# Prevalence of _Trichomonas tenax_ in the Population Affected by Periodantal Disease--A Review
## 1 Introduction  
It has been established that the oral cavity has a large number and a rich species composition of microorganisms forming its microflora [1]. Microorganisms adhere to various surfaces (the hard and soft tissues of the teeth, and the oropharyngeal mucosa) and form biofilms [2]. _Trichomonas tenax_ is a flagellate, anaerobic unicellular microorganism that belongs to the genus Trichomonas, of the family Trichomonadidae. It is part of the oral microflora. Its name is derived from the Greek words \"trichos\" meaning \"hair\", \"monas\" meaning \"simple organism\" and the Latin word \"tenere\" meaning \"hold fast\" [3]. _Trichomonas tenax_ was identified by [PERSON] in the second half of the 18 th century in solutions of tart [4]. It was initially named _Cercaria tenax_ and underwent several modifications until the final name, _Trichomonas tenax_, was accepted by [PERSON] in 1939 [5, 6]. Additionally, the human organism is inhabited by two more representatives of the Trichomonadidae family--_Trichomonas vaginalis_ and _Trichomonas hominis_. Their characteristics are presented in Table 1. It can be seen that _Trichomonas tenax_ looks more like _Trichomonas vaginalis_ than _Trichomonas hominis_[7]. _Trichomonas tenax_ inhabits the oral cavity of humans, with a higher incidence in individuals with poor oral hygiene, the presence of tartar and periodontal disease, which can lead to tooth loss in adults. It is typically found between teeth, in saliva, in periodontal pockets and less commonly in tonsillar crypts [6]. There is some evidence for its presence inthe duct of the submandibular salivary gland [8]. This oral protozoan is transmitted via saliva, sneezing and coughing drops, kissing or using contaminated subjects and water [9]. Cases of non-oral localizations of _Trichomonas tenax_ have been reported, including in sputum samples, bronchoalveolar lavage, pleural punctures in patients with diseases of the lower respiratory tract, the lungs and pleura during bronchiectasis and in lung abscesses, lung cancer and pyothorax. Pulmonary trichomoniasis is believed to develop after aspiration of the microorganism from the orophnx into the airways [10; 11]. The first case of _Trichomonas tenax_ detection in the cerebrospinal fluid of patients with polymicrobial meningitis was reported in 1976 [12]. In 1987, its presence alongside a mixed oral bacterial microflora in pus from a subhepatic abscess following perforation of a gastric ulcer was reported [13]. In 1988, the protozoan was found in the mucus of the dilated ducts of patients with fibrocystic mastopathy [14]. _Trichomonas tenax_ has been observed in an excised lymph node alongside the causative agent of tuberculosis, _Mycobacterium tuberculosis_[15]. Similar to _Trichomonas vaginalis_, _Trichomonas tenax_ may also cause tropical invasions [16]. Apart from humans, it has also been found in the oral cavities of domestic animals such as cats, dogs, horses, in the cloaca of birds and in the vaginas of monkeys [17; 18]. _Trichomonas tenax_ has been considered as a harmless commensal for a long time. Because of its association with periodontal disease, researchers have shifted their focus to its pathogenicity factors [19]. The secretory activity of _Trichomonas tenax_ has been studied. [PERSON] et al. reported the presence of fibronectin-like molecules on the surface of this flagellated microorganism in 1983. They examined two strains of _Trichomonas tenax_--one isolated from patients with ulcerative gingivitis and another maintained in culture for two years. Both strains exhibited positive fluorescence with anti-fibronectin antibodies. These fibronectin-like molecules are believed to facilitate adhesion to gingival cells and connective tissue and promote phagocytosis of the bacteria [20]. [PERSON] and [PERSON] continued the studies on proteolytic activity in cell extracts and culture filtrates of _Trichomonas tenax_ using SDS-polyacrylamideamide gels, identifying seven different proteolytic bands.