Evaluating the probiotic potential of Lactobacilli from yoghurts and their antagonistic activity against multidrug-resistant enteric bacteria, Yaounde, Cameroon

Introduction: Microbiota of the human gastrointestinal tract has health benefits. Enteric bacterial infection and consumption of antibiotics reduce their load. Fermented foods contain some beneficial bacteria that balance the dysbiosis and thus boost human health. This study aimed at identifying Lactobacilli from yoghurts in Yaoundé, evaluating their probiotic potential, and antagonistic effect against multidrug resistant enteric pathogens. Methods: This was a pilot research in which 12 yoghurts(six each) of two distinct industries, in Cameroon, were purchased from supermarkets. 20g of each sample was mixed with 18 mL of Man, Rogosa, and Sharp-cysteine (MRS-cysteine) broth and incubated anaerobically at 37°C for 48 hours. A 0.1mL of 10-4 serial dilution of the incubated broth was spread on an MRS-cysteine agar plate and incubated anaerobically at 37°C for 48 hours. On an MRS-cysteine agar plate, discrete creamy colonies were detected and purified. The isolates were identified using conventional PCR as well as the Vitek 2 compact technique.The isolates' probiotic capacity was assessed based on their tolerance to acid, bile salt, NaCl, stimulated gastric juice, and intestinal fluid. The spot method was used to determine their antagonistic activity in multidrug-resistant Salmonella enterica and Escherichia coli. Results: Four coccobacilli and three rod–shaped isolates were gram positive. They were identified as follows: three Lactobacillus plantarum, two L. buchneri and one L. parabuchneri and one L. fermentum. All isolates were non-haemolytic in defibrinated sheep blood. Five and three isolates could tolerate up to 3% and 4% sodium chloride respectively. L. buchneri2 had the highest mean percentage survival rate (MPSR) at pH 2 after 3 hours (103.67±0.26), while L. plantarum2 decreased to 99.47±0.22. L. plantarum3 had the greatest MPSR (82.35±2.33) in 0.3% bile salt after 3 hours, followed by L. buchneri1 and L. parabuchneri (34.87±3.33 and 31.39±1.15, respectively).The MPSR of Lactobacilli in stimulated gastric juice at pH 2.5 after 4 hours varied between species. L. plantarum3 cells were highly tolerant to stimulated gastric juice at pH 2.5 (131.86±16.3), whereas L. plantarum2 cells showed the least (92.89±1.27). In stimulated intestinal fluid at pH8 after 6hours, the isolate with least MPSR was L. buchneri 1 (57.52±52) while L. plantarum2 was the highest (97.01 ± 0.2). L. plantarum3 was the best Lactobacillus with antibacterial activities against multidrug resistant bacteria; Salmonella enterica (44 ±0.14), and E. coli (34±1.6). Discussion: The viability of L. plantarum after gastrointestinal fluid treatment and bile salt, among others, is suggestive of a good probiotic candidate, these findings tie with the report Lang et al. (2022), and Hassan et al. (2020). Research is required to explore additional probiotic criteria. Conclusion: L. plantarum could be recommended as the best potential probiotics follow by L. buchneri and L. fermentum that could eliminate multidrug-resistant enteric bacteria in cases of dysbiosis.