The CAMP test is also another important test for identification of GBS. The CAMP factor produced by GBS acts synergistically with the staphylococcal β-hemolysin inducing enhanced hemolysis of sheep or bovine erythrocytes. GBS is also able to hydrolyze hippurate and this test can also be used to identify presumptively GBS. Hemolytic GBS strains produce an orange-brick-red non-isoprenoid polyene (ornithine rhamnolipid) pigment (granadaene) when cultivated on granada medium that allows its straightforward identification. GBS can also be identified using MALDI-TOF (Matrix Assisted Laser Desorption/Ionization-Time of Flight) instruments. GBS colonies can additionally be identified tentatively after their appearance in chromogenic agar media, nevertheless GBS-like colonies that develop in chromogenic media should be confirmed as GBS using additional reliable tests (e.g.latex agglutination or the CAMP test) to avoid potential mis-identification. A summary of the laboratory techniques for GBS identification is depicted in Ref 7. GBS colonization
GBS is a normal component of the intestinal and vaginal microbiota in some women, GBS is an asymptomatic (presenting no symptoms) colonizer of the gastrointestinal tract and vagina in up to 30% of otherwise healthy adults, including pregnant women. GBS colonization may be permanent, intermittent or temporary. In different studies, GBS vaginal colonization rate ranges from 0% to 36%, most studies reporting colonization rates in sexually active women over 20%. It has been estimated that maternal GBS colonization worldwide is 18%, with regional variation from 11% to 35%. These variations in the reported prevalence of asymptomatic GBS colonization could be related to the detection methods used, and differences in populations sampled.
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).