Use of the Roche LightCycler Strep B Assay for Detection of Group B Streptococcus from Vaginal and Rectal Swabs

Abstract

The results for a real-time PCR assay, using the LightCycler Strep B analyte-specific reagents (Roche Diagnostics Corporation, Indianapolis, Ind.), were compared to a direct plate method combined with a broth enrichment culture method for detection of group B streptococcus colonization in pregnant women. Two separate evaluations were conducted using two different automated nucleic extraction instruments, the Guidelines from the Centers for Disease Control and Prevention recommend screening for vaginal or rectal carriage of group B streptococcus (GBS) (Streptococcus agalactiae) by culture in pregnant women at 35 to 37 weeks gestation (3). Both the vaginal and anal areas should be swabbed, and the culture method should include an enrichment broth. These recommendations are based on prior studies which have demonstrated that intrapartum surveillance for GBS and treatment of carriers significantly decreases early-onset (within 1 week after birth) GBS meningitis and sepsis in the newborn (2, 6, 7).Recently, real-time PCR methods have been applied for direct detection of GBS from vaginal/rectal swabs (1, 5). These methods have been demonstrated to be as sensitive as culture but have the added advantage of being much faster. Because of their speed, real-time PCR tests have the potential for screening at the time of delivery. This could decrease the overutilization of antibiotics, especially in pregnant women who do not have prepartum screening for GBS.The objective of the current study was to evaluate the ability of the LightCycler Strep B ptsI assay (Roche Diagnostics Corporation) to detect GBS carriage in pregnant women. This real-time PCR assay uses dual fluorescent resonance energy transfer (FRET) probes, also referred to as FRET hybridization probes. We compared the performance of this LightCycler assay to the results for a direct plate culture method combined with the results for a broth enrichment culture recommended by the Centers for Disease Control and Prevention. In addition, we evaluated two DNA extraction protocols, one using the MagNA Pure LC instrument (Roche Diagnostics Corporation) and the other using the lower-capacity MagNA Pure Compact instrument (Roche Diagnostics Corporation). MATERIALS AND METHODSStudy design. The study was approved by the Institutional Review Board of the Mayo Foundation. Two separate evaluations were conducted using the LightCycler Strep B assay, with either the MagNA Pure LC instrument or the MagNA Pure Compact instrument. For each of these evaluations, a different set of vaginal/rectal swabs were collected from pregnant women.For the MagNA Pure LC/LightCycler Strep B protocol, specimens were collected in June and July 2003. Eighteen specimens (10.3%) were excluded from the study because the patients from whom these swabs were collected declined to provide permission to use their specimens and medical histories for evaluation (Minnesota Statute 144.335). One hundred fifty-nine swabs from 154 patients were available for testing.For the MagNA Pure Compact/LightCycler Strep B pro...

Multicenter Evaluation of the BD Max GBS Assay for Detection of Group B Streptococci in Prenatal Vaginal and Rectal Screening Swab Specimens from Pregnant Women

“…Several PCR assays used to determine GBS colonization status in pregnant women have demonstrated substantial improvements in time to detection, without compromising performance characteristics. Studies evaluating the performance of PCR for GBS detection using direct patient specimens have demonstrated rates of GBS detection equivalent to those of broth-enriched cultures (4,5,8,9). In addition, studies evaluating the performance of PCR using broth-enriched specimens have exhibited variability in the detection rates of GBS compared to broth-enriched cultures.…”

Reduced Glutathione Mediates Resistance to H 2 S Toxicity in Oral Streptococci

“…The cultures were left untreated or were treated with 2 mM NaHS for 2 h. Cells were pelleted, and the resulting cell pellets were washed twice with 1ϫ PBS. The cell pellet was resuspended in 1% Triton X-100 (12) with 0.1-mm glass beads (Scientific Industries, Inc., NY, USA) and lysed through the simultaneous actions of agitation and vortexing for 15 min using a Disruptor Genie 2 (Scientific Industries, Inc.) (13). Efficiency of lysis was determined by plating on BHI agar plates.…”

Antibiotic Policies: Fighting Resistance

“…Theoretically, real-time PCR using appropriate primers can look for the presence of any bacteria in clinical samples, such as group A streptococcus (Uhl et al 2003), group B streptococcus (Uhl et al 2005), and Clostridium difficile (Belanger et al 2003). Detection of a panel of organisms, for example the causes of community-acquired pneumonia (Morozumi et al 2006), is often more clinically relevant, and could be extended to include viruses as well as bacteria.…”