Isolation and Identification of Effective Probiotics on Drug-Resistant Strains and Their Biofilms.

INTRODUCTION

This study aimed to identify, assess, and isolate strong lactobacilli demonstrating broad antibacterial and anti-biofilm activity against drug-resistant strains of . Additionally, the mechanism of inhibition of these organisms was to be determined.

METHODS

Over a 6-month period (from December 2021 to June 2022), 53 clinical strains were collected from clinical samples. Twenty probiotic strains were isolated from local dairy products. Antibacterial activity of strains' cell-free supernatant (CFS) was identified using the agar well diffusion method and the microbroth dilution test. Anti-biofilm effect was performed by the microtiter plate assay. The MTT assay was also used to look into the probiotics' cytotoxic effects on the L929 fibroblast cell line.

RESULTS

During the 6-month period, 53 clinical strains were obtained and identified. Out of 20 strains, the CFS of a strain (named L9) showed an inhibitory effect against all strains. Using the broth microdilution method, it was shown that the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of CFS extracts of L9 strains against strains were both ¼ mg/mL. The result of the anti-biofilm showed that the selected probiotic could inhibit biofilm formation. The most common organic acid produced by all strains, according to the HPLC method, was lactic acid, which was followed by acetic acid. The L929 fibroblast cell line was used in the cytotoxicity assay, which revealed that 100% of the cells in the L929 fibroblast cell line survived treatment with successive doses of CFSs for a full day.

CONCLUSION

The probiotic strain isolated from local yogurt in this study showed potential anti-biofilm and antimicrobial properties against all drug-resistant isolates. Given the increasing interest in probiotic microorganisms based on their high health benefits, further studies are recommended on the mechanisms of action between probiotics and strains to find new solutions for biological control and treatment of these infections without the use of antibiotics.