Differential phenotype of immune cells in blood and milk following pegylated granulocyte colony-stimulating factor therapy during a chronic Staphylococcus aureus infection in lactating Holsteins

A randomized control trial to test the effect of pegbovigrastim treatment at dry-off on plasma and milk oxylipid profiles during early mammary gland involution and the postparturient period

The early period of mammary gland involution is a critical juncture in the lactation cycle that can have significant effects on milk production and mammary gland health. Pegbovigrastim (PEG) administered 1 wk prior and on the day of parturition can enhance immune function and reduce the incidence of mastitis in the early postpartum period. Oxylipids are potent metabolites of polyunsaturated fatty acids (PUFA) and are important mediators of inflammation. The objective of this study was to evaluate effects of PEG given 1 wk before and at the day of dry-off (D0) on concentrations of oxylipids in plasma and milk from 7 d before D0 to 14 d after, as well as the effects during the first 14 d of the subsequent lactation. We hypothesized that both pro- and anti-inflammatory oxylipids would vary based on initiation of mammary gland involution and that pegbovigrastim would affect oxylipid concentrations, particularly those related to leukocytes. A complete randomized blocked design was used to enroll cows into either a PEG treatment group (n = 10) or control group (n = 10; CON). Blood samples were collected -7, -2, -1, 0, 1, 2, 4, 7, and 14 d relative to dry-off and 5, 10, and 14 d postcalving. Samples were analyzed for PUFA and oxylipids in milk and plasma by ultra-performance mass spectrometry and liquid chromatography tandem quadrupole mass spectrometry, respectively. Overall, 30 lipid mediators were measured in both milk and plasma. Repeated measures analyses revealed a significant interaction of treatment by time for milk 8-iso-keto-15-prostaglandin E2, prostaglandin F2α, plasma 8,12-iso-prostaglandin Fα-VI, 11-hydroxyeicosatetraenoic acid, and 12-hydroxyheptadecatienoic acid. The majority of milk PUFA and oxylipids differed significantly during early mammary gland involution and into the early postpartum period. This study demonstrated changes in oxylipids in milk secretions and plasma during early involution, and further investigation may illuminate multiple complex processes and reveal targets for optimization of mammary gland involution.

Comparative analysis of Streptococcus agalactiae serotypes Ia and II isolates from China and Pakistan in a murine model: A focus on pathogenesis and immune response

Bovine mastitis, caused by Streptococcus agalactiae (Group B Streptococcus; GBS), poses significant economic challenges to the global dairy industry. Mouse models serves as valuable tools for assessing GBS-induced infections as an alternative to large animals. This study aimed to investigate the LD50 dose, organ bacterial load, and quantification of peritoneal leukocyte populations for GBS serotypes Ia and II isolates from China and Pakistan. Additionally, we measured indicators such as lactoferrin, albumin, and myeloperoxidase (MPO) activity. Pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-2) and anti-inflammatory cytokines (IL-10 and TGF-β) in serum and tissue samples were evaluated using ELISA and qPCR, respectively. BALB/c mice (4 mice per group) received individual intraperitoneal injections of 100 μl containing specific bacterial inoculum concentrations (ranging from 105 to 109 CFU per mouse) of Chinese and Pakistani GBS isolates (serotypes Ia and II). Control groups received 100 μL of sterile PBS. Results revealed that the LD50 bacterial dose causing 50 % mortality in mice was 107 CFU. The highest bacterial load in all experimental groups was quantified in the peritoneum, followed by blood, mammary gland, liver, spleen, lungs, and brain. The most significant bacterial dissemination was observed in mice inoculated with Pakistani serotype Ia at 24 h, with a subsequent notable decline in bacterial counts at day 3. Notably, infection with Pakistani serotype Ia showed a trend of increased total leukocyte counts, significantly higher than Pakistani serotype II, Chinese Serotype Ia, and Chinese serotype II. A substantial influx of neutrophils and lymphocytes was observed in response to all tested serotypes, with Pakistani serotype Ia inducing a significantly higher influx compared to other groups (Pakistani serotype II, Chinese serotype Ia, and Chinese serotype II). Furthermore, TNF-α, IL-1β, IL-2, and IL-6 expressions were significantly increased in mice one day after infection with the Pakistani serotype Ia. Compared to mice infected with the Pakistani serotype II, Chinese Serotype Ia, and Chinese serotype II, those infected with the Pakistani serotype Ia isolate exhibited the highest production of IL-10 and TGF-β, along with significantly increased concentrations of lactoferrin, albumin, and MPO. These findings suggest that the persistence and severity of infection caused by the Pakistani serotype Ia may be linked to its ability to spread to deeper tissues. This study enhances our understanding of the clinical characteristics of bovine mastitis caused by S. agalactiae in China and Pakistan.

