The sensitivity of 332 strains of Serpulina hyodysenteriae isolated in Hungary between 1978 and 1992 was tested against seven chemotherapeutic drugs frequently used for the treatment of swine
dysentery, and the changes in the patterns of resistance were also monitored. All the strains remained sensitive to
carbadox, with minimum inhibitory concentrations (MIC) of only 0.05 to 0.40 microgram/ml at present. The susceptibility of the strains to
dimetridazole has gradually decreased, but about half of the strains are still sensitive, with large numbers of "moderately sensitive' strains; the MIC values varied within wide limits (0.1 to 50 micrograms/ml). Most of the strains were resistant to
tylosin, with MIC values from 0.1 to 100 micrograms/ml. The number of strains resistant to
lincomycin has gradually increased, but about half of the strains remain sensitive; the MIC values ranged from 0.2 to 100 micrograms/ml. Recently,
tiamulin has proved the most effective
antibiotic, but some resistant strains have already emerged (MIC values 0.05 to 50 micrograms/ml).
Monensin was good for the prevention of swine
dysentery, but resistance may evolve quickly; the MIC values ranged from 0.4 to 25 micrograms/ml. For
sedecamycin, the MIC values (6.25 to 100 micrograms/ml) were much higher than expected.