Abstract

Background: Over the past three decades, the use of probiotics has increased as growth promoters and effective supplements to reduce the pathogenicity of pathogens. In this regard, Lactobacillus bacteria are among the most common probiotics used, as they can help strengthening the digestive system and therefore reducing intestinal hystopathological damage when encountering pathogens. Objectives: This study aimed to evaluate the histopathologic effects of Lactobacillus acidophilus as a dietary supplement in zebrafish ration, as an appropriate laboratory model, and in the exposure to Escherichia coli O157: H7. Methods: In this project, 48 fish were grouped in 4 aquariums and monitored for 30 days; control group (C1A1) received basic ration; B1A1 group received control group ration and were exposed to E. coli O157: H7; Treatment 1 (T1A1) received basic ration containing L. acidophilus with no exposure to E. coliO157: H7, and Treatment 2 (T2A2) received basic ration containing L. acidophilus with exposure to E. coli O157: H7. During 30 days of the experiment, the samples were taken from the intestinal tissue in the days 15, 27, and 30 for the histopathological examinations. Results: The results of the findings showed a significant increase in the length of the intestinal villi and the number of goblet cells in the studied tissue in the group treated with a ration containing probiotic supplements compared to the control group (P < 0.001, P < 0.01, P < 0.05). Also, in the group exposed to E. coli O157: H7, histopathological changes including mild edema, inflammatory cell accumulation in the intestinal mucosal tissue, severe necrosis and epithelium loss in the intestinal tissue were evident. These symptoms were much lower in the group fed with probiotic. Conclusions: According to the obtained data, it can be concluded that feeding fish using L. acidophilus supplement can produce very beneficial effects in reducing tissue damage caused by E. coli O157: H7 infection in zebrafish intestines as a laboratory model.