Perfil de suscetibilidade de agentes causadores de mastite bovina subclínica a antimicrobianos e aos óleos essenciais de Castanha-do-Brasil e Semente de Girassol.

Abstract

Mastitis, an inflammatory process in the mammary glands, causes major economic losses to dairy farms. Its main cause is an infection caused by Staphylococcus aureus. Resistance to antimicrobials developed by agents which cause mastitis, along with the concern with traces of antibiotics in milk, has led to the search for alternatives for treating mastitis. Taking into account the importance of carrying out an antibiogram to select the most adequate antimicrobial therapy, this study aimed at evaluating not only the susceptibility profile of agents isolated from bovine mastitis, but also the antimicrobial activity of essential oils of Brazil nuts and sunflower seeds against these microorganisms. Microorganisms were isolated from cow milk with subclinical mastitis; they had previously been identified by biochemical tests and confirmed by the Vitek 2 system. The antibiogram was carried out by the agar diffusion method. The minimum inhibitory concentrations (MIC) of the essential oils were determined by the broth microdilution technique. Results showed that 86.7% of the Staphylococcus spp. was coagulase-positive; 73.3% of them was identified as S. aureus. The microorganisms isolated from coagulase-negative Staphylococcus were identified as S. lentus and S. sciuri. The antibiogram showed that 100.0% of the isolated microorganisms was resistant to trimethoprim; 96.7%, to tetracycline; 90.0%, to neomycin, norfloxacin and cefalexin; 86.7%, to gentamicin; 73.3%, to penicillin; 63.3%, to enrofloxacin; 53.3%, to amoxicillin and bacitracin; 56.7%, to ceftiofur; and 43.3%, to ampicillin. The MIC’s of Brazil nut oil were 36.30; 21.35; 15.62 and 10.41µg.mL -1 , for S. aureus, Enterococcus spp., Candida spp. and Cryptococcus laurentii, respectively. The MIC’s of sunflower seed oil were 23.5; 19.21; 7.81 and 1.2µg.mL -1 , for S. aureus, Enterococcus spp., Candida spp. and Cryptococcus laurentii, respectively. These results show that both oils in low concentrations display antimicrobial activity. Since bacteria have developed resistance against antibiotics which have been available for the treatment of mastitis, essential oils have become a potential therapeutic resource to control this disorder. However, further studies should be carried out to evaluate their effects.