High Doses of Halotolerant Gut-IndigenousLactobacillus plantarumReduce Cultivable Lactobacilli in Newborn Calves without Increasing Its Species Abundance
To elucidate the ecological effect of high oral doses of halotolerant (resistant to table salt) indigenous-gut bacteria on other commensals early in life, we conducted a culture-based study to quantify the effect of intestinalLactobacillus plantarumstrain of bovine origin (with remarkable aerobic growth capabilities and inhibitory activity againstEscherichia coliO157:H7 and F5) on clinical health and gut lactobacilli/coliforms in newborn calves. In a double-blind placebo-randomized trial twelve colostrum-fed calves, consecutively born at a farm, were fedL. plantarumwithin 12 hours from birth at low (107-8 CFU/day) or high concentrations (1010-11) or placebo (q24 h, 5 d; 10 d follow-up). We developed a 2.5% NaCl-selective culture strategy to facilitate the enumeration ofL. plantarum-strain-B80, and tested 384 samples (>1,152 cultures).L. plantarum-B80-like colonies were detected in a large proportion of calves (58%) even before their first 24 hours of life indicating endemic presence of the strain in the farm. In contrast to studies where human-derivedLactobacillusLGG orrhamnosushad notoriously high, but short-lived, colonization, we found thatL. plantarumcolonized stably with fecal shedding of6±1 log10·g−1(irrespective of dose,P>0.2). High doses significantly reduced other fecal lactic acid bacteria (e.g., lactobacilli,P<0.01) and slightly reduced body weight gain in calves after treatment. For the first time, a halotolerant strain ofL. plantarumwith inhibitory activity against a human pathogen has the ability to inhibit other lactobacilliin vivowithout changing its species abundance, causing transintestinal translocation, or inducing clinical disease. The future selection of probiotics based on halotolerance may expand therapeutic product applicability.