A randomized , double-blind , placebo-controlled , parallel group study with a two species probiotic combination -LSB- Lactobacillus acidophilus ( L. acidophilus ) ATCC @ and Bifidobacterium lactis ( B. lactis ) ATCC SD@ -RSB- on healthy adults during and after antibiotic treatment ( amoxicillin @ and @ mg clavulanate ) .