Optimizing qPCR for the Quantification of Periodontal Pathogens in a Complex Plaque Biofilm

Table 2: Comparison of Actual Cell Counts Versus a Standard Formula^{^*} in Estimating Total Bacteria Present in Pure Cultures

Bacteria	Cell Counts (x 10⁷)(CT)^{^a}	Total DNA (ng)^{^b}	Genome Size (MB)^{^c}	Cell Counts (x 10⁷)(SF)^{^d}
A. actinomycetemcomitans	2.24	40	2.11	2.62
T. denticola	1.68	47	2.84	2.29
P. gingivalis	2.50	44.5	2.34	2.63
T. forsythia	2.02	51	3.41	2.07
F. nucleatum	2.50	44.1	2.17	2.81
P. intermedia	3.53	94.5	2.70	4.81
C. rectus	2.70	51.4	1.71±	3.74

^* Standard formula: (Avogadro constant X amount of DNA in µg/µl) / (genome size X mw), where mw is the molecular weight per base pairs or nucleotide which is 660 Da); a: actual microscopic bacterial counts using a Petroff-Hausser counting chamber; b: total DNA isolated from each bacterial culture; c: Genome size based on published genome se-quence for each oral bacterial species; ±: estimated genome size based on published genome sequences for Campylobacter jejuni RM1221 and Campylobacter jejuni subsp. jejuni NCTC 11168 (http://www.ncbi.nlm.nih.gov/genomes/lproks.cgi);d: calculated cell numbers using the standard formula (SF; 5,11).