Abstract

This study aimed to isolate and characterise novel probiotic strains from the faeces of healthy albino Wistar rats. Lactic acid bacteria were isolated on MRS agar, and their probiotic properties were assessed through in vitro tests, including tolerance to simulated gastrointestinal juices, auto-aggregation assays, and antimicrobial activity. The antibiotic susceptibility and haemolysis tests were performed to assess the safety of the isolates. Isolates with probiotic potential were selected and identified by 16S rRNA gene sequencing. Five strains, R11, R21, R52, R71 and R81, were Gram-positive and catalase-negative, and they were able to survive the simulated digestive conditions with digestive enzymes and 1% bile salts and could auto-aggregate. All the strains inhibited the growth of indicator pathogens. Additionally, all five strains did not exhibit haemolytic activity and were sensitive to most test antibiotics.These five strains were identified as Enterococcus faecalis (R11), Enterococcus hirae (R21), Lactococcus garvieae (R71), Lactococcus garvieae (R52), and Enterococcus faecalis (R81). These strains hold potential as probiotic candidates, and further in vivo studies are necessary to evaluate their safety and establish putative health benefits.

Key words: Probiotic, Lactococcus, Enterococcus, rat faeces, haemolytic activity.