Screening for Group B Streptococcus Bacteria during Pregnancy Saves Lives

Prenatal screening tests are carried out at different stages in pregnancy and are extremely valuable in preventing diseases in newborns. One of the most important prenatal tests is for Group B Streptococcus (GBS). The screening is typically carried out between 35 to 37 weeks of pregnancy.

The newborn in the above picture, faced a life of disability because of Group B Streptococcus (GBS) infection [1]

What is GBS?

Group B Streptococcus (group B strep/GBS) is a type of bacteria that causes illness in people of all ages.  Group B strep disease can cause serious illnesses in newborns including septicemia (infection of the blood), pneumonia (infection in the lungs), and even meningitis (infection of the fluid and lining around the brain and spinal cord) within the first week of a baby's life [2,4]. In a recent case reported by BBC news, a newborn was affected by GBS and faced quadriplegic cerebral palsy and life-time disabilities [1]. However, GBS testing has the potential to prevent such cases.

The timing for this prenatal test is crucial for planning preventative measures. For women who are group B strep carriers, antibiotics given early in the pregnancy are not effective at preventing the transmission during labor. This is because Strep B bacteria can reoccur after taking antibiotics as they are part of the natural flora in the gastrointestinal tract. From here, it is easy for the bacteria to cause reinfection.  To adequately prevent reinfection during the time of labor, it is important for all pregnant women to be tested for group B strep between 35 to 37 weeks of pregnancy. If a pregnant mother’s swab sample is GBS positive, then intravenous Penicillin, Ampicillin, or Cephalosporin antibiotics are only given during labor until delivery. Group B streptococcus (GBS) is a type of bacterial infection that can be found in the vagina or rectum. Women who test positive for GBS are considered colonized, which includes 25% of all women. As a mother can pass GBS to her baby during delivery, GBS also affects about 1 in every 2,000 babies in the United States. Therefore, U.S. Centers for Disease Control (CDC), the American Academy of Pediatrics (AAP), and the American College of Obstetricians and Gynecologists (ACOG) recommend that all pregnant women get a routine GBS screening at 35 to 37 weeks [2].

Among babies, there are 2 main types of group B strep disease:

  • Early-onset — occurs during the first week of life. Approximately 90% of cases of early-onset disease continue to manifest within the first 24 hours of life.
  • Late-onset — occurs from the first week through three months of life.

       Testing for isolation and differentiation of Streptococcus agalactiae (GBS)  [3]

Testing Samples for Group B Streptococcus at Emery Pharma:

At Emery Pharma, we have supported clinical trials involving 200+ patient samples sent in Copan ESwab tubes for GBS screenings. The patient samples were grown in selective media and if the sample was found to be GBS positive, the next step was serotyping of GBS containing samples for 10 different serotypes (Ia-IX), later confirmed by a positive agglutination reaction. A testcard is used for GBS positive serotyping such as the one in the image above. A positive agglutination reaction is shown on the left of the figure, and a negative reaction is shown on the right.  If you would like to perform GBS screenings or evaluate drug efficacy with other pathogens, please contact us at

About the author:

Kiran Bijlani holds a Master’s and Ph.D. in Pharmaceutical Sciences with expertise in Pharmacology and Microbiology.


  1. Goldberg, Adrian, 5 March 2017, BBC News-5 Live Investigates, “Newborns at risk from deadly Group B Strep bacteria”
  2. Center for Disease Control and Prevention, 10 July 2017 “Protect Your Baby from Group B Strep!”
  3. Chromagar, Dr. A. Rambach, Clinical Microbiology, CHROMagar Step B, “Isolation and differentiation of Streptococcus agalactiae (GBS)”
  4. Deutscher M, Lewis M, Zell ER, et al. Incidence and severity of invasive Streptococcus pneumoniae, group A Streptococcus, and group B Streptococcus infections among pregnant and postpartum women. Clin Infect Dis. 2011;53(2):114–23.

Emery Pharma

Emery Pharma is a full-service contract research laboratory, specializing in analytical, bioanalytical chemistry, microbiology & cell biology services, custom synthesis, and general R&D and cGMP/GLP support.