GBS Detect™

Cat. no. A300 GBS Detect™, 15x100mm Plate, 17ml 10 plates/bag
Cat. no. A300BX GBS Detect™, 15x100mm Plate, 17ml 100 plates/box


Hardy Diagnostics GBS Detect™ is recommended for the isolation and detection of gamma-hemolytic (non-hemolytic) Group B Streptococcus by inducing beta-hemolysis on sheep blood agar upon subculture from enrichment broth procedures; such as Strep B Carrot Broth™ and LIM Broth.


Approximately 10-35% of women are asymptomatic carriers of group B streptococci (GBS) in the genital and gastrointestinal tracts. (7) GBS remains a leading cause of serious illness and death in newborn populations, and therefore, the detection of GBS in the vaginal-anorectal area is critical to the prevention of neonatal GBS disease. Several surveys have been conducted that show the incidence of neonatal sepsis and meningitis due to GBS is currently 0.5-3 cases per 1,000 live births, although there are substantial geographical and racial differences. (8) The case-fatality ratios are now declining due to prompt recognition and proper treatment. (9)

The Centers for Disease Control and Prevention (CDC) recommends the screening of all pregnant women for vaginal and rectal GBS colonization between 35 and 37 weeks of gestation using an enrichment broth followed by subculture to a Blood Agar plate (Cat. no. A10) or other appropriate media. (10) The use of a selective enrichment broth that incorporates chromogenic pigments, such as Strep B Carrot Broth™, has recently been included in CDC's Recommendations for the Prevention of Group B Streptococcal Disease. (27) Strep B Carrot Broth™ demonstrates increased sensitivity and specificity, reduced incubation time, reduced need for additional plated media, and elimination of the need to confirm positives with additional testing. (11-15,20-23)

A small percentage of GBS may not produce beta-hemolysis. GBS detection with the Strep B Carrot Broth™ Kit is only possible with beta-hemolytic colonies. There is evidence of a direct genetic linkage between pigment production in Strep B Carrot Broth™ and hemolysin production by GBS bacteria. Beta-hemolytic, pigment producing GBS occurs with 95.3 to 99.5% of all GBS strains isolated from clinical specimens. (17-19)

Subcultures of enrichment broths may contain non-hemolytic or gamma strains of GBS that may be missed by normal plating procedures, because non-hemolytic GBS is not readily distinguishable from other small non-hemolytic colonies. Therefore all LIM Broth cultures and negative Strep B Carrot Broth™ cultures should be subcultured to GBS Detect™ plates for detection of gamma-hemolytic GBS. GBS Detect plates contain special supplements that cause otherwise non-hemolytic strains of GBS to appear as beta-hemolytic, thus increasing the sensitivity of detection methods used to detect GBS colonization in pregnant women. Selective agents are added to suppress coliforms, staphylococci and other organisms that might be present as normal flora.

GBS Detect™ eliminates needless steps in screening for non-hemolytic group B streptococci and makes Strep B Carrot Broth™ a more sensitive method for all strains of GBS.


Ingredients per liter of deionized water:*

Pancreatic Digest of Casein 15.0gm
Peptic Digest of Soybean Meal 5.0gm
Sodium Chloride 5.0gm
Nucleic Acid 3.0gm
Selective Agents 15.3gm
Hemolysis Inducing Agents 20.0ml
Sheep Blood 50.0ml
Agar 15.0gm

Final pH 7.3 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.


Storage: Upon receipt store at 2-8ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), hemolysis, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.



Method of Use: Medium should be brought to room temperature prior to inoculation. Inoculate according to standard microbiological procedures.

1. Using a vaginal-rectal specimen, inoculate and incubate either LIM Broth (Cat. no. L57) or Strep B Carrot Broth™ (Cat. no. Z140) according to the procedures in the technical information sheets.

2. Subculture all LIM Broth or color negative Strep B Carrot Broth™ to a GBS Detect™ plate. Streak inoculum in four quadrants to obtain isolated colonies. Note: Isolated colonies must be obtained.

3. Incubate the GBS Detect™ plate for 18-24 hours at 35 +/- 2ºC. in an aerobic atmosphere.

4. After 18-24 hours observe for growth of beta-hemolytic gram-positive, catalase-negative colonies. GBS will produce large, tranparent zones of hemolysis, with a soft edge.

5. Using isolated colonies from the GBS Detect™ plate described in step 4, perform latex particle agglutination test (StrepPRO™ Grouping Kit, Cat. no. PL030HD) or other tests recommended for the detection of group B streptococci antigen following the procedure specified by the manufacturer.


Organisms other than GBS can produce faint or incomplete zones of hemolysis.


