Abstract
Background
In Cuba, little is known regarding the prevalence of Chlamydia trachomatis (CT) infection in adolescents and young people. We study the frequency of CT infection in these populations, and its association with clinical-epidemiological variables.
Methods
A total of 496 individuals aged 12 to 24 were recruited from November 2018 to November 2019. Of them, 302 were patients attending at sexually transmitted infections (STI) services and 194 were young volunteers. CT detections were carried out by real-time PCR and IgG serology.
Results
The prevalence of CT using PCR was 9.1% (45/496); 12.3% (37/302) for subjects attending STI service and 4.1% (8/194) for young volunteers, being significantly higher in the first group (OR=3.25; p=.001). CT IgG antibodies was detected in 38.6% (81/210). Individuals from 12 to 17 years old were more likely infected with CT (OR=2.21; p=.010). Infection was associated with the early onset of sexual intercourse, the frequent changing of sexual partners and black ethnicity.
Conclusions
The results suggest that Cuban adolescents and young populations are at highest risk of acquiring CT infection and developing reproductive complications. The data obtained advise the needs of implementation of a routine CT screening strategy, for timely diagnosis, detection and treatment at the earliest ages.
Introduction
Chlamydia trachomatis (CT) infection is the most common bacterial sexually transmitted infection (STI) in the world. According to the World Health Organization, an estimated 130 million new cases are reported each year, and the highest prevalence rates are reported in the Americas region, with 24.7 million. 1 The frequency of infection is higher in women between the ages of 15 and 49 years, with a global prevalence rate of 4.2%, while in men it is 2.7%. In most countries, the population groups with the highest incidence are adolescents between 15-19 years old, followed by young women between 20 and 24 years old and young individuals in general.2,3
CT infection causes symptoms and signs in the lower genital tract and several complications. Acute pelvic inflammatory disease is one of the most frequent complications of CT infection, particularly in adolescents and young women. This infection affects the ovaries, the fallopian tubes, and the uterus. The most serious complication is tubo-ovarian abscess. 4 Ectopic pregnancy and infertility are frequent long-term complications of CT infection, when not treated.4,5
Currently, highly sensitive nucleic acid amplification tests (NAATs) are the most recommended techniques for CT diagnosis. Real-time Polymerase Chain Reaction (real-time PCR) is the most widely used technique due to its excellent sensitivity and specificity indicators. 6 However, the overall burden of CT infection among young women is unknown since cross-sectional surveys and voluntary annual screening for CT using NAATs only capture active infections at a single point in time. 7 Consequently, according to a previous study, detection of antibodies to CT in serum is critical for identifying more than half of young women who had previous or in course CT infections. 8 The majority of the studies report CT infection prevalence based on independent NAATs or serological results.8–10 Together, serology and NAATs findings could be more efficient at detecting past and active CT infections in young women for guiding CT screening strategies at early age, and thus reduce the risk for future reproductive complications.
In Cuba, little is known regarding the prevalence rates of CT infection. The Cuban Ministry of Public Health has documented this problem, and the “National Strategic Plan for the Prevention and Control of STIs, HIV/AIDS and Hepatitis 2019-2023” aims to address it in depth. 11 The few reports published on this topic in Cuba have found variable CT infection rates that range between 1% and 6%, approximately.12,13 Those studies have been developed using NAATs and only included adult populations from specific risk groups. Thus, the objective of this study was to identify the frequency of CT infection and its association with socio-demographic and clinical-epidemiological variables, in sexually active adolescents and young populations, with different risk levels for STIs in Cuba.
Material and methods
Design and subjects
A cross-sectional study was conducted from November 2018 to November 2019. The study included adolescents and young people aged 12 to 24 years, sexually active, with different risk levels for STIs, who agreed to participate. Individuals who ever used specific antimicrobials to treat CT infections or any other antimicrobial during the month prior to the investigation were excluded. The study population involved subjects attending at the Child and Adolescent Gynecology Service for suspected STIs at three hospitals (Pediatric Hospital “Juan Manuel Márquez” and Pediatric Hospital “Cerro”, in Havana Province; and the General Clinical-Surgical Hospital “Arnaldo Milián Castro”, in Villa Clara province). Young individuals from the University of Havana, who voluntarily agreed to participate in the research, were also included. Clinical samples were collected, with prior signed informed consent by the participants or their legal guardians in the case of minors. A face-to-face questionnaire was applied to all the individuals included in the study to obtain information about socio-demographic and clinical-epidemiological variables.
