Resistência antimicrobiana de Bacillus subtillis em forma esporulada e germinativa

Abstract

One of the strategies used to enhance food efficiency in production animals is the use of probiotics, which are non-pathogenic micro-organisms used as food additives that trigger positive effects over the gastrointestinal tract of such animals, with Bacillus subtilis being one of the most used species. Although innocuous, it is necessary to keep vigilance over antimicrobial resistance on probiotics in order to avoid horizontal transfer of resistance genes to pathogenic agents. In this case, the present research aimed to evaluate antimicrobial resistance in B. subtilis’ G strain and compare it to a commercial strain (DSM) which is in the market already. The bacteria were grown in nutrient agar. Then, an antimicrobial sensibility test by disc diffusion was conducted, using amoxicillin + clavulanate, ceftiofur, enrofloxacin, gentamicin, sulfametoxazole + trimethoprim and tetracycline. The same test was performed to bacteria grown in nutrient agar added of metals that force bacterial sporulation. In such case, ceftriaxone, neomycin and norfloxacin were also used. To the germinative bacteria, a minimum inhibitory concentration test was also conducted, using microdilution method for gentamicin and erithromicin and a commercial test made by Laborclin company for vancomicin. The results shown that both strains in germinative form were sensible for all antimicrobials in the disc diffusion test. For the sporulated form, however, both strains were amoxicillin and sulfametoxazole-resistant, while DSM strain showed total resistance for tetracycline and G strain had only intermediary resistance. At the MIC test, DSM strain shown total resistance to gentamicin and intermediary resistance eritromicin, while G strain was intermediary for both antimicrobials. In conclusion, the tested strain presented similar antimicrobial resistance parameters to the commercial strain and is apt to probiotic usage.