Symposium review: Intramammary infections-Major pathogens and strain-associated complexity

Antimicrobial resistance of Streptococcus dysgalactiae, Streptococcus agalactiae, and Streptococcus canis in quarter milk samples from Bavaria, Southern Germany, between 2012 and 2022

The objective of this study was to analyze the in vitro antimicrobial resistance (AMR) of Streptococcus (Sc.) dysgalactiae, Sc. agalactiae, and Sc. canis over a 10-year period from 2012 to 2022 against the most commonly used antimicrobial agents. For this purpose, all quarter milk samples (QMS) submitted to the milk laboratory of the Bavarian Animal Health Service (TGD) were analyzed. Each QMS was tested using the California Mastitis Test (CMT) and categorized as negative (N), subclinical (S), or clinical (C) mastitis if the milk character was abnormal. Samples with Sc. dysgalactiae, Sc. agalactiae, or Sc. canis were included and a subset of isolates were further tested for in vitro antimicrobial resistance by breakpoint analysis with broth microdilution. Sc. dysgalactiae (61%, n = 65,750) was the most abundant pathogen among those 3 species, followed by Sc. agalactiae (28%, n = 30,486), and Sc. canis (11%, n = 11,336). All 3 species showed the highest resistance to the same 4 antimicrobial agents: erythromycin, marbofloxacin, pirlimycin, and cefalexin/kanamycin with varying degrees of resistance. Throughout the study period, Sc. dysgalactiae, Sc. agalactiae, and Sc. canis were largely susceptible to the remaining antimicrobial agents tested (penicillin, amoxicillin-clavulanate, oxacillin, cefazolin, cefoperazone, cefquinome). Only less than 14% of isolates of Sc. dysgalactiae and Sc. canis were resistant against any of the antimicrobials tested. Sc. agalactiae was the species with the highest percentage of resistant isolates. While the percentage of resistant isolates from Sc. canis and Sc. dysgalactiae decreased, the percentage of resistant Sc. agalactiae isolates increased since 2017. In summary, most isolates were not resistant to the most commonly used antimicrobial agents for mastitis therapy, including β-lactam antibiotics and penicillin should remain the first-choice therapy against streptococcal mastitis.

Pathogen group-specific risk factors for intramammary infection in water buffalo

A cross-sectional study was conducted to estimate the prevalence of intramammary infection (IMI) associated bacteria and to identify risk factors for pathogen group-specific IMI in water buffalo in Bangladesh. A California Mastitis Test (CMT) and bacteriological cultures were performed on 1,374 quarter milk samples collected from 763 water buffalo from 244 buffalo farms in nine districts in Bangladesh. Quarter, buffalo, and farm-related data were obtained through questionnaires and visual observations. A total of 618 quarter samples were found to be culture positive. Non-aureus staphylococci were the predominant IMI-associated bacterial species, and Staphylococcus (S.) chromogenes, S. hyicus, and S. epidermidis were the most common bacteria found. The proportion of non-aureus staphylococci or Mammaliicoccus sciuri (NASM), S. aureus, and other bacterial species identified in the buffalo quarter samples varied between buffalo farms. Therefore, different management practices, buffalo breeding factors, and nutrition were considered and further analyzed when estimating the IMI odds ratio (OR). The odds of IMI by any pathogen (OR: 1.8) or by NASM (OR: 2.2) was high in buffalo herds with poor milking hygiene. Poor cleanliness of the hind quarters had a high odds of IMI caused by any pathogen (OR: 2.0) or NASM (OR: 1.9). Twice daily milking (OR: 3.1) and farms with buffalo purchased from another herd (OR: 2.0) were associated with IMI by any pathogen. Asymmetrical udders were associated with IMI-caused by any bacteria (OR: 1.7). A poor body condition score showed higher odds of IMI by any pathogen (OR: 1.4) or by NASM (OR: 1.7). This study shows that the prevalence of IMI in water buffalo was high and varied between farms. In accordance with the literature, our data highlight that IMI can be partly controlled through better farm management, primarily by improving hygiene, milking management, breeding, and nutrition.

Associations between early lactation intramammary infections and udder health and performance during the first 180 days in milk in first-lactation organic dairy cows

Prior data from our group showed that first-lactation cows under organic management in United States have a high prevalence of Staphylococcus aureus, Streptococcus spp., and Staphylococcus chromogenes intramammary infections (IMI) in early lactation. Nonetheless, the relationship between IMI, udder health, and milk production in organically reared primiparous cows remains elusive. The objectives of this observational study were to investigate the relationship between presence and persistence of IMI in the first 35 d in milk (DIM) and somatic cell count (SCC) and milk production during the first 6 mo of lactation on first-lactation organic dairy cows. The analysis included a total of 1,348 composite milk samples collected during the first 35 DIM that were submitted for milk culture and 1,674 Dairy Herd Improvement Association (DHIA) tests during the first 180 DIM from 333 heifers in 4 organic dairy farms, enrolled between February 2019 and January 2020. The association between IMI in the first 35 DIM and new high SCC (SCC > 200,000 cells/mL) and milk production during the first 6 mo of lactation was investigated using Cox proportional hazards regression and mixed linear regression, respectively. The association between IMI persistence (harboring the same microorganism as reported by the laboratory for 2 or more samples) in the first 35 DIM and number of DHIA tests with high SCC during the first 6 mo of lactation was modeled using negative binomial regression. The presence of IMI by Staph. aureus (hazard ratio [HR] [95% confidence interval {CI}]: 3.35 [2.64, 4.25]) or Streptococcus spp. (HR [95% CI]: 2.25 [2.12, 2.39]) during the first 35 DIM was associated with an increased risk of new high SCC during the first 6 mo of lactation. Milk production was reduced when Streptococcus spp. were identified in milk samples. However, there was no evidence of a difference in milk production in Staph. aureus IMI. Isolation of non-aureus staphylococci and mammaliicocci was related to a mild increase in the hazards of high SCC (HR [95% CI]: 1.34 [0.97, 1.85]) and a decrease in milk production during one or more postpartum tests. Presence of gram-negative or Streptococcus-like organisms IMI was not associated with either high SCC or milk production. Presence of Bacillus IMI was associated with a lower hazard of new high SCC (HR [95% CI]: 0.45 [0.30, 0.68]), and higher milk production during the first 180 d of lactation (overall estimate [95% CI]: 1.7 kg/d [0.3, 3.0]). The persistence of IMI in the first 35 DIM was associated with the number of tests with high SCC during the lactation for all microorganisms except for Staphylococcus chromogenes. Therefore, our results suggest that the persistence of IMI in the first 35 DIM could be an important factor to understand the association between IMI detected in early lactation and lactational SCC and milk production in organic dairy heifers. Our study described associations between IMI, udder health, and milk production in first-lactation organic dairy cows that are consistent with findings from conventional dairy farms.

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.

Etiology, persistence, and risk factors of subclinical mastitis in a meat-producing sheep flock

Subclinical mastitis, the asymptomatic inflammation of the udder often caused by bacterial infection, is an important economic and welfare concern in meat-producing flocks. We conducted a longitudinal observational study to: (1) characterize the etiology, prevalence, incidence, and persistence of intramammary infections during the first 8 wk of lactation, and (2) investigate the potential risk factors of lactation stage, parity, and the number of lambs reared. Duplicate milk samples (n = 592) were collected aseptically from each udder half of 37 clinically healthy ewes (9 Hampshire, 22 Polypay, and 6 Targhee) weekly for their first 8 wk of lactation. A sample was considered a true infection if at least 100 CFU/mL of a bacterial species were isolated. Out of a total of 560 non-contaminated duplicate udder half samples, 186 (33.2%) were infected. The prevalence of subclinical mastitis in the first week of lactation was 26.0% at the udder half level and increased over lactation to 47.1% by 8 wk. Over the course of lactation, 34 of the 37 (91.9%) ewes had an intramammary infection in at least one udder half. The most common bacteria isolated were non-aureus Staphylococci (72.1%), Staphylococcus aureus (7.5%), and Mannheimia haemolytica (5.9%). The weekly incidence rate of new infections was 18.0% ± 10.2% (mean ± SD). Infections lasted 2.1 ± 2.1 wk, with 9.0% present the full 8 wk of observation. Spontaneous cures occurred in 36.0% of infection bouts but varied from 0% to 100% depending on the pathogen. The probability of subclinical mastitis infection increased as lactation progressed for ewes rearing single or multiple lambs and for ewes in their first or second parity, but not for ewes in later parities. In conclusion, intramammary infections in this flock were prevalent across lactation, parities, and litter sizes, and varied in their duration and spontaneous cure rate. Improved knowledge of the etiological agents and risk factors involved in subclinical mastitis is important in developing effective control measures in meat-producing flocks.

