Table of Contents
Definition and Overview of Chlamydia
The family of Chlamydiaceae contains 3 human pathogens:
Chlamydiae are immobile, gram-negative bacteria. The cell wall does not contain a peptidoglycan layer, but lipopolysaccharides. Common to all chlamydiae is their complex reproduction cycle. Due to a defect in their own energy metabolism, chlamydiae are dependent on the metabolism of the host.
Chlamydiae have the ability to establish long-term associations with host cells. When an infected host cell is starved for various nutrients such as amino acids (for example, tryptophan), iron, or vitamins, this has a negative consequence for Chlamydia because the organism is dependent on the host cell for those nutrients. Long-term cohort studies indicate that approximately 50% of those infected clear within a year, 80% within 2 years, and 90% within 3 years.
Starved chlamydiae enter a persistent growth state wherein they stop cell division and become morphologically aberrant by increasing in size. Persistent organisms remain viable, as they are capable of returning to a normal growth state once conditions in host cells improve.
|Chlamydophila trachomatis||Chlamydophila psittaci||Chlamydophila pneumoniae|
|Host||Human||Birds (especially parrots, pigeons, and budgies)||Human|
|Diseases||Serotypes A-C: trachoma (a chronic recurrent disorder of the conjunctivae and cornea of the eye)||Ornithosis/Psittacosis||Respiratory infections|
|Serotypes D-K: sexually transmitted urogenital infections and infections of the conjunctiva, perinatal infections|
|Serotypes L1, L2, L3: Lymphogranuloma venereum|
Epidemiology of Chlamydia
Globally, as of 2013, sexually transmitted chlamydia affected approximately 141 million people (3.1% of the population). It is more common in women (3.8%) than in men (2.5%). In 2013, it resulted in about 1,100 deaths, down from 1,500 in 1990.
In the United States, about 1.4 million cases were reported in 2014. The centers for disease control and prevention estimates that if unreported cases are included, there are about 2.8 million each year. Chlamydia affects approximately 2% of young people. Infections are most common among those aged 15–25 years. The infection is more common in U.S. women than in U.S. men. In 2013, infections resulted in about 1,100 deaths. Chlamydia infection is the most common bacterial sexually transmitted infection in the United Kingdom.
Chlamydia causes more than 250,000 cases of epididymitis and 250,000–500,000 cases of pelvic inflammatory disease every year in the United States. Women infected with chlamydia are up to five times more likely to become infected with human immunodeficiency virus (HIV) if exposed.
Epidemiology of Chlamydophila trachomatis
- 30%–50% of all sterility is caused by chlamydia.
- 90% of all sterility caused by tube closure are caused by infections with Chlamydophila trachomatis.
- Every fourth woman infected with chlamydia is affected by subsequent sterility.
Chlamydophila trachomatis is one of the most common pathogens of sexually transmitted diseases worldwide. According to the World health organization (2001), 89 million new infections with genital chlamydia occur worldwide per year. Particularly affected are persons with frequently changing sexual partners and children of infected mothers.
In pregnant women, 2%–3% are populated with C. trachomatis. Their infants are at a 50% risk of infection at birth.
The incidence of lymphogranuloma venereum has decreased worldwide, but the sexually transmitted infection is still endemic in Asia, Africa, South America, and parts of the Caribbean.
Trachoma occurs almost exclusively in tropical countries under poor hygienic conditions. After cataracts, trachoma is the second most common cause of blindness in the world.
Age group: Young adults (15–22 years)
Epidemiology of Chlamydophila psittaci
Risk groups are:
- Bird owners
- Animal keepers and vets
- Employees in pet shops, poultry farms, and slaughterhouses
Transmission takes place by direct contact or by inhalation of dust particles or feces. Human-to-human transmission has not yet been demonstrated.
Epidemiology of Chlamydophila pneumoniae
C. Pneumoniae is a very common worldwide cause of respiratory infections in humans. According to seroepidemiological investigations, prevalence begins at preschool age and is more than 50% for men and more than 70% for men in the 6th decade.
A high prevalence of seropositivity is to be expected: Everyone has probably had contact with C. pneumoniae at least once in a lifetime. In fact, 5%–15% of all outpatient cases of acquired pneumonia are caused by C. pneumoniae.
Age group: 60–80 years
Etiology and Pathogenesis of Chlamydia
Etiology and pathogenesis of Chlamydophila trachomatis
|Serotypes A-C:||Infectious eye secretions, contaminated hands and towels (smear infection), flies|
|Serotypes D-K:||Sexually transmitted, perinatal|
|Serotypes L1-L3:||Sexually transmitted, causes lymphogranuloma venereum, perinatal|
The incubation period is approximately 1–3 weeks.
Etiology and pathogenesis of Chlamydophila psittaci
Psittaci is the only zoonotic human pathogen from the Chlamydiaceae family. The excitation sources are mainly birds (chickens, ducks, pigeons, and exotic birds).
Transfer takes place by direct contact or by inhalation of dust particles or feces containing pathogens.
