Comparison of two selective media for the detection and enumeration of Lactobacilli in human faeces.

The enumeration of faecal bacteria is an important requirement for many studies of bowel health. One approach is the use of selective culture media for the culture and identification of genera or species from faeces. This study compares the culture of Lactobacilli from dilution series of faecal samples from six healthy human volunteers on two commonly used media, LAMVAB and Rogosa agar. Colonies were counted after a 72-h anaerobic incubation at 37 degrees C, and colony morphology recorded by a single observer. DNA was isolated from a representative number of colonies and genus-specific PCR, single-stranded conformation polymorphism (SSCP) and DNA sequencing performed. Total colony counts ranged from <3.00 to 7.48 log(10) cfu/g of faeces for LAMVAB and 5.09 to 7.66 log(10) cfu/g for Rogosa. For each subject, the total colony count was higher on Rogosa than that obtained with LAMVAB agar. SSCP analysis and DNA sequencing indicated that colony morphology was not an accurate predictor of genus identity. Growth of two species, Lactobacillus acidophilus and Lactobacillus gasseri, was not supported on LAMVAB medium. Rogosa agar was more likely to support growth of non-Lactobacillus species. Therefore, neither medium gave a fully accurate representation of the Lactobacilli species present in human faecal samples.

Colonic infection by Bilophila wadsworthia in pigs.

Bilophila wadsworthia is a common inhabitant of the human colon and has been associated with appendicitis and other local sites of inflammation in humans. Challenge-exposure or prevalence studies in laboratory and other animals have not been reported. B. wadsworthia is closely related phylogenetically to Desulfovibrio sp. and Lawsonia intracellularis, which are considered colon pathogens. We developed a PCR specific for B. wadsworthia DNA. Samples of bacterial DNA extracted from the feces of pigs on six farms in Australia and four farms in Venezuela were examined. Specific DNA of B. wadsworthia was detected in the feces of 58 of 161 Australian and 2 of 45 Venezuelan pigs, results comprising 100% of the neonatal pigs, 15% of the weaned grower pigs, and 27% of the adult sows tested. Single-stranded conformational polymorphism analysis of PCR product DNA derived from pigs or from known human strains showed an identical pattern. Histologic examination of the intestines of weaned B. wadsworthia-positive pigs found no or minor specific lesions in the small and large intestines, respectively. B. wadsworthia is apparently a common infection in neonatal pigs, but its prevalence decreases after weaning. The possible role of B. wadsworthia as an infection in animals and in human colons requires further study.