Genomic analysis and assessment of pathogenic (toxicogenic) potential of Staphylococcus haemolyticus and Bacillus paranthracis consortia isolated from bovine mastitis in Russia

Three stable microbial consortia, each composed of Bacillus paranthracis and Staphylococcus haemolyticus strains, were isolated from milk of cows diagnosed with mastitis in three geographically remote regions of Russia. The composition of these consortia remained stable following multiple passages on culture media. Apparently, this stability is due to the structure of the microbial biofilms formed by the communities. The virulence of the consortia depended on the B. paranthracis strains. It seems plausible that the ability of the consortia to cause mastitis in cattle was affected by mutations of the cytK gene of B. paranthracis.

Phytosphingosine alleviates Staphylococcus aureus-induced mastitis by inhibiting inflammatory responses and improving the blood-milk barrier in mice

Mastitis is one of the common diseases in dairy cows which threatens the health of cows and impacts on economic benefits seriously. Recent studies have been showed that Subacute Ruminal Acidosis (SARA) increased the susceptibility of cow mastitis. SARA leads the disturbance of the rumen microbiota, and the rumen bacterial disordered community is an important endogenous factor of cow mastitis. That is to say, cows which suffer from SARA have a disordered rumen microbiota, a prolonged decline in ruminal PH and a high level of lipopolysaccharide (LPS) in the rumen, blood. Therefore, ruminal metabolism is closely related to the rumen microbiota. However, the specific mechanism of SARA and mastitis still not clear. We found an intestinal metabolite according to the metabonomics, which is correlated to inflammation. Phytophingosine (PS), a product from rumen fluid and milk of the cows which suffer from SARA and mastitis. It has the effect of killing bacteria and anti-inflammatory. Emerging evidences indicate that PS can alleviate inflammatory diseases. However, how PS affects mastitis is largely unknown. In this study, we explored the concrete role of PS on Staphylococcus aureus (S. aureus) -induced mastitis in mice. We found that PS obviously decreased the level of the proinflammatory cytokines. Meanwhile, PS also significantly relieved the mammary gland inflammation caused by S. aureus and restored the function of the blood-milk barrier. Here, we showed that PS increased the expression of the classic Tight-junctions (TJs) proteins including ZO-1, Occludin and Claudin-3. Moreover, PS improves S. aureus-induced mastitis by inhibiting the activation of the NF-κB and NLRP3 signaling pathways. These data indicated that PS relieved S. aureus-induced mastitis effectively. This also provides a reference for exploring the correlation between the intestinal metabolism and inflammation.

Severity of Clinical Mastitis and Bacterial Shedding

The aim of this cross-sectional study was to investigate associated factors of the severity of clinical mastitis (CM). Milk samples of 249 cases of CM were microbiologically examined, of which 27.2% were mild, 38.5% moderate, and 34.3% severe mastitis. The samples were incubated aerobically and anaerobically to investigate the role of aerobic and anaerobic microorganisms. In addition, the pathogen shedding was quantitatively examined, and animal individual data, outside temperature and relative humidity, were collected to determine associated factors for the severity of CM. The pathogen isolated the most was Escherichia coli (35.2%), followed by Streptococcus spp. (16.4%). Non-aureus staphylococci (NaS) (15.4%) and other pathogens (e.g., Staphylococcus aureus, coryneforms) (15.4%) were the pathogens that were isolated the most for mild mastitis. Moderate mastitis was mostly caused by E. coli (38%). E. coli was also the most common pathogen in severe mastitis (50.6%), followed by Streptococcus spp. (16.4%), and Klebsiella spp. (10.3%). Obligate anaerobes (Clostridium spp.) were isolated in one case (0.4%) of moderate mastitis. The mortality rate (deceased or culled due to the mastitis in the following two weeks) was 34.5% for severe mastitis, 21.7% for moderate mastitis, and 4.4% for mild mastitis. The overall mortality rate of CM was 21.1%. The pathogen shedding (back logarithmized) was highest for severe mastitis (55,000 cfu/mL) and E. coli (91,200 cfu/mL). High pathogen shedding, low previous somatic cell count (SCC) before mastitis, high outside temperature, and high humidity were associated with severe courses of mastitis.

Exploring the Milk Microbiota of Healthy and Mastitic Nili Ravi Buffalo Using 16S rRNA Gene Base Metagenomic Analysis

The Nili Ravi, a buffalo breed from Pakistan, significantly contributes to the dairy industry. Mastitis is one of the major challenges affecting milk production in this breed. The objective of the current study was to identify the bacterial communities and diversity in healthy and mastitic milk of this breed. Milk samples (n = 14) were collected from Nili Ravi buffaloes with different udder health statuses, i.e., healthy (5), subclinical mastitis (4), and clinical mastitis (5). The DNAs were extracted, subjected to partial amplification of 16S rDNA (V3 and V4 regions), and sequenced using the Illumina platform. The results revealed variations in the bacterial communities in the milk of animals with different udder health statuses. Proteobacteria was the predominant phylum in the healthy group, while clinical and subclinical mastitis milk had a higher abundance of Firmicutes. Dominant bacterial genera in the healthy group were Streptococcus (11.60%), Herbaspirillum (7.65%), and Staphylococcus (4.70%), whereas the clinical mastitis group was dominated by Streptococcus (33.96%), Staphylococcus (7.87%), and Corynebacterium (2.68%), and the subclinical mastitis group was dominated by Bacillus (15.70%), Corynebacterium (6.70%), and Staphylococcus (6.58%). Assignment of operational taxonomic units at the species level resulted in most species being assigned to uncultured or unknown bacteria or remaining unassigned. Alpha diversity indices indicated lower microbial diversity in the clinical mastitis group, while beta diversity indices showed a scattered pattern of sample clustering in PCA plots among different groups. It is concluded that bacterial diversity in the milk of Nili Ravi buffaloes suffering from clinical mastitis is lower compared to healthy and subclinical mastitis cases. It is concluded that the variations in the microbiota of healthy and mastitic milk may be further investigated and exploited as signature microbes associated with the udder health status of Nili Ravi buffalo.

To seal or not to seal following an antimicrobial infusion at dry-off? A systematic review and multivariate meta-analysis of the incidence and prevalence of intramammary infections post-calving in dairy cows

Teat sealants (TSs) consist of sterile formulations with no antibacterial activity. Alone or in combination with antimicrobial (AM) or non-AM treatments, TSs have been commonly used in dairy cows at dry-off to prevent intra-mammary infections (IMIs) during the dry period. This study aimed to identify and synthesise the available evidence on the efficacy of combining TSs with AM treatments on the incidence and prevalence of IMIs. A comprehensive search of three electronic databases, two relevant conference proceedings, and reference lists of reviews and eligible articles was conducted to retrieve and identify studies that could answer the following question: in dairy cows, how does the efficacy of an AM-TS combination administered at dry-off compare with an AM alone for preventing new IMI? In addition to the general IMIs, bacterial species-specific data were extracted and combined into nine distinct pathogen groups: coagulase-positive and negative staphylococci; S. dysgalactiae; non-dysgalactiae Streptococci; E. coli; non-E. coli Enterobacteriaceae; Corynebacterium spp.; yeast and other frequent mastitis pathogens. The structural relationship between each study's prevalence and incidence, as the new (incidence) and persistent (uncured) infections make up the prevalence, was utilised to approximate a variance-covariance matrix for the within-study correlation between their study-specific log odds ratios (ORs). A bivariate random-effects meta-analysis was employed, utilising the within- and between-study correlations to synthesise both outcomes simultaneously. The risk of bias was assessed using the Cochrane ROBINS-I tool, and the quality of the body of evidence was rated using the GRADE approach. A total of 17 trials (16 studies), providing either IMIs incidence (n = 4), prevalence (n = 3) or both (n = 10), were identified. Overall, quarters infused with AM-TS combinations showed lower odds of new IMIs post-calving (OR=0.70; 95% CI=0.57-0.86; Wald test P < 0.001) than those which received only AMs. Across the pathogen groups, varying levels of reduction of new IMIs were found, where administration of TSs was most effective against S. dysgalactiae (OR=0.47; 95% CI=0.23-0.98), non-dysgalactiae streptococci (OR=0.60; 95% CI=0.49-0.74), E. coli (OR=0.62; 95% CI=0.50-0.77), Corynebacterium spp. (OR=0.68; 95% CI=0.52-0.90) and coagulase-negative staphylococci (OR=0.85; 95% CI=0.76-0.94). However, additional TS infusion did not significantly reduce new IMIs in the remaining pathogen groups. The current meta-analytic evidence supports the efficacy of using TS add-on infusions in dairy cows at dry-off for reducing the incidence and prevalence of IMIs post-calving; however, pathogen group differences should be considered.

