INHIBITION OF ENTEROPATHOGENS BY LACTOBACILLI STRAINS USED IN FERMENTED MILK

The inhibitory effect of lactobacilli on the growth of different patho gens was studied. The degree of inhibition was measured by disc assay in different media, showing that the inhibitory substance(s) can be ex tracellular and diffusible. The associative cultures were performed wi th lactobacilli and Escherichia coli in a relationship of 1:1 or 10(3) :1. In the first experiments, the E. coli inhibition began at 9 h afte r culturing. In the experiments with lower levels of different intesti nal pathogens, associative cultures were incubated for 4-6 h obtaining different degrees of inhibition with the highest being for E. coli an d Klebsiella pneumoniae. After a day of incubation. we did not recover viable pathogens from the mixed cultures, while lactobacilli grew to 10(8)-10(9) microorganisms per ml. The inhibition of pathogens was not due to pH alone, because the addition of different organic acids to c ulture media did not inhibit their normal growth. Lactobacillus casei and Lactobacillus acidophilus in this study can be considered a potent ial biotherapeutic treatment in patients infected with certain intesti nal pathogens.