THE INFLUENCES OF LACTOBACILLUS CELL-FREE SUPERNATANTS ON GROWTH AND VIRULENCE PROPERTIES OF CAMPYLOBACTER JEJUNI IN HUMAN ADENOCARCINOMA (HT-29) CELL CULTURE

Objective: Lactobacilli are the most commonly used probiotics. We examined the influence of cell-free supernatants (CFSs) of Lactobacillus acidophilus (La), L. fermentum (Lf), L. plantarum (Lp) and L. rhamnosus (Lr) on growth, adhesion and invasion of C. jejuni 81116 and RM1221 in human adenocarcinoma colon cells (HT-29). We also analyzed the influences of CFSs, C. jejuni and their combinations on HT-29 cell viability. Materials and Methods: Growth and adhesive-invasive bacteria counts were determined using the spectrophotometric method and colony counting method, respectively. We used methyl thiazolyl diphenyl-tetrazolium bromide (MTT) assay for detection of HT-29 cell viability. Results: During two and four hours of incubation, the growth of RM1221 was significantly decreased (p<0.0001) with the effects of the tested CFSs, while the decrease in growth of the 81116 strain was only significant (p<0.05) in the presence of La and Lp. All CFSs except La reduced the growth of both C. jejuni isolates at 24 hours of incubation. The adhesion of C. jejuni 81116 was significantly (p<0.0001) reduced in the presence of all CFSs. La and Lr statistically significantly (p<0.05 and p<0.005, respectively) reduced the adhesion of C. jejuni RM1221. Invasion of C. jejuni strains was shown not to be affected in presence of all CFSs. C. jejuni and each CFSs were found to influence the HT-29 viability differently. Conclusion: Our results suggest that CFSs have suppressive effects on the growth and adhesive properties of C. jejuni in a time-dependent manner. The viability of HT-29 depends on incubation time and which strain is tested.