ANTIMICROBIAL USE, INVITRO SUSCEPTIBILITY TEST AND TREATMENT OUTCOMES FOR STAPHYLOCOCCUS AUREUS BOVINE MASTITIS IN MEKI TOWN, ETHIOPIA

Abstract

Staphylococcus aureus is one of the causative agents of bovine mastitis. Despite recommendation of invitro susceptibility to decide treatment of mastitis, only simple clinical observation is used in the treatment of the disease in veterinary clinics. In line with many studies reporting invitro resistance of the bacteria, some investigators concluded that invitro susceptibility has poor predictive value for treatment outcome. No study was conducted to evaluate true relationship of invitro result with therapeutic outcomes in the context of our country and it is of paramount importance to evaluate relationship between invitro susceptibility result of beta-lactam drugs on use in the market and bacteriological in addition to other predicting factors. Hence, the study was conducted with the objectives of evaluation of farm level antimicrobial use, association of invitro susceptibility with treatment response and additional predicting risk factors for bacteriological cure of the disease. In the study prevalence of S. aureus was 47.4% in clinical and 57.8% in subclinical mastitis with p≥0.05. Out of the total 50 isolates, susceptibility range of 66.7- 71.9%, 61.1-65.6% and 59.4- 61.1% was found for amoxicillin, oxacillin and cefoxitin, respectively. Amongst quarters treated with intramammary infusion, higher bacteriological cure (p≤0.05) was observed in subclinical mastitis (82.4%) than in clinical mastitis (29.4%). A positive linear relationship was revealed between invitro antibacterial activity of antibiotics used for treatment (amoxicillin and oxacillin) and bacteriological cure of mastitic udder. The reduced bacteriological cure was found to be highly influenced by poor bedding hygiene, rough floor surface, soil floor, previous treatment for mastitis, poor animal body hygiene, previous cure failure, multiple parity and late lactation stage. Biofilm formation and presence of MRSA were amongst the contributory pathogen factors for bacteriological cure failure. Overall, invitro susceptibility showed positive linear relationship with bacteriological cure though environment, animal and pathogen factors contributed in the reduced bacteriological cure.