The effect of pegbovigrastim administration on the nonspecific immunity of calves

BACKGROUND

Prevention of diseases in the early rearing of calves is important, particularly because disease occurrence most often requires antimicrobial administration but reduction of their use in animals is a priority. Pegbovigrastim is known for its use as an immunoregulator in cows and heifers, but the effect of its administration on calves has not been fully investigated.

OBJECTIVES

Investigate whether administration of pegbovigrastim effectively stimulates nonspecific immunity in healthy calves.

ANIMALS

Eleven clinically healthy 5-week-old calves.

METHODS

Prospective observational study. Calves were randomly allocated to an experimental or control groups to receive pegbovigrastim or the same volume of phosphate-buffered saline twice over a 7-day period. To evaluate nonspecific immunity, the numbers of total leukocytes and cells in the appropriate cell fractions were determined. Cytometric analyses were carried out to identify cells expressing CD11b and to evaluate the phagocytic and oxidative burst activities of granulocytes and monocytes. Myeloperoxidase (MPO) and selected cytokines were assayed using ELISA.

RESULTS

Pegbovigrastim significantly increased the number of total leukocytes and of cells in all of the examined subsets (P < .05). The phagocytic activity of leukocytes expressed as mean fluorescence intensity was significantly potentiated after pegbovigrastim administration (P < .05). The cytokine response was modulated by pegbovigrastim administration toward anti-inflammatory activity.

CONCLUSIONS AND CLINICAL IMPORTANCE

Pegbovigrastim effectively stimulated nonspecific immunity in clinically healthy calves, which in the long term could make the prevention of diseases during early rearing possible by strengthening the immune defense mechanisms of the host.

Intramammary calcitriol treatment of mastitis alters profile of milk somatic cells and indicators of redox activity in milk

The objective of this experiment was to determine the effect of intramammary calcitriol treatment on indicators of inflammation during an intramammary bacterial infection. Lactating Holstein cows were challenged with intramammary Streptococcus uberis. At the onset of mild or moderate mastitis, cows were randomly assigned to receive 10 µg of intramammary calcitriol (CAL, n = 7) or placebo control (CON; n = 6) after every milking for 5 days. Data were analyzed by ANOVA with mixed models using the MIXED procedure of SAS with significance declared at P ≤ 0.05. Milk somatic cells, mastitis severity scores, rectal temperatures, and milk bacterial counts did not differ between treatments. Calcitriol decreased the percentage of CD11b+CD14- cells in milk compared with CON (CON = 81 vs. CAL = 61 ± 5%). Antioxidant potential and concentrations of 15-F2t- isoprostanes in milk of infected quarters also were lower in CAL compared with CON. Transcripts for the 25-hydroxyvitamin D 24-hydroxylase and inducible nitric oxide synthase were greater in milk somatic cells of CAL compared with CON, but those for β-defensin 7, metallothionein 1 A and 2 A, thioredoxin and thioredoxin reductase did not differ between treatments. Although clinical signs of severity did not differ, CAL influenced the composition of milk somatic cells and redox activity in milk of infected quarters.