Immune profiling of experimental murine mastitis reveals conserved response to mammary pathogenic Escherichia coli, Mycoplasma bovis, and Streptococcus uberis

Mastitis is one of the most prevalent and economically important diseases of dairy animals. The disease is caused by ascending bacterial infection through the teat canal. Among the most common mastitis-causing bacteria are Gram-negative coliforms, Gram-positive streptococci and staphylococci, and mycoplasma. The most prominent cellular hallmark of acute mammary infection is a massive recruitment of blood neutrophils into the tubular and alveolar milk spaces. The complex biological processes of leukocyte recruitment, activation, adhesion, and migration in the mammary gland remain largely elusive to date. While field research of mastitis in dairy animals contributed a lot to the development of mitigation, control, and even eradication programs, little progress was made toward understanding the molecular mechanisms underlying the pathogenesis of the disease. We report here experimental mastitis model systems in lactating mice challenged with field strains of common udder pathogens in dairy cows. We used these model systems to apply recently developed multiplex gene expression technology (Nanostring nCounter), which enabled us to study the expression of over 700 immune genes. Our analysis revealed a core of 100 genes that are similarly regulated and functionally or physically interacting in E. coli, M. bovis, and Strep uberis murine mastitis. Common significantly enriched gene sets include TNFɑ signaling via NFkB, Interferon gamma and alpha response, and IL6-JAK-STAT3 signaling. In addition, we show a significantly enriched expression of genes associated with neutrophil extracellular traps (NET) in glands challenged by the three pathogens. Ligand-receptor analysis revealed interactions shared by the three pathogens, including the interaction of the cytokines IL1β, IL1ɑ, and TNFɑ with their receptors, and proteins involved in immune cell recruitment such as complement C3 and ICAM1 (with CD11b), chemokines CCL3 and CCL4 (with CCR1), and CSF3 (with CSF3R). Taken together, our results show that mammary infection with E. coli, M. bovis, and Strep uberis culminated in the activation of a conserved core of immune genes and pathways including NET formation.

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.

Diversity and emergence of multi-resistant Staphylococcus spp. isolated from subclinical mastitis in cows in of the state of Piauí, Brazil

This research aimed to identify the diversity of bacterial species of the genus Staphylococcus spp. in subclinical mastitis in dairy herds in the state of Piauí, Northeastern Brazil, and to evaluate the phenotypic and genotypic resistance profile. Samples were obtained from a total of 17 dairy farms, amounting to 321 positive samples in the California Mastitis Test. Staphylococcus spp. were identified by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy. Subsequently, an antibiogram was performed, and a polymerase chain reaction was carried out to screen for resistance genes in the isolates. Among all the isolates, 59.45% (110/185) belonged to the Staphylococcus genus. Moreover, the following Staphylococcus spp. were identified Staphylococcus aureus, 68.1% (75/110); Staphylococcus chromogenes, 12.7% (14/110); Staphylococcus epidermidis, 5.4% (6/110); Staphylococcus sciuri, 4.5% (5/110); Staphylococcus warneri, 2.7% (3/110); Staphylococcus haemolyticus, 1.8% (2/110); Staphylococcus hominis, 1.8% (2/110); Staphylococcus arlettae, 0.9% (1/110); Staphylococcus capitis, 0.9% (1/110); and Staphylococcus gallinarum, 0.9% (1/110). The antibiogram showed a high frequency of resistance to penicillin and ampicillin, 70.0% (77/110) and 61.8% (68/110), respectively, and a low frequency of resistance to gentamicin and vancomycin, 10.9% (12/110) and 11.8% (13/110), respectively. In the genotypic tests for the different species of Staphylococcus spp., the occurrence of the blaZ gene was observed in 60.9% (67/110) of the isolates, followed by tetL and tetM, both with 20.0% (22/110) each, and the mecA and vanB genes were detected in 0.9% (1/110) of the samples. The identification of all Staphylococcus species isolated from subclinical mastitis cases and the phenotypic and genotypic resistance characterization in these isolates is of great importance for dairy farming in the state of Piauí, as well as for public health.

Effect of Glyceryl Monoolein Addition on the Foaming Properties and Stability of Whipped Oleogels

Medium Chain Triglyceride (MCT) oil was successfully combined with Glyceryl Monostearate (GMS) and Glyceryl Monoolein (GMO) to form oleogels that were subsequently whipped to form stable oleofoams. The co-crystallization of GMS and GMO at a ratio of 20:1, 20:2.5, and 20:5 within MCT oil was studied through Differential Scanning Calorimetry (DSC), X-ray Diffraction analysis (XRD), rheological analysis, Fluorescence Recovery after Photobleaching (FRAP), Fourier Transform Infrared Spectroscopy (FTIR), and polarized microscopy. The addition of 5% GMO resulted in the production of more stable oleogels in terms of crystal structure and higher peak melting point, rendering this formulation suitable for pharmaceutical applications that are intended to be used internally and those that require stability at temperatures close to 40 °C. All formulations were whipped to form oleofoams that were evaluated for their storage stability for prolonged period at different temperatures. The results show that oleofoams containing 5% MGO retained their foam characteristics even after 3 months of storage under different temperature conditions.

Research progress on the association between mastitis and gastrointestinal microbes in dairy cows and the effect of probiotics

Mastitis in dairy cows affects milk quality and thereby constrains the development of the dairy industry. A clear understanding of the pathogenesis of mastitis can help its treatment. Mastitis is caused by the invasion of pathogenic bacteria into the mammary gland through the mammary ducts. However, recent studies suggested that an endogenous entero-mammary pathway in dairy cattle might also be playing an important role in regulating mastitis. Also, probiotic intervention regulating host gut microbes has become an interesting tool to control mastitis. This review discusses the association of gastrointestinal microbes with mastitis and the mechanism of action of probiotics in dairy cows to provide new ideas for the management of mastitis in large-scale dairy farms.

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.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Staphylococcus aureus in cattle and horses

Staphylococcus aureus (S. aureus) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for cattle and horses in previous scientific opinions. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9, and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR S. aureus can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (60-90% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1, 2 and 4 (Categories A, B and D; 1-5%, 5-10% and 10-33% probability of meeting the criteria, respectively) and the AHAW Panel was uncertain whether it meets the criteria in Sections 3 and 5 (Categories C and E, 33-90% and 60-90% probability of meeting the criteria, respectively). The animal species to be listed for AMR S. aureus according to Article 8 criteria include mainly mammals, birds, reptiles and fish.

Mastitis Control and Intramammary Antimicrobial Stewardship in Ireland: Challenges and Opportunities

The Veterinary Medicines Regulation (EU 2019/6) came into force in all EU member states on 28 January 2022. This regulation places particular emphasis on prudent and responsible antimicrobial use in food animal production. Key changes include restrictions on the prophylactic use of antimicrobials in animals, and the possibility to reserve certain antimicrobials for humans only. The Regulation presents challenges to the Irish dairy industry, particularly with respect to current approaches to dry cow therapy. In response, the CellCheck technical working group (TWG, a technical group working in support of CellCheck, the national mastitis control programme) have developed pragmatic national and farm-level recommendations in support of improved mastitis control and intramammary antimicrobial stewardship in the Irish dairy industry. This paper outlines these recommendations, and provides an overview of the evidence considered to inform the TWG during its work (including the Regulation, policy perspectives, international best-practice, international scientific reviews and specific Irish challenges). In many key areas of concern, the TWG recognises the challenges in seeking to shape recommendations in the absence of robust and practical scientific evidence. For this reason, some of the recommended actions are pragmatic in nature, informed by national and international experiences. Periodic programme review will be needed, informed by ongoing monitoring of key performance indicators, to identify those actions that are most effective in an Irish context.

