Abstract: | The authors studied a synergistic effect of an arginine hydrolising, but glucose negative mycoplasma strain (9293/3/2/1) and Streptococcus (Str.) dysgalactiae. Both agents, as mono-infections, caused only slight mastitis, but if the udder had been previously infected with mycoplasma, Str. dysgalactiae provoked very severe mastitis. |