Multicenter Clinical Evaluation of the Xpert GBS LB Assay for Detection of Group B Streptococcus in Prenatal Screening Specimens

Abstract

dNeonatal infection with Streptococcus agalactiae (group B Streptococcus [GBS]) is a leading cause of sepsis and meningitis in newborns. Recent guidelines have recommended universal screening of all pregnant women to identify those colonized with GBS and administration of peripartum prophylaxis to those identified as carriers to reduce the risk of early-onset GBS disease in neonates. Enriched culture methods are the current standard for prenatal GBS screening; however, the implementation of more sensitive molecular diagnostic tests may be able to further reduce the risk of early-onset GBS infection. We report a clinical evaluation of the Xpert GBS LB assay, a molecular diagnostic test for the identification of GBS from broth-enriched vaginal/rectal specimens obtained during routine prenatal screening. A total of 826 specimens were collected from women undergoing prenatal screening (35 to 37 weeks' gestation) and tested at one of three clinical centers. Each swab specimen was tested directly prior to enrichment using the Xpert GBS assay. Following 18 to 24 h of broth enrichment, each specimen was tested using the Xpert GBS LB assay and the FDA-cleared Smart GBS assay as a molecular diagnostic comparator. Results obtained using all three molecular tests were compared to those for broth-enriched culture as the gold standard. The sensitivity and specificity of the Xpert GBS LB assay were 99.0% and 92.4%, respectively, compared to those for the gold standard culture. The Smart GBS molecular test demonstrated sensitivity and specificity of 96.8% and 95.5%, respectively. The sensitivities of the two broth-enriched molecular methods were superior to those for direct testing of specimens using the Xpert GBS assay, which demonstrated sensitivity and specificity of 85.7% and 96.2%, respectively. S treptococcus agalactiae (group B Streptococcus [GBS]) is aGram-positive bacterium associated with transient colonization of mucosal membranes throughout the body, including the vagina, gastrointestinal tract, and urethra (1). GBS rarely causes disease in healthy individuals but can cause serious illness in immunocompromised patients, elderly individuals, and newborn infants (2). Of particular concern is neonatal infection caused by vertical transmission during labor and birthing. Transmission from an asymptomatically colonized mother to the neonate can result in early-onset invasive GBS disease, which is a leading cause of sepsis and meningitis in newborns in the United States (3). Early-onset GBS disease in newborns can result in death or longterm disabilities such as mental retardation and hearing or vision loss (4). Because these infections are acquired through direct contact of the neonate with GBS in the mother's urogenital tract during delivery, it has become a universal practice to screen pregnant women for vaginal/rectal colonization with GBS at 35 to 37 weeks' gestation (5). The identification of GBS during routine screening results in administration of intrapartum prophylaxis to mitigate transmission of bacteria and red...

Clinical value of polymerase chain reaction in detecting group B streptococcus during labor

“…It therefore offers little advantage in the acute situation. 16 The present results can be of use in the battle against antibiotic resistance and the improvement of neonatal health. Antibiotic resistance is an ever-growing problem, and unnecessary use of antibiotics is a key issue.…”

“…This enrichment, however, takes time (12–24 h) and is something of a compromise between the old technique (culture) and the new (PCR). It therefore offers little advantage in the acute situation …”

Detection and genomic analysis of genital group B streptococcus in pregnant Korean women

“…The higher GBS positive rate obtained in the present study might be related to sample collection and detection methods. In particular, the study was performed by real‐time PCR using vaginal‐rectal specimens obtained using ESwabs, which have been reported to increase the sensitivity for GBS screening, and at a tertiary hospital, which cares for a higher proportion of complicated cases …”

Streptococcus agalactiae Strains with Chromosomal Deletions Evade Detection with Molecular Methods

“…These measures have been effective, with current rates of EO-GBS disease in the United States at record lows (i.e., 0.3 per 1,000 live births) (6). Several U.S. Food and Drug Administration (FDA)-cleared NAATs can be used to detect GBS in enrichment broth, and at least one FDA-cleared test can be used directly on vaginal/rectal swabs without broth enrichment for intrapartum testing (7)(8)(9)(10)(11)(12)(13). Intrapartum testing results are critical for women who present in labor prior to 35 weeks, who failed to have the surveillance cultures performed before time of delivery, or who do not have other indications for antimicrobial therapy to prevent EO-GBS disease (10).…”

“…Intrapartum testing to detect GBS colonization is also used in many regions of the world in lieu of antepartum surveillance testing (14)(15)(16). In many laboratories, NAATs have replaced subcultures of enrichment broths to agar media because of NAATs' improved workflow efficiency and its enhanced sensitivity, especially for the detection of nonhemolytic GBS strains or strains that do not produce CAMP factor, which may go undetected by culture (8,17). A recent study by Gendrin et al indicates that nonhemolytic strains of GBS still remain virulent, thus detecting them is important for guiding antimicrobial prophylaxis (17).…”