The Rumen Microbiota Contributes to the Development of Mastitis in Dairy Cows

Mastitis, a highly prevalent disease in dairy cows, is commonly caused by local infection of the mammary gland. Our previous studies have suggested that the gut microbiota plays an important role in the development of mastitis in mice. However, the effects of rumen microbiota on bovine mastitis and the related mechanisms remain unclear. In this study, we assessed the effects and mechanisms of rumen microbiota on bovine mastitis based on the subacute rumen acidosis (SARA) model induced by feeding Holstein Frisian cows a high-concentrate diet for 8 weeks. Then, the inflammatory responses in the mammary gland and the bacterial communities of rumen fluid, feces, and milk were analyzed. The results showed that SARA induced mastitis symptoms in the mammary gland; activated a systemic inflammatory response; and increased the permeability of the blood-milk barrier, gut barrier, and rumen barrier. Further research showed that lipopolysaccharides (LPS), derived from the gut of SARA cows, translocated into the blood and accumulated in the mammary glands. Furthermore, the abundance of Stenotrophomonas was increased in the rumen of SARA cows, and mastitis was induced by oral administration of Stenotrophomonas in lactating mice. In conclusion, our findings suggested that mastitis is induced by exogenous pathogenic microorganisms as well as by endogenous pathogenic factors. Specifically, the elevated abundance of Stenotrophomonas in the rumen and LPS translocation from the rumen to the mammary gland were important endogenous factors that induced mastitis. Our study provides a foundation for novel therapeutic strategies that target the rumen microbiota in cow mastitis. IMPORTANCE Mastitis is a common and frequently occurring disease of humans and animals, especially in dairy farming, which has caused huge economic losses and brought harmful substance residues, drug-resistant bacteria, and other public health risks. The traditional viewpoint indicates that mastitis is mainly caused by exogenous pathogenic bacteria infecting the mammary gland. Our study found that the occurrence of mastitis was induced by the endogenous pathway. Evidence has shown that rumen-derived LPS enters the mammary gland through blood circulation, damaging the blood-milk barrier and then inducing inflammation of the mammary gland in cows. In addition, a higher abundance of Stenotrophomonas in the rumen was closely associated with the development of mastitis. This study provides a basis for novel therapeutic strategies that exploit the rumen microbiota against mastitis in cows.

Meloxicam in Combating Clinical Mastitis: Nanotechnology-Driven Hope and Opportunities

Mastitis has well-recognized harmful effects on dairy farm profitability. Furthermore, mastitis impairs the milk component synthesizing ability of secretary tissues. Various therapies are available for the treatment of clinical mastitis. Meloxicam exhibits preferential binding to Cyclooxygenase-2 (COX-2) receptor and consequently generates fewer negative gastrointestinal side effects than nonspecific COX inhibitors such as flunixin meglumine and ketoprofen. Toward this end, research efforts directed at understanding the use of meloxicam alone and in combination with other antibiotics to improve milk quality and production. Therefore, in this review, we have highlighted the mechanism, biopharmaceutical challenges, and merits of meloxicam usage in dairy cattle mastitis. In addition, we also presented the integration of artificial neural network, in silico docking, and nanotechnology-driven topical drug delivery cargo as future opportunity for efficient delivery of meloxicam in the management of clinical mastitis.

Evaluation of the relative expression of genes associated with adherence after different hours of co-culture between Streptococcus uberis and MAC-T cells

Streptococcus uberis is an environmental pathogen associated with subclinical and clinical IMI in both lactating and non-lactating cows. RC19 strain was isolated from a cow with subclinical mastitis, qualitatively classified as moderate biofilm producer in Todd Hewitt medium (THB), and it showed a high value of the adhered bacteria (CFU/ml). Hence, the aims of this study were (a) to determine ability to adhere to and internalize into epithelial cells MAC-T for 1, 2 and 3 h, (b) to evaluate the relative expression of adherence-associated genes from co-cultures of S. uberis with MAC-T cells at 1, 2 and 3 h. We hypothesized that upon contact with bovine mammary epithelial cells, S. uberis upregulates adherence-associated genes encoding adhesins, which enable it a higher adherence to and/or internalization into host cells. Four to six genes increased their R with regard to the control after initial contact with MAC-T cells (group 1) at 1, 2 and 3 h. The highest value of R was observed at 2 h after co-culture between RC19 and MAC-T cells.

Differential Expression Profiles of lncRNA Following LPS-Induced Inflammation in Bovine Mammary Epithelial Cells

Bovine mastitis is an inflammatory response of mammary glands caused by pathogenic microorganisms such as Escherichia coli (E. coli). As a key virulence factor of E. coli, lipopolysaccharide (LPS) triggers innate immune responses via activation of the toll-like-receptor 4 (TLR4) signaling pathway. However, the molecular regulatory network of LPS-induced bovine mastitis has yet to be fully mapped. In this study, bovine mammary epithelial cell lines MAC-T were exposed to LPS for 0, 6 and 12 h to assess the expression profiles of long non-coding RNAs (lncRNAs) using RNA-seq. Differentially expressed lncRNAs (DElncRNAs) were filtered out of the raw data for subsequent analyses. A total of 2,257 lncRNAs, including 210 annotated and 2047 novel lncRNAs were detected in all samples. A large proportion of lncRNAs were present in a high abundance, and 112 DElncRNAs were screened out at different time points. Compared with 0 h, there were 22 up- and 25 down-regulated lncRNAs in the 6 h of post-infection (hpi) group, and 27 up- and 22 down-regulated lncRNAs in the 12 hpi group. Compared with the 6 hpi group, 32 lncRNAs were up-regulated and 25 lncRNAs were down-regulated in the 12 hpi group. These DElncRNAs are involved in the regulation of a variety of immune-related processes including inflammatory responses bMECs exposed to LPS. Furthermore, lncRNA TCONS_00039271 and TCONS_00139850 were respectively significance down- and up-regulated, and their target genes involve in regulating inflammation-related signaling pathways (i.e.,Notch, NF-κB, MAPK, PI3K-Akt and mTOR signaling pathway), thereby regulating the occurrence and development of E. coli mastitis. This study provides a resource for lncRNA research on the molecular regulation of bovine mastitis.

Ewe Vaginal Microbiota: Associations With Pregnancy Outcome and Changes During Gestation

Reproductive performance is paramount to the success of livestock production enterprises focused on lamb meat production. Reproductive success is influenced by various factors, possibly including the reproductive tract microbial communities present at the time of copulation and throughout pregnancy. There are few publications that identify the vaginal microbial communities of livestock, and even fewer exist for sheep. To compare ewe vaginal microbial communities, vaginal swabs were taken from 67 Hampshire and Hampshire X Suffolk crossbred ewes from the Iowa State University sheep farm at a pre-breeding time point (S1) and after pregnancy testing (S2). Animals that were determined pregnant were sampled again within a few days of expected parturition (S3). DNA was extracted from these swabs, and 16S rRNA gene Illumina MiSeq amplicon sequencing was conducted to fingerprint the bacterial communities found within this system. Pre-breeding time point samples showed no differences in community structure between animals later found to be pregnant or non-pregnant, but significant changes were detected in species richness (Chao; P < 0.001) and species diversity (Shannon; P < 0.001) at the second sampling time point. A higher microbial diversity within the S2 time point samples may suggest a more stable environment driven by pregnancy, as this increased diversity is maintained in pregnant animals from the S2 to the S3 time point. Additionally, several bacterial phylotypes, such as Mannheimia, Oscillospiraceae-like OTUs and Alistipes, were more abundant at either the S1 or S2 time points in animals that established pregnancy, suggesting a beneficial effect on pregnancy outcome. This study identifies changes within the microbial communities of the ewe vagina before and during gestation and offers inferences on how these changes may impact pregnancy outcome. Information presented herein offers new knowledge about sheep vaginal microbial communities and serves as a starting point to help guide researchers to improve sheep reproductive performance in the future.

Bacterial species-specific modulatory effects on phenotype and function of camel blood leukocytes

Background

Recent studies have reported pathogen-species-specific modulating effects on the innate immune system. Escherichia coli, Staphylococcus aureus, and Streptococcus agalactiae are important pathogenic bacteria responsible for different infectious diseases in several animal species. In the present study, a whole blood culture with S. aureus, E. coli, or S. agalactiae and flow cytometry were used to investigate, whether stimulation with different bacterial species induces different immunomodulation patterns in camel leukocytes. The expression of different cell surface myeloid markers and cell adhesion molecules on monocytes and neutrophils was investigated. In addition, the capacity of monocytes and neutrophils to produce reactive oxygen species (ROS) was analyzed.

Results

Stimulation with either of the bacterial species resulted in the expansion of the camel CD14^highMHCII^high monocyte subset with a reduced fraction of CD14^highMHCII^low monocytes. For the CD14^lowMHCII^high monocytes, however, only stimulation with S. aureus or S. agalactiae increased their fractions in blood. Although all bacterial species elicited the upregulation of cell surface MHC class II molecules on granulocytes, the increase was, however, highest on cells stimulated with S. aureus. The expression levels of the two adhesion molecules, CD11a and CD18, on neutrophils and monocytes were differently affected by bacterial stimulation. Functionally, E. coli failed to stimulate ROS production in monocytes, while induced a strong ROS production response in granulocytes. S. agalactiae elicited a week ROS production in granulocytes when compared to the other two pathogens.

Conclusions

The different responsiveness of monocytes and granulocytes toward different bacterial species indicates different host-pathogen interaction mechanisms for the two cell populations. In addition, the phenotypic and functional differences between cells stimulated with E. coli, S. aureus, or S. agalactiae suggests pathogen-species-specific modulating effects of the bacterial pathogens on the camel innate myeloid cells.

