Vulvovaginal symptoms are among the most common reasons for women attending a health facility. The symptoms of vaginal discharge that a woman may perceive as abnormal include vulval irritation and itching. More than 30 bacteria, viruses, and parasites are known to be sexually transmitted. The most frequently identified include Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum, and Trichomonas vaginalis, with over 350 million infections yearly worldwide [1]. Urogenital trichomoniasis is the only parasitic STI recognized as the most common non-viral STI globally, with 250 million new cases annually [2]. The infection is usually asymptomatic in men, although it may be associated with urethral discharge or dysuria. However, clinical manifestations in women are more frequent, with various symptoms such as greenish-yellow leucorrhea, dysuria, and vaginal mucosa with hemorrhagic staining [3]. In addition, T. vaginalis infection can cause complications in pregnant women, such as the premature rupture of membranes, premature delivery with low birth weight, infertility, or cervical cancer [4]. The transmission of T. vaginalis is extremely heterogeneous and depends on several factors, including socioeconomic status, age, hygiene habits, sexual behavior, post-menstrual phase, and access to health care. In addition, association with other infectious agents of the urogenital tract, such as mycoplasma, is often reported [5,6]. Mycoplasmas (M. hominis and Ureaplasma spp.) are commensals of the lower urogenital tract. Colonization varies with age, race, socioeconomic status, sexual activity, and hormonal status, and increases during pregnancy [7]. Ureaplasma spp. can be found vaginally in 30% of women, while M. hominis is found in less than 10% and these infections can cause cervicitis, infertility, premature delivery, or spontaneous abortion in pregnant women [8]. These consequences justify preventing these infections, especially in women of childbearing age. In addition, studies have suggested a symbiotic relationship between T. vaginalis and Mycoplasma hominis, but the potential synergy between these two pathogens has yet to be evaluated under clinical conditions [9]. In Senegal, most patients with signs suggestive of STIs (urethral discharge and vaginal discharge syndromes) are often diagnosed presumptively using a syndromic approach. However, this approach may lack sensitivity and specificity in some settings and lead to the mismanagement of several conditions, including urogenital trichomoniasis and Mycoplasma infections [10]. In addition, biological confirmation of these infections remains poor in many health facilities due to a lack of appropriate laboratories [11]. This results in a lack of available data on the epidemiology of Mycoplasma spp. and T. vaginalis co-infection, particularly in at-risk populations such as women of childbearing age. In this context, we conducted this study at the Ouakam Military Hospital. The aim was to determine the characteristics of T. vaginalis and mycoplasma (M. hominis and U. urealyticum) co-infection among women referred to the microbiology laboratory.

Our goal was to evaluate Mycoplasma spp. and Trichomonas vaginalis infections in women in Dakar. Patients aged 20–30 were the most represented, followed by those aged 31–40. One possible explanation is that hospital-based investigation of women presenting with STI clinical signs are likely to detect genital infections in women who are sexually active and of childbearing age.

Trichomoniasis, caused by T. vaginalis, is a widely prevalent sexually transmitted infection (STI) worldwide. However, its prevalence varies significantly in different countries [2,13]. Limited data are available in Senegal regarding the epidemiological profile of T. vaginalis infections. Our study found an overall frequency of 3.5%, consistent with previous research conducted in Dakar by Tine, who reported a frequency rate of 3.07% [14]. In addition, patients aged between 41 and 50 had the highest percentage of impact at 5.3%, though the difference was not statistically significant. In contrast, Tine et al.'s study showed that women under 25 were the most affected [14]. Reports from Egypt, Iran, and the USA indicate that urogenital trichomoniasis is prevalent among women aged 25 to 45 [15,16,17]. Urogenital trichomoniasis is more prevalent in sexually active age groups, which includes this age group, making them more exposed and more susceptible to infection [8,18]. Our study found a lower incidence of T. vaginalis infection than that reported in other countries. For instance, a prevalence of 9.5% was recorded in Zimbabwe [19]. Additionally, in many cities in Nigeria, frequencies of 18.66%, 24.1%, and 10.99% were reported in Zaria, Zos, and Maiduguri, respectively [20,21,22]. Differences in disease exposure or diagnostic methods could cause differences in frequency. In our study, only fresh direct examination and Gram-staining techniques were used, while it has been found that combining direct examination with culture is more effective for diagnosing urogenital trichomoniasis [23]. Previous studies have shown a strong link between urogenital trichomoniasis and low education, smoking, and sexual behavior [8,24]. However, our research did not collect any data on these variables.

