Gardnerella Selective Agar

Cat. no. G292 Gardnerella Selective Agar, 15x100mm Plate, 18ml 10 plates/bag


Hardy Diagnostics Gardnerella Selective Agar is recommended for the selective isolation and differentiation of Gardnerella vaginalis from clinical specimens.


Gardnerella vaginalis is considered one of the leading causes of bacterial vaginitis. Conflicting interpretations on the clinical significance of this organism have varied over the years, along with its taxonomic classification.(2,5,10) Consequently, the organism has been suggested as the etiologic agent in a variety of other urogenital and reproductive diseases, including preterm birth, chorioamnionitis, urinary tract infections, newborn infections, and septicemia.(4) Because G. vaginalis may be isolated from patients with nonspecific vaginitis and asymptomatic patients, use of selective and differential media to detect the organism in mixed cultures significantly improve isolation rates.(3,5)

Detection of G. vaginalis on standard blood-containing media in routine clinical practice may be difficult, as normal flora such as lactobacilli and streptococci grow and produce similar alpha hemolysis.(2) Mickelsen et al. developed a semi-selective medium containing 1% corn starch to distinguish G. vaginalis colonies by their hydrolytic clearing on opaque starch medium.(5) Gardnerella Selective Agar is based on this formulation and contains selective agents to inhibit the growth of normal competing flora, including yeast.

Gardnerella Selective Agar contains animal peptones, peptic digest of casein, yeast and beef extracts, which provide carbon, nitrogen, amino acids, and essential minerals to support microbial growth. Sodium chloride is added to maintain osmotic equilibrium. The medium is supplemented with corn starch to aid in the detection of hydrolytic colonies. Bromcresol purple is the pH indicator and agar is the solidifying agent. Colistin, nalidixic acid and amphotericin B are selective agents used to inhibit the growth of competing flora present in the sample. Organisms, such as G. vaginalis, capable of hydrolyzing starch create acid byproducts that change the surrounding medium yellow.


Ingredients per liter of deionized water:*

Pancreatic Digest of Casein 12.0gm
Proteose Peptone 10.0gm
Peptic Digest of Animal Tissue 5.0gm
Sodium Chloride 5.0gm
Beef Extract 3.0gm
Yeast Extract 3.0gm
Corn Starch 1.0gm
Colistin 0.01gm
Nalidixic Acid 0.01gm
Amphotericin B 0.004gm
Bromcresol Purple 1.2ml
Agar 13.5gm

Final pH 7.0 +/- 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), contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.



Specimen Collection: Specimens should be submitted directly to the laboratory without delay and protected from excessive heat and cold. If there is a delay in processing, specimens should be inoculated into an appropriate transport medium and refrigerated until inoculation. Consult listed references for more information on specimen collection.(2,6-10)

Method of Use:

1. Bring medium to room temperature prior to use.

2. Inoculate the surface of the medium and streak for isolation.

3. Incubate plates at 35ºC. for 24-48 hours using an atmosphere containing 5-10% CO2: a candle jar, CO2 incubator or CO2 Gen Compact (Cat. no. CD020C) may be used.

4. Proceed with confirmatory testing on suspect colonies that produce a yellowing of the medium.


Gardnerella vaginalis will demonstrate growth and a yellowing of the medium surrounding colonies.

Enterococcus faecalis may grow, but will not produce a yellow color change.


G. vaginalis isolates should be incubated in a 5-10% CO2 enriched atmosphere for best results.(2,6-9)


Standard microbiological supplies and equipment such as loops, swabs, applicator sticks, other culture media, incinerators, and incubators, atmospheric chambers, CO2 Gen (Cat. no. CD020C), etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Gardnerella vaginalis
ATCC® 14018***
A 24-48hr 35°C CO2** Growth; yellow color change in medium surrounding colonies
Enterococcus faecalis
ATCC® 29212
A 24-48hr 35°C CO2** Growth; no color change
Pseudomonas aeruginosa
ATCC® 27853
B 24hr 35°C Aerobic Partial to complete inhibition
Proteus mirabilis
ATCC® 12453
B 24hr 35°C Aerobic Partial to complete inhibition
Escherichia coli
ATCC® 25922***
B 24hr 35°C Aerobic Partial to complete inhibition
Candida albicans
ATCC® 10231
B 24hr 35°C Aerobic Partial to complete inhibition

** Atmosphere of incubation is enriched with 5-10% CO2.

*** Recommended QC strains for User Quality Control according to the CLSI document M22 when applicable.



Gardnerella Selective Agar should appear slightly opalescent, and purple in color.

Gardneralla vaginalis (ATCC® 14018) colonies growing on Gardnerella Selective Agar (Cat. no. G292). Incubated in CO2 for 24 hours at 35ºC.

Enterococcus faecalis (ATCC® 29212) colonies growing on Gardnerella Selective Agar (Cat. no. G292). Incubated in CO2 for 24 hours at 35ºC.


1. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

2. Catlin, B.W. 1992. Gardnerella vaginalis: Characteristics, Clinical Considerations, and Controversies. Clin. Microbio. Rev.; 5(3):213-237.

3. Hammann, R., A. Kronibus, N. Lang, and H. Werner. 1987. Quantitative studies on the vaginal flora of asymptomatic women and patients with vaginitis and vaginosis. Zbl. Bakt. A.; 265:451-461.

4. Martius, J. and D.A. Eschenbach. 1990. The role of bacterial vaginosis as a cause of amniotic fluid infection, chorioamnionitis and prematurity. Arch. Gynecol. Obstet.; 247:1-13.

5. Mickelsen, P.A., L.R. McCarthy and M.E. Mangum. 1977. New differential medium for the isolation of Corynebacterium vaginale. J. Clin. Microbiol.; 5:488-489.

6. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

7. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

8. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

9. Koneman, E.W., et al. Color Atlas and Textbook of Diagnostic Microbiology, J.B. Lippincott Company, Philadelphia, PA.

10. Piot, P. et al. 1982. Identification of Gardnerella (Haemophilus) vaginalis. J. Clin. Microbiol.; 15:19-24.

11. Quality Assurance for Commercially Prepared Microbiological Culture Media, M22. Clinical and Laboratory Standards Institute (CLSI - formerly NCCLS), Wayne, PA.