Inhibitory Effect of Lactobacillus strains isolated from the feces of children on the pathogenic bacteria of the intestines and stomach

Lactic acid bacteria are characterized as gram positive, usually non motile, non-spore forming bacteria that affect the health conditions of their hosts due to production of lactic acid and other fermentative yields. The aim of this study was to isolate Lactobacillus strains from stool sample of children and to determine their antimicrobial activity against common pathogenic bacteria such as Escherichia coli, Salmonella typhimurium and Helicobacter pylori.

The bacteria were isolated from the stool samples via cultivation on MRS agar media. Identification of the lactobacilli was performed based on their morphological, physiological and biochemical characteristics. Inhibitory effect of isolated lactobacilli on pathogenic bacteria was assessed by well diffusion and disk diffusion methods. After centrifuging the cultured bacteria and their sedimentation in the tubes, the pathogenic bacteria were plated on MRS agar. Following adding 100µl lactobacillus supernatant to the wells, the results were interpreted after 24-48 h.

19 samples out of 40 samples (47.5 %) had inhibitory effect on the studied pathogenic bacteria. L. plantarum, L. fermentum and L. rhamnosus were isolated more than other species. Maximum inhibitory effects of lactobacilli were observed against Escherichia coli and Salmonella. The widest antimicrobial hollow were obtained when the pathogenic bacteria were exposed to the supernatants of L. rhamnosus and L.fermentum.

In conclusion, the result showed that Lactobacillus strains are useful for treatment of persistent diarrhea and gastrointestinal disease and their consumption as dairy products would be effective for both prevention and treatment.