Abstract:
In order to evaluate the antibacterial activity of probiotics extracted from fermented dairy products,
four types of natural yogurts manufactured and marketed in the Algerian market were selected:
SOUMMAM, HODNA, DANONE and NUMIDIA. Using the decimal dilution method, 500
microliter of each suspension was taken, isolated in carefully prepared culture media and then
purified. More than 30 probiotic bacteria and 10 yeasts underwent morphological identification
carried out by staining tests to distinguish Gram positive and Gram negative bacteria as well as the
search for catalase enzyme for better precision.
The antibacterial power was examined by the well diffusion method against three active
pathogenic strains: two Gram-negative; Escherichia coli, Pseudomonas, and one Gram-positive;
Staphylococcus aureus for comparison between these four products. The results revealed that 49
isolates having a probiotic effect including 10 isolates are yeasts. According to the statistical study
carried out by SPSS 20 software, Hodna yogurt is the richest in probiotics compared to other types.
Probiotics show different antibacterial activity against the three pathogenic strains, considering
that Staphylococcus aureus and Escherichia coli are more sensitive than Pseudomonas. On the
other hand, the study showed that seven (7) probiotics are the most active. Bacteria and yeasts
exhibit distinct antibacterial activity, generally higher in bacteria due to their greater abundance
than yeasts.
