Factors Influencing Therapy Decisions in Clinical Cases of Grain-Positive Mastitis

Abstract

Therapy of clinical mastitis caused by gram-positive bacteria was reviewed, and a retrospective study was conducted. Reported cure rates for mastitis appear higher shortly after treatment. Apparent cure rates are markedly overestimated with only one follow-up culture by as much as 69%; these false cures can be attributed to antibiotic therapy. Spontaneous cure rates of mastitis are often not significantly different from those with antibiotic therapy. Most (93%) food animal veterinarians use steroidal and/or non-steroidal anti-inflammatory therapy. Clinical mastitis signs are considered responsive to this type of therapy, however, most studies of anti-inflammatory drugs concern their effectiveness against coliform mastitis, rather than gram-positive clinical mastitis. Oxytocin therapy for clinical cases of Strep sp. mastitis was compared with amoxicillin or cephapirin therapy; cure rates were not statistically different. Clinical gram-positive mastitis was found in 1464 quarters in the current retrospective study. Treatments used were: amoxicillin (n=21), cephapirin (n=122), cloxacillin (n=89), erythromycin (n=109), penicillin (n=93), unknown treatment (n=574), untreated (n=456). Bacterial cure rates for treated and untreated cases, respectively for each gram-positive agent were: Strep ag 518/691 (75%), 6/41 (15%); Strep sp. 60/73 (82%), 101/171 (59%); S. aureus 84/149 (56%), 51/ 149 (34%); Staph sp. 68/95 (72%), 72/95 (76%). Routine antibiotic treatment of these cases lost $123.50 for each case cured. Financial loss was worse for herds with no Strep ag present. Treatment of clinical mastitis caused by gram-positive organisms other than Strep ag with antibiotic therapy was not indicated by the results of this study.