Introduction: Dried plums are a source of antioxidants, polyphenolics, and dietary fiber, which we hypothesize could have a prebiotic effect, improve metabolism and bowel health, and mitigate effects of acute gastroenteritis. We tested this using rats on dried plum and control diets, subsequently infected with the common pathogenic bacteria Campylobacter jejuni.
Methods: Rats received normal chow or dried plum plus normal chow, with an inclusion requirement of prune consumption >7% bodyweight (n=10). Uninfected rats were euthanized after 6 weeks on diet. Remaining rats were gavaged with C. jejuni and euthanized 30 days post infection. DNA was extracted from luminal contents and total bacteria, Methanobrevibacter smithii, Bifidobacteria spp., Lactobacillus spp., Bacteroidetes spp., Firmicutes spp., Faecalibacterium prausnitzii, and segmented filamentous bacteria (SFB) were quantitated by qPCR. Gene expression was evaluated by RT-qPCR for β-defensin2, TNF-α, pregnane X receptor (PXR), (mucin) Muc-2, and (interleukin) IL-8.
Results: We observed no change in animal weights or rate of colonization or clearance of the pathogen. Percent liquid content in stool was increased pre- and post-infection with plum diet. Total bacteria levels in rats on plum diet were equivalent to controls in large intestine pre-infection but decreased post-infection, and were decreased in the small intestine pre-infection. Luminal composition was enriched in percent Bifidobacteria and M. smithii, and overall levels of lactobacillus and Bifidobacteria are significantly increased with plum diet. The percent content of Firmicuites was decreased post-infection on plum diet. While there was no significant change in Bacteroidetes content, or Bacteroidetes to Firmicuites ratio, there were more rats with elevated Bacteroidetes post-infection (increased mean) on plum diet. We did not find significant change in F. prausnitzii or SFB. Gene expression of β-defensin2 was elevated post-infection and PXR levels were lower in rats on plum diet both pre- and post-infection. We did not see any significant changes in TNF-α, Muc-2, or IL-8.
Conclusion: Rats on dried plum diet have increased lactobacillus, Bifidobacteria, and M. smithii suggesting a pre-biotic effect. While M. smithii is not considered a beneficial probiotic, it is associated with slowed gut transit could play a role in balancing diarrheal indications post-infection. Plum fed rats also have decreased Firmicuites, which is associated with metabolic dysregulation and obesity, after C. jejuni exposure. With plum diet, PXR is suppressed, possibly decreasing sensitivity to toxin exposure and β-defensin2 was elevated post infection, potentially enhancing host immune defense to the pathogen. This research was supported by an industry grant from This research is supported by the California Dried Plum Board.