Pulmonary trichomoniasis: improved diagnosis by using polymerase chain reaction targeting Trichomonas tenax 18S rRNA gene in sputum specimens

Abstract

A polymerase chain reaction (PCR) assay targeting species-specific region in 18 small subunit ribosomal RNA gene of Trichomonas tenax was used to examine sputum specimens in order to diagnose pulmonary trichomoniasis caused by T. tenax. It was compared with wet mount preparation, Giemsa-stained smear, and Kupferberg Trichononas broth culture for detection of T. tenax trophozoites in sputum. The study included 250 individuals; 100 immunocompromised patients with chest complaints (group I) and 100 patients with chronic pulmonary diseases (group II), and 50 healthy individuals as controls (group III). 20 cases among all examined were positive in one or more method giving for pulmonary trichomniasis a total prevalence of 8%; 12 cases (12%) in group I, 8 cases (8%) in group II, and none in group III, with no significant difference between groups I & II. Pulmonary trichomoniasis was prevalent at age ranged between 31 to 50 years, and in total males (10%) than females (5.5%) with no significant difference. Among the 200 examined patients, pulmonary trichomoniasis had a prevalence of 3% by wet mount, 2.5% by Giemsa-stained smear, 7% by culture, compared to 10% by PCR. Culture was used as reference standard. All culture positive specimens were PCR positive showing a product at 0.8 Kb long by agarose gel electrophoresis, and giving a 100% sensitivity. Wet mount, Giemsa-stained smear, and culture had a sensitivity of 43%, 35.7%, and 70%, respectively. No PCR negative specimens were positive by any of the other methods. 6 specimens were culture negative PCR positive and remained PCR positive when retested 3 times. The calculated specificity of PCR was 97%. NO PCR target product was amplified with DNAs of T. vaginalis and various pulmonary pathogens. The results are discussed.