A study of bovine mastitis, milking procedures and management practices on 25 Estonian dairy herds

Phenotypic and genotypic characterization of erythromycin-resistant Staphylococcus aureus isolated from bovine subclinical mastitis in Egypt

Background and Aim

Subclinical mastitis (SCM) caused by erythromycin-resistant Staphylococcus aureus is a significant disease in lactating animals. Therefore, it is crucial to understand the genetic factors contributing to erythromycin resistance in S. aureus. This study aimed to estimate the prevalence of S. aureus in milk from subclinical mastitic cattle and buffaloes and tank milk samples as identified by probe-based real-time polymerase chain reaction (PCR) and the genotypic assessment of macrolide and erythromycin resistance profiles, as well as to analyze the phylogenetic relatedness of our local isolates of S. aureus.

Materials and Methods

In total, 285 milk samples were analyzed using the California mastitis test to detect SCM. Milk samples were cultured on different specific Staphylococcus media. The presence of S. aureus was confirmed by Gram staining, the catalase and coagulase tests, the detection of hemolytic activity, DNase agar testing, and biofilm activity in Congo red medium. The genotypic identification of S. aureus (nuc) was performed. The determinants of erythromycin (ermA, ermB, ermC, and ermT) and macrolide resistance (msrA) were screened in all isolates. DNA sequencing of our local isolates of S. aureus was used to analyze their phylogenetic relatedness. Moreover, histopathological examination of tissue specimens of mammary gland was performed.

Results

The S. aureus positivity rates were 36.4%, 48.8%, and 63.6% in cattle, buffalo, and bulk tank milk, respectively. Probe-based real-time PCR molecularly confirmed all 62 S. aureus isolates. Thirty-one isolates were subjected to PCR to create profiles of their genotypic erythromycin resistance. ermA, ermB, ermC, and ermT were present in 5 (8%), 26 (41.9%), 18 (29%), and 15 (24.1%) S. aureus isolates, respectively. Moreover, msrA was found in three (4.8%) strains. Eight PCR products were produced using standard PCR for DNA sequencing. Multiple sequence alignment, phylogenetic tree construction, and analysis of nuc in S. aureus revealed a high degree of homology (100%) with S. aureus strains isolated from milk in cases of bovine mastitis in India and Kenya. Histological analysis of udder tissues revealed extensive aggregation of mononuclear inflammatory cells in the interstitial connective tissue, primarily lymphocytes, and macrophages.

Conclusion

This study showed a high prevalence of erythromycin resistance in S. aureus isolates. This information is vital for controlling mastitis and the spread of resistance genes between bacterial strains and hosts. Moreover, the probe-based real-time PCR approach is helpful for the rapid screening of S. aureus isolates and the consequent efficient treatment and control of S. aureus mastitis.

Advances in Diagnostic Approaches and Therapeutic Management in Bovine Mastitis

Mastitis causes huge economic losses to dairy farmers worldwide, which largely negatively affects the quality and quantity of milk. Mastitis decreases overall milk production, degrades milk quality, increases milk losses because of milk being discarded, and increases overall production costs due to higher treatment and labour costs and premature culling. This review article discusses mastitis with respect to its clinical epidemiology, the pathogens involved, economic losses, and basic and advanced diagnostic tools that have been used in recent times to diagnose mastitis effectively. There is an increasing focus on the application of novel therapeutic approaches as an alternative to conventional antibiotic therapy because of the decreasing effectiveness of antibiotics, emergence of antibiotic-resistant bacteria, issue of antibiotic residues in the food chain, food safety issues, and environmental impacts. This article also discussed nanoparticles'/chitosan's roles in antibiotic-resistant strains and ethno-veterinary practices for mastitis treatment in dairy cattle.

Effectiveness of Intramammary Antibiotics, Internal Teat Sealants, or Both at Dry-Off in Dairy Cows: Milk Production and Somatic Cell Count Outcomes

Mastitis is the greatest disease challenge for dairy producers, with substantial economic impacts due to lost milk production. Amongst the approaches implemented to control and prevent mastitis on dairies are vaccination, pre- and post-milking teat dips, and treatments at dry-off including intramammary antibiotics and teat sealants. The objectives of our study were to evaluate the effect of different treatments at dry-off on the subsequent lactation's milk production and somatic cell count (SCC). A single-blinded controlled block randomized clinical trial was conducted between December 2016 and August 2018 on eight herds from four of the top ten milk-producing counties in California: Tulare, Kings, Stanislaus, and San Joaquin. The trial was repeated with cows enrolled during the winter and summer seasons to account for seasonal variability. Eligible cows were treated at dry-off with either intramammary antibiotics (AB), internal teat sealant (TS), AB + TS, or did not receive any treatment (control), and were followed through 150 days in milk (DIM) post-calving. The milk production and SCC data were extracted from monthly test day milk records (Dairy Comp 305, Valley Ag Software, Tulare, CA, USA). Two-piece spline linear mixed models were used to model the milk production (kg) and natural logarithm-transformed SCC. After accounting for parity, breed, season, and dry period duration, the milk model showed a significant increase in milk production (1.84 kg/day) in cows treated with AB + TS at dry-off in comparison to controls. There was no significant difference in the milk produced by cows that received either AB or TS (0.12 kg/day, and 0.67 kg/day, respectively) in comparison to the untreated cows. Different dry cow treatments were associated with a significant reduction in ln SCC during the first 150 DIM. The greatest reduction was associated with using AB + TS, followed by AB, and finally TS in comparison to controls. Dairies with high SCC may benefit from treating cows at dry-off with AB, TS, or both.

Molecular characterization of genes responsible for biofilm formation in Staphylococcus aureus isolated from mastitic cows

Background and Aim:

Mastitis is considered a significant disease of lactating animals. There are new attitudes for recognizing genes responsible for causing this disease to overcome and change the manipulation of this problem. This study aimed to isolate and identify Staphylococcusaureus strains from mastitic bovine animals and detect some specific biofilm-forming genes (icaA, icaD, and biofilm-associated protein [bap] genes clfA, fnbA, agrI, agrII, agrIII, agrIV, and cna).

