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Updated: Feb 28, 2026
A Murine Model of Group B Streptococcus Vaginal Colonization
Published on: November 16, 2016
Bovine intra-mammary challenge with Streptococcus dysgalactiae spp. Dysgalactiae to explore the effect on the
Susan Maye1, James Flynn1, Catherine Stanton1
1Teagasc Food Research Centre,Moorepark,Fermoy,County Cork,Ireland.
Insights
High somatic cell counts (SCC) in bovine milk indicate increased Complement activity, enhancing the innate immune response against mastitis infections. This heightened activity effectively inhibits bacterial growth, particularly E. coli O111.
Area of Science:
- Veterinary Immunology
- Bovine Mastitis Research
- Innate Immune Response
Background:
- Complement activity in bovine milk is crucial for innate immunity against mammary infections.
- Somatic cell count (SCC) in milk is a key indicator of localized mastitis infection.
- Previous studies indicated a correlation between high SCC and reduced bacterial growth, suggesting a role for Complement.
Purpose of the Study:
- To investigate the effect of induced sub-clinical mastitis on Complement activity in bovine milk.
- To determine the relationship between somatic cell count (SCC) and Complement-mediated bacterial inhibition in infected mammary glands.
- To confirm Complement pathway activation during bovine mastitis using ELISA.
Main Methods:
- Induction of sub-clinical mastitis via inoculation with Str. dysgalactiae spp. dysgalactiae in selected udder quarters of dairy cows.
- Monitoring of somatic cell counts (SCC) in milk from segregated quarters post-inoculation.
- Bactericidal sequestration assays using E. coli O111 as a marker strain to assess bacterial inhibition.
- ELISA assays to detect specific Complement pathway activation components.
Main Results:
- Induced mastitis led to increased SCC in affected quarters, correlating with enhanced E. coli O111 inhibition.
- Higher Complement activity was directly linked to increased SCC in milk from inflamed mammary glands.
- Milk from unchallenged quarters showed significantly less bacterial inhibition compared to milk from affected quarters.
- ELISA confirmed elevated Complement activity in milk samples from quarters with higher SCC.
Conclusions:
- Elevated somatic cell counts in bovine milk during mastitis are associated with increased Complement activity.
- Complement-mediated bacterial inhibition is enhanced in milk from infected mammary glands, contributing to the innate immune response.
- Monitoring Complement activity in milk, alongside SCC, can provide valuable insights into bovine mammary health and immune status.
Abstract:
Recently published work as described by the authors highlighted the extent of Complement activity in bovine milk. Localised mastitis infection occurring in the mammary glands of dairy cows is readily detectable by the levels of somatic cells in milk. Thus, it is opportune to monitor Complement activity in milks in association with the animal's innate immune response to mammary infection. Preliminary screening of milk samples taken randomly showed that milk with a high somatic cell count (SCC) reduced growth of the Complement-sensitive strain E. coli O111 to a greater extent (P < 0·05) than when the marker microorganism was grown in milk heated for the purpose of inactivating Complement. A follow-up study set out to determine the effect on Complement activity when a sub-clinical mastitis infection was induced in the mammary gland of four lactating dairy cows. The effect of Str. dysgalactiae spp. dysgalactiae inoculation into selected individual udder quarters of the mammary glands of each animal was followed by monitoring of SCC levels in the milks from the segregated udder samples during subsequent milking. At 72 and 96 h post inoculation (PI), the SCCs for the challenged quarter were increased compared to normal values. At the same time, the bactericidal sequestration assay identified increased E. coli O111 inhibition that can be directly linked to greater Complement activity in those quarter milks affected by induced inflammation. Thus, it can be identified that the high SCC milks were more effective in limiting E. coli O111 growth. Milks from the unchallenged quarters in all four cows were significantly less effective at reducing growth of the assay strain (P < 0·05). An ELISA assay targeting specific activation components of the Complement pathways confirmed that greater bacterial inhibition observed during the bactericidal sequestration assay was attributable to higher Complement activity in the milk samples from the affected quarters, i.e., with higher SCC. The induced infection was confirmed as self-limiting in three of the affected animals and their SCC returned to normal levels within 14 d PI, while the fourth cow required brief antibiotic intervention.
