Streptococcus dysgalactiae

Streptococcus dysgalactiae: Strep sector (streptococci), small turquoise colonies, marked with No. 1; Streptococcus uberis: Strep sector (streptococci), small violet colonies, No. 2.
Streptococcus dysgalactiae ClearMilk Test

Milk from a sick dairy cow is usually a source of Streptococcus dysgalactiae; mastitis is not very contagious and occurs only sporadically in a herd. Streptococcus dysgalactiae persists on the udder skin, in small skin fissures but also on a vaginal mucous membrane, in tonsils, in amniotic sacs in cases of abortion, in a contaminated uterus. The bacterium has a strong affinity for the mammary gland and is able to adhere to the walls of the excretory ducts of the udder and persist there for many weeks. Streptococcus dysgalactiae infection is facilitated by simultaneous Mycoplasma infection of the mammary gland. 

The disease is usually subclinical but can also develop into an acute mastitis with severe impairment of the overall health.

In the photo of the ClearMilk test from a farm (above) we can see that the grown bacterial colony of Streptococcus dysgalactiae can be well differentiated by the colour from e. g. Streptococcus uberis. Other important streptococci causing mastitis can also be differentiated by colour – see the photos in the Causal agents guide here. In case of doubt, it is recommended to perform the quick verification in our laboratory with our MALDI TOF machine and to determine antibiotic susceptibility.