Materials and Methods:

A total of 121 mastitic milk samples were analyzed using biochemical tests (catalase test, oxidative-fermentative test, and coagulase test) and Gram stain. Multiplex polymerase chain reaction was applied to characterize biofilm genes (icaA, icaD, bap, clfA, and fnbA) in addition to (agrI, agrII, agrIII, agrIV, and cna).

Results:

Among the 121 milk samples, 35 staphylococci isolates were derived with an incidence of 28.92% (35/121); among them, 19 are coagulase positive. Ninety percent of the isolates had ica genes (icaA and icaD) while bap gene was not recognized in any isolate. In addition, the incidence of fnbA, can, andclfA was 89.5% each. The prevalence of agr specific groups (agrI, agrII, agrIII, and agrIV) was 78.9%, 52.6%, 10.5%, and 15.8%, respectively.

Conclusion:

This study concluded that S. aureus has variant mechanisms of pathogenicity to form biofilm devoid of carrying a specific gene.

Prevalence of bovine mastitis and main risk factors in Tunisia

Tunisian milk chain is in danger with a dramatical reduction of milk production over the last years. Improving the quality of milk seems mandatory to improve farmers' income, but for the moment, there is only scarce data on milk quality management in Tunisia. In this context, the aims of our study were first to describe the prevalence of bovine mastitis in 267 cows from 71 representative small dairy farms in the North (43.7%) and Center (56.3%) regions of Tunisia, using mastitis detection by California Mastitis Test (CMT) on milk quarter and clinical signs, and second, to assess possible risk factors for mastitis from animal, environment, and breeding management. In parallel, cow and bulk milk somatic cell count (SCC) were analyzed. Our results demonstrated that 60.3% of cows showed mastitis as determined by CMT and clinical examinations. Increased stage of lactation, parity, udder depth, and type of milking were significantly (P < 0.05) associated with increased odds of mastitis prevalence. The mean of individual cow SCC (ISCC) and bulk milk SCC (BMSCC) was very high (1083 × 10³ cells/mL and 698 × 10³ cells/mL, respectively), all ranks and stages of lactations combined. These high values confirm the infectious origin of mastitis that we found caused mainly by Staphylococcus aureus and coagulase-negative Staphylococci. In conclusion, control of the identified risks factors and improved biosecurity measures must be encouraged to restore udder health and milk quality and thus productivity and durability of Tunisian milk chain.

Effect of Pre-Milking Teat Foam Disinfection on the Prevention of New Mastitis Rates in Early Lactation

Simple Summary

The benefits of pre-milking teat disinfection have varied depending on management, practices and bacterial strains present in the environment, with some studies stating a reduction in the incidence of new infections and other studies stating little benefit of pre-milking teat disinfection. Furthermore, the effectiveness of pre-milking teat disinfection using foam has not previously been evaluated in a pasture-based dairy herd. This study has shown little benefit of applying a foaming pre-milking teat disinfectant in early lactation in a pasture-based dairy herd. However, the foaming teat disinfectant reduced bacterial counts on teat skin and may reduce the bacterial contamination of milk.

Abstract

The objective of this study was to determine the benefit of pre-milking teat foam disinfection on the prevention of new infections by contagious and environmental bacteria in two spring calving herds managed outdoors (Herd 1 [H1]; 331 cows and Herd 2 [H2]; 142 cows). Four pre-milking teat preparation treatments were applied post calving; with each herd receiving two treatments; using a split udder design (for approx. 15 weeks). These treatments included; (1) ‘water wash, foam application and dry wipe (WFD) in H1′; (2) ‘water wash and dry wipe (WD)’ in H1; (3) ‘foam application and dry wipe (FD)’ in H2; (4) ‘no teat cleaning preparation (NP)’ in H2. Individual quarter foremilk samples were collected on four occasions and all clinical and sub-clinical cases were recorded. The mean SCC of quarter foremilk samples was 134 × 10³ cells/mL and 127 × 10³ cells/mL for WD and WFD, respectively, and 109 × 10³ cells/mL and 89 × 10³ cells/mL for NP and FD, respectively (p > 0.05). Lower bacterial counts were observed on teat skin that received a foaming treatment. Pre-milking teat disinfection using a foaming product may be of little benefit, in early lactation, for a pasture-based dairy herd.

PacBio sequencing revealed variation in the microbiota diversity, species richness and composition between milk collected from healthy and mastitis cows

Mastitis is the economically most important disease of dairy cows. This study used PacBio single-molecule real-time sequencing technology to sequence the full-length 16S rRNAs from 27 milk samples (18 from mastitis and nine from healthy cows; the cows were at different stages of lactation). We observed that healthy or late stage milk microbiota had significantly higher microbial diversity and richness. The community composition of the microbiota of different groups also varied greatly. The healthy cow milk microbiota was predominantly comprised of Lactococcus lactis, Acinetobacter johnsonii, and Bacteroides dorei, while the milk from mastitis cows was predominantly comprised of Bacillus cereus. The prevalence of L. lactis and B. cereus in the milk samples was confirmed by digital droplets PCR. Differences in the milk microbiota diversity and composition could suggest an important role for some these microbes in protecting the host from mastitis while others associated with mastitis. The results of our research serve as useful references for designing strategies to prevent and treat mastitis.

Milk Lactose as a Biomarker of Subclinical Mastitis in Dairy Cows

Bovine subclinical mastitis can cause great harm to dairy herds because of its negative impact on milk production and quality and cow health. Improved diagnostic tools are needed to maximise the control of subclinical mastitis distribution and ensure the high quality of milk as an industrial product. Between 2015 and 2020, seventy-two dairy herds were screened for bovine subclinical mastitis causative agents to identify the relationship between seasons, lactose levels and subclinical mastitis infection. The predominant species found in the milk samples were mixed microbiota, coagulase-negative Staphylococcus and Staphylococcus aureus. Yeasts were found exclusively in autumn, while Enterococcus spp. and Escherichia coli were only found in summer and autumn. A negative correlation was detected between milk lactose and number of somatic cells in milk (-0.471; p < 0.001). The lactose levels in milk were closely associated with the prevalence (%) of subclinical mastitis pathogens, such as Streptococcus agalactiae (y = -1.8011x + 10.867, R2 = 0.9298), Staph. aureus (y = -3.5216x + 25.957, R2 = 0.8604) and other Streptococci (y = -0.5956x + 7.6179, R2 = 0.6656). These findings suggest that milk lactose may be used as a biomarker of suspected udder inflammation in modern health prevention programmes for cows to reduce the prevalence of subclinical mastitis pathogens in dairy cattle herds.

