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Relative to the previous nomograms (10 predictors or 71% accuracy) our tool relies on fewer variables (6) and shows superior accuracy in European men. Accuracy in American men is substantially lower. Racial, clinical and biochemical differences may explain the observed discrepancy in predictive accuracy.

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A real-time PCR assay that uses two fluorescence resonance energy transfer probe sets and targets the tuf gene of staphylococci is described here. One probe set detects the Staphylococcus genus, whereas the other probe set is specific for Staphylococcus aureus. One hundred thirty-eight cultured isolates, which contained 41 isolates of staphylococci representing at least nine species, and 100 positive blood cultures that contained gram-positive cocci in clusters were tested. This assay was 100% sensitive and 100% specific for the detection of the Staphylococcus genus and of S. aureus.The genus Staphylococcus currently consists of 38 species (14, 15). Among staphylococci, Staphylococcus aureus is the most virulent species and the most important pathogen, but the incidence of infections caused by coagulase-negative staphylococci (CoNS) has increased throughout the world (2,28,29). S. epidermidis and other CoNS are common members of the normal flora of skin and mucous membranes and are therefore common contaminants in culture, particularly in blood cultures. A conundrum often exists in the interpretation of cultures that contain these microorganisms, since CoNS have also become an important cause of hospital-acquired infections (5, 9, 21). It is most important to distinguish between S. aureus and CoNS in clinical samples, given the differences in virulence between these organisms (2,28,29). It is also important, however, to confirm the presence of CoNS given the increasing importance of CoNS infections (27,33).Phenotypic methods have been the standard means of differentiating S. aureus from CoNS and for differentiating the members of CoNS. These methods all require growth of the organisms followed by biochemical testing, are time-consuming, and may still occasionally produce inaccurate results (7,8,23,26). A variety of genotypic methods have been explored for the rapid detection of S. aureus and/or for the detection and differentiation of CoNS. These methods include the use of traditional in situ hybridization, peptide-nucleic acid in situ hybridization, and a variety of nucleic acid amplification-based methods (1,3,11,13,17,18,22).We designed a single broad-range PCR primer set directed toward the tuf gene to amplify the most clinically relevant staphylococci. For this study, PCR products were detected by use of a LightCycler instrument (Roche Diagnostics, Indianapolis, Ind.) and two sets of fluorescence resonance energy transfer (FRET) hybridization probes. The first set of FRET hybridization probes was designed to detect a signature sequence of the Staphylococcus genus, whereas the second set of FRET hybridization probes was designed to specifically detect S. aureus. This assay can detect S. aureus and CoNS simultaneously and can differentiate S. aureus by a postamplification melt curve analysis using the F3 channel of the LightCycler system.We validated this dual-FRET-probe real-time PCR assay for Staphylococcus with lysates from 138 cultivated bacterial reference strains and well-characterized clinical isolates...