Genomic Analysis of Staphylococcus aureus Isolates Associated With Peracute Non-gangrenous or Gangrenous Mastitis and Comparison With Other Mastitis-Associated Staphylococcus aureus Isolates

Staphylococcus aureus is a highly prevalent cause of mastitis in dairy herds worldwide, capable of causing outcomes that vary from subclinical to peracute gangrenous mastitis. We performed a comparative genomic analysis between 14 isolates of S. aureus, originating from peracute bovine mastitis with very severe signs (9 gangrenous, 5 non-gangrenous) and six isolates originating from subclinical or clinical mastitis with mild to moderate signs, to find differences that could be associated with the clinical outcome of mastitis. Of the 296 virulence factors studied, 219 were detected in all isolates. No difference in the presence of virulence genes was detected between the peracute and control groups. None of the virulence factors were significantly associated with only a single study group. Most of the variation in virulence gene profiles existed between the clonal complexes. Our isolates belonged to five clonal complexes (CC97, CC133, CC151, CC479, and CC522), of which CC522 has previously been detected only in isolates originating from caprine and ovine mastitis, but not from bovine mastitis. For statistical analysis, we sorted the CCs into two groups. The group of CCs including CC133, CC479, and CC522 was associated with gangrenous mastitis, in contrast to the group of CCs including CC97 and CC151. The presence of virulence genes does not explain the clinical outcome of mastitis, but may be affected by allelic variation, and especially different regulation and thus expression in the virulence genes.

Invited review: A critical appraisal of mastitis vaccines for dairy cows

Infections of the mammary gland remain a frequent disease of dairy ruminants that negatively affect animal welfare, milk quality, farmer serenity, and farming profitability and cause an increase in use of antimicrobials. There is a need for efficacious vaccines to alleviate the burden of mastitis in dairy farming, but this need has not been satisfactorily fulfilled despite decades of research. A careful appraisal of past and current research on mastitis vaccines reveals the peculiarities but also the commonalities among mammary gland infections associated with the major mastitis pathogens Escherichia coli, Staphylococcus aureus, Streptococcus uberis, Streptococcus agalactiae, or Streptococcus dysgalactiae. A major pitfall is that the immune mechanisms of effective protection have not been fully identified. Until now, vaccine development has been directed toward the generation of antibodies. In this review, we drew up an inventory of the main approaches used to design vaccines that aim at the major pathogens for the mammary gland, and we critically appraised the current and tentative vaccines. In particular, we sought to relate efficacy to vaccine-induced defense mechanisms to shed light on some possible reasons for current vaccine shortcomings. Based on the lessons learned from past attempts and the recent results of current research, the design of effective vaccines may take a new turn in the years to come.

Phage vB_PaeS-PAJD-1 Rescues Murine Mastitis Infected With Multidrug-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is a Gram-negative pathogen that causes a variety of infections in humans and animals. Due to the inappropriate use of antibiotics, multi-drug resistant (MDR) P. aeruginosa strains have emerged and are prevailing. In recent years, cow mastitis caused by MDR P. aeruginosa has attracted attention. In this study, a microbial community analysis revealed that P. aeruginosa could be a cause of pathogen-induced cow mastitis. Five MDR P. aeruginosa strains were isolated from milk diagnosed as mastitis positive. To seek an alternative antibacterial agent against MDR, P. aeruginosa, a lytic phage, designated vB_PaeS_PAJD-1 (PAJD-1), was isolated from dairy farm sewage. PAJD-1 was morphologically classified as Siphoviridae and was estimated to be about 57.9 kb. Phage PAJD-1 showed broad host ranges and a strong lytic ability. A one-step growth curve analysis showed a relatively short latency period (20 min) and a relatively high burst size (223 PFU per infected cell). Phage PAJD-1 remained stable over wide temperature and pH ranges. Intramammary-administered PAJD-1 reduced bacterial concentrations and repaired mammary glands in mice with mastitis induced by MDR P. aeruginosa. Furthermore, the cell wall hydrolase (termed endolysin) from phage PAJD-1 exhibited a strong bacteriolytic and a wide antibacterial spectrum against MDR P. aeruginosa. These findings present phage PAJD-1 as a candidate for phagotherapy against MDR P. aeruginosa infection.

Potential factors involved in the early pathogenesis of Streptococcus uberis mastitis: a review

Bovine mastitis is an inflammation of the mammary gland, which could be the result of allergy, physical trauma, or invasion by pathogens as Streptococcus uberis. This pathogen is an environmental pathogen associated with subclinical and clinical intramammary infection (IMI) in both lactating and non-lactating cows, which can persist in the udder and cause a chronic infection in the mammary gland. In spite of the important economic losses and increased prevalence caused by S. uberis mastitis, virulence factors involved in bacterial colonization of mammary glands and the pathogenic mechanisms are not yet clear. In the last 30 years, several studies have defined adherence and internalization of S. uberis as the early stages in IMI. S. uberis adheres to and invades into mammary gland cells, and this ability has been observed in in vitro assays. Until now, these abilities have not been determined in vivo challenges since they have been difficult to study. Bacterial surface proteins are able to bind to extracellular matrix protein components such as fibronectin, collagen and laminin, as well as proteins in milk. These proteins play a role in adhesion to host cells and have been denominated microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). This article aims to summarize our current knowledge on the most relevant properties of the potential factors involved in the early pathogenesis of S. uberis mastitis.

An Inventory of CiaR-Dependent Small Regulatory RNAs in Streptococci

Bacteria adapt to the different environments encountered by rapid and tightly controlled regulations involving complex networks. A first line of control is transcriptional with regulators such as two-component systems (TCSs) that respond to physical and chemical perturbations. It is followed by posttranscriptional regulations in which small regulatory RNAs (sRNAs) may affect RNA translation. Streptococci are opportunistic pathogens for humans and farm animals. The TCS CiaRH is highly conserved among this genus and crucial in bacterial survival under stressful conditions. In several streptococcal species, some sRNAs belong to the CiaRH regulon and are called csRNAs for cia-dependent sRNAs. In this review, we start by focusing on the Streptococcus species harboring a CiaRH TCS. Then the role of CiaRH in streptococcal pathogenesis is discussed in the context of recent studies. Finally, we give an overview of csRNAs and their functions in Streptococci with a focus on their importance in bacterial adaptation and virulence.

Prevalence of Mastitis and Antibiotic Resistance of Bacterial Isolates from CMT Positive Milk Samples Obtained from Dairy Cows, Camels, and Goats in Two Pastoral Districts in Southern Ethiopia

Simple Summary

A study was carried out from August 2017 to February 2018 on lactating dairy cows, one-humped dromedary camels, and goats to determine mastitis in the Bule Hora and Dugda Dawa districts of in Southern Ethiopia. Milk samples from 564 udder quarters and udder halves from 171 animals consisting of 60 dairy cows, 51 camels, and 60 goats were tested for mastitis. Sixty-four positive udder milk samples were cultured, and bacterial mastitis pathogens were isolated and identified. The antibiotic resistance of bacterial isolates from milk with mastitis was tested against nine antimicrobials commonly used in the study area. Cow-level prevalence of mastitis in dairy cows, camels, and goats was 33.3%, 26.3%, and 25%, respectively. The quarter-level prevalence of mastitis in cows, camels and goats was 17.6%, 14.5%, and 20%, respectively. In cattle, the prevalence was significantly higher in Dugda Dawa than in Bule Hora. Major bacterial isolates were coagulase-negative Staphylococcus species (39.1%), S. aureus (17.2%), S. hyicus (14.1%), and S. intermedius and Escherichia coli (9.4% each). In camels, udder abnormality and mastitis were significantly higher in late lactation than in early lactation. Mastitis tends to increase with parity in camels. E. coli isolates were highly resistant to spectinomycin, vancomycin, and doxycycline, whereas most S. aureus isolates were multidrug-resistant. Most of the rural and periurban communities in this area consume raw milk, which indicates a high risk of infection with multidrug-resistant bacteria. We recommend community-focused training programs to improve community awareness of the risk of raw milk consumption and the need to boil milk.

Abstract

A study was carried out from August 2017 to February 2018 on lactating dairy cows, one-humped dromedary camels, and goats to determine mastitis in the Bule Hora and Dugda Dawa districts of in Southern Ethiopia. Milk samples from 564 udder quarters and udder halves from 171 animals consisting of 60 dairy cows, 51 camels, and 60 goats were tested for mastitis. Sixty-four positive udder milk samples were cultured, and bacterial mastitis pathogens were isolated and identified. The antibiotic resistance of bacterial isolates from milk with mastitis was tested against nine antimicrobials commonly used in the study area. Cow- and quarter-level prevalence of mastitis in dairy cows, camels, and goats was 33.3%, 26.3%, and 25% and 17.6%, 14.5%, and 20%, respectively. In cattle, the prevalence was significantly higher in Dugda Dawa than in Bule Hora. Major bacterial isolates were coagulase-negative Staphylococcus species (39.1%), S. aureus (17.2%), S. hyicus (14.1%), and S. intermedius and Escherichia coli (9.4% each). In camels, udder abnormality and mastitis were significantly higher in late lactation than in early lactation. Mastitis tends to increase with parity in camels. E. coli isolates were highly resistant to spectinomycin, vancomycin, and doxycycline, whereas most S. aureus isolates were multidrug-resistant. Most of the rural and periurban communities in this area consume raw milk, which indicates a high risk of infection with multidrug-resistant bacteria. We recommend a community-focused training program to improve community awareness of the need to boil milk and the risk of raw milk consumption.