Standard microbiological supplies and equipment such as loops, swabs, applicator sticks, LIM Broth (Cat. no. L57), Strep B Carrot Broth™ (Cat. no. Z140), StrepPRO™ Grouping Kit (Cat. no. PL030HD), other culture media, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method Incubation Results
Time Temperature Atmosphere
Streptococcus agalactiae
ATCC® 13813
A 24hr 35°C Aerobic Growth; beta-hemolysis
Streptococcus agalactiae
Clinical Strain
A 24hr 35°C Aerobic Growth; beta-hemolysis
Enterococcus faecalis
ATCC® 29212
A 24hr 35°C Aerobic Partial to complete inhibition


Physical Appearance

GBS Detect™ should appear opaque, and cherry red in color.

S. agalactiae growing on GBS Detect™

Streptococcus agalactiae (ATCC ® 13813) colonies growing on GBS Detect™ (Cat. no. A300) showing beta-hemolytic colonies. This strain is not hemolytic on a regular blood agar plate. Incubated aerobically for 24 hours at 35ºC.


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10. Schrag, S., Gorwitz, R., Fultz-Butts, K., Schuchat, A. 2002. Prevention of perinatal group B streptococcal disease. Revised guidelines from CDC: MMWR Recommendations and Reports / 6;51(RR-11):1-22.

11. Overman, S.B., D.D. Eley, B.E. Jacobs, J.A. Ribes. 2002. Evaluation of methods to increase the sensitivity and timeliness of detection of Streptococcus agalactiae in pregnant women. J. Clin. Microbiol.; 40(11):4329-31.

12. de la Rosa, M., M. Perez, C. Carazo, L. Pareja, J.I. Peis and F. Hernandez. 1992. New Granada Medium for detection and identification of group B streptococci. J. Clin. Microbiol.; 30:1019-1021.

13. Garcia Gil, E., M.C. Rodriguez, R. Bartolome, B. Berjano, L. Cabero and A. Andreu. 1999. Evaluation of the Granada Agar plate for detection of vaginal and rectal group B streptococci in pregnant women. J. Clin. Microbiol.; 37:2648-2651.

14. Rosa-Fraile Manuel, J. Rodriguez-Granger, M. Cueto-Lopez, A. Sampedro, E. Biel Gaye, J.M. Haro and A. Andreu. 1999. Use of Granada Medium to detect group B streptococcal colonization in pregnant women. J. Clin. Microbiol.; 37:2674-2677.

15. Rosa-Fraile, Manuel, A. Sampedro, J. Varela, M. Garcia-Pena, and G. Gimenez-Gallego. 1999. Identification of a peptide pigment from mammal albumins responsible for enhanced pigment production by group B streptococci. Clin. Diag. Lab. Imm.; 6:425-426.

16. B. Spellerberg, B. Pohl, G. Haase, S. Martin, J. Weber-Heynemann and R. Lütticken. 1999. Identification of Genetic Determinants for the Hemolytic Activity of Streptococcus agalactiae by ISS1 Transposition. J. Bacteriol.; 181: 3212-3219.

17. Young, Uh, et al. 1998. Serotypes and Biochemical Reaction Patterns of Group B Streptococci. Korean J. Clin. Path.; 18:386-390.

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20. da Gloria Carvalho, M., R. Facklam, D. Jackson, B. Beall, and L. McGee. 2009. Evaluation of Three Commercial Broth Media for Pigment Detection and Identification of a Group B Streptococcus (Streptococcus agalactiae). J. Clin. Microbiol.; Vol. 47, No. 12, p.4161-4163.

21. Block, T., E. Munson, A. Culver, K. Vaughan, and J. Hryciuk. 2008. Comparison of Carrot Broth- and Selective Todd-Hewitt Broth-Enhanced PCR Protocols for Real-Time Detection of Streptococcus agalactiae in Prenatal Vaginal/Anorectal Specimens. J. Clin. Microbiol.; Vol. 46, No. 11, p.3615-3620.

22. Church, D.L., H. Baxter, T. Lloyd, B. Miller, and S. Elsayed. 2008. Evaluation of Strep B Carrot Broth™ versus Lim Broth for Detection of Group B Streptococcus Colonization Status of Near-Term Pregnant Women. J. Clin. Microbiol.; Vol. 46, No. 8, p.2780-2782.

23. Czerepuszko, D.J., and M.J. Lewis. 2010. Comparison of LIM Broth with PNA FISH to Carrot Broth with PNA FISH for Identification of Group B Streptococcus in Prenatal Vaginal/Rectal Specimens. A poster presentation at American Society for Microbiology, San Diego, CA.