Hierarchical oligonucleotide primer extension as a time- and cost-effective approach for quantitative determination of Bifidobacterium spp. in infant feces.

The Bifidobacterium spp. present in 10 infant fecal samples (4 from infants with eczema and 6 from healthy infants) were quantified with both hierarchical oligonucleotide primer extension (HOPE) and fluorescence in situ hybridization-flow cytometry. The relative abundances of Bifidobacterium longum and B. catenulatum with respect to the total bifidobacteria had a poor correlation (rho, <0.600; P value, >0.208), presumably due to differences in primer specificity and the level of hybridization stringency of both methods. In contrast, the relative abundances of organisms of the genus Bifidobacterium against the total amplified 16S rRNA genes and those of B. adolescentis, B. bifidum, and B. breve against the genus Bifidobacterium exhibited a good statistical correlation (rho, >0.783; P value, <0.066). This good comparability supports HOPE as a method to achieve high-throughput quantitative determination of bacterial targets in a time- and cost-effective manner.