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METRONIDAZOLE DIAGNOSTIC DISCS (50 µG)

Code: DD0008

SULPHONAMIDE DIAGNOSTIC DISCS (1000 µG)

Code: DD0011

An aid in the identification of Gardnerella vaginalis.

Contents
DD0008. 1 cartridge. containing 50 discs.
DD0011. 1 cartridge. containing 50 discs.

Disc Contents
DD0008 Metronidazole 50 mg
DD0011 Sulphonamide 1000 mg

Description
Smith and Dunkelberg¹ reported that metronidazole, previously thought to inhibit obligately anaerobic bacteria only was found in vitro to inhibit the growth of facultatively anaerobic strains of Gardnerella vaginalis when using the agar diffusion method.
Small pleomorphic Gram negative rods associated with `non-specific’ bacterial vaginitis were recognised by Gardner and Dukes² as the aetiologic agent. They named the organism Haemophilus vaginalis. However, in obvious conflict with the accepted definition of the genus Haemophilus it does not have a requirement for Haemin (X factor), Nicotinamide Adenine Dinucleotide (NAD or V factor) or any other co-enzyme-like growth factor. On the basis of microscopic morphology, Zinnemann and Turner³ argued that it should be reclassified in the genus Corynebacterium and suggested the name Corynebacterium vaginale.
Taxonomic studies^4,5 have led to the naming of a new genus Gardnerella for inclusion of the organisms previously classified as Haemophilus vaginalis or Corynebacterium vaginale with the type species Gardnerella vaginalis.
Bailey et al.⁶ have recommended that the susceptibility and resistance to metronidazole and sulphonamide in conjunction with fermentation tests should be used as an aid in the separation of Gardnerella vaginalis from other possibly unrecognised biotypes of Gardnerella vaginalis or other vaginal bacteria that presumptively resemble the organism. They recommended a content of 50 mg metronidazole per disc.

Bacterial group or species susceptibility to discs of:

S: Susceptible R: Resistant
It has been shown⁷ that in the treatment of Gardnerella vaginalis- associated vaginitis with metronidazole, the hydroxy metabolite may contribute a significant antimicrobial effect, in view of its excellent activity in vitro. The diagnosis and treatment of non-specific vaginitis has been reviewed⁸.

Technique
Inoculate the isolation medium with the specimen and place a 50 mg metronidazole disc and a 1000 mg sulphonamide disc on an area of the plate where heavy, but not confluent, growth can be expected. Smith and Dunkelberg¹ incubated at 35°C in air containing approximately 8% carbon dioxide, but more recently Ralph et al.⁹ in a study of MICs of a number of antibiotics for Gardnerella vaginalis reported that susceptibility to metronidazole was significantly increased by incubation in an anaerobic atmosphere and more reliable results may be expected by incubation under these conditions.
Gardnerella vaginalis is best isolated on Columbia Agar CM0331 with Gardnerella vaginalis Supplement SR0119.

Quality Control
Use known strains of Gardnerella vaginalis to monitor the performance of the discs.

References
1 Smith R. F. and Dunkelberg W. E. (1977) Sex. Trans. Dis. 4. 20-21.
2 Gardner H. L. and Dukes C. D. (1955) Am. J. Obstet. Gynecol. 60. 962-976.
3 Zinnemann K. and Turner G. C. (1963) J. Pathol. Bacteriol. 85. 213-219.
4 Piot P., Van Dyke E., Goodfellow M. and Falkow S. (1980) J. Gen. Microbiol. 119. 373-396.
5 Greenwood J. R. and Pickett M. J. (1980) Int. J. Syst. Becteriol. 30. 170-178.
6 Bailey R. K., Voss J. L. and Smith R. F. (1979) J. Clin. Microbiol. 9. 65-71.
7 Ralph E. D. and Amatnieks Y. E. (1980) Sex. Trans. Dis. 7. 157-160.
8 Clay J. (1981) J. Antimicrob. Chemotherapy 7. 501-504.
9 Ralph E. D., Austin T. W., Pattison F. L. M. and Schieven B. C. (1979) Sex. Trans. Dis. 6. 199-202.