Formação de biofilme e mecanismo de efluxo em isolados de Rhodococcus equi

Abstract

The goal of this study was to determine the occurrence of two resistance mechanisms described in micro-organisms, but not described in R. equi isolates from horses and environment samples. The first mechanism studied it was the biofilm formation in R. equi isolates from clinical (n=41) and fecal (n=72) equine samples. In order to verify the biofilm formation it was employed the biofilm-culturing assay (with and without glucose supplementation) and the epifluorescence microscopy method. Biofilm-producers R. equi isolates (n=8) were selected and analyzed by two in vitro susceptibility tests with three antimicrobial agents belonging to macrolides group and commonly used in equine rhodococcosis treatment. The biofilm formation was observed in 80.5% of fecal and 63.4% of clinical isolates of R. equi. The methods used in this study were useful to verify the biofilm formation by R. equi isolates. However, the glucose supplementation was an important factor for biofilm formation in fecal samples. Antimicrobial resistance was demonstrated in biofilm antimicrobial susceptibility test. The second mechanism studied included the efflux system in R. equi isolates from clinical (n=30), fecal (n=30) and soil (n=30) sources. The presence of req_39680 gene, encoding a putative efflux system, was determined by PCR. Phenotypic expression of efflux systems was determined in agar containing ethidium bromide. The req_39680 gene was detected in 60% of the isolates and the phenotypic expression in 20%. In clinical isolates was observed high correlation between the presence of this gene and the expression of efflux systems. Both mechanisms studied were demonstrated in R. equi and may be contributing to increase the antimicrobial resistance, as well as to be associated to the survival of R. equi in the environment and host.