Sexually transmitted infections (STIs) represent a major global public health concern, contributing significantly to morbidity, infertility, adverse pregnancy outcomes, and increased susceptibility to HIV. Among the wide array of bacterial STIs, Chlamydia trachomatis and Treponema pallidum, the causative agents of chlamydial infection and syphilis respectively, are among the most frequently reported and clinically significant pathogens [1-3]. Chlamydia trachomatis is the most commonly reported bacterial STI worldwide, particularly affecting sexually active adolescents and young adults. It often presents with minimal or no symptoms, especially in females, leading to underdiagnosis and increased transmission. If left untreated, chlamydial infection can lead to severe reproductive complications such as pelvic inflammatory disease, ectopic pregnancy, and infertility [4-6]. Syphilis, caused by Treponema pallidum, continues to re-emerge as a public health threat globally. Although it presents with a well-defined clinical progression—ranging from primary ulcers to latent and tertiary forms—it may go unnoticed in its early stages, especially when co-infected with other STIs. The presence of genital ulcers caused by syphilis has also been shown to increase the risk of HIV acquisition [7-9].

Recent studies have shown that co-infection with Chlamydia trachomatis and Treponema pallidum is not uncommon and may influence the clinical course and transmission dynamics of both infections. Co-infections can also complicate diagnosis and management, as the symptoms may overlap or mask one another. Patients attending STI clinics are often at higher risk for multiple infections due to high-risk sexual behaviors, including unprotected intercourse, multiple sexual partners, and inconsistent health-seeking behavior [10-12]. Despite global and national surveillance efforts, data on the co-occurrence of chlamydial infection and syphilis in many developing countries, including India, remains limited. This information is crucial to improve diagnostic protocols, enhance patient management, and formulate targeted public health interventions [13, 14].

Hence, this study was conducted with the aim of determining the association between Chlamydia trachomatis infection and syphilis among patients attending the STD clinic in a tertiary care hospital. The results are expected to contribute to the growing understanding of STI co-infections and underscore the need for integrated screening and treatment approaches.

This cross-sectional observational study was conducted over a period of 6 months at the STD clinic of a tertiary care hospital. This study was conducted at department of Microbiology, Government Medical College, Nalgonda, Telangana, India from March 2024 to February 2025. A total of 40 patients presenting with signs and symptoms suggestive of sexually transmitted infections (STIs) were enrolled after obtaining informed consent. Demographic and clinical information including age, gender, sexual history, condom usage, number of sexual partners, and history of previous STIs were recorded using a structured questionnaire. Blood samples were collected from all participants for the detection of syphilis. Screening was performed using the Venereal Disease Research Laboratory (VDRL) test, and reactive samples were confirmed using the Treponema pallidum hemagglutination assay (TPHA). For the detection of Chlamydia trachomatis, endocervical swabs (for females) and urethral swabs or first-catch urine samples (for males) were collected. Nucleic acid amplification tests (NAAT), considered the gold standard for chlamydia diagnosis, and were employed for the detection of C. trachomatis DNA.

Inclusion Criteria:

• Patients aged 18 years and above.
• Patients presenting with symptoms suggestive of STIs (e.g., genital discharge, ulcers, dysuria, lower abdominal pain).
• Patients willing to give informed written consent.
• Both male and female patients attending the STD clinic.

Exclusion Criteria:

• Patients who had received antibiotic treatment in the past 4 weeks.
• Patients with known immunocompromised states (e.g., HIV-positive individuals).
• Pregnant women (due to additional ethical considerations).
• Patients unwilling or unable to provide consent.
• Inadequate or improperly collected clinical samples.

Statistical Analysis:

Data were analyzed using appropriate statistical methods to determine the prevalence of single and co-infections, and associations with demographic or behavioral variables were assessed using chi-square or Fisher's exact test where applicable. A p-value of <0.05 was considered statistically significant.

A total of 40 patients presenting with symptoms of sexually transmitted infections (STIs) were enrolled in the study. The results were analyzed to assess the prevalence and correlation between Chlamydia trachomatis and Treponema pallidum infections and their association with demographic and behavioral factors.

Table 1: Age and Sex Distribution of Study Participants

The majority of patients were in the 26–35 years age group (42.5%), with a slight male predominance (55%). This indicates that the most sexually active age group is more likely to acquire STIs.

