Rapid Stain Visualizes Sexually Transmitted Parasite

The protozoan parasite that causes trichomoniasis can be stained easily and rapidly with Modified Field's Stain (MF).

Trichomonas vaginalis, a flagellate protozoan parasite commonly found in the human genitourinary tract, is transmitted primarily by sexual intercourse. Diagnosis is usually by in vitro culture method and staining with either Giemsa stain or Gram stain.


A more rapid staining technique facilitates identification especially made from vaginal swabs. The three staining methods, Giemsa, Gram and MF, were compared at the Faculty of Medicine, University of Malaya (Kuala Lumpur, Malaysia). Sediment from both axenic and xenic cultures was used to make thin smears on clean glass slides for staining. Sediment from xenic cultures was also inserted into freshly collected urine samples and subsequently centrifuged. Smears were also made from spiked urine samples for staining purposes. The smears from the sediment at the bottom of culture tubes were performed in triplicates. Urine samples were obtained from the patients providing vaginal swabs, which were subsequently centrifuged.

The Giemsa stain took 20 minutes, but was it found to be tedious in preparation time, although provided good contrast for morphological identification of the parasite. The Gram stain took only five minutes, but was the poorest with no contrast for parasite identification. The Modified Field stain was very rapid, taking only 20 seconds and it confers sharper staining contrast, which differentiates the nucleus and the cytoplasm of the organism.

The authors concluded that for the first time a rapid staining method using MF stain facilitates the identification of T. vaginalis. The protocol is simple and rapid but also the contrast showing nucleus, cytoplasm, vacuoles, and flagella was clearly visible and is equal if not better than Giemsa. MF staining offers a rapid staining protocol in laboratories and is recommended that it be used widely. The only observation to take note is that staining must be done on slides within 12 hours after smearing as the contrast becomes lesser when the duration of fixing and staining increases more than 12 hours. The results of the study were published in the October 2010 issue of Diagnostic Microbiology and Infectious Disease. It has been estimated that more than 170 million people worldwide are infected with T. vaginalis per year.

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University of Malaya