Resistência antimicrobiana em cepas de Bacillus subtilis selecionadas para uso em animais

Abstract

Maximizing weight gain of producing animals is one of the main research fields for prouctivity raise in Pecuary, and one of the methods for so is the addition of probiotics to animal food, which consist in non-pathogenic micro-organisms that can benefit its host’s health, being Bacillus subtilis on of the most used species. Considering such panorama, the present research aimed to evaluate antimicrobial resistance in C and E strains of Bacillus subtilis. The bacteria were grown in conventional nutrient agar and nutritional agar modified for sporulation. Then, antimicrobial sensibility test by disc-difusion was performed using the antibiotics amoxicillin + clavulanic acid, gentamicin, ceftiofur, enrofloxacin, sulfametoxazole + trimethoprim, tetraciclin ceftriaxone, neomycin and norfloxacin. In vegetative bacteria, minimum inhibitory concentration (MIC) test was also performed for gentamicin, enrofloxacin and tetraciclin by serial dilution method, and for vancomicin by a Laborclin commercial test. The results for disc-difusion for the vegetative form have indicated that C strain was resistant only for sulfametoxazole and E strain was sensible for all antimicrobials. At sporulated form, both strains were resistant to amoxicillin and sulfametoxazole, and C strain also to tetraciclin. For the MIC test, both strains were sensible to all antimicrobials. In conclusion, the metal-added nutrient agar was efficient to induce sporulation and both strains are sensible to the tested antimicrobials, which allow them to be safely used as probiotics.