Subclinical Clostridioides difficile colonization in piglets could be a potential source of this bacterium for community-acquired C. difficile infection. The purposes of this study were to assess the effect of specimen type and processing on C. difficile isolation, culture, and detection by polymerase chain reaction (PCR), and to determine the occurrence of C. difficile in piglets of different ages. We compared different culture procedures-direct plating, ethanol shock, and an enrichment step-to isolate C. difficile from swine feces and rectal swabs. DNA was isolated directly from feces, processed feces, and bacterial isolates to detect the triose phosphate isomerase (tpi) gene and identify the toxins A and B genes. The results show that ethanol shock increased the C. difficile isolation from feces, while it decreased it for rectal swabs, in comparison with direct plating. The use of the enrichment broth gave the highest C. difficile recovery from both types of specimen. Our findings show low sensitivity for tpi gene detection after the DNA extraction directly from feces and an increase in PCR-positive samples when feces were processed before the DNA extraction. The overall prevalence of C. difficile was 16.9% (22/130), of which 100% were found to be toxigenic as assessed by the enrichment culture of fecal samples. The rate of isolation of positive samples decreased with the animal age, regardless of the presence or absence of diarrhea. Our results demonstrate the persistent reservoir of toxigenic C. difficile in fecal samples of piglets and support the impact of specimen processing on its isolation.
Keywords: Clostridioides difficile; DNA extraction; enrichment culture; ethanol shock; foodborne transmission; rectal swab.