Managing trichomonal vaginitis refractory to conventional treatment with metronidazole

Trichomoniasis as seen in a chronic vaginitis clinic

Objective: We sought to determine the clinical and laboratory features of trichomonas vaginitis (TV) in a chronic vaginitis clinic.

Methods: We studied 45 women with symptomatic TV attending a specialty chronic vaginitis clinic. These patients were older than the usual symptomatic patients with TV. They frequently described unusual chronicity of symptoms, half being referred because of clinical resistance and the other half referred because of chronic vaginitis of unknown etiology.

Results: In spite of the chronicity of infection, the signs and symptoms of florid inflammation were still evident and high numbers of polymorphonuclear leukocytes and parasitic load were present.

Conclusions: A longstanding infection, especially if previously untreated, invariably responded to conventional nitroimidazole therapy. In addition, the majority of patients seen with clinical resistance to the conventional doses of metronidazole responded to high-dose oral metronidazole therapy. Unsuspected TV should always be considered in low-risk patients with chronic vulvovaginal symptoms.

Treatment of infections caused by metronidazole-resistant Trichomonas vaginalis

Infections with the sexually transmitted protozoan Trichomonas vaginalis are usually treated with metronidazole, a 5-nitroimidazole drug derived from the antibiotic azomycin. Metronidazole treatment is generally efficient in eliminating T. vaginalis infection and has a low risk of serious side effects. However, studies have shown that at least 5% of clinical cases of trichomoniasis are caused by parasites resistant to the drug. The lack of approved alternative therapies for T. vaginalis treatment means that higher and sometimes toxic doses of metronidazole are the only option for patients with resistant disease. Clearly, studies of the treatment and prevention of refractory trichomoniasis are essential. This review describes the mechanisms of metronidazole resistance in T. vaginalis and provides a summary of trichomonicidal and vaccine candidate drugs.

Metronidazole. A therapeutic review and update

The nitroimidazole antibiotic metronidazole has a limited spectrum of activity that encompasses various protozoans and most Gram-negative and Gram-positive anaerobic bacteria. Metronidazole has activity against protozoans like Entamoeba histolytica, Giardia lamblia and Trichomonas vaginalis, for which the drug was first approved as an effective treatment. Anaerobic bacteria which are typically sensitive are primarily Gram-negative anaerobes belonging to the Bacteroides and Fusobacterium spp. Gram-positive anaerobes such as peptostreptococci and Clostridia spp. are likely to test sensitive to metronidazole, but resistant isolates are probably encountered with greater frequency than with the Gram-negative anaerobes. Gardnerella vaginalis is a pleomorphic Gram-variable bacterial bacillus that is also susceptible to metronidazole. Helicobacter pylori has been strongly associated with gastritis and duodenal ulcers. Classic regimens for eradicating this pathogen have included metronidazole, usually with acid suppression medication plus bismuth and amoxicillin. The activity of metronidazole against anaerobic bowel flora has been used for prophylaxis and treatment of patients with Crohn's disease who might develop an infectious complication. Treatment of Clostridium difficile-induced pseudomembraneous colitis has usually been with oral metronidazole or vancomycin, but the lower cost and similar efficacy of metronidazole, coupled with the increased concern about imprudent use of vancomycin leading to increased resistance in enterococci, have made metronidazole the preferred agent here. Metronidazole has played an important role in anaerobic-related infections. Advantages to using metronidazole are the percentage of sensitive Gram-negative anaerobes, its availability as oral and intravenous dosage forms, its rapid bacterial killing, its good tissue penetration, its considerably lower chance of inducing C. difficile colitis, and expense. Metronidazole has notable effectiveness in treating anaerobic brain abscesses. Metronidazole is a cost-effective agent due to its low acquisition cost, its pharmacokinetics and pharmacodynamics, an acceptable adverse effect profile, and its undiminished antimicrobial activity. While its role as part of a therapeutic regimen for treating mixed aerobic/anaerobic infections has been reduced by newer, more expensive combination therapies, these new combinations have not been shown to have any therapeutic advantage over metronidazole. Although the use of metronidazole on a global scale has been curtailed by newer agents for various infections, metronidazole still has a role for these and other therapeutic uses. Many clinicians still consider metronidazole to be the 'gold standard' antibiotic against which all other antibiotics with anaerobic activity should be compared.

Metronidazole resistant trichomoniasis successfully treated with paromomycin

Management of a 42 year old female patient diagnosed with trichomoniasis is described. She failed to respond to recommended oral and high dose oral and topical metronidazole. Various options used in previously reported cases of metronidazole resistant trichomoniasis also failed to cure her condition. MIC showed the organism to be resistant to metronidazole. Cure was achieved with the use of topical intravaginal paromomycin.

Sexually acquired metronidazole-resistant trichomoniasis in a lesbian couple

A lesbian couple in a monogamous relationship each presented with vaginal discharge demonstrable on culture to contain Trichomonas vaginalis. Their symptoms had failed to respond to standard regimens of metronidazole, and subsequent microbiological sensitivities confirmed resistance of the trichomonads to metronidazole (minimum inhibitory concentrations in aerobic conditions > 8 mcg/ml). In addition, the couple denied use of penetrative sex toys or recent male partners, supporting the concept of transmission through mutual masturbation.

Bacterial vaginosis and trichomoniasis: epidemiology and management of recurrent disease

Effective therapies exist for the treatment of both vaginal trichomoniasis and bacterial vaginosis (BV). Recurrent trichomonas infection is uncommon, and significant metronidazole resistance remains rare. The management of metronidazole-resistant trichomoniasis is dependent on susceptibility studies, which can be used to guide higher doses of metronidazole therapy. Recurrent BV is common. A mechanism for reestablishing the normal vaginal flora with H₂O₂-producing lactobacilli remains elusive. The management of this recurrent infection is based upon a longer duration of therapy with currently available antibiotic regimens and documentation of a clinical response using composite clinical criteria and Gram's stain of the vaginal secretions.

Trichomonal vaginitis refractory to treatment: case report

A woman initially aged 25 was treated for seven years for symptomatic vaginal trichomoniasis. Throughout that period the patient received 5-nitroimidazoles at conventional and high dosages, antimicrobial agents to eliminate vaginal organisms capable of interfering with treatment, acidifying preparations, and vaccination with inactivated Lactobacillus acidophilus. Despite all the regimens used, the condition remained refractory to treatment.