Distribution of the Lactobacillus acidophilus Complex in Human Fecal Specimens Examined by Restriction Fragment Length Polymorphism of the 16S rRNA Genes

Fresh fecal samples from healthy volunteers were examined for their content of the Lactobacillus acidophilus complex (LAC). A two-step isolation method for fecal lactobacilli was developed and employed in this study. Isolates of lactobacilli were identified according to their restriction fragment length polymorphism (RFLP) of genes coding for ribosomal RNA. Our results suggested that all samples contain lactobacilli and the most dominant species of human fecal lactobacilli is L. paracasei. In addition, several strains of LAC were recovered from specimens of volunteers. Among six LAC species, namely, A1: L. acidophilus, A2: L. crispatus, A3: L. amylovorus, A4: L. gallinarum, B1: L. gasseri, and B2: L. johnsonii, isolates classified into cluster B were recovered from 6 out of 15 volunteers; however isolates of cluster A were recovered from 3 of 15 volunteers. Four of 15 volunteers had strains of L. gasseri, 3 of them had strains of L. johnsonii, and strains of L. amylovorus were also isolated from specimens of 3 of 15 volunteers. These findings suggest that group B of LAC is the predominant cluster of LAC found in human feces and L. amylovorus was the only species of cluster A found in this study. No volunteer with blood type O had LAC in the fecal Lactobacillus flora.