An Outbreak of Subclinical Mastitis in a Dairy Herd Caused by a Novel Streptococcus canis Sequence Type (ST55)

Simple Summary

Although Streptococcus (S). canis is mainly isolated from carnivores, intramammary infection in dairy cows caused by this bacterium have been reported. Cats and dogs with access to the barn have been considered as the main source of these infections. Here, we report subclinical mastitis and substantially increased bulk milk somatic cell counts in a dairy herd. During a herd visit, management and hygiene practices were evaluated and data from the milk quality control program were retrieved. Furthermore, quarter milk samples, mucosal swabs from farm cats and a dog, and swabs from the milking unit were aseptically collected. The samples were examined bacteriologically, and S. canis was identified using conventional phenotypic methods and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Genetic relationships between S. canis isolates were determined by multilocus sequence typing, revealing that all S. canis isolates shared the same sequence type, presenting a new combination of alleles for which a new number (ST55) was assigned. As the most likely source of intramammary infection, a farmyard cat was identified. The concurrent treatment of all positive cows and the improvement of management (no further access of carnivores to the barn) lead to positive results, including a decreased somatic cell count.

Abstract

The present case report provides data on the phenotypic and genotypic properties of S. canis isolated from nine dairy cows with subclinical mastitis (SCC greater than 200,000 cells/mL in the quarter milk sample, no clinical signs) and from a cat living in the barn and reports the eradication of the pathogen from the herd with an automatic milking system. The isolates were identified using conventional bacteriology, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) and genetic relationships were investigated by multilocus sequence typing (MLST). Udder health management and hygiene instructions comprised the removal of the carnivores from the barn, strict monitoring of milking hygiene and techniques to avoid new infections via the milking robot, with simultaneous therapy for all infected cows. Phenotypic and genotypic properties of all isolates were identical. MLST revealed a unique sequence type (ST55) and a farmyard cat was identified as the most likely source of the S. canis infection in cows. The simultaneous treatment of all infected cows and management and hygiene improvements lead to a decreased SCC within four weeks.

Effects of Melatonin on Dairy Herd Improvement (DHI) of Holstein Cow with High SCS

Mastitis is a common disease in cows breeding. The milk quality will be significantly reduced with increased milk somatic cells, which often occurs in cows with mastitis. In this study, the influence of seasonal changes, age and lactation stages in the Dairy Herd Improvement (DHI) of cows was investigated. Then, the Dairy Herd Improvement (DHI) of cows with high somatic cell score (SCS) after melatonin treatment was systemically investigated. The results showed that melatonin significantly suppressed the milk somatic cell score under all of the tested conditions. The melatonin treatment also improved the milk nutritional value by reducing its fat but increasing its lactose and protein contents. The application of melatonin significantly improved the DHI. The beneficial effects of melatonin on DHI are likely attributed to the antioxidant and anti-inflammatory activities of melatonin.

Analysis of virulence traits of Staphylococcus aureus isolated from bovine mastitis in semi-intensive and family dairy farms

BACKGROUND

Staphylococcus aureus is one of the main microorganisms that causes bovine mastitis, and its well-known virulence characteristics and interactions with the environment are used to aid the design of more efficient therapies.

OBJECTIVES

To determine whether the virulence traits, such as antibiotic resistance and biofilm-forming and internalization abilities, of S. aureus isolated from bovine mastitis are related to dairy production system types.

METHODS

The study was performed in the Mexican states of Guanajuato and Michoacan. Semi-intensive dairy farms (SIDFs) and family dairy farms (FDFs) (454 and 363 cows, respectively) were included. The 194 milk samples from mastitis affected quarters were collected and 92 strains of S. aureus were isolated and identified by biochemical and molecular tests. Antibiotic resistance, biofilm and internalization assays were performed on 30 randomly selected isolated strains to determine virulence traits, and these strains were equally allocated to the 2 dairy production systems.

RESULTS

All 30 selected strains displayed a high degree of resistance (50%-91.7%) to the antibiotics tested, but no significant difference was found between SIDF and FDF isolates. S. aureus strains from SIDFs had an average biofilm forming capacity of up to 36% (18.9%-53.1%), while S. aureus strains from FDFs registered an average of up to 53% (31.5%-77.8%) (p > 0.05). Internalization assays revealed a higher frequency of internalization capacity for strains isolated from FDFs (33.3%) than for those isolated from SIDFs (6.7%) (p > 0.05). fnbpA gen was detected in 46.6% of FDF strains and 33.3% of SIDF strains, and this difference was significant (p < 0.05).

CONCLUSIONS

Our findings show that the virulence traits of S. aureus isolates analyzed in this study, depend significantly on several factors, such as phenotype, genotype, and environmental conditions, which are significantly related to dairy production system type and daily management practices.

Prevalence, Antimicrobial Resistance Profiles, Virulence and Enterotoxins-Determinant Genes of MRSA Isolated from Subclinical Bovine Mastitis in Egypt

Subclinical mastitis caused by Staphylococcus aureus has worldwide public health significance. Here, we aimed to determine the prevalence of S. aureus, antimicrobial resistance profiles, and the virulence and enterotoxins determinant genes of MRSA strains that caused subclinical bovine mastitis. Milk samples were collected from 120 lactating animals (50 buffaloes and 70 dairy cattle) from different farms located in Ismailia Province (Egypt). The collected samples were investigated for subclinical mastitis using a California mastitis test. The total prevalence of S. aureus was 35.9% (84/234) with 36.3% (53/146) in cattle and 31% (31/88) in buffaloes. Antimicrobial susceptibility testing showed that 35.7% (30/84) of the isolated strains were resistant to cefoxitin, defined as methicillin-resistant S. aureus (MRSA), with 37.7% (20/53) in cattle and 32.2% (10/31) in buffaloes. Using PCR, 100% of the tested strains harbored coa and mecA genes, while 86.6% were positive for spa gene, with remarkable gene size polymorphism. Additionally, 10% of the tested strains contained the pvl gene. Further, using multiplex PCR, 26.6% of the tested samples had sea gene, two strains had sec gene and only one strain had sea and sec genes. The seb and sed genes were absent in the tested strains. In conclusion, mecA, coa and spa virulence genes were widely distributed in MRSA strains isolated from bovine milk, whereas the sea gene was the most predominant enterotoxin gene. Notably, this is the first report that emphasizes the prevalence of pvl gene of MRSA isolated from bovine milk in Egypt.