T. vaginalis infection can cause non-specific biological changes, including significant inflammatory and cytolytic actions induced by the parasites. The severity of these pathogenic actions varies depending on the host and the strains of T. vaginalis [25,26]. Our research found that T. vaginalis infection caused a notable alteration in the vaginal flora, specifically of types III and IV. These findings align with previous longitudinal studies that indicate a higher likelihood of acquiring T. vaginalis in individuals with bacterial vaginosis [27,28].

According to our research, 50.5% of symptomatic patients had U. urealyticum, and 18.2% had M. hominis. The prevalence of most genital mycoplasma remained stable throughout the study. We could not compare our findings to previous studies on the trend of genital mycoplasma prevalence in symptomatic patients in Senegal during this period. Previously in Dakar, Tine et al. reported in their research, conducted at the Centre Hospitalier National et Universitaire de Fann, a similar prevalence of 54.9% for U. urealyticum. In comparison, the frequency of M. hominis infections was much higher at 57.4% [14]. Furthermore, according to several studies conducted in South Korea, the prevalence of U. urealyticum in symptomatic patients was higher than that of M. hominis. According to Moon et al., the prevalence of U. urealyticum and M. hominis was 21.3% and 2.9%, respectively [29], whereas it was 65.6% and 11.8% according to Kweon et al. [30], and 48.8% and 25.3% according to Jang et al. [31]. Similar values have been reported in Poland [32] and China [33]. The prevalence rates of M. hominis infection of 48%, 42.8%, 80%, and 70% have been reported in Cameroon, Korea, South Africa, and Papua New Guinea, respectively [34,35,36,37].

Our research indicates that M. hominis and U. urealyticum infections are more frequent in women under 40 years. However, the differences between age groups were not significant enough to draw a statistical conclusion. Tine et al. found a similar trend in their study, with the highest prevalence of STIs in patients under 45 [14]. One possible reason is that people within this age range tend to be sexually active and in their reproductive years, which may increase their susceptibility to such infections [8,18]. Furthermore, Mycoplasma caused significant biological changes, such as increased white blood cells observed on fresh examination. In addition, a significant association of these infections with type III or IV vaginal flora was noted. Indeed, Mycoplasma infections of the female urogenital tract are commonly associated with bacterial vaginosis [38,39], pelvic inflammatory disease, and cervicitis, which may result in increased white blood cell secretion [40].

As a dynamic environment, the female urogenital tract presents with a resident microflora of various species. The coexistence of other sexually transmitted microorganisms is quite common. It is due to several factors, such as a common route of transmission, the sexual behavior of the host, and the resident flora [41]. However, little attention has been paid to the presence of vaginal co-infections and their clinical and diagnostic implications. A symbiotic association between T. vaginalis and M. hominis, two microorganisms infecting the vaginal tract, has been demonstrated [37,42].

In our research, out of the 66 patients who had T. vaginalis infection, 45 patients had a co-infection with M. hominis, which is 68.2%. Additionally, it was observed that 88% of the cases had an association with U. urealyticum. The symbiotic relationship between T. vaginalis and Mycoplasma has been described in several studies [9,42]. It has been established that T. vaginalis can act as a niche and vector for transmitting M. hominis [43]. In addition, Mycoplasmas harbored by T. vaginalis have the privilege of evading the host immune response and enhancing the virulence of T. vaginalis [44]. This clinically significant symbiosis between these two obligate human microorganisms suggests that the routine screening of patients with T. vaginalis infection for mycoplasma is a better approach to optimize STI treatment practices [45]. In many cases, co-infection with Trichomonas and Mycoplasma may reduce susceptibility to antimicrobial agents, complicating the infection's eradication [37,43].

While this study provided relevant evidence on the association between T. vaginalis and mycoplasma, it has some limitations.

Firstly, laboratory tests included antimicrobial susceptibility testing; no follow-up assessment was performed after treatment. Further investigations would provide a better understanding of the effect of co-infection on treatment response in routine practice [46,47]. Secondly, the detection of T. vaginalis was based on fresh microscopic examination and staining as part of standard routine practice, and no additional investigations such as culture or PCR were performed. This may have led to an underestimation of its prevalence, as it is well established that culture in combination with direct microscopy is more sensitive to detection [48].

This study reveals that a higher percentage of the population was infected with U. urealyticum, while less than a quarter was infected with M. hominis. While the prevalence of T. vaginalis infection was low, an important co-infection with Mycoplasma spp. was observed. This emphasizes the importance of screening for mycoplasma in patients with urogenital trichomoniasis.