Randomized controlled trial of pegbovigrastim as an adjunct therapy for naturally occurring severe clinical mastitis cases in dairy cows

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Treatment with pegbovigrastim increased survival after a case of severe clinical mastitis.

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Treatment with pegbovigrastim had no effect on subsequent bacteriological cure.

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Treatment with pegbovigrastim had no effect on subsequent milk production.

The main objective of this study was to quantify the effect of pegbovigrastim (PEG) as an adjunct therapy for naturally occurring severe mastitis cases on survival, intramammary bacteriological cure, and subsequent milk production. A double-blinded, randomized controlled trial was conducted on a single commercial dairy farm. During the study period, all cows having a case of severe clinical mastitis, defined as the presence of abnormal milk and inflammation in one quarter or more combined with the presence of systemic signs (pyrexia, dehydration, or recumbency), were enrolled in the study. In addition to a standardized therapy combining systemic and intramammary antimicrobials as well as systemic anti-inflammatory drugs, cows received a subcutaneous injection of either 2.7 mL of 0.9% sterile saline (control group; CON) or 2.7 mL of PEG (PEG group). A milk sample for bacteriological analysis was taken before treatment was administered and a second sample was taken 14 d after enrollment. Survival (30 d post-treatment) and bacteriological cure (14 d post-treatment) were analyzed by survival analysis and chi-squared tests, respectively, whereas daily milk production was treated as a repeated measure in mixed regression models. The 77 cows enrolled in the study were of parity 2 to 4 (mean = 3) and between 3 and 302 d in milk (mean = 154). The bacteria identified in milk at enrollment were Klebsiella spp. (n = 48; 62%), Escherichia coli (n = 16; 21%), Enterobacter spp. (n = 10; 13%), or no growth (n = 3; 4%). The probability of survival during the first 30 d after treatment was higher in the PEG group (84%) than in the control group (46%). Daily milk production over the 30-d period following treatment and bacteriological cure 14 d post-treatment did not differ between groups. Overall, cows treated with PEG as an adjunct therapy for naturally occurring cases of severe clinical mastitis had a better survival than cows treated with saline.

Case report: characterization of a persistent, treatment-resistant, novel Staphylococcus aureus infection causing chronic mastitis in a Holstein dairy cow

Background

Mastitis is the most common health concern plaguing the modern dairy cow and costs dairy producers estimates of two billion dollars annually. Staphylococcus aureus infections are prevalent, displaying varied disease presentation and markedly low cure rates. Neutrophils are considered the first line of defense against mastitis causing bacteria and are frequently targeted in the development of treatment and prevention technologies. We describe a case of naturally occurring, chronic mastitis in a Holstein cow (1428), caused by a novel strain of S. aureus that was not able to be cleared by antibiotic treatment.

Case presentation

The infection was identified in a single quarter, 2 months into the cow’s first lactation. The infection persisted for the following 20 months, including through dry off, and a second calving and lactation. This case of mastitis was associated with a consistently high somatic cell count, however presented with no other clinical signs. This cow was unsuccessfully treated with antibiotics commonly used to treat mastitis, consisting of two rounds of treatment during lactation and an additional round at the beginning of dry off. The chronic infection was also unchanged through an experimental mid-lactation treatment with pegylated granulocyte-colony stimulating factor (PEG-gCSF) and an additional periparturient treatment with PEG-gCSF. We isolated milk neutrophils from 1428 and compared them to two cows challenged with experimental S. aureus, strain Newbould 305. Neutrophils from 1428’s milk had higher surface expression of myeloperoxidase compared to experimental Newbould challenged animals, as well as increased presence of Neutrophil Extracellular Traps. This suggests a heightened activation state of neutrophils sourced from 1428’s naturally occurring infection. Upon postmortem examination, the affected quarter revealed multifocal abscesses separated by fibrous connective tissues. Abscesses were most common in the gland cistern and collecting duct region. Microscopically, the inflammatory reaction was pyogranulomatous to granulomatous and consistent with botryomycosis. Colonies of Gram-positive cocci were found within the eosinophilic matrix of the Splendore-Hoeppli reaction within granulomas and intracellularly within the acinar epithelium.

