DIVERSITY OF CULTURABLE LACTOBACILLUS POPULATIONS FROM THE NEONATAL AND ADULT GASTROINTESTINAL TRACT

Abstract

Purpose: We undertook this study to examine the diversity of the culturable lactobacilli population in neonatal and adult human subjects and to identify any dominant strains that may be shared across a number of individuals. Methods: To genetically fingerprint lactobacilli of human intestinal origin (using 7 neonates and 12 adults), isolated on Lactobacillus selective agar (LBS), pulse field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA (RAPD) PCR were used to group individual lactobacilli, which were subsequently speciated using 16S rDNA sequencing. Results: Four of the 7 neonates and 5 of 12 adults contained a predominant Lactobacillus strain. Some of the adults harboured multiple Lactobacillus strains with two adults having three different strains and one adult having two different strains. No Lactobacillus were found in 3 neonates and 4 adults. The Lactobacillus species identified in the neonatal samples included Lb. gasseri, Lb. salivarius, Lb brevis and Lb. reuteri which differed significantly from the adult populations, where Lb. rhamnosus and Lb. casei/paracasei were most commonly encountered. In one case, the same Lactobacillus strain, identified as Lb. casei/paracasei species was isolated from two adults, which had indistinguishable PFGE patterns. Interestingly, this strain was found in 100% of isolates from one sample and in the other case was present in 80% of isolates, while the remaining 20% were identified as Lb. rhamnosus. In an effort to analyze dominant lactobacilli from the neonatal small intestine, an ileostomy sample was also examined from a preterm infant at both 50 and 74 days old by plating on LBS. In this case, a single dominant strain was isolated at the two time points, identified as Lactobacillus casei. This indicates that the same strain dominated in the neonatal small intestine over three weeks. Conclusions: The results reaffirm the differences in Lactobacillus populations in the gastrointestinal tract both between individual subjects and between the neonate and adult where clearly different species prevail. Such information may be important when selecting strains as potential probiotics for particular target groups.