Bacteriology of the Labrador dog gut: a cultural and genotypic approach

Aims: To carry out an extensive study of the microflora composition of the Labrador dog gut. Methods and Results: Faecal specimens from four Labradors were collected and plated onto growth media designed to recover total anaerobes, bacteroides, bifidobacteria, lactobacilli, clostridia, Gram-positive cocci, total aerobes and coliforms. Morphologically different isolates were collected from all agars inoculated with faeces from one canine individual (repeated four times). A total of 157 out of 171 isolates were identified using 16S rRNA gene sequencing. Sequence analysis showed that agar selectivity was poor, especially when bacteroides and Gram-positive cocci were the targets. Bifidobacteria were not detected in any of the samples analysed, indicating their presence at low or negligible levels. The gene sequences of many of the isolates (n =45, representing 29% of the total) did not correlate with known species in the Ribosomal Database Project and EMBL databases, suggesting the presence of novel gut diversity. Conclusions: Traditional culture methods fail to reflect the bacterial diversity present in Labrador dog faeces. Significance and Impact of the Study: This study has shown the value of molecular-based methodologies for determining bacterial profiles in the Labrador dog gut microbiota, but has also exposed the limitations of purportedly selective agars.