Clinical samples
For CT nucleic acid detection, in case of females, vaginal swabs and 20 mL of urine samples were collected and placed together in a single tube, discharging vaginal swab content into the urine. For males, only urine samples were taken. Serum samples obtained at the same time as genitourinary samples were used for serological diagnosis.
Sample processing and DNA extraction
Urine samples were centrifuged at 17,000 r/min (15,000 g) for 30 min at 4°C. The supernatant was discarded and the pellet was resuspended in 2 mL of Minimal Essential Medium (MEM, Gibco™, USA), followed by vortex homogenization (Vortex Mixer VM-10, DAIHAN Scientific Co., Ltd, Korea).
For DNA extraction, 200 µL of each sample were used. This procedure was performed by means of the commercial QIAamp® DNA Mini Kit (QIAGEN, Hilden, Germany) following the manufacturer’s protocol.
C. trachomatis Real Time PCR (RT-PCR)
For nucleic acid CT detection, 10 µl of purified DNA from each sample was used to achieve the Sacace™ C. trachomatis Real-TM test (Sacace Biotechnologies, Italy), as per manufacturer's instructions.
C. trachomatis IgG detection
An ELISA for indirect detection of IgG antibodies to CT in serum (Human Diagnostics Worldwide, Germany) was developed according to the manufacturer's instructions.
Ethical considerations
The study was approved by the scientific and medical ethics committees of the Institute of Tropical Medicine “Pedro Kouri” (IPK) (Code: CEI-IPK-10-20). The study was conducted according to the latest revision of the Declaration of Helsinki 14 and the Guidelines of the Council for International Organizations of Medical Sciences (WHO-CIOMS). 15
Statistical analysis
A database including socio-demographic, clinical-epidemiological, and behavioral variables was analyzed using the SPSS statistical software package version 22.0 (SPSS, Inc., Chicago, IL). Descriptive statistical analyses were determined as absolute and relative frequencies. Proportions were compared using Pearson Chi square (X2) statistical test. Univariate analysis was used to calculate odds ratios (ORs) and 95% CIs as estimates of the relative risk for CT detection results associated with the various predictor variables.
Results
Socio-demographic, clinical-epidemiological characteristics and C. trachomatis infection detected by real-time PCR in the study population
Socio-demographic, clinical-epidemiological characteristics and Chlamydia trachomatis infection frequency in Cuban young and adolescent population. November 2018 to November 2019.
The total prevalence of CT infection detected by real-time PCR in the study population was 9.1% (45/496). For subjects attending the Child and Adolescent Gynecology Service for suspected STIs, CT was found in 12.3% (37/302), and in 4.1% (8/194) of those young volunteer subjects, being the first group more likely to be infected with CT (OR=3.25; 95% CI=1.48-7.13; p=.001).
The frequency of CT infection varied by age group in the population under study, although it was significantly greater in people between the ages of 12 and 17 (OR=2.21; 95% CI=1.89-4.11; p=.010). Likewise, subjects with junior high school education level were more likely to be infected with CT (OR=3.15; 95% CI=1.69-5.87; p=.000, as well as Black individuals (OR=3.40; 95% CI=1.55-7.43; p=.004). Furthermore, those subjects who started sexual intercourse at age 15 or younger showed a higher frequency of CT infection (OR=2.35; 95% CI=1.13–4.86; p=.012). A higher risk of CT infection (OR=2.34; 95% CI=1.09–5.03; p=.029) was also associated with changing sexual partners twice or more in the last year.
The frequency of CT was significantly higher for Black individuals (OR=3.09; 95% CI=1.31–7.27; p=.013) and with education level of junior high school (OR=2.11 95% CI=1.04–4.20; p=.027) who were attending the Child and Adolescent Gynecology Service for suspected STIs. However, among young volunteer subjects, no differences were found based on the frequency of CT infection.
Gynecological history, clinical data and C. trachomatis infection by real-time PCR in the studied female population
Gynecological history, clinical data and Chlamydia trachomatis infection frequency in Cuban young and adolescent female population. November 2018 to November 2019.
The most common signs and symptoms reported by female patients were leucorrhea, lower abdominal pain, and genital odour. However, those with lower abdominal pain (OR=2.00; 95% CI=1.02–3.93; p=.037) and acute pelvic inflammatory disease (OR=2.34; 95% CI=1.19–4.61; p=.014) were more likely to have a positive PCR to CT. These symptoms were more frequent among female patients attending the STI services compared to the young volunteer females. Therefore, female patients with STIs had a higher risk of acute pelvic inflammatory disease (OR=9.66; 95% CI=4.33–21.56; p=.000) and lower abdominal pain (OR=2.04; 95% CI=1.23–3.39; p=.003) compared to the others.
