Abstracts accepted for publication only

Objectives: It has been hypothesized that disturbances in the intestinal flora could be a factor in the onset and persistence of IBS complaints.The aim of the study was to analyse the effect of Lactobacillus casei Shirota (LcS) on the faecal flora of IBS patients.Methods: In a randomised, placebo controlled, double blind study, IBS patients fulfilling the Rome criteria II were included.Patients took 2 bottles daily for 8 weeks, containing either LcS or placebo.Faecal samples were collected before intervention (week -2/0,S1), at the end of intervention (week 6/8,S2) and during follow-up (week 14/16,S3).Microbial populations (Bacteroides, anaerobes, bifidobacteria, coliforms, clostridia, and lactobacilli) were enumerated using quantitative plating.Total bacterial counts were performed using FISH.Bacterial DNA was analysed by quantitative Real-Time PCR for the detection of Atopobium spp., Bacteroides-Prevotella-Porphyromonas group, Clostridium coccoides-Eubacterium rectale group, Clostridium leptum subgroup, Clostridium difficile, Clostridium perfringens, Desulfovibrio desulfuricans group, and Bifidobacterium spp.Statistical analysis was performed using Mann-Whitney U tests or Paired Wilcoxon tests.P < 0.05 was considered statistically significant.Results: No significant differences in total bacterial counts were seen between the treatment and placebo group.Using quantitative plating, no significant differences were seen for the different bacterial groups between both groups.Significantly lower bacterial counts were seen in both groups for clostridia for S2 compared to S1 and S3.In the placebo group, significantly higher amounts of bifidobacteria and lactobacilli were detected for S2 compared to S1.Using qRT-PCR, significantly lower counts for D. desulfuricans group were seen in the placebo group compared to the treatment group.In the treatment group significant differences were seen only for S2 compared to S3, whereas in the placebo group, no significant differences were detected for the different bacterial groups at the different sampling points.Analysis at the IBS subtype level revealed differences in microbiota between the different subtypes.Conclusions: Although significant changes in the microbiota were seen during intake of LcS in the treatment group, differences in microbial populations between both groups were not significant.Interestingly, specific findings are likely to be associated with a specific IBS subtype rather than with IBS in general.