Evaluation de l’activité antibactérienne des souches probiotiques extraites de différents types de yaourts

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.