The objective of the present study was to characterize lactobacilli isolates from the feces of male Wistar rats. Various physiological features of the candidate probiotic isolates were preliminarily investigated, including tolerance to simulated gastric juice and bile salts, antimicrobial activity, antibiotic susceptibility and in vitro aggregation. Based on their morphological and biochemical characteristics, four potential probiotic isolates (CS2, CS3, CS4, and CS7) were screened. The isolates showed good tolerance to stimulated gastric juice and bile salts. CS4 and CS7 exhibited strong antibacterial activities against the pathogens tested as assessed in neutral pH culture supernatants. All lactobacilli isolates were susceptible to all the tested antibiotics, except vancomycin. Moreover, the isolate CS4 and CS7 were found to possess stronger cell surface traits such as hydrophobicity, auto-aggregation and co-aggregation capacity. In addition, CS4 and CS7 had greater β-galactosidase activities than the others. Biochemical tests and 16S rRNA gene sequencing confirmed that CS2, CS3, CS4 and CS7 are Lactobacillus intestinalis PJ2, L. sakei PJ3, L. helveticus PJ4, and L. plantarum PJ7, respectively. Based on the obtained results, L. helveticus PJ4 and L. plantarum PJ7 are ideal in vitro probiotic candidates and require further in vivo evaluation.
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