Abstract
ObjectiveThe present study was designed to evaluate the inhibitory effect of lactic acid bacteria (LAB) isolates from the fermented cocoa juice and their cell-free culture supernatants (CFS) against Helicobacter pylori strains and their potential as good probiotic. Isolation of lactic acid bacteria (LAB) was performed by culture and subculture of sample on MRS agar. Morphological characteristics, Gram staining and catalase reaction were used to identify the isolates. The antagonistic activity of LAB was tested using the agar spot-on-lawn method and the inhibitory effect of CFS using well diffusion assay. Acid tolerance and resistance to antibiotics tests were used to evaluate the probiotic potential of LAB isolates.ResultsAntagonistic effect was observed in 65.52% of isolated LAB. Isolate LAB19 showed the broader spectrum of antagonistic effect. The overall inhibitory activity was two to three folds reduced when CFSs were used instead of LAB isolates themselves. Our data showed that LAB19 controlled H. pylori growth using bacteriocins and that LAB4′, LAB8, LAB11′, LAB12, LAB13′, LAB15, LAB16 and LAB17 were through organic acids. LAB9, LAB11′ and LAB12 showed properties of probiotic tested. In this study, nine LAB isolates were found to possess anti-Helicobacter activity and some preliminary probiotic properties.
Highlights
Helicobacter pylori is one of the most common agent implicated in bacterial infection worldwide [1]
Our data showed that LAB19 controlled H. pylori growth using bacteriocins and that LAB4′, LAB8, LAB11′, LAB12, LAB13′, LAB15, LAB16 and LAB17 were through organic acids
Each value represents the mean of three determination (–) no activity HP, Helicobacter pylori; LAB, lactic acid bacteria
Summary
Isolation and identification of lactic acid bacteria (LAB) Fifty strains were purified from the above fermented food and 29 (58%) were characterized as LAB. Antagonistic activity of isolated LAB Antagonistic effect was noticed in 65.52% (19/29) of the tested LAB isolates with inhibition zones ranging from 6 to 30 mm (Table 1). Each value represents the mean of three determination (–) no activity HP, Helicobacter pylori; LAB, lactic acid bacteria. Each value represents the mean of three determination (–) no activity CFS, cell free culture supernatants; HP, Helicobacter pylori; LAB, lactic acid bacteria. Instead of the others CFSs, no significant difference was found between activity of the native and neutralized CFS from LAB19 cells (Additional file 1). LAB9′ and LAB11 isolates demonstrated a tolerance to acidic pH after incubation for 6 h and up to 24 h for LAB12 (Additional file 4) They were susceptible to antibiotics used with diameter of inhibition zones ranging from 23 to 44 mm (Additional file 5)
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