Abstract
The tolerance of the multiple antibiotic resistant strain, Lactobacillus casei PSR3002, to artificialdigestive fluids and to sodium deoxycholate was compared in vitro with that of its parent strain (L.caseiYIT0091), other lactobacilli, streptococci and bifidobacteria.
The tolerance of L. casei PSR3002 to both artificial intestinal juice and artificial gastric juice wassimilar to that of L. casei YIT0091. Three-hour cultures of the two strains were studied forsusceptibility to artificial gastric juice at various pH values. At pH value above 2.7, there was littledifference between the two strains. At pH 2.5, however, in viable cell count both strains showed amarked decrease.
The higher the concentration of bile, the lower the viable cell count of the two strains. Thenthe elongation of the cells was recognized microscopically.
L. casei PSR3002 showed a longer lag-phase and slower growth than L. casei YIT0091 whenincubated in the artificial intestinal juice after exposure to the artificial gastric juice at pH 2.7 andpH 2.5. The most tolerant to the artificial gastric juice were 4 strains of L. casei and 2 strains of L.acidophilus, which were followed by L. plantarum YIT0062 and Streptococcus faecalis ATCC10541.
The most resistant to sodium deoxycholate solution were S. faecalis ATCC10541, L. casei YIT0091, L. casei PSR3002, L. casei 1-136, L. plantarum YIT0062, and L. acidophilus A-34. Their 50%growth inhibitory concentrations ranged from 330 to 600 mcg/ml. In contrast, Streptococcus thermophilus YIT2001, L. bulgaricus YIT2001, and L. jugurti LJ-4 were less tolerant to a 50% growthinhibitory concentration within a range from 55 to 90 mcg/ml.