The pathogens are partly infectious even after drying out for as long as 4 weeks. The incubation period of the ornithosis is about 1–4 weeks.
Etiology and pathogenesis of Chlamydophila pneumoniae
Pneumoniae is transmitted from person to person in an aerogenic pathway and by salivary contact.
The incubation time is estimated to be about 1–4 weeks.
Pneumoniae may remain persistent for a long time in the upper respiratory tract. It is likely that an infected person will infect others over a long period of time.
Clinical Findings of Chlamydia
Symptoms of Chlamydophila trachomatis infection
Urogenital chlamydia infection
The pathogens can persist for years undetected in the body and possibly even become chronic.
Clinical manifestation of Chlamydophila trachomatis in men and women
|Primary stage||Herpetiform papules, ulcer, rapid scalp-free healing|
|Secondary stage||Inguinal, painful lymphadenopathy (bubo)|
|Tertiary stage||Fibrotic transformation of the lymph nodes, inflammation with ulceration, obliteration of the lymphatics, edema of the genital/extremity (elephantiasis), fever, arthralgia, splenomegaly, erythema nodosum|
Newborn chlamydiosis presents as conjunctivitis (60%) or pneumonia (40%).
Typical symptoms of inclusion body conjunctivitis are:
- Purulent, mucopurulent, hemorrhagic inflammation of the conjunctiva
- Eyelid edema
- Follicular infiltration of the inner lid
- First on one side, then on both
- Mostly inconsequential healing
Typical symptoms of neonatal pneumonia are:
- Increased respiratory effort
- Snorkeling breathing sounds
- Refusal of food
- In severe cases, cyanosis
Follicular keratoconjunctivitis is caused by an initial infection. Repeated infections and, among others, bacterial superinfections lead to the formation of granulomas. The result of the granulomas is scarred shrinkage of the conjunctiva of the eyelids and entropion. Over time, the cornea changes and becomes turbid.
Symptoms and clinical findings of Chlamydophila psittaci infection
The typical symptoms of ornithosis include:
Fever, chills, and headaches
- Atypical and interstitial pneumonia
- Dry, persistent, nonproductive cough
- Extrapulmonary manifestations: hepatosplenomegaly (70% of patients), myocarditis, encephalitis, and exanthema
Symptoms of Chlamydophila pneumoniae infection
Frequently, the course of C. pneumoniae infections is asymptomatic.
- Acute and chronic infections of the upper respiratory tract (pharyngitis, sinusitis, and bronchitis)
- Outpatient pneumonia
- All symptoms of infection with C. psittaci can also occur in C. pneumoniae.
Complications of Chlamydia
Possible complications of chlamydia infection
|C. trachomatis||C. psittaci||C. pneumoniae|
|Arthritic disorders: joint inflammation||Myocarditis, pericarditis, endocarditis, thrombophlebitis, central nervous system involvement||Carditis, meningoradiculitis, erythema nodosum, reactive arthritis|
Smear for determination of chlamydia pathogens
The pathogen can be detected via:
- Trachoma: conjunctiva smear
- Eye infection: conjunctiva smear
- Urogenital infections: cervical or vaginal smear, possibly urethral smear
- Lymphogranuloma venereum: lymph node aspirate, ulcer smear
Direct detection of chlamydia antigens can be carried out by fluorescence-labeled antibodies or enzyme-linked immunosorbent assay. Alternative with high specificity and sensitivity is polymerase chain reaction (PCR).
The pathogen is detected indirectly by serum antibody determinations. It must be specifically investigated for the appropriate species (i.e., Chlamydophila trachomatis, C. pneumoniae, or C. psittaci). The diagnosis of genital chlamydia evolved rapidly from the 1990s through 2006. Nucleic acid amplification tests (NAATs), such as PCR, transcription-mediated amplification (TMA), and DNA strand displacement amplification (SDA), now are mainstays.
Differential Diagnosis of Chlamydia
Chlamydia infection and similar medical conditions
|C. trachomatis||C. psittaci||C. pneumoniae|
|Pathogens that trigger atypical pneumonia:||See C. psittaci|
Therapy of Chlamydia
The drugs of choice in chlamydia are antibiotics.
|C. trachomatis||C. pneumoniae, C. psittaci|
|Tetracyclines (doxycyclin)||Tetracyclines (doxycyclin)|
||Macrolides (erythromycin, azithromycin)|
|Duration of treatment: at least 14 days||Duration of treatment: 10–21 days|
Prevention of Chlamydia
Prevention measures for C. trachomatis
- Follow the principles of preventing sexually transmitted infections.
- Since January 1, 2008, many sexually active women younger than 25 years have been offered chlamydia screening (which may be reimbursed by health insurance).
- Trachoma: SAFE strategy, a global program for the elimination of trachoma from the World health organization: surgery + antibiotics + facial cleanliness + environmental improvement
Prevention measures for C. psittaci
- Compulsory reporting: compliance with the veterinary rules of disease control
- Early diagnosis and therapy in cases of suspicion
Which chlamydia infection is notifiable?