Suitability of somatic cell count, electrical conductivity, and lactate dehydrogenase activity in foremilk before versus after alveolar milk ejection for mastitis detection

Mastitis is responsible for substantial economic loss and significant animal welfare concerns for the dairy industry. Sensors that measure electrical conductivity (EC) and enzyme concentrations of lactate dehydrogenase (LDH) are presently used for automatic detection of mastitis. However, EC is not sensitive enough to detect mastitis, and the ability of LDH activity to identify mastitis caused by different pathogens is a potential option that needs to be investigated. This study was conducted to test the following hypotheses: (a) strict foremilk before milk ejection is more informative in detecting mastitis, in general, than foremilk removed after cows were stimulated for milk ejection; and (b) the value of LDH activity as a mastitis indicator depends on the type of pathogen associated with the infection. Milk samples (before afternoon milking) from 48 Holstein-Friesian cows at the University of Sydney's dairy farm (Camden, New South Wales, Australia) with EC > 7.5 mS/cm in any of the 4 quarters were collected over a period of 2 mo. Quarter milk samples (n = 343) from 48 cows were collected manually in the automatic milking rotary in 3 steps: foremilk before (strict foremilk) and after milk ejection, followed by an aseptic sample for bacteriological culture. The EC (mS), LDH (U/L), SCC (cells/mL), and milk protein and fat content (%) of foremilk in both sampling times were compared and used as predictors for gram-positive and gram-negative mastitis. Quarter (n = 515) observations from 44 cows were analyzed using a logistic mixed or linear mixed model, with cow and quarter nested within cow as random effects. Milk from both sampling times was also assessed by producing a receiver operating characteristic (ROC) curve and calculating the area under the curve (AUC) to determine ability to detect mastitis. Overall, EC and LDH were greater and milk protein (%) was lower in strict foremilk than in milk fractions obtained after milk ejection. Data from strict foremilk samples had slightly higher AUC values (0.98 to 0.99 vs. 0.97 to 0.98, respectively) than did the after-ejection milk samples. Although gram-negative coliform mastitis had significantly higher LDH activity than did gram-positive mastitis (6.19 vs. 5.34 log₁₀ U/L), the robustness of this result is questionable due to limited sample size. We concluded that milk samples taken before ejection can influence major mastitis indicators, suggesting that automatic milking system sensors could be modified to monitor milk before ejection for more efficient mastitis detection.

Neutralization of Interleukin-17A Attenuates Lipopolysaccharide-Induced Mastitis by Inhibiting Neutrophil Infiltration and the Inflammatory Response

Mastitis has been recognized as a common and major disease of cows with a strong impact on dairy farming. Interleukin-17A (IL-17A) has been shown to mediate crucial crosstalk between the immune system and various epithelial tissues, initiating a series of defensive mechanisms against bacterial and fungal infections. This crosstalk is especially involved in neutrophil infiltration. To evaluate the role of IL-17A in immune defense in the mammary gland in mice, we tested the effects of depleting IL-17A on changes in pathology, neutrophil infiltration, and pro-inflammatory cytokine levels in the mammary gland stimulated by lipopolysaccharide (LPS). Further, the effects of IL-17A on the activation of the nuclear factor-κB (NF-κB) signaling pathway during mastitis induced by LPS were also studied. The results showed that the production of IL-17A was significantly elevated during mastitis induced by LPS. IL-17A blockade via an intraperitoneal antibody injection protected against LPS-induced mastitis, as indicated by decreased neutrophil infiltration, myeloperoxidase activity, pro-inflammatory cytokines levels, and NF-κB signaling pathway molecule phosphorylation in response to LPS. In conclusion, an elevated IL-17 level plays a crucial role during mastitis, and anti-IL-17A antibody blockade protects against LPS-induced mammary gland inflammation induced through the NF-κB signaling pathway, which provides a new potential treatment target for mastitis.

Isolation and characterization of Corynebacterium spp. from bulk tank raw cow's milk of different dairy farms in Germany

We detected Corynebacterium spp. in raw milk samples of three farms by means of a selective, tellurite-containing medium. The isolated strains were identified based on full 16S rRNA gene sequences and partial rpoB gene sequences as C. xerosis, C. variabile, C. lactis, C. callunae, C. confusum, C. glutamicum and C. crudilactis. The identification based on 16S rRNA and rpoB sequences was not reliable for isolates of C. xerosis. Chemotaxonomic markers of the isolates, fatty acids, acyl type of peptidoglycan, presence and length of mycolic acids, quinone patterns, and polar lipids, were in accord with the known characteristics of these species. Biochemical profiles, analyzed with the API Coryne system, were able to differentiate all groups, but were unable to identify the strains due to an inappropriate database for raw-milk associated corynebacteria. Most of the tested isolates showed a single-substance resistance against oxacillin, but three single isolates were classified as multidrug resistant.

