From the NMC Newsletter Udder Topics, August, 2000. Coagulase-negative staphylococcus (CNS) species are the organisms most frequently isolated from bovine milk samples. Mastitis researchers do not classify CNS as contagious or environmental pathogens.They designate them as skin flora opportunists since CNS are a part of the normal teat skin flora.oagulase-negative staphylococcus (CNS) species are the organisms most frequently isolated from bovine milk samples. Mastitis researchers do not classify CNS as contagious or environmental pathogens.