GENITAL SWAB

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Specimen: (i) cervical swab collected from the endocervical canal during speculum examination; (ii) vaginal swab; (iii) swab of urethral discharge and/or urethral sampling using fine wire swab. Smears should be made directly on a clean glass slide; unfixed slides should be handled with care and transported to the laboratory in a suitable container. A separate swab should be placed in eg Stuart’s transport medium and trichomonas broth; swabs in transport medium are not recommended for making smears.

Method: Microscopy of wet film; Gram stain and direct IF; culture including Neisseria gonorrhoeae, Chlamydia trachomatis, Candida albicans, Gardnerella vaginalis, Group B streptococcus (pathogenic in the neonate), Haemophilus influenzae. Some laboratories also culture for Trichomonas vaginalis. EIA and/or molecular genetics for Chlamydia trachomatis.

Application: Investigation of mucopurulent cervicitis (see cervical lesion ), vaginal discharge , urethral discharge (see urethritis ), pelvic inflammatory disease , endometritis, postpartum fever, perinatal infection.

Interpretation: Microscopy of wet film: excess pus cells suggest infection; motile trichomonads indicate trichomoniasis, yeasts and hyphae suggest candidiasis; “clue” cells without an excess of pus cells suggest Gardnerella vaginalis infection.

Gram stain: the presence and relative numbers of pus cells and epithelial cells influence interpretation; presence of yeasts supports a diagnosis of candidiasis; intra- and extra-cellular Gram-negative diplococci suggest gonorrhoea.

Direct IF of cervical and urethral swabs: specific fluorescence with appropriate morphology may identify Chlamydia trachomatis.

Culture: results must be interpreted in conjunction with clinical information and the results of microscopy of wet film and Gram stain. Culture is the most sensitive and readily available method of establishing the diagnosis of gonorrhoea and chlamydial infections, however, nucleic acid probes (with or without PCR amplification) have a greater sensitivity and are being used more frequently. See MOLECULAR GENETICS - MICROBIAL .

Reference: Sweet RL and Gibbs RS. Infectious Diseases of the Female Genital Tract. 2nd ed. Williams and Wilkins 1990.

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