Adaptação do método da redutase para avaliação da sensibilidade antimicrobiana em leite de vacas com mastite

Abstract

In this study we propose to adapt the reductase test using methylene blue as an indicator of bacterial activity to verify the sensitivity of mastitis-causing bacteria to trade antimicrobial agents due to the difficulty in microbiological diagnosis and antibiogram in the routine of dairy farms. For this, samples of milk from cows with subclinical and clinical mastitis were evaluated on the reduction time of methylene blue (RTMB) 0.02% with and without the addition of antimicrobial agents in different stages. First, milk samples from cows with subclinical mastitis were evaluated for RTMB front of five antibiotics available on the market in three different concentrations compared to control with the addition of methylene blue (MB). A second step were evaluated the effect of time of action of antibiotics on bacteria in milk in relation to the RTMB and the effect of temperature. There was no significant difference in the RTMB over volumes of antibiotics and the MB and the incubation temperature. However, the RTMB was different among the different antibiotics. The sensitivity to antibiotics added was determined statistically from the average of the RTMB treated samples compared to controls. The clinical efficacy of the reductase test was evaluated in 26 cows with clinical mastitis treated randomly with commercially available antibiotics. At the same time, samples of milk from each cow treated were sent for culture, identification and in vitro sensitivity testing. Seven days after the last intramammary treatment, animals were assessed by the wired cup test and CMT comparing the sensitivity of the TRAM relation to antibiogram. The tests were consistent with the results of the clinical test and no significant difference. The reductase test by addition of antibiotics proved to be useful in the choice of antimicrobial use in the treatment of mammary quarter affected by clinical or subclinical mastitis.