A randomized , double-blind , placebo-controlled , parallel group study with a two species probiotic combination [ Lactobacillus acidophilus ( L. acidophilus ) ATCC 700396 and Bifidobacterium lactis ( B. lactis ) ATCC SD5220 ] on healthy adults during and after antibiotic treatment ( amoxicillin 875 and 125 mg clavulanate ) .