Antimicrobial potential of eleven Lacticaseibacillus paracasei strains isolated from mountain anthills

Toncho Dinev, Nikolina Rusenova, Katya Velichkova and Georgi Beev

Abstract: Probiotics with antimicrobial activity are important alternative to antibiotics, which are ever more restricted because of the developing microbial resistance and some adverse effects following frequent application. The aim of the present study is to determine the antibacterial and antifungal activity of supernatants of eleven Lacticaseibacillus paracasei strains (FR1-11) isolated from mountain anthills and identified by Amplified Ribosomal DNA Restriction Analysis (ARDRA). Antimicrobial activity was determined against reference strains of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Penicillium chrysogenum, Aspergillus niger, Aspergillus carbonarius, Aspergillus ochraceus, Aspergillus parasiticus, Fusarium oxysporum, Fusarium graminearum and clinical isolates of Bacillus cereus, Listeria monocytogenesand Salmonella enteritidis using agar well diffusion method. All strains of Lacticaseibacillus paracasei inhibited the growth of Staphylococcus aureus, Listeria monocytogenes, Salmonella enteritidis and Penicillium chrysogenum, 10 strains – Pseudomonas aeruginosa, 9 strains – Aspergillus carbonarius, 6 strains – Fusarium oxysporum, 5 strains – Escherichia coli, and 3 strains – Bacillus cereus. There are no active strains against Aspergillus niger, Aspergillus ochraceus, Aspergillus parasiticus and Fusarium graminearum. The highest antibacterial activity was measured against Pseudomonas aeruginosa with 14.7 mm inhibition zone of FR3 strain. The largest zones of inhibition against fungal strains were 12 mm, determined by the activity of FR2 and FR4 strains against Penicillium chrysogenum. As a whole, the supernatants of Lacticaseibacillus paracasei strains showed higher activity against bacterial strains compared to fungal strains.

Keywords: antibacterial; antifungal; ARDRA; Lacticaseibacillus paracasei

Date published: 2022-10-17