Antibacterial effect of the probiotic candidate isolated from kishk sold in Upper Egypt

Abstract

Kishk is a traditional dry fermented dairy product prepared from a mixture of salted sour butter milk or yoghurt with wheat grains. Goal was to evaluate the microbiological quality, together with isolation and identification of LAB from kishk and assessed their protective effects against E. coli and Pseudomonas aeruginosa in vitro and in vivo. One hundred samples of kishk were randomly obtained from farmers’ houses and food stores in the Assuit province, Egypt. Total viable count and, total yeasts and molds were performed by plating the samples on selective media. Further, LAB were isolated on de Man Rogosa and Sharpe (MRS) agar and identified by biochemical tests. The antagonistic effect of the obtained LAB was evaluated against two of foodborne patogens (E. coli and Pseudomonas aeruginosa) in vitro using well diffusion method and in vivo after inoculation in cow’s milk. The average count of total bacterial counts and, total yeasts and molds were 8.13 ± 0.09 and 2.92 ± 0.16 log₁₀ CFU/g, respectively. On the basis of phenotypical examination, LAB were identified and classified into three groups of LAB namely Lactobacillus, Leuconostoc and Lactococcus. Notably, LAB had more inhibitory activity against against E. coli in comparison to Pseudomonas aeruginosa in vitro. However, there was no changes in the mean count of the tested organisms versus control group after inoculation in milk. This study discovered that kishk contain LAB bacteria that have antagonistic properties on E. coli and Pseudomonas aeruginosa. Hence, kishk could be a useful candidate for the human health.