Prevalence of subclinical mastitis in Finnish dairy cows: changes during recent decades and impact of cow and herd factors

Background

The dairy industry has undergone substantial structural changes as intensive farming has developed during recent decades. Mastitis continues to be the most common production disease of dairy cows. Nationwide surveys of mastitis prevalence are useful in monitoring udder health of dairy herds and to study the impact of structural changes on the dairy industry. This survey on bovine subclinical mastitis was the first based on cow composite milk somatic cell count (SCC) data from the Finnish national health monitoring and milk recording database. A cow with composite milk SCC ≥200,000 cells/ml in at least one of the four test milkings during the year was considered to have subclinical mastitis and a cow with composite milk SCC ≥200,000 cells/ml in three or in all four test milkings during the year to have chronic subclinical mastitis. The aim of the study was to determine the prevalence of subclinical mastitis and chronic subclinical mastitis in Finland in 1991, 2001 and 2010 and to investigate cow and herd factors associated with elevated SCC.

Results

Prevalence of subclinical mastitis in Finland decreased over recent decades from 22.3% (1991) and 20.1% (2001) to 19.0% (2010). Prevalence of chronic subclinical mastitis was 20.4% in 1991, 15.5% in 2001 and 16.1% in 2010. The most significant cow and herd factors associated with subclinical mastitis or high milk SCC were increasing parity, Holstein breed, free-stalls with an automatic milking system and organic production. Milk SCC were highest from July to September. Main factors associated with chronic mastitis were increasing parity and Holstein breed.

Conclusions

Prevalence of subclinical mastitis in Finland decreased over recent decades, the greatest change taking place during the first decade of the study. Prevalence of chronic subclinical mastitis significantly decreased from 1991. The most significant factors associated with both types of mastitis were increasing parity and Holstein breed, and for subclinical mastitis also free-stalls with automatic milking. National surveys on mastitis prevalence should be carried out at regular intervals to monitor udder health of dairy cows and to study the impact of the ongoing structural changes in the dairy industry to enable interventions related to udder health to be made when needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-017-0288-x) contains supplementary material, which is available to authorized users.

Short communication: Identification of Corynebacterium bovis by MALDI-mass spectrometry

Corynebacterium bovis is a mastitis-causing microorganism responsible for economic losses related to decrease in milk production. The aim of the study was identify Corynebacterium spp. strains recovered from milk samples of subclinical mastitis by using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Samples were collected during a 10-mo mastitis-monitoring program in a high-production dairy farm. In this study, 80 strains were analyzed; from these 54 (67.5%) were identified at species level as Corynebacterium bovis, 24 (31.2%) isolates were identified at the genus level as Corynebacterium spp., and only 1 (1.35%) isolated had unreliable identification. Results demonstrated that MALDI-MS could be an important technique for the identification of Corynebacterium spp. in milk.

Influence of selenium and vitamin e supplementation during pregnancy on udder health and milk quality in dairy cows at parturition

Selenium and vitamin E ranks among very important antioxidant agents protecting the organism from the effect of reactive oxygen forms. The deficiency of both nutrients during pregnancy in cows often result in metabolic disorders and increased of cases of related diseases (mastitis, retained placenta and other reproductive disorders). The aim of the present work was to study the influence of different dose of parenteral administration selenium and vitamin E in dairy cows prior to parturition on selected metabolic parameters, udder health and milk quality. A total in herd of 270 Holstein cattle in east of Slovakia in a two-four lactation-gestation cycle the control group (C) and 2 experimental groups (D, D1) were selected. All groups were similarly housed, managed and fed with the diet containing from 36 to 42 mg vitamin E and 0.2 mg.kg-1 Se of DM through the study period. In group D a products containing vitamin E and selenium were administered IM four weeks prior to the expected date of parturition in total dose of 1000 mg of dl-α-tocopherol acetate and of 44 mg sodium selenite per cow, respectively. In group D1 the same products were administered twice, four and two weeks prior to parturition. Blood samples were 4 weeks prior to predicted calving date (the time of treatment), on parturition day and at 14th day after calving for assessment of plasma vitamin E and selenium concentrations. Blood samples of the calves were drawn from jugular vein at birth and first colostrum was also collected. The occurrence of the mastitis and retained placenta during the first 14th day after calving were evaluated in all groups. Higher plasmatic and colostral concentrations of selenium and vitamin E were found only in group with repeat application of Se and vitamin E (D1) collected on the day of parturition. At the 14th day of postpartal period a trend of lower occurrence of mastitis was observed in group D1 compared to D group, administered IM once and control group. Parenteral supplementation of selenium and vitamin E during pregnancy had no impact on their transmission into the milk and on the presence of bacterial agents in raw milk obtained from dairy cows diagnosed with mastitis. 

Intramammary treatment with gentamicin in lactating cows with clinical and subclinical mastitis

Abstract The study evaluated the microbiological profile of milk samples collected before and after mastitis treatment with gentamicin and investigated biofilms production and antimicrobial susceptibility of Staphylococcus spp. isolated. The presence of gentamicin residues in milk after the recommended withdrawal period was also evaluated. Antimicrobial residues were analyzed by Delvotest® SP NT over a period of 12 days beginning after 24 hours the last gentamicin application. Some of Staphylococcus spp. isolates were biofilm producers (19.05%). Staphylococcus spp. showed high levels of resistance to neomycin (16.95%), penicillin G (10.17%), and ampicillin (10.17%). Multidrug resistance to all antibiotics tested was observed in 1.69% of the Staphylococcus spp. isolates. Among 1440 mammary quarter milk samples 24.95% presented gentamicin residues after the withdrawal period. Gentamicin residues were also detected in 3.8% of samples from calibrated glass recorder jar (n=383) 4.1 days after treatment. The indiscriminate use of antibiotics may lead to the emergence of multidrug-resistant strains as well as increasing the risk of presence of residues of these drugs in milk. These problems affect the milk quality and may become a public health problem.

