Screening and characterization of Sahiwal cattle calves-origin lactic acid bacteria based on desired probiotic attributes for potential application

Probiotics are living microorganisms that confer health benefits to host when administered in adequate amounts. To develop novel host-specific probiotic for their application as feed additive, the present study was undertaken to isolate and characterize probiotic strains of indigenous cattle-calves origin. A total of 55 colonies were isolated from 12 healthy calves, with 34 of the isolates being Gram-positive, catalase-negative and vancomycin-resistant. Furthermore, eleven isolates showed tolerance to acid (pH 2.0) and thirteen isolates tolerated bile salts (0.3%). Seven common acid and bile tolerance strains were further investigated for other probiotic attributes and displayed higher (<i>p</i>&lt; 0.05) auto-aggregation and cell surface hydrophobicity values. Moreover, all seven isolates had potent antibacterial activity against pathobiont <i>E. coli</i> as well as significant co-aggregation capacity and enzyme activity. <i>In vitro</i> biosafety assessment revealed that all seven isolates were non-hemolytic, negative for mucin degradation and susceptible to most of the antibiotics. Based on the obtained findings, heatmap and principal component analysis identified four highly effective probiotic candidates confirmed by 16S rDNA sequencing as <i>Limosilactobacillus reuteri</i> SW23, <i>Limosilactobacillus reuteri</i> SW26, <i>Limosilactobacillus reuteri</i> SW27 and <i>Enterococcus faecium</i> SW28, respectively. Further studies on biosafety aspect are warranted for the application of these strains in animal as potential probiotics.HIGHLIGHTS<i>L. reuteri</i> SW23, <i>L. reuteri</i> SW26, <i>L. reuteri</i> SW28 and <i>Enterococcus faecium</i> SW28 were successfully isolated and identified from indigenous calves’ feces.These microbes were characterized for potential probiotics attributes.Heatmap analysis and principal component analysis (PCA) was used along with probiotic attributes to select highly effective probiotic candidates. <i>L. reuteri</i> SW23, <i>L. reuteri</i> SW26, <i>L. reuteri</i> SW28 and <i>Enterococcus faecium</i> SW28 were successfully isolated and identified from indigenous calves’ feces. These microbes were characterized for potential probiotics attributes. Heatmap analysis and principal component analysis (PCA) was used along with probiotic attributes to select highly effective probiotic candidates.