Background Nitroimidazoles, in particular metronidazole and tinidazole are used to treat anaerobic protozoa, which include Trichomonas vaginalis, Giardia duodenalis and Entamoeba histolytica. In South Africa information about metronidazole resistance of T. vaginalis isolates is limited. This pilot study aimed to determine the metronidazole antimicrobial drug resistance and genetic relatedness of T. vaginalis isolates obtained from women attending the anti-retroviral clinic at the Tshwane District Hospital, Pretoria.

Methods Self-collected vaginal swabs were collected from HIV positive women until 30 T. vaginalis positive samples were obtained. Metronidazole antimicrobial drug resistance of T. vaginalis isolates was determined in vitro by microdilution and microtitre methods. The strain relatedness was determined by the random amplified polymorphic DNA (RAPD) assay using five primers (TV1, TV2, TV3, TV5 and TV6). Dendrogrammes were constructed from the RAPD assay’s fingerprinting data using GelComparII.

Results Metronidazole resistance was detected in 6% (2/30) of the T. vaginalis isolates. The minimal inhibitory concentration (MIC) was between 0.06 µg/ml and 25 µg/ml. No correlation was observed between metronidazole resistance and a specific protozoal genetic cluster.

Conclusion A low prevalence of T. vaginalis metronidazole resistance was detected in the clinical setting. The MIC values are in agreement with those reported in literature. The two metronidazole resistant isolates are from genetically diverse backgrounds. It is important to monitor the changes in the MIC values of the circulating T. vaginalis protozoa to ensure that the syndromic management of trichomoniasis used in South Africa, is adequate.