Complimentary Reflex Test Determines Drug Resistance in Trichomoniasis

A drug resistance-reflex assay for Trichomonas vaginalis is currently only available from commercial laboratories but will be performed at no additional charge when T. vaginalis is detected in a patient’s specimen.

This new assay will provide another tool for clinicians to make appropriate decisions pertaining to treatment regimens to achieve an effective cure for T. vaginalis, a flagellated protozoan parasite, and the most common nonviral sexually transmitted pathogen with more than seven million cases of trichomoniasis each year in the US.

The reflex test can now detect metronidazole resistance in a subset of T. vaginalis positive specimens by real-time polymerase chain reaction (rt-PCR). The new assay detects a T. vaginalis gene mutation highly associated with metronidazole resistance with a 91% positive predictive value (PPV). This test was developed using 100 well-characterized T. vaginalis isolates from the US Centers of Disease Control (CDC; Atlanta, GA, USA).

Patients are normally treated with a single oral dose of metronidazole, an antibiotic used to treat infections caused by anaerobic bacteria and parasites. Although generally effective, some T. vaginalis strains are resistant to metronidazole. If metronidazole treatment fails, the only other approved treatment is the related drug tinidazole. Therefore, identifying T. vaginalis resistance to metronidazole can help guide clinicians in prescribing an effective therapy for their T. vaginalis patients at the time of diagnosis.

Although metronidazole treatment is reported to be 85% to 95% effective, recent reports suggest that between 2.5% and 10% of clinical T. vaginalis isolates exhibit some degree of metronidazole resistance. A viable culture of T. vaginalis must be obtained using a specialized collection and transport device. The assay was developed by Medical Diagnostic Laboratories, (MDL; Hamilton, NJ, USA).

Eli Mordechai, PhD, Chief Executive Officer of MDL said, "We are pleased to offer this new diagnostic test for patients infected with Trichomonas vaginalis, an extremely common sexually transmitted infection. This test will be especially useful in identifying select strains of Trichomonas vaginalis that are resistant to the most widely prescribed drug, metronidazole."

Related Links:
US Centers of Disease Control
Medical Diagnostic Laboratories