Antimicrobial susceptibility of Brachyspira hyodysenteriae isolated from 21 Polish farms

Abstract

Swine dysentery (SD) is a common disease among pigs worldwide, which contributes to major production losses. Antimicrobial susceptibility testing of B. hyodysenteriae, the etiological agent of SD, is mainly performed by the agar dilution method. This method has certain limitations due to difficulties in interpretation of results. The aim of this study was the analysis of antimicrobial susceptibility of Brachyspira hyodysenteriae (B. hyodysenteriae) Polish field isolates by broth microdilution procedure. The study was performed on 21 isolates of B. hyodysenteriae, collected between January 2006 to December 2010 from cases of swine dysentery. VetMIC TM Brachyspira panels with antimicrobial agents (tiamulin, valnemulin, doxycycline, lincomycin, tylosin and ampicillin) were used for susceptibility testing of B. hyodysenteriae. The minimal inhibitory concentration (MIC) was determined by the broth dilution procedure. The lowest antimicrobial activity was demonstrated for tylosin and lincomycin, with inhibition of bacterial growth using concentrations >128 μg/ml and 32 μg/ml, respectively. In the case of doxycycline, the MIC values were ≤ 2.0 μg/ml. No decreased susceptibility to tiamulin was found among the Polish isolates and MIC values for this antibiotic did not exceed 1.0 μg/ml. The results of the present study confirmed that Polish B. hyodysenteriae isolates were susceptible to the main antibiotics (tiamulin and valnemulin) used in treatment of swine dysentery. Further studies are necessary to evaluate a possible slow decrease in susceptibility to tiamulin and valnemulin of B. hyodysenteriae strains in Poland.

Minimum inhibitory concentration of Brazilian Brachyspira hyodysenteriae strains

“…For doxycycline, the MIC50 values were comparable to those found by Zmudzki et al (2012) and Alvarez et al (2013), but the MIC90 was elevated compared with the previously described values (Karlsson et al 2002, Rohde et al 2004, Pringle et al 2007, Hidalgo et al 2009, 2011, Zmudzki et al 2012, Alvarez et al 2013, Mirajkar & Gebhart 2013. Decreased susceptibility to doxycycline has been associated with a mutation at position 1058 of the 16S rRNA gene for B. hyodysenteriae (Pringle et al 2007).…”

“…For valnemulin, the results were similar to those previously reported (Karlsson et al 1999, 2002, Rohde et al 2004, Hidalgo et al 2009, 2011, Zmudzki et al 2012, Alvarez et al 2013, Mirajkar & Gebhart 2013. The MIC50 results for tiamulin were higher than those published elsewhere, but the MIC90 was similar to the results obtained by Rohde et al (2004), Hidalgo et al (2011) and by Alvarez et al (2013).…”

“…Identifying the sensitivity pattern of Brazilian strains is important for establishing swine dysentery control and eradication programs, mainly due to the emergence of B. hyodysenteriae strains with reduced susceptibility to multiple antimicrobials, based on microbiological cut-off points, which was observed in both the present work and other studies in different countries (Karlsson et al 2002, Rohde et al 2004, Hidalgo et al 2009, 2011, Zmudzki et al 2012, Alvarez et al 2013, Mirajkar & Gebhart 2013. In addition, low sensitivity is relevant for resistance monitoring programmes as it is an indication of early resistance and allows the implementation of measures to prevent the emergence of strains with high resistance (Pringle et al 2012).…”

“…Hidalgo et al (2011) identified a mutation in the 23S gene at position 2059 associated with resistance to tylvalosin. For lincomycin, the MIC50 was higher compared with that reported in the literature (Karlsson et al 1999, Karlsson et al 2002, Karlsson et al 2003, Rohde et al 2004, Hidalgo et al 2011, Zmudzki et al 2012, Mirajkar & Gebhart 2013, however, the MIC 90 was similar to those obtained by Hidalgo et al (2009) and Alvarez et al (2013).…”

“…The results for tylosin were similar to those found in the literature regarding both the MIC50 and MIC90 (Table 1). High resistance to tylosin was expected based on the selective pressure caused by the widespread use of this drug in therapeutic and prophylactic programmes in recent years (Karlsson et al 2002, Rohde et al 2004, Hidalgo et al 2009, 2011, Zmudzki et al 2012, Alvarez et al 2013, Mirajkar & Gebhart 2013. The mechanism of tylosin resistance is related to mutations in the 23S ribosomal RNA gene at position 2058, inhibiting its binding (Karlsson et al 1999(Karlsson et al , 2004.…”