Oncolytic bacteria: past, present and future.

More than a century ago, independent groups raised the possibility of using bacteria to selectively infect tumours. Such treatment induces an immune reaction that can cause tumour rejection and protect the patient against further recurrences. One of the first holistic approximations to use bacteria in cancer treatment was performed by William Coley, considered the father of immune-therapy, at the end of XIX century. Since then, many groups have used different bacteria to test their antitumour activity in animal models and patients. The basis for this reactivity implies that innate immune responses activated upon bacteria recognition, also react against the tumour. Different publications have addressed several aspects of oncolytic bacteria. In the present review, we will focus on revisiting the historical aspects using bacteria as oncolytic agents and how they led to the current clinical trials. In addition, we address the molecules present in oncolytic bacteria that induce specific toxic effects against the tumors as well as the activation of host immune responses in order to trigger antitumour immunity. Finally, we discuss future perspectives that could be considered in the different fields implicated in the implementation of this kind of therapy in order to improve the current use of bacteria as oncolytic agents.

Grape antioxidant dietary fiber stimulates Lactobacillus growth in rat cecum.

UNLABELLED: The digesta is a highly active biological system where epithelial cells, microbiota, nondigestible dietary components, and a large number of metabolic products interact. The gut microbiota can be modulated by both endogenous and exogenous substrates. Undigested dietary residues are substrates for colonic microbiota and may influence gut microbial ecology. The objective of this work was to study the capacity of grape antioxidant dietary fiber (GADF), which is rich in polyphenols, to modify the bacterial profile in the cecum of rats. Male adult Wistar rats were fed for 4 wk with diets containing either cellulose or GADF as dietary fiber. The effect of GADF on bacterial growth was evaluated in vitro and on the cecal microbiota of rats using quantitative real time polymerase chain reaction (RT-PCR). The results showed that GADF intake stimulates proliferation of Lactobacillus and slightly affects the composition of Bifidobacterium species. GADF was also found to have a stimulative effect on Lactobacillus reuteri and Lactobacillus acidophilus in vitro. These findings suggest that the consumption of a diet rich in plant foods with high dietary fiber and polyphenol content may enhance the gastrointestinal health of the host through microbiota modulation. PRACTICAL APPLICATION: Grape antioxidant fiber combines nutritional and physiological properties of dietary fiber and natural antioxidants from grapes. Grape antioxidant fiber could be used as an ingredient for functional foods and as a dietary supplement to increase the intake of dietary fiber and bioactive compounds.

Molecular and microbiological analysis of caecal microbiota in rats fed with diets supplemented either with prebiotics or probiotics.

The potential health-improving effects of both a prebiotic and a probiotic infant formula have been evaluated in a rat model. Two groups of 10 rats were fed with either prebiotics containing fructo-oligosaccharides or probiotics containing viable Bifidobacterium lactis and Streptococcus thermophilus. The composition of their caecal microbiota was analyzed both by classical plate count of the main bacterial groups and by PCR amplification of a V3 fragment of 16S rRNA genes and denaturing gradient gel electrophoresis (DGGE). Both diets induced a significant reduction of clostridia and Bacteroides spp. compared to a control diet, whereas prebiotics were also able to reduce the number of coliforms and to increase the presence of bifidobacteria. DGGE analysis showed a significant increase of 16S rRNA gene fragments in rats fed with either probotics or prebiotics. Nineteen bands were sequenced and most of them showed similarity to cultured bacteria. Detection of Bifidobacterium spp. by this technique using genus-specific primers only permitted these bacteria to be detected in prebiotics-fed rats, whereas the use of Lactobacillus group-specific primers gave similar results in rats fed with any diet, in agreement with the plate count results.