Bacteroides tectum sp. nov. and Characteristics of Other Nonpigmented Bacteroides Isolates from Soft-Tissue Infections from Cats and Dogs

Abstract

Sixty strains of obligately anaerobic gram-negative nonsporeforming nonpigmented Bacteroides species were isolated from subcutaneous abscesses and pyothoraxes of cats and dogs. All of these strains grew well in bile and produced acetic, propionic, and succinic acids as major products of fatty acid metabolism. Phenotypic and deoxyribonucleic acid (DNA) homology data divided the strains into five groups. Only three strains were members of Bacteroides fragilis, as determined by biochemical and DNA homology analyses. All of the other strains showed negligible levels of DNA homology with human strains of B. fragilis, Bacteroides distasonis, Bacteroides vulgatus, Bacteroides thetaiotaomicron, and Bacteroides ovatus, although they did have substantial ribosomal ribonucleic acid homology with these species. One group comprising 52 strains is proposed as a new species, Bacteroides tectum, having three distinct homology clusters. Strains of B. tectum are obligately anaerobic, gram-negative, nonmotile, nonpigmented, nonsporeforming rods that grow well in bile, do not produce indole, and only weakly ferment carbohydrates. They have a DNA guanine-plus-cytosine ratio of 46 mol% but do not exhibit DNA homology with phenotypically similar human strains of Bacteroides.