Dairy origin lactobacilli: functional analyses and antagonistic potential against multidrug-resistant foodborne pathogens
2020
Saqalein, M. | Kabir, S. | Khurshid, M. | Nisar, M. A. | Hayat, S. | Muzammil, S. | Taj, Z. | Shahid, M. | Waseem, M. | Shahzad, A. | Rasool, M. H. | Rizvi, N. B. | Waheed, S. | Nawaz, Z.
The present work was designed to characterise novel indigenous strains of lactobacilli and to identify and evaluate their antagonistic activity against enteric pathogens. A total of four lactobacilli strains were isolated from Dahi samples (continental yogurt) and characterised using phenotypic and biochemical tests, and by 16S rDNA sequencing. The isolates were identified as Lactobacillus paracasei SABA3, L. paracasei SABA4, L. fermentum SABA5, and L. casei SABA6. The probiotic potential of these strains was assessed under the gastrointestinal simulating environment. The antagonistic activity of lactic acid bacilli (LAB) strains against multidrug-resistant (MDR) test pathogens was determined by in vitro assays. Moreover, the bactericidal activity of cell-free culture supernatant (CFCS) was determined by agar well diffusion and growth inhibition assays. All the LAB strains were tolerant to 0.3% bile salts, extreme acidic conditions (stomach environment) as well as pH > 6.5 (small intestine); and can efficiently grow at 37°C. Moreover, the isolates were found as non-haemolytic which confirms their safety and use as potential probiotics. The genetic screening has shown the presence of qnrS, tetK, tetW, vanR, vanX, and qnrA antibiotic-resistant determinants. The L. fermentum SABA5 exhibited the strongest bactericidal activity against the pathogenic bacterial species among all of these potential probiotic strains. The CFCS inhibited the proliferation of pathogenic bacterial species in a concentration-dependent manner. The chromatographic profiling of all isolates depicted lactic acid as a major fermentation product.
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