Streptococcus agalactiae en gestantes: diagnóstico y profilaxis

Streptococcus agalactiae, also known as group B Streptococci, is the main bacterium that causes early-onset invasive neonatal disease. Approximately 10% to 63% of fetuses acquire the bacteria during birth if pregnant women have recto-vaginal colonization with group B Streptococci; around 2% of the exposed newborns develop an invasive disease, and the mortality rate is approximately 2% to 3% in term infants, and up to 20% in premature infants. It has been shown that intrapartum antibiotics can prevent the transmissions, and consequently it often avoids that the neonate suffers from the disease. In fact, such practice has decreased the incidence of early-onset group B streptococcal disease in the United States; its national incidence has declined from an estimated 1.7 cases per 1000 live births in 1990 to 0.3 cases per 1000 live births in 2003. As consequence, screening of pregnant women is recommended; the standard method to identify pregnant women colonized with the bacteria is the recto-vaginal culture for group B Streptococci at 35-37 weeks of gestation. Accordingly, clinical laboratories must be prepared to offer the appropriate diagnostic techniques, and the physicians should incorporate into their daily routine the universal screening as well as chemoprophylaxis of pregnant women colonized Streptococcus agalactiae. This review article includes a general overview of colonization by S. agalactiae on pregnant women, the diagnosis of the colonization, its treatment, and prevention of early-onset invasive neonatal disease. Streptococcus agalactiae o Streptococcus del Grupo B es la principal bacteria que causa enfermedad invasiva temprana en los neonatos. La bacteria es transmitida durante el parto al 10% a 63% de los fetos de madre con colonización recto-vaginal; aproximadamente un 2% de los neonatos que adquieren la bacteria desarrollan una enfermedad invasiva y la mortalidad es de aproximadamente el 2% al 3% en los neonatos a término y hasta del 20% en prematuros. Se ha demostrado que la administración de antibióticos a la madre colonizada, al momento del parto, puede prevenir la transmisión de la bacteria y como tal, la enfermedad en el neonato; de hecho, esta práctica ha disminuido la incidencia de la enfermedad invasiva temprana en Estados Unidos de 1,7 casos/1.000 nacidos vivos, a comienzos de los años 1990, a 0,3 casos/1.000 nacidos vivos a partir del año 2003. Por tal razón, se recomienda el tamizaje de las gestantes y el método estándar recomendad