After incubation the enrichment broth is subcultured to blood agar plates and GBS like colonies are identified by the CAMP test or using latex agglutination with GBS antisera. After incubation the enrichment broth can also be subcultured to granada medium agar  where GBS grows as pink-red colonies or to chromogenic agars, where GBS grows as colored colonies. GBS-like colonies that develop in chromogenic media should be confirmed as GBS using additional reliable tests to avoid mis-identification.Nucleic acid amplification tests (NAAT) such as polymerase chain reaction (PCR) and DNA hybridization probes have been developed for identifying GBS directly from recto-vaginal samples, but they still cannot replace antenatal culture for the most accurate detection of GBS carriers. Intrapartum NAAT without enrichment has a high false negative rate and the use of intrapartum NAAT without enrichment to rule out the need for IAP. Vaccination
Though IAP for EOD prevention is associated with a large decline in the incidence of the disease, there is, however, no effective strategy for preventing late-onset neonatal GBS disease.Vaccination is considered an ideal solution to prevent not only EOD and LOD but also GBS infections in adults at risk. Nevertheless, though research and clinical trials for the development of an effective vaccine to prevent GBS infections are underway, no vaccine was available in 2020. The capsular polysaccharide of GBS is not only an important GBS virulence factor but it is also an excellent candidate for the development of an effective vaccine. Protein-based vaccines are also in development.
This new recommendation provides a five-week window  for valid culture results that includes births that occur up to a gestational age of at least 41 weeks. The culture-based screening approach is followed in most developed countries such as the United States,  France, Spain, Belgium, Canada, Argentina, and Australia. The risk-based strategy is followed in the United Kingdom, and the Netherlands. Screening for GBS colonization
Though the GBS colonization status of women can change during pregnancy, cultures to detect GBS carried out ≤5 weeks before delivery predict quite accurately the GBS carrier status at delivery. In contrast, if the prenatal culture is performed more than five weeks before delivery it is unreliable for predicting accurately the GBS carrier status at delivery.The clinical specimens recommended for culture of GBS at 36–37 weeks’ gestation, this recommendation provides a 5-week window for valid culture results that includes births that occur up to a gestational age of at least 41 weeks  (32–34 weeks of gestation for women with twins) are swabs collected the lower vagina (near the introitus) and then from the rectum (through the anal sphincter) without use of a speculum. Vaginal-rectal samples should be collected using a flocked swab preferably, since flocked swabs releases samples and microorganisms more effectively than fiber swabs. Following the recommendations of the Centers for Disease Control and Prevention of United States  (CDC) these swabs should be placed into a non-nutritive transport medium and later inoculated into a selective enrichment broth, Todd Hewitt broth with selective antibiotics  (enrichment culture).