Gardnerella vaginalis is a facultatively anaerobic gram-variable rod. It has been demonstrated to cause a wide variety of infections; however, it is most commonly recognized for its role as one of the organisms responsible for bacterial vaginosis (BV). BV is the most common cause of vaginitis and the most common infection encountered in the outpatient gynaecological setting. Originally Ellner et al (1) developed a blood agar namely Columbia Agar for rapid growth of the haemolytic organisms with improved pigmentation and defined haemolytic reactions. Greenwood et al (2) further modified this medium by increasing the peptone concentration and used human blood instead of sheep blood for the isolation and differentiation of G. vaginalisbased on beta haemolysis (3, 4). Vaginalis Agar Base is used for the isolation of G. vaginalis from vaginal discharges (5).Peptic digest of animal tissue, casein enzymic hydrolysate, yeast extract and beef extract provide nitrogenous compounds, carbon, sulphur, vitamin B complex and trace ingredients required for growth. Cornstarch serves as the energy source. Blood supplies additional nutrients and also aids in identification.
Typical colonies of G. vaginalis appear small and white coloured. This medium is recommended for determin ation of haemolytic reaction of G. vaginalis and not for other microorganisms. If the specimen is suspected to contain streptococci or other haemolytic microorganisms, then a Soyabean Casein Digest Agar (with 5% v/v sheep blood) plate should be inoculated parallel to this medium to ensure the haemolytic reaction.
Storage and Shelf-life:
Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.
References:
1. Ellner P. D., Stoessel C. J., Drakeford E., Vasi F., 1966, Am. J. Clin. Pathol., 45 : 502.
2. Greenwood J. R., Martin M. J., Mack E. G., 1977, Health Lab. Sci., 14: 102.
3. Greenwood J. R. and Pickett M. J., 1980, Int. J. Syst. Bacteriol., 30: 170.
4. Piot P., Van Dyek E., Goodfellow M., Falkow S., 1980, J. Gen. Microbiol., 119: 373.
5. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore