Birmingham P et al. - The direct quantification of the concentration of viable bacterial mRNA with real-time quantitative reverse transcription polymerase chain reaction allows identification of both culture-positive bacterial infection and so-called unculturable bacterial infection in a simulated septic arthritis model. Because real-time quantitative reverse transcription polymerase chain reaction detects live bacteria, its application in combination with other polymerase chain reaction-based methods for speciation could dramatically improve the way that joint infections are diagnosed and treated.