Table 2: Prevalence of Syphilis and Chlamydia Infections

Syphilis was the most prevalent infection (45%), followed by chlamydia (30%). Co-infection with both pathogens was observed in 17.5% of patients, demonstrating a significant overlap of STI pathogens among high-risk individuals.

Table 3: Di8stribution of Co-infection According to Sex

Males showed a higher rate of co-infection (22.7%) compared to females (11.1%). This may reflect increased exposure to high-risk sexual behavior among males attending the STD clinic.

Table 4: Risk Factors Associated with Co-infection

The most common risk factor among co-infected individuals was non-use of condoms (100%), followed closely by multiple sexual partners (85.7%). These behaviors significantly increase the likelihood of acquiring multiple STIs.

Table 5: Correlation between Age Group and Co-infection Rate

The highest co-infection rate was observed in the 26–35 years age group (23.5%), highlighting this age group as a particularly vulnerable population due to increased sexual activity and lower preventive practices.

This study evaluated the association between Chlamydia trachomatis infection and syphilis among 40 patients attending an STD clinic at a tertiary care hospital. The findings reveal a considerable prevalence of both infections individually, and a notable proportion (17.5%) of co-infections, underscoring the clinical and public health importance of STI co-occurrence. The overall prevalence of syphilis in this study (45%) aligns with previous studies which have reported resurgence in syphilis cases, particularly among high-risk populations (Fenton et al., 2008). This resurgence may be attributed to changing sexual behaviors, low condom usage, and poor STI awareness [15, 16].

Chlamydia infection was identified in 30% of the study population, which is consistent with the findings of Stamm (1999), who reported C. trachomatis as the most common bacterial STI globally. This pathogen often remains asymptomatic, especially in females, contributing to undiagnosed and untreated cases that perpetuate its transmission. Co-infection with both C. trachomatis and T. pallidum was observed in 17.5% of patients. This association has been reported in other studies as well. For instance, Hook & Handsfield (2008) noted that co-infections are common in individuals with high-risk sexual behaviors, making routine screening essential. Similarly, Peeling et al. (2004) highlighted the need for integrated diagnostic strategies to detect multiple STIs simultaneously due to overlapping risk factors [17-19].

Our findings also show a higher rate of co-infections among males (22.7%) compared to females (11.1%), which may reflect differences in healthcare-seeking behavior or risk exposure. This observation is similar to that of Kent et al. (2005), who reported higher STI rates among men due to lower condom use and greater engagement in casual sex. Patients aged 26–35 years had the highest rates of both single and dual infections. This is the most sexually active age group and is often underrepresented in health promotion programs. As noted by Workowski & Bolan (2015), targeted interventions for this demographic are essential for effective STI control [20-22].

Behavioral risk factors were significantly associated with co-infection in this study. All co-infected patients reported inconsistent or no condom use, and 85.7% had multiple sexual partners. These factors are well established in STI epidemiology literature. For example, Wasserheit (1992) emphasized the importance of behavioral interventions alongside clinical management in reducing STI transmission. Moreover, the use of nucleic acid amplification tests (NAAT) for chlamydia diagnosis and dual serological testing for syphilis in this study improved detection accuracy. The importance of NAAT has also been highlighted by Gaydos & Quinn (2000), who described its superior sensitivity and specificity in detecting asymptomatic C. trachomatis infections [23].

The co-occurrence of these infections necessitates a syndromic and integrated approach to STI management. Several authors have called for combined screening programs. For example, Ghanem et al. (2007) emphasized that the presence of one STI should prompt investigation for others, especially among high-risk individuals. Despite its relevance, this study had limitations including a small sample size and its cross-sectional design, which limits causal interpretation. Larger, multicentric studies are needed to validate these findings and explore molecular correlations between co-infecting pathogens [24].

This study highlights a significant prevalence of both Chlamydia trachomatis and Treponema pallidum infections among patients attending an STD clinic, with a notable proportion presenting with co-infections. The findings underscore the importance of routine dual screening for STIs, especially among sexually active individuals with high-risk behaviors such as multiple sexual partners and inconsistent condom use. The co-infection rate emphasizes the synergistic nature of sexually transmitted pathogens and the need for integrated diagnostic and treatment protocols. Early identification and management of co-infections are essential not only for individual patient care but also for reducing community-level transmission. Public health strategies should focus on increasing awareness, promoting safe sex practices, and implementing syndromic surveillance and comprehensive STI screening programs in high-risk populations. Future studies with larger sample sizes and longitudinal designs are recommended to establish causal relationships and assess treatment outcomes in co-infected individuals.

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