Mackenzie BW, et al. - In the present study, the researchers sought to examine polymerase chain reaction (PCR) primer pairs for measuring absolute abundances of Staphylococcus aureus and Staphylococcus epidermidis, then compared bacterial community composition and absolute abundances of these species between chronic rhinosinusitis (CRS) patients and controls. Six candidate Staphylococcus species-specific primer pairs have been tested in silico and in vitro against pure bacterial isolates. In 40 CRS (CRS without nasal polyposis [CRSsNP] = 22, CRS with nasal polyposis [CRSwNP] = 18) patients and 14 controls, quantitative PCR (qPCR) for absolute quantification of S. aureus, S. epidermidis, and overall bacterial load have been evaluated. In almost all patients, bacterial community sequencing detected Staphylococcus-assigned sequences, however, it could not differentiate between S. aureus and S. epidermidis. Primer pairs that can distinguish between these species were presented in this analysis. In both CRS patients and controls, a very high prevalence of S. aureus was reported.