Analysis of Ureaplasma urealyticum, Chlamydia trachomatis, Mycoplasma genitalium and Neisseria gonorrhoeae infections among obstetrics and gynecological outpatients in southwest China: a retrospective study

Ureaplasma urealyticum (UU), Chlamydia trachomatis (CT), Mycoplasma genitalium (MG), and Neisseria gonorrhoeae (NG) are the common sexually transmitted pathogens of the reproductive tract. Previous studies have found that these pathogen infections are closely related to some gynecological diseases, such as non-gonococcal urethritis, vaginitis, cervicitis, endometritis, and even infertility [1, 2]. Generally, UU, CT, MG, and NG exist in epithelial cells and mostly do not invade the blood. UU belongs to the ureaplasma group with a circular double-stranded DNA genome. It is the smallest and simplest cell capable of self-reproduction. In recent years, UU is one of the main pathogens that cause non-gonococcal urethritis, accounting for approximately 70% of all cases [3, 4]. It’s worth noting that UU infections tends to occur in young people, especially after unclean sexual intercourse, resulting in infertility, abortion and fetal growth retardation, and other fertility problems in women of childbearing age [5, 6]. CT is an intracellular parasite that contains DNA and RNA, with an infection rate of 9.8% [7, 8]. It has a variety of serotypes, and different serotypes may cause different clinical manifestations in humans [9]. MG has the least genomic of all mycoplasmas. It also causes non-gonococcal urethritis and inflammation of the cervix or endometrium in women, with an infection rate of up to 25% [10]. NG is a gram-negative diplococcus. The main clinical manifestations of NG infection are urethritis and cervicitis [9]. Among the above four pathogens, NG is the only one that can be observed under the microscope by gram staining [11]. The clinical manifestations of patients with UU, CT, MG, and CT infections are varied, and even some patients have no obvious clinical symptoms. Therefore, a better understanding of the infection status and characteristics of these pathogens is necessary.

Simultaneous amplification and testing (SAT) is a molecular diagnostic method based on isothermal amplification of pathogen RNA, which can accurately and rapidly detect a variety of pathogens [12]. The application of SAT in the detection of RNA of pathogens of sexually transmitted diseases can overcome the disadvantages of traditional microbial culture methods. SAT method is more time-saving and more sensitive. Besides, SAT test targets the RNA of pathogens, which adequately reflects a patient’s infection status and avoids antibiotic overuse. In this study, we included 3225 outpatients in the department of obstetrics and gynecology to evaluate the prevalence characteristics of UU, CT, MG, and NG in the southwest of China using the SAT method. A better understanding of UU, CT, MG, and NG infection can help policymakers identify and address their specific strategy for the prevention, testing, and treatment of these infections.

The aim of this study was to detect UU, CT, MG, and NG infections in urogenital swabs from outpatients of obstetrics and gynecology in southwest China by SAT method. These findings would contribute to a better understanding of the current epidemiological features of UU, CT, MG, and NG among obstetrics and gynecological outpatients in southwest China and thus facilitate to develop a more effective intervention, prevention, and treatment of reproductive tract infection. As shown above, the infection rate of UU was significantly higher than that of the CT, MG, and NG infections and UU also played a major role even in the mixed infections. For the prevalence of UU, CT, MG, and NG in different age groups, UU, CT, and MG infections were more common in women of reproductive age (aged 25–34 years), while NG infection was more prominent in women aged 30–34 years and over 40 years. In addition, maternal UU infection may lead to premature delivery, low birth weight, and neonatal pneumonia, but not all patients with UU infection have obvious clinical manifestations [13]. These results are consistent with previous studies [5, 6, 14]. In this study, women with UU positive pregnancies were tracked, among which ten were premature, 2 were low weight, and 4 were neonatal pneumonia (As shown in Fig. 2). As for abortion, some studies found that the positive rate of UU was as high as 84.4% from the aborted tissues [13]. The perinatal infection caused by UU has become a new problem in modern obstetrics. Therefore, the SAT test is necessary for women before pregnancy. In the study of antibiotic sensitivity of UU, we found that UU was sensitive to pristinamycin, doxycycline, tetracycline, clarithromycin, and josamycin, with over 90% of all samples tested being susceptibility to these antibodies.

Additionally, in this study, the positive rate of NG was very low; this might be due to the fact that a large proportion of NG has been detected in routine leucorrhea microscopy tests. However, UU, CT, and MG are difficult to be diagnosed by routine microscopic examination of vaginal or cervical secretions. Mycoplasma and chlamydia are also difficult to be identified by microbial culture due to their slow growth and high nutrient requirements [15, 16]. In particular, the culture of MG in clinical specimens is more difficult to succeed [17]. SAT method is designed to amplify 16S rRNA in cells, thus providing a more sensitive and faster method for the detection of pathogens, such as mycobacterium tuberculosis complex, enterovirus 71, UU, CT, NG, and MG [15, 18‐20]. As we can see in Fig. 2 that urogenital tract infections such as UU are likely to be asymptomatic in most patients. When the immune system is weakened, or a woman is pregnant, UU infection may cause inflammation of the female reproductive system. It may also spread through the placenta into the uterine cavity and cause adverse consequences such as abortion, premature delivery or low birth weight due to the increase of progesterone and the suppression of cellular immunity. Currently, there are no vaccines related to other genitourinary pathogens other than HPV, and the research and development of the vaccine is an area worth looking forward to [21]. In general, screening for UU, CT, MG, and NG before pregnancy is important even for women without clinical symptoms to effectively promote the early diagnosis and treatment of these infections, and to avoid adverse pregnancy outcomes.

The study still has some limitations. Firstly, all the experiments were conducted at the West China Second University Hospital, which is the largest women’s and children’s hospital in southwest China, but a larger study in multiple centers may make the data more convincing. Secondly, due to the limitations of retrospective studies, the sample size of the patients with UU infection and drug susceptibility analysis is small, so it is necessary further to increase the sample size for analysis in future studies. Finally, although we can provide data on the prevalence of infections, it is difficult to draw any conclusions about the role or the mechanisms of these infections in pregnancy outcomes. Further research will be carried out on this part in the future.

Our study retrospectively analyzed the prevalence of UU, CT, MG, and NG infections among obstetrics and gynecological outpatients in southwest China and tracked the pregnancy outcomes in women with UU infection. Considering high prevalence of UU among the population in southwest China, urogenital infection screening is recommended in symptomatic patients with suspected urogenital infections and women pre-pregnancy. In conclusion, our study could contribute to a better understanding of the current epidemiological features of UU, CT, MG, and NG among obstetrics and gynecological outpatients in southwest China, and thus facilitate to development of more effective intervention, prevention, and treatment of urogenital infections.