Comparative Analysis of Milk Microbiomes and Their Association with Bovine Mastitis in Two Farms in Central Russia

Bovine mastitis is a widespread infectious disease. In addition to the economic damages associated with reduced milk yield due to mastitis, the problem of food contamination by microorganism metabolites, in particular toxins, is also a concern. Horizontal transfer of microorganisms from animal populations to humans can also be complicated by antibiotic resistance. Therefore, bovine mastitis is relevant to the study of microbiology and veterinary medicine. In this study, we investigated the microbiome of milk samples from healthy cows and cows with different forms of mastitis from individual quarters of the udder of cows during first and second lactation. Total DNA was extracted from milk samples. The V3-V4 regions of the bacterial 16S rRNA genes from each sample were amplified to generate a library via high-throughput sequencing. We revealed significant dominance of several operational taxonomic units (OTUs) corresponding mostly to groups of Staphylococcus aureus, Aerococcus spp., and Streptococcus spp. In addition, we unexpectedly identified Streptococcus thermophilus in samples with high SCC quantities. We found some infectious agents that characterized summer mastitis. We demonstrated that in Central Russia, mastitis is associated with a wide variety of causal organisms. We observed some differences in the diversity of the two investigated farms. However, we did not find any significant difference among healthy, mastitis and subclinical samples according to their SCC status from either farms by principal component analysis. Linear discriminant analysis effect size (LEfSe) confirmed the presence of several indicator genera in farms from Moscow and the Tula Region. These results confirm the complex bacterial etiology of bovine mastitis.

Changes in the Microbiome of Milk in Cows with Mastitis

Analysis of milk micrbiomes from healthy cows and cows with different (clinical and subclinical) forms of mastitis was performed at two farms of the Central Russia. An increase in the operational taxonomic units (OTUs) of bacteria of the phylum Proteоbacteria belonging primarily to Pseudomonadales, Burkholderiales, as well as Streptococcaceae, Staphylococcaceae, and Bacillaceae in the animals with mastitis was detected. The Planococcaceae OTU percentage decreased. The ratio of rarely presented OTUs also changed in the milk of animals with mastitis.

Feeding a Saccharomyces cerevisiae fermentation product improves udder health and immune response to a Streptococcus uberis mastitis challenge in mid-lactation dairy cows

Background

We aimed to characterize the protective effects and the molecular mechanisms of action of a Saccharomyces cerevisiae fermentation product (NTK) in response to a mastitis challenge. Eighteen mid-lactation multiparous Holstein cows (n = 9/group) were fed the control diet (CON) or CON supplemented with 19 g/d NTK for 45 d (phase 1, P1) and then infected in the right rear quarter with 2500 CFU of Streptococcus uberis (phase 2, P2). After 36-h, mammary gland and liver biopsies were collected and antibiotic treatment started until the end of P2 (9 d post challenge). Cows were then followed until day 75 (phase 3, P3). Milk yield (MY) and dry matter intake (DMI) were recorded daily. Milk samples for somatic cell score were collected, and rectal and udder temperature, heart and respiration rate were recorded during the challenge period (P2) together with blood samples for metabolite and immune function analyses. Data were analyzed by phase using the PROC MIXED procedure in SAS. Biopsies were used for transcriptomic analysis via RNA-sequencing, followed by pathway analysis.

Results

DMI and MY were not affected by diet in P1, but an interaction with time was recorded in P2 indicating a better recovery from the challenge in NTK compared with CON. NTK reduced rectal temperature, somatic cell score, and temperature of the infected quarter during the challenge. Transcriptome data supported these findings, as NTK supplementation upregulated mammary genes related to immune cell antibacterial function (e.g., CATHL4, NOS2), epithelial tissue protection (e.g. IL17C), and anti-inflammatory activity (e.g., ATF3, BAG3, IER3, G-CSF, GRO1, ZFAND2A). Pathway analysis indicated upregulation of tumor necrosis factor α, heat shock protein response, and p21 related pathways in the response to mastitis in NTK cows. Other pathways for detoxification and cytoprotection functions along with the tight junction pathway were also upregulated in NTK-fed cows.

Conclusions

Overall, results highlighted molecular networks involved in the protective effect of NTK prophylactic supplementation on udder health during a subclinical mastitic event.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00560-8.

Identification and Phenotype of MAIT Cells in Cattle and Their Response to Bacterial Infections

Mucosal-associated invariant T (MAIT) cells are a population of innate-like T cells that utilize a semi-invariant T cell receptor (TCR) α chain and are restricted by the highly conserved antigen presenting molecule MR1. MR1 presents microbial riboflavin biosynthesis derived metabolites produced by bacteria and fungi. Consistent with their ability to sense ligands derived from bacterial sources, MAIT cells have been associated with the immune response to a variety of bacterial infections, such as Mycobacterium spp., Salmonella spp. and Escherichia coli. To date, MAIT cells have been studied in humans, non-human primates and mice. However, they have only been putatively identified in cattle by PCR based methods; no phenotypic or functional analyses have been performed. Here, we identified a MAIT cell population in cattle utilizing MR1 tetramers and high-throughput TCR sequencing. Phenotypic analysis of cattle MAIT cells revealed features highly analogous to those of MAIT cells in humans and mice, including expression of an orthologous TRAV1-TRAJ33 TCR α chain, an effector memory phenotype irrespective of tissue localization, and expression of the transcription factors PLZF and EOMES. We determined the frequency of MAIT cells in peripheral blood and multiple tissues, finding that cattle MAIT cells are enriched in mucosal tissues as well as in the mesenteric lymph node. Cattle MAIT cells were responsive to stimulation by 5-OP-RU and riboflavin biosynthesis competent bacteria in vitro. Furthermore, MAIT cells in milk increased in frequency in cows with mastitis. Following challenge with virulent Mycobacterium bovis, a causative agent of bovine tuberculosis and a zoonosis, peripheral blood MAIT cells expressed higher levels of perforin. Thus, MAIT cells are implicated in the immune response to two major bacterial infections in cattle. These data suggest that MAIT cells are functionally highly conserved and that cattle are an excellent large animal model to study the role of MAIT cells in important zoonotic infections.

Essential Oils in Livestock: From Health to Food Quality

Using plant essential oils (EOs) contributes to the growing number of natural plants' applications in livestock. Scientific data supporting the efficacy of EOs as anti-inflammatory, antibacterial and antioxidant molecules accumulates over time; however, the cumulative evidence is not always sufficient. EOs antioxidant properties have been investigated mainly from human perspectives. Still, so far, our review is the first to combine the beneficial supporting properties of EOs in a One Health approach and as an animal product quality enhancer, opening new possibilities for their utilization in the livestock and nutrition sectors. We aim to compile the currently available data on the main anti-inflammatory effects of EOs, whether encapsulated or not, with a focus on mammary gland inflammation. We will also review the EOs' antioxidant activities when given in the diet or as a food preservative to counteract oxidative stress. We emphasize EOs' in vitro and in vivo ruminal microbiota and mechanisms of action to promote animal health and performance. Given the concept of DOHaD (Developmental Origin of Health and Diseases), supplementing animals with EOs in early life opens new perspectives in the nutrition sector. However, effective evaluation of the significant safety components is required before extending their use to livestock and veterinary medicine.

Heat stress and cow factors affect bacteria shedding pattern from naturally infected mammary gland quarters in dairy cattle

Mastitis-causing pathogens are shed from infected mammary gland quarters and thus contribute to an increased risk of new intramammary infections. The objective of the current study was to investigate the shedding characteristics of various mastitis-causing pathogens and associated animal-specific (somatic cell score and parity) and environmental (heat stress) factors. In a longitudinal study, infected udder quarters were sampled consecutively on 5 dairy farms in Germany. To capture climatic factors, temperature-humidity index (THI) was calculated. In the laboratory analysis, the pathogens and their counts in the milk samples were determined. A generalized linear mixed model with gamma link was used to evaluate the factors influencing pathogen-shedding characteristics. The variables somatic cell count, pathogen, parity, and THI had significant influence on pathogen shedding. Staphylococci were shed in lower values than streptococci. The pathogen shedding from mammary gland quarters with intramammary infections was higher in the first and second lactation than in higher lactations. Exceeding the THI threshold 60 resulted in higher pathogen counts on the same day. This was only caused by the pathogens yeasts and Streptococcus uberis. Possible mechanisms causing differences in pathogen shedding are changes in the counts due to influenced milk quantities, better growth conditions at higher temperatures, or altered immunological reactions. The mechanisms often remain speculative and require further investigation. The study underlines the contribution of cows with high somatic cell counts regarding the transmission of mastitis pathogens within a herd. Furthermore, it becomes clear that heat stress in Germany influences udder health and that prevention measures are useful.

