Do we need a different approach to GBS screening?

Abstract

Group B Streptococcus (GBS) infections remain an important cause of perinatal complications, despite advanced preventive measures. The most common clinical symptoms of early-onset disease, diagnosed in neonates up to 7 days of life, are sepsis and pneumonia. Late-onset disease is diagnosed in children between 7 and 89 days of life and presents also in forms of other infections. As a result of collaborative efforts of clinicians, researchers and many organizations, various recommendations for intrapartum prevention of perinatal GBS disease have been issued so far. Revised 2002 CDC guidelines for the prevention of early-onset GBS disease recommended universal culture-based screening of all pregnant women at 35–37 weeks of gestation to optimize the identification of those who should receive intrapartum antibiotic prophylaxis (IAP). They were customized by the Polish Gynecological Society and applied in Poland as well. As a result of preventive efforts worldwide, global incidence of GBS infections has declined dramatically over the past 15 years. About 10-30% of pregnant women are colonized with Group B Streptococcus. According to the literature, GBS culture at 35 to 37 weeks of gestation has about 95% negative predictive value for the absence of colonization at the time of labor. However, studies reporting early-onset GBS disease in newborns found that about 60 to 80% of all cases occurred in neonates with negative maternal screening during pregnancy. If the only available screening test is vagino-rectal swab during pregnancy, about 7.5% of women with GBS colonization during labor are not administered IAP. It seems optimal to perform routine screening not during pregnancy, but directly before the delivery – preferably at the time of regular uterine contractions or the rupture of membranes. As the screening test should be widely accessible and rapid, the usual microbiological culture is not a suitable option.Recently, new biochemical and genetic methods have become available. Polymerase chain reaction (PCR) and optical immunoassay are candidates for rapid patient intrapartum GBS testing to determine whether women in labor are colonized with GBS. PCR tests have the sensitivity of over 90% with the specificity of 99%, which is about 13% higher than microbiological culture. According to the literature, IAP does not reduce the overall neonatal mortality, mortality due to GBS infection, or due to other bacterial infections. The incidence of early-onset GBS infection was reduced with IAP in comparison to no intrapartum prophylaxis, but there was no difference in late-onset GBS disease occurrence. Besides GBS, IAP may influence maternal and neonatal infections caused by other pathogens. Moreover, it can also induce GBS and no-GBS pathogen resistance to antibiotics. It therefore seems necessary to replace the current type of GBS screening with GBS DNA PCR intrapartal test – a rapid, highly sensitive and specific method of carrier identification – in order to optimize IAP and, eventually, to decrease the rate of early onset GBS disease in neonates.