The non-toxigenic strain of Clostridioides difficile Z31 can prevent infection by C. difficile in experimental model piglets.

One of the main challenges associated with Clostridioides difficile infection (CDI) in humans and domestic animals is the lack of an effective preventive strategy. One strategy with promising results is the oral administration of non-toxigenic strains of C. difficile (NTCD). Recently, Z31, a NTCD strain isolated from a healthy dog, showed promising results to prevent CDI in hamsters. Thus, the present study aimed to evaluate the capacity of Z31 to prevent CDI in piglets using an experimental model. Twenty neonatal piglets were randomly distributed in three groups: G1 - 106 spores of Z31 followed by 107 spores of a toxigenic C. difficile strain (n = 7), G2 (positive control) - 107 spores of a toxigenic C. difficile strain (n = 7), and G3 (negative control) - no biological inoculum (n = 6). All animals were kept in individual insulators and observed for 60 h. Data regarding clinical signs, macro and microscopic lesions, toxigenic culture of C. difficile, and detection of A/B toxins in the feces were evaluated. All evaluated parameters were significantly lower in animals that received Z31 compared to the positive control. Thus, oral administration of Z31 was able to prevent CDI in piglets in an experimental model.

Effect of domestication on microorganism diversity and anaerobic digestion of food waste.

To accomplish the rapid start-up and stable operation of biogas digesters, an efficient inoculum is required. To obtain such an inoculum for food waste anaerobic digestion, we domesticated dairy manure anaerobic digestion residue by adding food waste every day. After 36 days, the pH and biogas yield stabilized signifying the completion of domestication. During domestication, the microbial communities in the inocula were investigated by constructing 16S rDNA clone libraries. We evaluated the effect of the domesticated inoculum by testing batch food waste anaerobic digestion with a non-domesticated inoculum as a control. The pH and methane yield of the digestion systems were determined as measurement indices. Domestication changed the composition and proportion of bacteria and archaea in the inocula. Of the bacteria, Clostridia (49.3%), Bacteroidales (19.5%), and Anaerolinaceae (8.1%) species were dominant in the seed sludge; Anaerolinaceae (49.0%), Clostridia (28.4%), and Bacteroidales (9.1%), in domestication sludge. Methanosaeta was the dominant genus in both of the seed (94.3%) and domestication (74.3%) sludge. However, the diversity of methanogenic archaea was higher in the domestication than in seed sludge. Methanoculleus, which was absent from the seed sludge, appeared in the domestication sludge (21.7%). When the domesticated inoculum was used, the digestion system worked stably (organic loading rate: 20 gVS/L; methane yield: 292.2 ± 9.8 mL/gVS; VS = volatile solids), whereas the digestion system inoculated with seed sludge failed to generate biogas. The results indicate that inoculum domestication ensures efficient and stable anaerobic digestion by enriching the methanogenic strains.