Antimicrobial Effect and Antibiotic Resistance of Lactic Acid Bacteria from some Commercial Dairy Products

Abstract

Over the past few years lactic acid bacteria (LAB) have received considerable attention as probiotic commonly consumed in fermented foods, such as some yoghurts and fermented milk drinks, and claimed antimicrobial effects against different human pathogens. Therefore, the objective of the study was to investigate the antimicrobial activity of 24 commercial dairy products and the antibiotic resistance in LAB isolated from these products. The antimicrobial effect of commercial products on growth inhibition of Candida albicans and Salmonella enteritidis was investigated using disc diffusion method, while to test the antibiotic resistance of LAB isolated from dairy were used: ampicillin (SAM, 20 µg), amoxicillin (AMC, 30 µg), ciprofloxacin (CIP, 1 µg) and trimethroprim-sulfamethoxazole (STX, 25 µg). It was found that 8 fermented foods have antifungal activity and the highest effect was produced by Napolact Kefir and a probiotic yoghurt Leeb Vital Bio, but only 2 products (Covalact Sana, Danone Activia) maintained the antimicrobial effect in 7 days expired products. Covalact Sana, Napolact Sana Bio and Pilos (kefir and yoghurt) presented the highest antibacterial effect on Salmonella sp. strain. The study revealed high susceptibility of consortium LAB strains from tested dairy products to ampicillin. This preliminary research offers consumers supplementary information about the health benefits of some commercial dairy products.

Keywords

• antimicrobial effects
• antibiotic resistance
• dairy products
• lactic acid bacteria (lab)
• probiotic