistics. The study comprised 546 milk samples from subclinical and clinical mastitis at 14 farms from 9 districts in the country. A total of 92 Staphylococcus aureus strains were isolated from tested samples and identified by nuc PCR. The results demonstrated high levels of resistance to sulfadimethoxine (87%), followed by resistance to penicillin (33.7%), erythromycin (13%), streptomycin (8.7%), tetracycline (6.5%) and gentamicin (1.1%). The comparison of both phenotypic tests with respect to 9 antimicrobials revealed strong agreement with kappa coefficient 0.836. An almost complete agreement was evidenced between phenotypic resistance to penicillin and blaZ gene presence, to methicillin with mecA gene, to tetracycline with tet genes, but the agreement between erythromycin resistance and erm genes presence was moderate. This study was the first to demonstrate discrepancy between the behaviour to cefoxitin in the disk diffusion test and oxacillin in the MIC test for an isolate shown to carry the mecA gene in the subsequent genetic analysis. Considering the detected discrepancies for some of isolates, an integral evaluation through phenotypic and molecular methods for monitoring of antimicrobial resistance of Staphylococcus aureus is recommended.

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

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

Milk Quality and Safety in a One Health Perspective: Results of a Prevalence Study on Dairy Herds in Lombardy (Italy)

Mastitis is one of the major diseases of dairy cows that affects milk quality and quantity and increases the potential risk for the presence of antimicrobial residues (AR) in milk, which could lead to the development of antimicrobial resistance (AMR) among human pathogens. Even if the presence of AR in milk and milk products is low in many countries, the threat is not negligible and cannot be ignored. These problems may be investigated by applying a One Health approach, and this prevalence study aimed to estimate the risks for human health related to milk production applied to dairy herds in Lombardy. Three hundred thirty-one bulk tank milk samples were randomly collected and analyzed by CombiFoss 7 and MilkoScan 7 (milk quality, bacteria, and somatic cell count), an HPLC system coupled to a Q-Exactive Orbitrap (AR), and qPCR (contagious pathogens). The data were analyzed by a generalized linear model. The results showed a relatively high prevalence of contagious pathogens (S. aureus 28.1%; Str. agalactiae 7.3%; M. bovis 3%), which primarily affect milk nutritional components decreasing mainly milk fat content (range 1%–2.5%), but did not show them to be associated to an increase of the risk of antimicrobial residues. These latter ones were recovered only in 7/331 samples at concentrations far below official MLRs. The results support currently active surveillance programs’ efficacy in reducing AR risks, which may be further improved by prioritizing them based on geographical area characteristics.

MSC-ACE2 Ameliorates Streptococcus uberis-Induced Inflammatory Injury in Mammary Epithelial Cells by Upregulating the IL-10/STAT3/SOCS3 Pathway

In the dairy industry, Streptococcus uberis (S. uberis) is one of the most important pathogenic bacteria associated with mastitis in milk-producing cows, causing vast economic loss. To date, the only real effective method of treating and preventing streptococcal mastitis is antimicrobial therapy. In many inflammatory diseases, mesenchymal stem cells (MSCs) and angiotensin-converting enzyme 2 (ACE2) play an anti-inflammatory and anti-injurious role. Accordingly, we hypothesized that MSCs overexpressing ACE2 (MSC-ACE2) would ameliorate the inflammatory injury caused by S. uberis in mammary epithelial cells more efficiently than MSC alone. By activating the transcription 3/suppressor of cytokine signaling 3 (IL-10/STAT3/SOCS3) signaling pathway, MSC-ACE2 inhibited the NF-κB, MAPKs, apoptosis, and pyroptosis passways. Moreover, MSC-ACE2 overturned the downregulation of Occludin, Zonula occludens 1 (ZO-1), and Claudin-3 expression levels caused by S. uberis, suggesting that MSC-ACE2 promotes the repair of the blood-milk barrier. MSC-ACE2 demonstrated greater effectiveness than MSC alone, as expected. Based on these results, MSC-ACE2 effectively inhibits EpH4-Ev cell’s inflammatory responses induced by S. uberis, and would be an effective therapeutic tool for treating streptococcal mastitis.

Nrf2 and NF-κB/NLRP3 inflammasome pathways are involved in Prototheca bovis infections of mouse mammary gland tissue and mammary epithelial cells

Prototheca bovis is a serious pathogen for animals, but pathogenesis of P. bovis mastitis is unclear. The objective was to characterize how P. bovis induces inflammatory responses in mouse mammary gland tissue and mammary epithelial cells (mMECs). Prototheca bovis damaged mammary gland tissue and mitochondrial structure, and induced oxidative stress, as evident by significant increases in mtROS and MDA concentrations and significant decreases in T-SOD activity in both mammary gland tissue and mMECs. Expression of Nrf2, HO-1 and Keap1 proteins was significantly changed in mammary gland tissue and mMECs after P. bovis infection. Additionally, cytokines (IL-1β, IL-6 and IL-18) and protein expressions in NF-κB and in the NLRP3 inflammasome pathway were significantly increased in mammary gland tissue and mMECs. In the P. bovis group, treatment with N-acetyl-l-cysteine (NAC) significantly decreased protein expression in NF-κB and the NLRP3 inflammasome pathway, as well as IL-1β, IL-6 and IL-18, whereas protein expression in the Nrf2 pathway was significantly changed. Inhibition of NF-κB or NLRP3 significantly decreased expression of IL-1β and IL-18 proteins in mMECs infected with P. bovis. Additionally, activating Nrf2 inhibited expression of NLRP3 and IL-1β. In conclusion, P. bovis induced an inflammatory response via the NF-κB/NLRP3 inflammasome pathway; however, scavenging ROS or activating Nrf2 mitigated the inflammatory response in infected mMECs.