Effects of bovine subclinical mastitis caused by Corynebacterium spp. on somatic cell count, milk yield and composition by comparing contralateral quarters

Subclinical mastitis caused by Corynebacterium spp. (as a group and at the species level) was investigated by evaluating contralateral (healthy and infected) mammary quarters for somatic cell count (SCC), milk yield and composition. Selection of cows with subclinical mastitis caused by Corynebacterium spp. was performed by microbiological culture of composite samples collected from 1242 dairy cows from 21 dairy herds. For each of the selected cows, milk yield was measured and milk samples were collected at the mammary quarter level (i.e., 1140 mammary samples collected from 285 cows) for analysis of milk composition and SCC. The identification of Corynebacterium spp. isolates was performed by 16S rRNA gene sequencing. One hundred and eighty Corynebacterium spp. isolates were identified, of which 167 (92.77%) were C.bovis and eight (4.44%) non-C.bovis; for five of the Corynebacterium spp. isolates (2.77%), sequencing of 16S rRNA genes did not allow identification at the species level. Mammary quarters infected with Corynebacterium spp. as a group had a higher geometric mean SCC (197,900 cells/mL) than healthy contralateral mammary quarters (85,800 cells/mL). Species of Corynebacterium non-C.bovis were infrequently isolated and did not change SCC, milk yield or milk solid contents when evaluated at the contralateral quarter level. Although C.bovis infection showed no effect on milk yield, fat, protein, casein or total solids in milk, it increased SCC and decreased lactose and milk solids non-fat content.

Prevalence of bovine subclinical mastitis, its etiology and diagnosis of antibiotic resistance of dairy farms in four municipalities of a tropical region of Mexico

A region-wide survey was conducted in the tropical area of Tierra Caliente, State of Guerrero, Mexico to estimate the prevalence of subclinical bovine mastitis (SCM), distribution of mastitis pathogens, and in vitro antimicrobial susceptibility of different mastitis pathogens in dairy farms. In total, 1036 quarter milk samples were obtained from 259 cows at 87 different dairy farms. Collected quarter milk samples were submitted for California Mastitis Test (CMT), bacteriological examination, and testing for antimicrobial susceptibility. Overall prevalence of SCM in the studied area was 20.5 %. Prevalence in the different regions was as follows: 28 % in Arcelia municipality, 21 % in Tlalchapa municipality, 19.4 % in Pungarabato municipality, and 14.3 % in Finch Cutzamala municipality. Of all positive isolates, 97.5 % were Gram-negative bacteria. Moreover, of all positive isolates, 37.5 % were Proteus vulgaris, 25 % Salmonella spp., 12.5 % Enterobacter aerogenes, and 10 % Escherichia coli. Klebsiella pneumonia and E. coli were sensitive for netilmicin antimicrobial. However, E. coli was sensitive for pefloxacin and gentamicin with a sensitivity for pefloxacin for E. aerogenes, while Staphylococci were sensitive for gentamicin and dicloxacillin. It could be concluded that practices such as the implementation of mastitis control programs, improved milking hygiene together with an intramammary treatment with netilmicin, pefloxacin, and gentamicin antimicrobials should be considered for mastitis prevention in the study area of Tierra Caliente, in the tropical area of Guerrero, Mexico.

Expression of CD14 and toll-like receptors 2 and 4 by milk neutrophils in bovine mammary glands infected with Corynebacterium bovis

This study evaluated the expression of CD14, toll-like receptor (TLR) 2 and TLR4 on the surface of milk neutrophils in bovine mammary glands infected with Corynebacterium bovis. Here, we used 23 culture-negative control quarters with no abnormal secretion on the strip cup test and milk somatic cell count lower than 1x105 cells/mL, and 14 C. bovis infected quarters. The identification of neutrophils, as well as, the percentage of neutrophils that expressed CD14, TLR2 and TLR4 were analyzed by flow cytometry using monoclonal antibodies. The present study encountered no significant difference in the percentages of milk neutrophils that expressed TLR2 and TLR4 or in the expression of TLR4 by milk neutrophils. Conversely, a lower median fluorescence intensity of TLR2 in milk neutrophils was observed in C. bovis-infected quarters. The percentage of neutrophils that expressed CD14 and the median fluorescence intensity of CD14 in milk neutrophils was also lower in C. bovis-infected quarters.

Identification of Corynebacterium spp. isolated from bovine intramammary infections by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Corynebacterium species (spp.) are among the most frequently isolated pathogens associated with subclinical mastitis in dairy cows. However, simple, fast, and reliable methods for the identification of species of the genus Corynebacterium are not currently available. This study aimed to evaluate the usefulness of matrix-assisted laser desorption ionization/mass spectrometry (MALDI-TOF MS) for identifying Corynebacterium spp. isolated from the mammary glands of dairy cows. Corynebacterium spp. were isolated from milk samples via microbiological culture (n=180) and were analyzed by MALDI-TOF MS and 16S rRNA gene sequencing. Using MALDI-TOF MS methodology, 161 Corynebacterium spp. isolates (89.4%) were correctly identified at the species level, whereas 12 isolates (6.7%) were identified at the genus level. Most isolates that were identified at the species level with 16 S rRNA gene sequencing were identified as Corynebacterium bovis (n=156; 86.7%) were also identified as C. bovis with MALDI-TOF MS. Five Corynebacterium spp. isolates (2.8%) were not correctly identified at the species level with MALDI-TOF MS and 2 isolates (1.1%) were considered unidentified because despite having MALDI-TOF MS scores >2, only the genus level was correctly identified. Therefore, MALDI-TOF MS could serve as an alternative method for species-level diagnoses of bovine intramammary infections caused by Corynebacterium spp.

Incidence of staphylococci and streptococci during winter in mastitic milk of sahiwal cow and murrah buffaloes

Mastitis is a serious problem in dairy sector and among various aetiological agents, the incidence of staphylococci and streptococci remains high in milking animal. The present study was focused on detection of staphylococci and streptococci in winter season. Milk samples (117) of mastitic animals were tested for presence of staphylococci and streptococci using biochemical and PCR based assays. The testing revealed majority of animals (90.6%) were infected with more than one causative agent. Amongst 117 sample, 109 and 90 comprised of staphylococci and 90 streptococci, respectively. Distribution proportion of S. aureus, S. epidermidis, S. agalactiae, S. uberis and S. dysgalactiae among the mastitic cases was found as 64.9, 7.7, 5.1, 1.7, 48.7, 65.8 and 0.8%, respectively. Streptococci and staphylococci were observed in different combinations and the frequent were S. aureus/S. agalactiae/S. uberis, S. aureus/S. uberis, S. aureus/S. agalactiae and S. agalactiae/S. uberis which were accounted for 23.9, 19.7, 5.9 and 2.6%, respectively. Approximately half of the (52.1%) cases were observed for reoccurrence of mastitis. Reoccurrence of mastitis in winter season among these cases was significantly low as compared to summer (cattle-5 cases; buffaloes-2 cases). In addition, prevalence of S. aureus, S. agalactiae, S. uberis, and S. epidermidis in reoccurring mastitic cases was 73.7, 63.9, 45.9 and 6.6%, respectively. The observations revealed mastitis causing pathogens remains in hidden phase in winter season; however, cannot be neglected. The observation might be helpful in culling or segregation of cows for mastitis reduction programmes.

