Abstract
Bovine enteric bacterial pathogens are a major cause of health decline in agricultural cattle populations. The identification of host-derived microbiota with probiotic characteristics is key for the development of treatments utilizing pathogen displacement and recolonization by commensal flora. In this study, intestinal microbiota in fecal samples from four Holstein dairy cows were analyzed using 16S ribosomal RNA gene next-generation sequencing, leading to the identification of three Lactobacillus isolates (Lactobacillus gasseri, Lactobacillus reuteri, and Lactobacillus salivarius). By taking advantage of the preferential growth in acidified culture media, bacterial characteristics examination, and restriction fragment length polymorphism analysis of 16S rRNA genes, the three lactic acid bacteria (LAB) strains were successfully isolated. The three LAB isolates possess the prerequisite growth tolerances for probiotic functionality, as well as exhibit effective antimicrobial potency against enteric bacterial pathogens of cattle, including Escherichia coli O157:H7, Mycobacterium avium subspecies paratuberculosis, and Salmonella species (Salmonella enteritidis, Salmonella typhimurium, and Salmonella Dublin). Moreover, the LAB isolates showed significant adhesion to cattle intestine, implying greater survivability potential due to their species specificity when administered in the same host species. The LAB isolates were sensitive to most antibiotics with notable resistances of L. gasseri to streptomycin and L. salivarius to kanamycin. Genes attributed to specific antibiotic resistances demonstrated a low risk of lateral transfer in a conjugation study. Our in vitro results demonstrate the promising probiotic characteristics of these newly identified Lactobacillus strains and their considerable potential to serve as probiotics feed supplements for cows.
Highlights
Probiotics are live microorganisms that benefit humans and animals by promoting intestinal tract health
The V3–V4 regions of the bacteria 16S rRNA extracted from healthy cow rectal samples were subjected to an Illumina MiSeq Platform for sequencing
Because the fecal sample from cow 414 had both robust Lactobacillus colonization and the most homogeneous Lactobacillus species distribution (Figure 1), Lactobacillus bacteria for further characterization were isolated from the cow 414 sample
Summary
Probiotics are live microorganisms that benefit humans and animals by promoting intestinal tract health. The major beneficial attributes of probiotics include the ability to compete with enteric pathogens, the contribution to increased digestive capacity, the enhancement of mucosal immunity, and the reduction of intestinal pH. As a result of these characteristics, probiotics create an unfavorable environment for the growth of enteric pathogens and act to prevent disease-causing bacteria from colonizing the intestine. Probiotic bacteria reduce a host’s inflammatory responses by stabilizing the gut microbial environment, fortifying the intestinal permeability barrier, facilitating the degradation of enteral antigens, and altering their antigenicity and immunogenicity [1]. Several probiotic strains (Bifidobacterium species, Lactobacillus species, Saccharomyces boulardii, and Streptococcus thermophilus) have been effectively utilized for young cattle with positive results on overall health, feed efficiency, weight gain, and immunocompetence [2]
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