Elimination of infected cows from the herd can occur via culling, dry cow therapy or lactation therapy. Cows that don't respond are culled. Some drugs may cure no Staph. The cost of treating 20 cows with Staph. This is certainly not cost effective.
Combination therapy increases the cost of therapy as well as potential for antibiotic residues.
In some herds, cows with clinical episodes caused by Staph. Normally, these organisms either cause a sever infection in early lactation or are cleared from the udder without causing clinical mastitis. However, some environmental streptococci infections and, possibly, coliform infections can persist nonclinically for a complete lactation. However, environmental strep. Acute clinical cases caused by environmental bacteria cause both udder and systemic problems.