Interaction between bovine mammary epithelial cells and planktonic or biofilm Staphylococcus aureus: The bacterial lifestyle determines its internalization ability and the pathogen recognition

The main cause of mastitis, one of the most costly diseases in the dairy industry, is bacterial intramammary infection. Many of these bacteria are biofilm formers. Biofilms have been associated with resistance to antibiotics and to the host immune system. Here, we evaluated different experimental models representing bacterial biofilm lifestyle with the aim to study bacterial invasion into bovine mammary epithelial cells and the interaction of these cells with planktonic or biofilm Staphylococcus aureus. Staphylococcus aureus V329, its nonbiofilm-forming mutant and bovine mammary alveolar cells (MAC-T) were used. Bacterial invasion was studied using the gentamicin exclusion test, cell viability by trypan blue exclusion technique, TLR2 expression by flow cytometry, IL1β/IL6 production by ELISA and IL8/TNFα gene expression by real-time polymerase chain reaction. Biofilm and planktonic S. aureus showed differences in their invasion ability, with the biofilm mode showing a lower ability. Planktonic S. aureus reduced MAC-T viability after 6 h of co-culture, while biofilms did so at 24 h. MAC-T infected with planktonic bacteria showed increased TLR2 expression. Both lifestyles increased IL8 expression and IL1β/IL6 production but did not modify TNFα expression. Our results demonstrate that the bacterial lifestyle affects the invasion behavior, suggesting that biofilms reduce the bacteria-epithelial cell interaction. Planktonic cultures seem to induce higher cellular activation than biofilms. Further knowledge about the complex host-biofilm interaction is necessary to design more efficient therapies against bovine mastitis.

Identification of novel molecular markers of mastitis caused by Staphylococcus aureus using gene expression profiling in two consecutive generations of Chinese Holstein dairy cattle

Background

Mastitis in dairy cows caused by Staphylococcus aureus is a major problem hindering economic growth in dairy farms worldwide. It is difficult to prevent or eliminate due to its asymptomatic nature and long persistence of infection. Although transcriptomic responses of bovine mammary gland cells to pathogens that cause mastitis have been studied, the common responses of peripheral blood leukocytes to S. aureus infection across two consecutive generations of dairy cattle have not been investigated.

Methods

In the current study, RNA-Seq was used to profile the transcriptomes of peripheral blood leukocytes sampled from S. aureus-infected mothers and their S. aureus-infected daughters, and also healthy non-infected mothers and their healthy daughters. Differential gene expression was evaluated as follows: 1) S. aureus-infected cows versus healthy non-infected cows (S vs. H, which include all the mothers and daughters), 2) S. aureus-infected mothers versus healthy non-infected mothers (SM vs. HM), and 3) S. aureus-infected daughters versus healthy non-infected daughters (SMD vs. HMD).

Results

Analysis of all identified expressed genes in the four groups (SM, SMD, HM, and HMD) showed that EPOR, IL9, IFNL3, CCL26, IL26 were exclusively expressed in both the HM and HMD groups, and that they were significantly (P <  0.05) enriched for the cytokine-cytokine receptor interaction pathway. A total of 17, 13 and 10 differentially expressed genes (DEGs) (FDR P_adj. < 0.1 and |FC| > 1.2) were detected in the three comparisons, respectively. DEGs with P <  0.05 and |FC| > 2 were used for functional enrichment analyses. For the S vs. H comparison, DEGs detected included CCL20, IL13 and MMP3, which are associated with the IL-17 signaling pathway. In the SM vs. HM and SMD vs. HMD comparisons, five (BLA-DQB, C1R, C2, FCGR1A, and KRT10) and six (BLA-DQB, C3AR1, CFI, FCAR, FCGR3A, and LOC10498484) genes, respectively, were involved in the S. aureus infection pathway.

Conclusions

Our study provides insights into the transcriptomic responses of bovine peripheral blood leukocytes across two generations of cattle naturally infected with S. aureus. The genes highlighted in this study could serve as expression biomarkers for mastitis and may also contain sequence variation that can be used for genetic improvement of dairy cattle for resilience to mastitis.

Effect of bismuth subnitrate on in vitro growth of major mastitis pathogens

The mode of action of bismuth subnitrate in teat sealant formulations as a preventative for intramammary infections during the dry period is unknown. Although previous studies proposed an action mechanism-creating a physical barrier in the teat canal to prevent bacterial invasion-it has not been proven experimentally. We hypothesized that bismuth subnitrate has an inhibitory effect on bacterial growth, in addition to its barrier effect. The objective of this study was to assess the effect of bismuth subnitrate on bacterial growth of major mastitis-causing agents. A strain of Streptococcus uberis (SR115), 2 strains of Staphylococcus aureus (SA3971/59 and SA1), and a strain of Escherichia coli (P17.14291) were tested in vitro for their ability to grow in the presence or absence of bismuth subnitrate. Disk diffusion testing, impedance measurement, and evaluation of bacterial growth in shaking conditions were the methods used to test this hypothesis. A reduction of growth in the presence of bismuth subnitrate occurred for all the strains tested. However, we observed strain and species variations in the extent of growth inhibition. These results suggest that an inhibitory effect on bacterial growth by bismuth subnitrate could partially explain the efficacy of bismuth-based formulations for preventing intramammary infections over the dry period. Further research is required to test the effect of teat sealant formulations on bacterial growth.

Genome Sequence of a Staphylococcus aureus Strain Isolated from a Dairy Cow That Was Nonresponsive to Antibiotic Treatment

Staphylococcus aureus can cause mastitis in dairy cattle. We report the genome sequence of a Staphylococcus aureus strain isolated from a dairy cow with a chronic case of mastitis. The infection with this strain of Staphylococcus aureus was not cleared from the animal with antibiotic treatment.

Staphylococcus aureus can cause mastitis in dairy cattle. We report the genome sequence of a Staphylococcus aureus strain isolated from a dairy cow with a chronic case of mastitis. The infection with this strain of Staphylococcus aureus was not cleared from the animal with antibiotic treatment.

Antimicrobial susceptibility of nine udder pathogens recovered from bovine clinical mastitis milk in Europe 2015-2016: VetPath results

VetPath is an ongoing pan-European antimicrobial susceptibility monitoring programme collecting pathogens from diseased cattle, pigs and poultry not recently treated with antibiotics. Non-duplicate isolates (n = 1244) were obtained from cows with acute clinical mastitis in eight countries during 2015-2016 for centrally antimicrobial susceptibility testing according CLSI standards. Among Escherichia coli (n = 225), resistance was high to ampicillin and tetracycline, moderate to kanamycin and low to amoxicillin/clavulanic acid and cefazolin. The MIC_50/90 of danofloxacin, enrofloxacin and marbofloxacin were 0.03 and 0.06 μg/mL. For Klebsiella spp. (n = 70), similar results were noted, except for ampicillin and kanamycin. We detected 3.7 % (11/295) Enterobacteriaceae isolates carrying an ESBL/AmpC gene. Staphylococcus aureus (n = 247) and coagulase-negative staphylococci (CoNS; n = 189) isolates were susceptible to most antimicrobials tested except to penicillin (25.1 and 29.1 % resistance). Two S. aureus and thirteen CoNS isolates harboured mecA gene. Streptococcus uberis isolates (n = 208) were susceptible to β-lactam antibiotics (87.1-94.7 % susceptibility), 23.9 % were resistant to erythromycin and 37.5 % to tetracycline. Resistance to pirlimycin was moderate. For Streptococcus dysgalactiae (n = 132) the latter figures were 10.6 and 43.2 %; pirlimycin resistance was low. MIC values for Streptococcus agalactiae, Trueperella pyogenes and Corynebacterium spp. were generally low. This current VetPath study shows that mastitis pathogens were susceptible to most antimicrobials with exceptions of staphylococci against penicillin and streptococci against erythromycin or tetracycline. For most antimicrobials, the percentage resistance and MIC_50/90 values among the major pathogens were comparable to that of the preceeding VetPath surveys. This work highlights the high need to set additional clinical breakpoints for antimicrobials frequently used to treat mastitis.

