SUSCEPTIBILITY OF POULTRY LACTOBACILLI TO IONOPHORE ANTIBIOTICS

The susceptibility of four poultry Lactobacillus strains to monensin, narasin, lasalocid, salinomycin and maduramicin was investigated using two different systems of lactobacilli cultivation. In the MRS broth ( Oxoid) with glucose, the growth of lactobacilli was inhibited at ionop hore concentrations as low as 0.4-5 mu g/ml. On the other hand, the gr owth of lactobacilli in the mixture of a commercial concentrate with w ater (1:2) was not influenced by ionophores at 100 mu g/g. It follows from these results that lactobacilli are much more resistant to ionoph ores in their natural environment than in laboratory cultures on gluco se. It was concluded that: probiotic lactobacilli can be added to iono phore-containing concentrates; antibiotic susceptibility data obtained in liquid cultures with glucose are misleading.