Chlamydia

Introduction

Chlamydia is the most common global sexually transmitted infection (STI) and is caused by the bacterium Chlamydia trachomatis. Chlamydia infection affects both males and females and can often be asymptomatic although in some people it can be the cause of significant morbidity and future complications.   

There are a wide variety of issues that Chlamydia infection can cause which can be split into the following categories: 

- Male only - conditions such as epididymitis and prostatitis. 

- Female predominance - conditions such as cervicitis, ectopic pregnancy, and pelvic inflammatory disease. 

- Both males and females - conditions that develop outside the reproductive tract such as conjunctivitis, pharyngitis, and lymphogranuloma venereum. 

The gold standard treatment for Chlamydia infection is with antibiotics, and prognosis is generally very good provided patients adhere to the antibiotic therapy (1).   

Aetiology/causes

Chlamydia is a bacterial infection caused by the bacteria Chlamydia trachomatis. This bacterium belongs to the chlamydophila genus and it is a gram-negative bacteria. Bacteria are classed as either gram positive or gram negative depending on their cell wall properties. Distinguishing between gram negative and positive bacteria helps target therapy to the most appropriate antibiotic. 

There are over 18 different variant strains of Chlamydia trachomatis, resulting in different diseases. These include: 

- Trachoma - This is the leading infectious cause of blindness worldwide and is an ocular illness resulting from conjunctivitis (chronic inflammation of the eye). Variants A-C tend to cause Trachoma. 

- Genital tract infections - Caused by variants D-K 

-  Lymphogranuloma venereum (LGV) - Variants L1 - L3 

The bacterium is transmitted between individuals in most cases via sexual intercourse in all of vaginal, anal, and oral sex. It can also be passed from an infected mother to their child during childbirth and result in neonatal chlamydia which can lead to complications for the newborn child. The main risk factors for chlamydia infection include: 

- Being highly sexually active with multiple partners 

- Regularly engaging in unprotected sex (no use of condoms) 

-  History of sex work or illicit drug use 

- Engaging in MSM activities (2). 

Diagnostic Approach

The main test used in the diagnosis of Chlamydial infection is the Nucleic Acid Amplification Test (NAAT). This involves taking a swab sample from either the penis or the vagina. This can be performed in two main ways:  

- Non-invasive sampling - Through sampling of the urine or vagina 

- Invasive sampling - A penile or endocervical swab 

Patients often prefer the non-invasive sampling as it is more comfortable, and recent studies have shown that both are equally as effective in detecting Chlamydia infection (5). In cases where rectal or pharyngeal chlamydia infection is suspected, a swab sample can be taken at the relevant sites. The NAAT works by amplifying the genetic material in the swab to a point where any Chlamydial genetic material can be picked up. 

Other investigations such as direct immunofluorescence and enzyme immunoassay can be used however the gold standard remains as Nucleic Acid Amplification testing. It is worth noting that even if the NAAT is negative yet the symptoms and history fit the description of chlamydia, treatment may be recommended anyway to cover any undetectable Chlamydia. 

In the UK it is recommended that a full STI (sexually transmitted infection) workup is performed in patients with suspected Chlamydial infection. This is because co-infection with other STIs such as HIV, gonorrhoea, and syphilis, is common. Furthermore, it is recommended to patients who test positive for Chlamydia that their partner also be tested in case they might be asymptomatic. 

Before commencing treatment, you may be asked to take a pregnancy test as certain antibiotics such as doxycycline are not suitable in pregnancy and can lead to newborn complications (6).   

Epidemiology

Chlamydia is the most common sexually transmitted infection worldwide, affecting 4.2% of women and 2.7% of men worldwide. Since most people are asymptomatic, it follows that this may be an underestimate. Infections are more common in people under the age of 25 due to increased high risk sexual behavior practices and has a higher prevalence in females compared to men (3).   

Management Plan

Chlamydia is caused by bacterial infection with Chlamydia trachomatis, and hence antibiotics are the main treatment of choice. Treatment is important even in asymptomatic individuals as it can be used to prevent the occurrence of complications such as Pelvic Inflammatory disease and infertility. Furthermore, treatment helps to reduce transmission rates in the community which is especially important due to the high and growing prevalence of Chlamydia infection. 

There are a variety of different antibiotics which can be used to treat Chlamydia infection which include: 

- Azithromycin - 1g taken orally as a single dose 

- Doxycycline - 100mg taken twice daily for 7 days 

- Other alternatives such as erythromycin, levofloxacin, and ofloxacin 

Azithromycin is often used and preferred by patients due to it being required to be administered only once as a single dose. Doxycycline should be avoided in pregnancy and hence alternatives such as azithromycin/erythromycin can be offered instead. 

Alongside appropriate antibiotic treatment, safe sex education and advice regarding protecting should also be given to patients; particularly important in high risk groups such as MSM and young people. Patients should be instructed to avoid sexual activity for one week as they may still be infectious. Ideally you should have retesting a few weeks after treatment to ensure that the Chlamydia has been successfully cleared. Any co-infections e.g. gonorrhoea/syphilis can also be treated with appropriate antibiotics at the same time as treating chlamydia (7).  

Prognosis

Most patients have asymptomatic disease, and for symptomatic patients, antibiotics have a 95% cure rate provided that the patient adheres to their antibiotic therapy (1). However, reinfection with Chlamydia is common, particularly in high-risk populations. Repetitive infection with chlamydia can lead to chronic pelvic pain alongside infertility associated with scarring of the fallopian tubes.