Function of milk polymorphonuclear neutrophil leukocytes in bovine mammary glands infected with Corynebacterium bovis

Corynebacterium bovis is one of the most commonly isolated bacteria from aseptically collected bovine milk samples. The objective of the current study was to characterize the bovine innate immune response by evaluating milk polymorphonuclear neutrophilic leukocytes (PMNL) in mammary glands infected with C. bovis. Twenty quarters infected with C. bovis and 28 culture-negative quarters (with milk somatic cell count <1×10(5) cells/mL) were used. The percentages of milk PMNL and the PMNL expression of L-selectin (CD62L), β2-integrin (CD11b), and one of the endothelial-selectin ligands (CD44), as well as the levels of intracellular reactive oxygen species (ROS) and the phagocytosis of Staphylococcus aureus, were evaluated by flow cytometry. The apoptosis and necrosis rates of the PMNL were quantified using dual-color flow cytometry with fluorescein-labeled annexin and propidium iodide. The present study revealed a higher percentage of PMNL in the milk from C. bovis-infected quarters, although no significant differences were found in levels of CD44, CD62L, or CD11b expression among the PMNL. A lower percentage of apoptotic PMNL was observed in C. bovis-infected quarters, as well as higher percentages of viable PMNL and of PMNL that produced intracellular ROS. However, no alterations were observed in phagocytosis of Staph. aureus by the PMNL or in intensity of intracellular ROS production by PMNL. Thus, results from this investigation of the PMNL function support, at least in part, the fact that intramammary infections by C. bovis may offer protection against intramammary infections by other bacteria.

Prevalence of mastitis in dairy cows from smallholder farms in Zimbabwe

A cross-sectional study was conducted to determine the prevalence of sub-clinical and clinical mastitis and the associated factors in cows from selected smallholder dairy farms in Zimbabwe. Physical examinations were conducted on all lactating cows for evidence of signs of clinical mastitis. Composite milk samples were collected from all lactating cows for bacterial culture and somatic cell counting. Cows were categorised as clinical if they exhibited clinical features of mastitis, or sub-clinical if no apparent signs were present but they had a positive bacterial isolation and a somatic cell count of at least 300 x 103 cells/mL. Farm-level factors were obtained through a structured questionnaire. The association of mastitis and animal- and herd-level factors were analysed using logistic regression. A total of 584 animals from 73 farms were tested. Overall, 21.1%(123/584) had mastitis, 16.3%(95/584) had sub-clinical mastitis and 4.8% (28/584) had clinical mastitis. Herd-level prevalence was 49.3%. Coagulase-negative staphylococci (27.6%),  Escherichia coli (25.2%),  Staphylococcus aureus(16.3%), Klebsiella spp. (15.5%) and Streptococcus spp. (1.6%) were the most common isolates. In individual cows, pure dairy herds (OR = 6.3) and dairy crosses (OR = 3.1) were more likely to have mastitis compared to Mashona cows. Farms that used pre-milking teat dipping were associated with reduced mastitis prevalence. Further research is needed on the prevalence of mastitis and a comparison of data for both smallholder and commercial dairy farms in all regions of Zimbabwe should be undertaken.

Draft genome sequence of Corynebacterium bovis DSM 20582, which causes clinical mastitis in dairy cows

Bovine mastitis represents the most economically important disease in dairy cows and can be caused by Corynebacterium bovis, a commensal in the bovine udder. The draft genome sequence provides insights into the adaptation of this bacterium to the bovine habitat and its lipolytic capabilities to utilize components of cow's milk.

Milk amyloid A and selected serum proteins in cows suffering from mastitis

The aim of this work was to evaluate the influence of clinical and sub-clinical mastitis on the concentrations of mammary associated isotype of serum amyloid A (M-SAA) in milk samples, as well as on the concentrations of haptoglobin (Hp) and serum amyloid A (SAA), and some other biochemical variables in blood serum of dairy cows (n = 41). The concentrations of aforementioned variables were measured in 4 groups of cows divided according to the results of the clinical examination of the udder and to the results of California Mastitis Test (CMT): group 1 – cows without clinical changes on the mammary gland and with negative CMT, group 2 – cows without clinical changes on the mammary gland and with weakly positive CMT, group 3 – cows without clinical changes on the mammary gland and with strongly positive CMT and group 4 – cows with clinical changes on the mammary gland and changes in milk appearance. The concentrations of M-SAA were analyzed also in 145 quarter’s milk samples which were categorized according to the same criteria as cows used in the study. By the evaluation of M-SAA concentrations in composite milk samples we found significantly the highest mean value in cows with clinical signs of mastitis. Similar findings were recorded in the M-SAA concentrations in quarter’s milk samples. Moreover, higher concentrations of M-SAA were found also in samples from mammary quarters without clinical changes and positive CMT. The analyses of Hp and SAA concentrations showed a trend of higher values in cows with clinical mastitis. The lowest mean concentration of albumin we found in cows with clinical signs of mastitis. Our results indicate elevated production of M-SAA in cows with clinical changes on mammary gland, and suggest the usefulness of this indicator also in the diagnosing of sub-clinical mastitis.

Udder pathogens and their resistance to antimicrobial agents in dairy cows in Estonia

Background

The goal of this study was to estimate the distribution of udder pathogens and their antibiotic resistance in Estonia during the years 2007-2009.

