Abstract: Objective: To explore the effect of mixed Lactobacillus acidophilus and Lactobacillus plantarum cultures (1:1, V/V) on intestinal flora disorder in mice by fluorescence in situ hybridization combined with flow cytometry (FISH-FC) and to elucidate the regulation mechanisms. Methods: The inhibitory activity of the mixture on pathogenic bacteria was determined in vitro. Antibiotic-associated diarrhea mouse model was established by giving specific-pathogen-free (SPF) mice drinking water containing clindamycin hydrochloride at the dose of 2.8 mg/mL for 7 days. Predominant bacteria such as Enterobacteriaceae, C. coccoides-E.rectale and Bacteroides-Prevotella were quantified by FISH-FC method. After diarrhea was successfully induced, the model mice were administered with the mixture of Lactobacillus acidophilus and Lactobacillus plantarum at different amounts of 107, 108, 109 CFU/mL by gavage. Sterile saline was used as the control. Results: Compared with the control, the administration of the mixture containing Lactobacillus acidophilus and Lactobacillus plantarum could result in the fast recovery of disordered intestinal flora (P ＜0.01). The effective dose was 107 CFU/mL. Conclusion: Direct antimicrobial effect may be one of the mechanisms for regulating intestinal flora disorder.

Key words: FISH-FC, Lactobacillus acidophilus, Lactobacillus plantarum, antibiotic-associated intestinal flora disorder