Chlamydia trachomatis

Chlamydia trachomatis is an obligate intracellular bacterium responsible for a significant portion of sexually transmitted infections (STIs) worldwide, as well as various ocular diseases. 

It primarily targets the columnar epithelium of the cervix, urethra, rectum, lungs, and eyes, leading to conditions such as trachoma, the leading cause of preventable blindness, and genital infections, which are often asymptomatic but can result in serious complications like pelvic inflammatory disease and infertility. 

C. trachomatis relies on the host for metabolic needs, evading immune defenses and manipulating host cells to create a favorable environment for replication. 

With no effective vaccine available, antibiotic treatment remains essential, although concerns about resistance are emerging. 

Advances in molecular diagnostics, particularly nucleic acid amplification tests (NAATs), have greatly improved the detection and management of C. trachomatis infections, making these tests the gold standard for diagnosis across various clinical presentations.

What is Chlamydia spp.?

Chlamydia spp. are obligate intracellular bacteria that cause various diseases in humans and animals, including atypical pneumonia, eye infections like trachoma (the leading cause of bacterial blindness globally), and genital infections, making it the most common cause of sexually transmitted diseases (STDs) [5.]. 

These pathogens replicate within a specialized membrane compartment in host cells, employing secreted effectors to survive in the hostile intracellular environment [11.].

‍Chlamydia spp. depend on the host for metabolic requirements while evading immune defenses [11.]. They manipulate host cytoskeletal and membrane trafficking pathways to create a replication-competent niche [26.].

With no effective vaccine available, antibiotic treatment is essential, but concerns about tetracycline resistance have emerged [7., 11.].

Host defense peptides (HDPs) show promise as alternative antimicrobial agents, with C. trachomatis being particularly sensitive to their effects [7.]. 

Recent advances in chlamydial proteomics and genetics have improved our understanding of Chlamydia-host interactions, paving the way for new research avenues [11.].

What is Chlamydia trachomatis? 

Chlamydia trachomatis is a leading cause of sexually transmitted infections (STIs) globally, affecting millions each year [21., 28.].

This intracellular bacterium targets the columnar epithelium of the cervix, urethra, rectum, lungs, and eyes, leading to a range of infections. 

Ocular Infections

Ocular infections caused by C. trachomatis include trachoma, the leading preventable cause of blindness worldwide [18., 21.]. Newborns can acquire conjunctivitis during childbirth if the mother is infected [28.]. 

Symptoms of C. trachomatis Ocular Infections

Symptoms of ocular infections vary from mild conjunctivitis to severe conditions like trachoma, with common signs including follicular conjunctival reaction and mucoid discharge [17., 6.]. 

Genital Infections

C. trachomatis genital infections are also widespread, often asymptomatic, but can lead to urethritis, cervicitis, epididymitis, and severe complications like pelvic inflammatory disease and infertility in women [31., 32.]. 

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Transmission of C. trachomatis occurs through sexual contact or from mother to infant during childbirth, contributing to its persistent spread in populations [4., 33.]. 

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Symptoms of C. trachomatis Genital Infections

The C. trachomatis genital infection often remains asymptomatic in approximately 50% of infected men and 70% of infected women [31.].

When symptomatic, it can manifest as urethritis, cervicitis, or epididymitis [32.]. In women, untreated infections can lead to serious complications such as pelvic inflammatory disease, ectopic pregnancy, and tubal factor infertility [32.].

The asymptomatic nature of many infections contributes to sustained transmission within communities [33.]. 

When symptoms are present, chlamydial genital infections can present with a variety of symptoms in both females and males. 

In females, when symptoms are present, they may include vaginal discharge, bleeding after sexual intercourse or between menstrual periods, lower abdominal pain, pelvic pain, painful intercourse, and dysuria (painful urination) [8.].

In males, symptoms, if present, can include dysuria, urethral discharge, and scrotal pain or swelling [8.].

Laboratory Testing for Chlamydia spp.

Testing Recommendations for Chlamydia spp. Infections

The CDC's guidelines for testing Chlamydia trachomatis emphasize nucleic acid amplification tests (NAATs) as the preferred diagnostic tool due to their superior sensitivity, specificity, and versatility across various specimen types [20., 23.]. 

The polymerase chain reaction (PCR) test is one example of this type of testing [27.].

NAATs are recommended for detecting genital, ocular, and respiratory chlamydial infections, as well as anorectal and oropharyngeal infections, except in specific cases such as child sexual assault or potential treatment failures, where culture and susceptibility testing may be required [23.].

Testing for Ocular Chlamydial Infections

In diagnosing ocular chlamydial infections, while tissue culture is a traditional method, newer point-of-care dipstick assays have proven more accurate than clinical signs for identifying ocular trachoma [10.]. 

Rapid diagnostic tests based on PCR also show promise for effective point-of-care testing, enhancing the ability to detect and manage chlamydial infections.

Testing for Genital Chlamydia Infections

For genital infections, which are often asymptomatic, NAATs are considered the gold standard, capable of detecting the infection in urine, vaginal swabs, and other mucosal swabs. 

Although culture was once the gold standard for diagnosing chlamydia, it is no longer recommended for routine use due to its lower sensitivity, longer turnaround time, and technical complexity, but it remains essential in certain cases like pediatric or medico-legal situations [8., 20., 23.].

Sample Collection

Nucleic acid amplification tests (NAATs) are often performed on urine and swab samples. 

These tests can be performed on non-invasive samples such as first-catch urine (FCU) and self-obtained vaginal swabs (SVS), making them more acceptable to patients than traditional invasive methods [16.].

To diagnose an ocular infection, an ocular swab sample is typically taken from the conjunctiva (or other relevant site if testing for non-ocular infections) using a sterile swab [15.].

Chlamydia Trachomatis Treatment

C. trachomatis Genital Infection Treatments [8.].

The CDC's 2021 guidelines recommend doxycycline 100 mg orally twice daily for 7 days as the first-line treatment for Chlamydia trachomatis genital infections. 

For pregnant patients, the preferred treatment is a single dose of azithromycin 1 g orally. 

Patients should abstain from sexual intercourse until completing the 7-day treatment or for 7 days after the single-dose regimen, and until their sexual partners have been treated. 

Routine test of cure is not necessary except in cases of pregnancy, suspected nonadherence, persistent symptoms, or suspected reinfection. 

Screening for reinfection is advised for all patients 3 months after treatment.

Trachoma Treatments [10.]

Oral azithromycin is the treatment of choice. 

Antibiotics may reduce active trachoma, but evidence is not consistent.