Methods

The bacteriological findings reported in this study originate from quarter milk samples collected from cows on Estonian dairy farms that had clinical or subclinical mastitis. The samples were submitted by local veterinarians to the Estonian Veterinary and Food Laboratory during 2007-2009. Milk samples were examined by conventional bacteriology. In vitro antimicrobial susceptibility testing was performed with the disc diffusion test. Logistic regression with a random herd effect to control for clustering was used for statistical analysis.

Results

During the study period, 3058 clinical mastitis samples from 190 farms and 5146 subclinical mastitis samples from 274 farms were investigated. Positive results were found in 57% of the samples (4680 out of 8204), and the proportion did not differ according to year (p > 0.05). The proportion of bacteriologically negative samples was 22.3% and that of mixed growth was 20.6%. Streptococcus uberis (Str. uberis) was the bacterium isolated most frequently (18.4%) from cases of clinical mastitis, followed by Escherichia coli (E. coli) (15.9%) and Streptococcus agalactiae (Str. agalactiae) (11.9%). The bacteria that caused subclinical mastitis were mainly Staphylococcus aureus (S. aureus) (20%) and coagulase-negative staphylococci (CNS) (15.4%). The probability of isolating S. aureus from milk samples was significantly higher on farms that had fewer than 30 cows, when compared with farms that had more than 100 cows (p < 0.005). A significantly higher risk of Str. agalactiae infection was found on farms with more than 600 cows (p = 0.034) compared with smaller farms. The proportion of S. aureus and CNS isolates that were resistant to penicillin was 61.4% and 38.5%, respectively. Among the E. coli isolates, ampicillin, streptomycin and tetracycline resistance were observed in 24.3%, 15.6% and 13.5%, respectively.

Conclusions

This study showed that the main pathogens associated with clinical mastitis were Str. uberis and E. coli. Subclinical mastitis was caused mainly by S. aureus and CNS. The number of S. aureus and Str. agalactiae isolates depended on herd size. Antimicrobial resistance was highly prevalent, especially penicillin resistance in S. aureus and CNS.

Phenotyping and genotyping of streptococci in bovine milk in Argentinean dairy herds

Most veterinary and milk hygiene laboratories identify streptococci and enterococci based on serological and biochemical tests. The analysis of 16S rDNA was suggested to be used for more exact identification; however, its use has not been considered so far in monitoring studies. The objective of the present study was to compare a conventional phenotypic method with restriction fragment length polymorphism analysis of 16S rDNA (16S rDNA RFLP) for identification of streptococci isolated from composite milk samples collected in connection with intramammary infection (IMI) in six Argentinean dairy farms. Composite milk samples (n = 1223) from cows belonging to six herds were collected for bacteriological analysis. Twelve reference strains and fifty streptococci or streptococcuslike isolates were identified to species level by the API 20 Strep system, conventional biochemical tests and 16S rDNA RFLP in a blind assay. The remaining streptococci or streptococcus-like isolates (n = 40) were identified to the species level both by 16S rDNA RFLP and conventional biochemical tests. As indicated by Kappa values, agreement between the 16S rDNA RFLP and the conventional scheme for identification of Streptococcus agalactiae, S. dysgalactiae, S. uberis, S. equinus and Enterococcus faecalis was 0.91, 0.73, 0.92, 0.81 and 0.85, respectively. Together with the less frequently isolated streptococcal species, the conventional scheme correctly identified 77 out of 90 isolates (85.5%). Thus, the use of 16S rDNA RFLP is considered valuable for monitoring studies due to its affordable cost for standard laboratories.

Identification of immunoreactive extracellular proteins of Streptococcus agalactiae in bovine mastitis

Streptococcus agalactiae is a common pathogen that causes bovine mastitis. The aims of this study were to evaluate the antibody response against S. agalactiae extracellular proteins in the whey and serum of naturally infected bovines and to identify possible immunodominant extracellular antigens. IgG1 antibodies against S. agalactiae extracellular proteins were elevated in the whey and serum of naturally infected bovines. In the whey, the levels of IgG1 specific for S. agalactiae extracellular proteins were similar in infected and noninfected milk quarters from the same cow, and the production of antibodies specific for S. agalactiae extracellular proteins was induced only by infection with this bacterium. The immunoreactivity of extracellular proteins with bovine whey was clearly different in infected versus control animals. Group B protective surface protein and 5'-nucleotidase family protein were 2 major immunoreactive proteins that were detected only in the whey of infected cows, suggesting that these proteins may be important in the pathogenesis of S. agalactiae-induced mastitis. This information could be used to diagnose S. agalactiae infection. In addition, these antigens may be useful as carrier proteins for serotype-specific polysaccharides in conjugate vaccines.

Effect of bovine lactoferrin on the internalization of coagulase-negative staphylococci into bovine mammary epithelial cells under in-vitro conditions

Coagulase-negative staphylococci (CNS) have emerged as bovine mastitis pathogens in many countries. CNS mastitis is generally mild but can persist in the udder for long periods. Pathogenesis of CNS intramammary infection is not well understood. In the present study, adhesion, invasion and intracellular replication of twenty-two CNS strains isolated from bovine mastitis and the effect of bovine lactoferrin (bLf) on the internalization were studied in vitro in a bovine mammary epithelial (BME) cell model. The CNS strains were of Staphylococcus chromogenes, Staph. simulans, Staph. epidermidis, Staph. haemolyticus and Staph. cohnii urealyticus; two strains of Staph. aureus were used as controls. Seven of the CNS strains originated from persistent and five from transient mastitis infections. The in-vitro susceptibility of the strains to bLf was also investigated. All CNS species examined had an adhesive ability equal to that of Staph. aureus, but internalization varied among staphylococcal strains. The antagonistic effect of bLf on the adhesion and invasion of CNS strains was weak, but bLf significantly decreased intracellular replication and replication rates of CNS. No correlation between the in-vitro susceptibility of the strain to bLf or internalization among clinical signs of mastitis was established. No difference between the persistent and transient CNS strains in adhesion, invasion or replication rate was recorded. This in-vitro BME cell model can be used to study the virulence potential of mastitis pathogens, although the severity and persistence of eventual infections shall be further investigated in vivo. The role of bLf in intramammary infection caused by CNS may be limited.