Abstract:The objective of this study was to investigate the effects of direct vat set Lactobacillus（DVSL）on antibiotics-induced alterations of the intestinal microbiota in mice.Thirty-six four-week-old male BALB/c mice were randomly assigned to a control group，an antibiotic exposure group，and a DVSL group，with 12 individuals each.During the first seven days，antibiotic exposure mice received 40 mg ceftriaxone per day，and DVSL mice received 40 mg ceftriaxone and 109CFU DVSL per day.Over the subsequent 21 days，DVSL mice received 109CFU DVSL by gavage，and antibiotic exposure mice received normal saline at the same volume by gavage.Control group mice received normal saline at the same volume throughout the experiment.All mice were killed at the end of the fourth week，quantitative real-time polymerase chain reaction（qPCR）and next-generation sequencing were used to analyze fecal bacteria，and hematoxylin-eosin staining was used to examine intestinal pathological characteristics.DVSL and antibiotic exposure mice showed significantly reduced body weight since day 3 compared to the controls （P<0.01）.The body weight of DVSL and antibiotic exposure mice returned to normal between days 18 and 21.In the first week，the overall abundance and diversity of fecal bacteria in antibiotic exposure and in DVSL mice were significantly lower than in the controls （P<0.01）；Bacteroidetes was the dominant taxon of fecal bacteria in the control group，whereas Firmicutes was predominant in the other two groups.In the fourth week，Firmicutes and Bacteroidetes were predominant in feces of DVSL and antibiotic exposure mice，and the composition of the fecal bacterial community in DVSL mice was more similar to that of the controls.No significant differences between the three treatments were observed regarding intestinal pathological characteristics （P>0.05）.In conclusion，antibiotic intervention affected not only body weight gain，but also influenced the intestinal microbiota and relative abundances.DVSL helped mitigate body weight loss induced by antibiotics and could help ameliorate intestinal microbiota disorders.