On the other hand, the male population of the study included 88 subjects who reported symptoms and signs of dysuria (12/88; 13.6%), urethritis (8/88; 9.1%), genital itching (5/88; 5.7%), urethral discharge (4/88; 4.5%), and genital odour (1/88; 1.1%). The frequency of CT infection according to these symptoms were 16.7% (2/12), 12.5% (1/8), 0.0% (0/5), 50.0% (2/4) and 0.0% (0/1), respectively.
C. trachomatis IgG detection
Univariate analyses for the socio-demographic, clinical-epidemiological characteristics and the serological results for Chlamydia trachomatis infection in young and adolescent Cuban population. November 2018 to November 2019.
Significantly statistical variables (p values and OR) are highlighted in bold.
Results of univariate analysis for the socio-demographic, clinical-epidemiological characteristics and the serological results for CT infection showed that adolescents and young patients attending STI service had a significantly higher prevalence of IgG antibodies. Individuals aged 12 to 17 years were more likely to be positive for IgG to CT and probably the same aged group of adolescents with a junior high school education level had a higher prevalence of IgG antibodies, and thus, education level was probably a confounding factor in univariate analyses. Symptoms and signs of lower genital tract infection were associated with CT positive serology. Patients with positive real-time PCR were almost 10 times more likely to be positive for IgG detection (Table 3).
Univariate analyses of the gynecological history, clinical data and the serological results for Chlamydia trachomatis infection of the studied Cuban young and adolescent female population. November 2018 to November 2019.
Significantly statistical variables (p values and OR) are highlighted in bold.
Discussion
High prevalence of STIs is described in adolescents and young populations worldwide, since around 50% of them suffer at least one of these infections. Particularly, within bacterial infections, C. trachomatis is the most common. 16
There are few Cuban studies using NAATs that estimate the frequency of CT infection, either by conventional PCR or by real-time PCR. Previous Cuban studies have been conducted in adult patients with a history of infertility, HIV seropositivity, or with symptoms of urogenital tract diseases. In these works, the prevalence fluctuated between 1% and 6%.12,13 The most recent Cuban study published in 2020 on the co-circulation of the Human Papillomavirus and CT in Cuban women found 1% of positivity to CT. Nevertheless, the positive cases, even when they were asymptomatic, corresponded exclusively to those younger than 25 years of age, with no history of confirmed STIs. 17
In the present study, the analyzed population included 496 individuals younger than 24 years old. A higher general percentage of CT infection was detected by real-time PCR (9.1%), compared to other Cuban studies. The prevalence was even higher (12.3%) in the group of patients with suspected STIs; in which more than 50% were aged 12 to 17 years.
The high prevalence rate to CT obtained by NAAT in our study is similar to other research in adolescents and young people from Latin and North America, and Africa.18–20 Furthermore, we obtained also a high seroprevalence of CT infection (38.6%); even though IgG results were available only for 210 individuals. Patients with positive real-time PCR were almost 10 times more likely to be positive for IgG detection. Serology is widely recognized as a test for detection of CT infections, although it is unable to distinguish past from recent infections. It allows estimating the proportion of women in whom one or more CT infections have been previously missed because they were not diagnosed by NAAT. The detection of past CT infections by serology is irrelevant for treatment but emphasizes the importance of screening at this high-risk populations. According to a previous study, the estimate prevalence of CT infection based on serological testing could be critical for identifying more than half of young women who had previous or in course CT infections. Detectable levels of IgG are reached about 2 weeks after acquiring CT infection, even in the course of symptomatic or asymptomatic disease. 21 In Cuba, currently, the asymptomatic active infections in young populations are not diagnosed because routine screening is not usually performed. Accurate CT infection prevalence measures, including serology and NAAT results, are important for guiding recommendations on CT screening strategies at early age, according to the onset of sexual practices in each population, and prevent future sequelae of the infection. 8
Several studies have investigated the impact of STIs during childhood and adolescence, highlighting the multiple risk factors for their acquisition. The higher frequency of CT infection is related to the early onset of sexual intercourse, the frequent change of sexual partners, and the use of contraceptives, which consequently, predisposes to the acquisition of STIs. Co-infection with other STIs such as Neisseria gonorrhoeae, Condyloma accuminata, and genital herpes and also the presence of various signs and symptoms of the lower genital tract could be predictors for CT infection. 22
In our study, a high percentage of adolescents attending STI consultations were females. This is probably because women, even from a very young age, regularly attend these services, since they are more often symptomatic. Such is the case of acute pelvic inflammatory disease, which sometimes is very painful. 23 However, we did not found any distinction in CT infection between males and females.