Conclusions

Collectively, we describe a unique case of chronic mastitis, the characterization of which provides valuable insight into the mechanics of S. aureus treatment resistance and immune escape.

Actions of colony-stimulating factor 3 on the maturing oocyte and developing embryo in cattle

Colony-stimulating factor 3 (CSF3), also known as granulocyte colony-stimulating factor, is used to reduce the incidence of mastitis in cattle. Here, we tested whether recombinant bovine CSF3 at 1, 10, or 100 ng/mL acts on the bovine oocyte during maturation or on the developing embryo to modify competence for development and characteristics of the resultant blastocyst. For experiment 1, oocytes were matured with or without CSF3. The resultant embryos were cultured in a serum-free medium for 7.5 d. There was no effect of CSF3 on cleavage or on development to the blastocyst stage except that 100 ng/mL reduced the percent of putative zygotes and cleaved embryos becoming blastocysts. Expression of transcripts for 93 genes in blastocysts was evaluated by RT-PCR using the Fluidigm platform. Transcript abundance was affected by one or more concentrations of CSF3 for four genes only (CYP11A1, NOTCH2, RAC1, and YAP1). For experiment 2, cumulus-oocyte complexes (COC) were fertilized with either X- or Y-sorted semen. Putative zygotes were cultured in medium containing CSF3 treatments added at the beginning of culture. There was no effect of CSF3, sex, or the interaction on the percent of putative zygotes that cleaved or on the percent of putative zygotes or cleaved embryos becoming a blastocyst. For experiment 3, CSF3 was added from day 4 to 7.5 of development. There was no effect of CSF3 on development to the blastocyst stage. Transcript abundance of 10 genes was increased by 100 ng/mL CSF3, including markers of epiblast (NANOG, SOX2), hypoblast (ALPL, FN1, KDM2B, and PDGFRA), epiblast and hypoblast (HNF4A) and trophectoderm (TJAP1). Results are indicative that concentrations of CSF3 higher than typical after therapeutic administration can reduce oocyte competence and act on the embryo to affect characteristics of the blastocyst.

Identification of a reliable fixative solution to preserve the complex architecture of bacterial biofilms for scanning electron microscopy evaluation

Bacterial biofilms are organized sessile communities of bacteria enclosed in extracellular polymeric substances (EPS). To analyze organization of bacteria and EPS in high resolution and high magnification by scanning electron microscopy (SEM), it is important to preserve the complex architecture of biofilms. Therefore, fixation abilities of formalin, glutaraldehyde, and Methacarn (methanol/chloroform/acetic acid-6:3:1) fixatives were evaluated to identify which fixative would best preserve the complex structure of bacterial biofilms. Economically important Gram-negative Mannheimia haemolytica, the major pathogen associated with bovine respiratory disease complex, and Gram-positive Staphylococcus aureus, the major cause of chronic mastitis in cattle, bacteria were selected since both form biofilms on solid-liquid interface. For SEM analysis, round glass coverslips were placed into the wells of 24-well plates and diluted M. haemolytica or S. aureus cultures were added, and incubated at 37°C for 48–72 h under static growth conditions. Culture media were aspirated and biofilms were fixed with an individual fixative for 48 h. SEM examination revealed that all three fixatives were effective preserving the bacterial cell morphology, however only Methacarn fixative could consistently preserve the complex structure of biofilms. EPS layers were clearly visible on the top, in the middle, and in the bottom of the biofilms with Methacarn fixative. Biomass and three-dimensional structure of the biofilms were further confirmed spectrophotometrically following crystal violet staining and by confocal microscopy after viability staining. These findings demonstrate that Methacarn fixative solution is superior to the other fixatives evaluated to preserve the complex architecture of biofilms grown on glass coverslips for SEM evaluation.