Determinação dos padrões de Concentração Mínima Inibitória (MIC) e caracterização genotípica de cepas de Brachyspira hyodysenteriae isoladas de suínos com quadros clínicos de disenteria suína no Brasil

Abstract

The objectives of this study were to characterize molecularly Brachyspira hyodysenteriae isolates obtained from pigs in Brazil and to evaluate their antimicrobial susceptibility profiles based on Minimal Inhibitory Concentration test (MIC). The MICs of 22 Brazilian isolates of B. hyodysenteriae from 2011 to 2013 were performed using the following antimicrobial molecules: tylosin, tiamulin, valnemulin, lincomycin and tilvalosin. Outbreaks of swine dysentery were diagnosed based on clinical presentation, gross and microscopic lesions, duplex PCR for B. hyodysenteriae and B. pilosicoli and Nox gene sequencing. All MIC values were consistently higher or equal than the microbiological cutoff described in the literature. MICs 50 and 90 for the tested drugs were, respectively, 2 g / ml and 8 g / ml for doxycycline 2g / ml and > and 4g / ml for valnemulin, 8g/mL and 8 g / ml for tiamulin, 16 g/ ml and 32 g / ml for tylvalosin , 64 g / ml and > 64 g / ml for lincomycin and > 128 g / ml and > 128 g / ml for tylosin. These results largely corroborate the literature, except the highest scores found for tiamulin, doxycycline and tilvalosin. All samples submitted to phylogenetic analysis based on the Nox gene sequence were similar among themselves, with 100 % identity to B. hyodysenteriae. One of the Brachyspiras isolates was confirmed to be B. murdochii by Nox gene sequence analysis, therefore was excluded from antimicrobial susceptibility Analysis.