Identification of Herpes Simplex Virus (HSV) Shedding in the Female Genital Tract of Pregnant and Nonpregnant Women by GeneXpert PCR, Routine PCR, and Culture

PCR detection of HSV DNA shedding in the female genital tract using the GeneXpert system (Cepheid, Sunnyvale CA) will be compared with traditional (routine) PCR (pregnant and nonpregnant women) and with HSV culture (nonpregnant women). The GeneXpert system performs all sample-processing steps and real-time PCR in a single integrated cartridge. The standard cartridge is an inexpensive disposable plastic cartridge with filtration and ultrasonic lysis capabilities. It consists chiefly of several combined molded plastic components: a cartridge body containing eleven fluid reservoirs or chambers along with an attached PCR tube, a specialized valve body with an ultrasonic interface containing a sub-micron filter and glass lysis beads, and a rotary valve with an axial syringe barrel. The operation of the cartridge is simple. The rotary valve contains an inlet and an outlet port. Fluid such as a sample buffer can be drawn up into a syringe drive through the inlet port of the rotary valve and then dispensed into any other chamber within the cartridge by rotating the valve and expelling the fluid through the outlet port. The fluid can either be passed through a filter contained within the valve assembly or it can be passed directly into the next chamber without filtration, depending on the path that is chosen. The cartridge fluidics and subsequent real-time PCR all are performed within the GeneXpert instrument. The GeneXpert contains multiple modules (ICORE units) that can be independently programmed to drive the syringe/rotary valve, and to perform four-color real-time PCR. Each cartridge fits inside one module, and all processing, PCR, and analysis steps are performed automatically. Each ICORE module can be run and analyzed independently, so batching of samples is unnecessary.