Hepatic Transcriptome Analysis Identifies Divergent Pathogen-Specific Targeting-Strategies to Modulate the Innate Immune System in Response to Intramammary Infection

Mastitis is one of the major risks for public health and animal welfare in the dairy industry. Two of the most important pathogens to cause mastitis in dairy cattle are Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). While S. aureus generally induces a chronic and subclinical mastitis, E. coli is an important etiological pathogen resulting in an acute and clinical mastitis. The liver plays a central role in both, the metabolic and inflammatory physiology of the dairy cow, which is particularly challenged in the early lactation due to high metabolic and immunological demands. In the current study, we challenged the mammary glands of Holstein cows with S. aureus or E. coli, respectively, mimicking an early lactation infection. We compared the animals' liver transcriptomes with those of untreated controls to investigate the hepatic response of the individuals. Both, S. aureus and E. coli elicited systemic effects on the host after intramammary challenge and seemed to use pathogen-specific targeting strategies to bypass the innate immune system. The most striking result of our study is that we demonstrate for the first time that S. aureus intramammary challenge causes an immune response beyond the original local site of the mastitis. We found that in the peripheral liver tissue defined biological pathways are switched on in a coordinated manner to balance the immune response in the entire organism. TGFB1 signaling plays a crucial role in this context. Important pathways involving actin and integrin, key components of the cytoskeleton, were downregulated in the liver of S. aureus infected cows. In the hepatic transcriptome of E. coli infected cows, important components of the complement system were significantly lower expressed compared to the control cows. Notably, while S. aureus inhibits the cell signaling by Rho GTPases in the liver, E. coli switches the complement system off. Also, metabolic hepatic pathways (e.g., lipid metabolism) are affected after mammary gland challenge, demonstrating that the liver restricts metabolic tasks in favor of the predominant immune response after infection. Our results provide new insights for the infection-induced modifications of the dairy cow's hepatic transcriptome following mastitis.

Silver(i) complexes with different pyridine-4,5-dicarboxylate ligands as efficient agents for the control of cow mastitis associated pathogens

Infections of the cow udder leading to mastitis and lower milk quality are one of the biggest problems in the dairy industry worldwide. Unfortunately, therapeutic options for the treatment of cow mastitis are limited as a consequence of the development of pathogens that are resistant to conventionally used antibiotics. In the search for agents that will be active against cow mastitis associated pathogens, in the present study, five new silver(i) complexes with different chelating pyridine-4,5-dicarboxylate types of ligands, [Ag(NO₃)(py-2py)]_n (1), [Ag(NO₃)(py-2metz)]_n (2), [Ag(CH₃CN)(py-2py)]BF₄ (3), [Ag(py-2tz)₂]BF₄ (4) and [Ag(py-2metz)₂]BF₄ (5), py-2py is dimethyl 2,2'-bipyridine-4,5-dicarboxylate, py-2metz is dimethyl 2-(4-methylthiazol-2-yl)pyridine-4,5-dicarboxylate and py-2tz is dimethyl 2-(thiazol-2-yl)pyridine-4,5-dicarboxylate, were synthesized, structurally characterized and assessed for in vitro antimicrobial activity using both standard bioassay and clinical isolates from a contaminated milk sample obtained from a cow with mastitis. These complexes showed remarkable activity against the standard panel of microorganisms and a selection of clinical isolates from the milk of the cow diagnosed with mastitis. With the aim of determining the therapeutic potential of silver(i) complexes, their toxicity in vivo against the model organism, Caenorhabditis elegans (C. elegans), was investigated. The complexes that had the best therapeutic profile, 2 and 5, induced bacterial membrane depolarization and the production of reactive oxygen species (ROS) in Candida albicans cells and inhibited the hyphae as well as the biofilm formation. Taken together, the presented data suggest that the silver(i) complexes with pyridine ligands could be considered for the treatment of microbial pathogens, which are causative agents of cow mastitis.

Bonelli R, A. Penna B, P. Albuquerque J, M. Souza R, M. F. Cerqueira A. Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview

In animal husbandry, antimicrobial agents have been administered as supplements to increase production over the last 60 years. Large-scale animal production has increased the importance of antibiotic management because it may favor the evolution of antimicrobial resistance and select resistant strains. Brazil is a significant producer and exporter of animal-derived food. Although Brazil is still preparing a national surveillance plan, several changes in legislation and timely programs have been implemented. Thus, Brazilian data on antimicrobial resistance in bacteria associated with animals come from official programs and the scientific community. This review aims to update and discuss the available Brazilian data on this topic, emphasizing legal aspects, incidence, and genetics of the resistance reported by studies published since 2009, focusing on farm animals and derived foods with the most global public health impact. Studies are related to poultry, cattle, and pigs, and mainly concentrate on non-typhoid Salmonella, Escherichia coli, and Staphylococcus aureus. We also describe legal aspects of antimicrobial use in this context; and the current occurrence of genetic elements associated with resistance to beta-lactams, colistin, and fluoroquinolones, among other antimicrobial agents. Data here presented may be useful to provide a better understanding of the Brazilian status on antimicrobial resistance related to farm animals and animal-derived food products.

Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview

In animal husbandry, antimicrobial agents have been administered as supplements to increase production over the last 60 years. Large-scale animal production has increased the importance of antibiotic management because it may favor the evolution of antimicrobial resistance and select resistant strains. Brazil is a significant producer and exporter of animal-derived food. Although Brazil is still preparing a national surveillance plan, several changes in legislation and timely programs have been implemented. Thus, Brazilian data on antimicrobial resistance in bacteria associated with animals come from official programs and the scientific community. This review aims to update and discuss the available Brazilian data on this topic, emphasizing legal aspects, incidence, and genetics of the resistance reported by studies published since 2009, focusing on farm animals and derived foods with the most global public health impact. Studies are related to poultry, cattle, and pigs, and mainly concentrate on non-typhoid Salmonella, Escherichia coli, and Staphylococcus aureus. We also describe legal aspects of antimicrobial use in this context; and the current occurrence of genetic elements associated with resistance to beta-lactams, colistin, and fluoroquinolones, among other antimicrobial agents. Data here presented may be useful to provide a better understanding of the Brazilian status on antimicrobial resistance related to farm animals and animal-derived food products.

Biosensors for On-Farm Diagnosis of Mastitis

Bovine mastitis is an inflammation of the mammary gland caused by a multitude of pathogens with devastating consequences for the dairy industry. Global annual losses are estimated to be around €30 bn and are caused by significant milk losses, poor milk quality, culling of chronically infected animals, and occasional deaths. Moreover, mastitis management routinely implies the administration of antibiotics to treat and prevent the disease which poses serious risks regarding the emergence of antibiotic resistance. Conventional diagnostic methods based on somatic cell counts (SCC) and plate-culture techniques are accurate in identifying the disease, the respective infectious agents and antibiotic resistant phenotypes. However, pressure exists to develop less lengthy approaches, capable of providing on-site information concerning the infection, and in this way, guide, and hasten the most adequate treatment. Biosensors are analytical tools that convert the presence of biological compounds into an electric signal. Benefitting from high signal-to-noise ratios and fast response times, when properly tuned, they can detect the presence of specific cells and cell markers with high sensitivity. In combination with microfluidics, they provide the means for development of automated and portable diagnostic devices. Still, while biosensors are growing at a fast pace in human diagnostics, applications for the veterinary market, and specifically, for the diagnosis of mastitis remain limited. This review highlights current approaches for mastitis diagnosis and describes the latest outcomes in biosensors and lab-on-chip devices with the potential to become real alternatives to standard practices. Focus is given to those technologies that, in a near future, will enable for an on-farm diagnosis of mastitis.

Intraepithelial neutrophils in mammary, urinary and gall bladder infections

Neutrophil mobilization is a crucial response to protect the host against invading microorganisms. Neutrophil recruitment and removal have to be tightly regulated to prevent uncontrolled inflammation and excessive release of their toxic content causing tissue damage and subsequent organ dysfunctions. We show here the presence of live and apoptotic neutrophils in the cytoplasm of inflamed mammary, urinary and gall bladder epithelial cells following infection with E. coli and Salmonella bacteria. The entry process commenced with adherence of transmigrated neutrophils to the apical membrane of inflamed epithelial cells. Next, nuclear rearrangement and elongation associated with extensive actin polymerization enabled neutrophils to crawl and invaginate the apical membrane into cytoplasmic double membrane compartments. Scission of the invaginated cell membrane from the entry point and loss of these surrounding membranes released intracellular neutrophils into the cytoplasm where they undergone apoptotic death. The co-occurrence of this observation with bacterial invasion and formation of intracellular bacterial communities (IBCs) might link entry of infected neutrophils to the formation of IBCs and chronic carriage in E. coli mastitis and cystitis and Salmonella cholecystitis.