According to our research, the prevalence of CT infection was significantly higher in people who started sexual intercourse at age 15 or younger, had at least two sexual partners in the previous year, and had lower abdominal pain or acute pelvic inflammatory disease. Acute pelvic inflammatory disease is frequent in adolescents, due to the early onset of and the increase in sexual activity. It is suggested that the risk of developing this condition is three times higher in women under 20 than it is in those between the ages of 25 and 29. 24 Many authors report this symptom as one of the most frequent in active CT infection.5,25,26 However, according to our findings, this symptom was not associated with positive serology, probably because the majority of patients with positive IgG did not have an acute CT infection. IgG positive results were more frequently detected in women who reported having two or more pregnancies, and they were also associated with symptoms and signs related to lower genital infections, such as lower abdominal pain, genital odour and cervicitis. These factors have potential implications for guiding CT screening strategies in Cuban populations at higher risk of infection.
Studies conducted worldwide reveal that certain socioeconomic, demographic, cultural, and epidemiological factors, which define a higher or lower risk, can have an impact on the distribution of CT infection, as happens with other infectious agents. 27 This finding relates to the early onset of sexual intercourse, and also to certain sexual risk behaviors, which largely depend on sexual education, but mainly on the social, cultural and economic environment that can influence the behavior of certain population groups, such as adolescents and young people. 22
In a study conducted in Havana in 2017, 110 teenagers with STI diagnoses and a control group were involved. The average age of onset of sexual intercourse of the studied population was 12 years old. The research revealed a low risk perception for STIs. Affective feelings and moral values were not sufficiently considered in sex practices, and there was a lack of knowledge regarding STIs and their prevention. The study found a correlation between high frequency of STIs and low educational and sociocultural level in some Cuban social groups, mainly in young people and adolescents. 28 These data suggest that routine STI screening needs to start as early as possible and continue throughout sexual activity.
The risk of CT infection may be conditioned by a set of sociodemographic, epidemiological, socioeconomic and environmental factors, as occurs in most infectious processes. In our study, CT infection was about 3.4-fold more frequent in Black people, mainly women, compared with White ones. The reason for the higher CT infection prevalence in Black individuals remains unknown, although some studies suggest that the possibility of acquiring CT infection could be related to socioeconomic, ethnic and demographic aspects, mainly due to racial and economic disparities that increase risk behaviors for STI acquisition. 29
In Cuba, the social equity gaps have been explored and the results are heterogeneous. The gaps are presented by mean of seven dimensions: equity and social mobility, education, employment, health and well-being, socioeconomic disadvantage, social integration, racism and discrimination. These analyses showed inequalities by racism in areas such as education, health and well-being, employment, and socioeconomic disadvantage. 30 This issue requires further investigations that cover social, economic, gender and racial aspects in greater depth, as possible risk factors for the acquisition of CT infection and other STIs.
Our study has some limitations, such as the inaccuracy of most clinical data and sexual history information provided by subjects during face-to-face interviews, making it impossible to confirm their veracity. On the other hand, the number of available serology results was low compared to the total number of participants in the research. It could affect the results of CT prevalence measure of CT infections, particularly in the group of symptomatic adolescents and young patients with suspected STIs, who only provided 33 of 302 patients with available serology results. Finally, we only studied subjects from Havana and Villa Clara provinces, thus, it is unclear whether our findings apply to other populations and to other geographic areas in Cuba.
In conclusion, this study is the first to be conducted for the detection of CT in adolescent and young Cuban population, using NAAT and serology as two independent measurements of CT prevalence. It is of particular attention the results obtained regarding the highest prevalence of CT infection into the group of subjects attending at the Child and Adolescent Gynecology Service for suspected STIs, mainly those from 12 to 17 years old, who showed a wide range of signs and symptoms of genitourinary tract infections or some complication of the lower genital tract. The results indicate that the Cuban child and adolescent population under study may be susceptible to complications resulting from CT infection, particularly in asymptomatic cases.
The data obtained from this work support the need for further studies in CT and other STI and suggests the implementation of a CT screening program for the detection and timely treatment of these infections at the earliest ages, and thus avoid future sequelae or complications that may affect the sexual and reproductive life of the Cuban population.
Footnotes
Acknowledgements
The authors thank the patients and physicians from pediatric hospitals and young volunteers from Havana University who participated in the study. We are also grateful to Prof. Yosiel Molina Gomez for useful comments, suggestions and corrections for English language improvement on an earlier version of the paper.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Ministry of Health of Cuba and NGO MediCuba Europa.