Isolation of a stable clone of the ameboid-adherent (AA) variant of Trichomonas vaginalis.

The human urogenital protozoan parasite Trichomonas vaginalis is usually described as a free-swimming, actively motile, and ellipsoid, ovoidal, or rounded organism (Jirovec and Petrfi, 1968, Advances in Parasitology 6: 117-188; Honigberg, 1978, In Parasitic Protozoa, Vol. II, Academic Press, New York, pp. 275-454). Frequently mentioned, however, are "ameboid" forms that are nonmotile or sluggishly motile, have delicate and irregular outer margins and short or missing and relatively inactive flagella, and tend to develop pseudopodia-like cytoplasmic extensions; and "adherent" forms that tend to stick to adjacent glass or cellular surfaces (Farris and Honigberg, 1970, Journal of Parasitology 56: 849-882; Cappucinelli, 1975, International Journal for Parasitology 5: 57-61; Nielsen, 1975, Acta Pathologica et Microbiologica Scandinavica, Sect. B 83: 581-589). The ameboid shape and the adhesive tendency are presumably different manifestations of a single variant. We will call the usual form ovoid-motile (OM), and the variant, ameboid-adherent (AA). Evidence that the ameboid trait correlates with pathogenicity (see Rasmussen et al., 1986, Genito-urinary Medicine 62: 240-246) emphasises the potential importance of the AA form, but heretofore pure AA strains have not been easy to identify, and proven strains have not been available for study. In this communication we describe the isolation of a stable strain of pure AA type (Fig. 1). Most wild-type T. vaginalis populations are mixtures of OM and AA organisms. Fresh isolates contain many AA forms; old laboratory strains very few. Glebski (1969,Wiadomosci Parazytologizcne 15: 245-249 (cited by Honigberg, 1978)) counted 13% irregular forms in fresh vaginal material vs. 1% in laboratory cultures. Nielsen noted that the ameboid behavior of isolates from 3 patients disappeared after propagation for 3-4 wk in Diamond's medium. Cappucinelli noted that several strains were adherent when first isolated but lost this property after several weeks in Diamond's medium. We studied random axenic isolates (ECU nos. 1, 7, 8, 9) obtained from the East Carolina University Student Health Clinic (with the kind cooperation of Dr. Harry H. Mclean); strain JHHMN (kindly contributed by Dr. Carl F. T. Mattern, Baltimore, Maryland); and Honigberg's ameboid strain JH30A obtained from the American Type Culture Collection, ATCC no. 30235). Of these the ECU strains and JH-HMN were phenotypically OM, while JH30A was AA when received but developed OM characteristics on subculture. We used our ascorbic acid medium