Navjyot K. Vidwan and Mary Allen Staat
The name chlamydiae is derived from the Greek word “chlamys” representing the cloak-like mantle worn by men in Ancient Greece.1Upon initial discovery, chlamydiae were thought to be intracellular pathogens that cloaked the nucleus of an infected cell. Scientists have since discovered that chlamydiae are nonmotile, gram-negative, obligatory intracellular bacteria.
The four recognized species within the genus of Chlamydia are C psittaci, C pneumoniae, and C trachomatis, all of which cause disease in humans (Table 259-1), and C pecorum which causes disease in pigs, sheep, and cattle, but not in humans.1Chlamydia psittaci is responsible for psittacosis (ornithosis). Chlamydia pneumoniae causes pneumonia, pharyngitis, and bronchitis. Chlamydia trachomatis has at least 15 different serotypes, known as serovars, that are associated with a spectrum of diseases. Serovars A to C are associated with trachoma, D to K with genital infections, and L1 to L3 with lymphogranuloma venereum. The most common infections of C trachomatis are those of the genital tract which present as urethritis and epididymitis in the male and cervicitis and salpingitis in the female. Neonates can present with conjunctivitis and pneumonia infection acquired by passage through an infected mother’s genital tract.
Chlamydia psittaci or the new proposed name Chlamydophila psittaci is an obligate intracellular, gram-negative bacterium.2 Psittacosis is contracted by human beings from infected birds and their contaminated droppings; however, mammals such as sheep, cattle, goats, and cats have also been shown to transmit infection to humans.2-8 The birds show a spectrum of disease as they can have no evidence of disease or could appear ill and die. Birds transmit the disease to humans by the respiratory route from feces, fecal dust, or secretions of infected animals. The incidence among poultry workers, pet shop workers, and exotic bird importers can be high. Person-to-person transmission is also possible, and health care personnel can acquire the disease from patients.
Table 259-1. Chlamydial Infections in Humans
C psittaci should be included in the differential diagnosis for atypical pneumonia and is difficult to distinguish between C psittaci pneumonia and other causes of community-acquired pneumonia such as Legionella pneumophilia, Mycoplasma pneumoniae, or Coxiella burnetii. The onset of symptoms of psittacosis typically present 5 to 10 days after exposure.2 Clinically, two main forms of the infection occur. The more common form presents with symptoms of fever, chills, headache, and pneumonia; less commonly, the illness may present as a severe influenza-like illness or mild case of typhoid feve. If pneumonia is present, as it is in most patients, the cough is prominent and the sputum may be blood-streaked. Delay in diagnosis and treatment can lead to septic shock, multiorgan failure, pancreatitis, and myocarditis, which are all severe complications of the disease.
A diagnosis of psittacosis can be confirmed by one of three confirmatory laboratory studies combined with a history of potential exposure and a clinical history suggestive of the illness.10 The first laboratory method is culture from respiratory secretions yielding positive growth of C psittaci. The second method is using complement fixation (CF) or microimmunofluorescence (MIF) techniques to demonstrate a 4-fold or greater increase between paired acute- and convalescent-phase serum specimens collected 2 weeks apart. The third method is detection of IgM antibody against C psittaci by MIF (to a reciprocal titer of greater than or equal to 16). Elevated CF titers also may result from C pneumoniae and C trachomatis infections; therefore, MIF assays should be used to distinguish C psittaci infection from infection with other Chlamydial species.
TREATMENT AND PREVENTION
The treatment of choice for C psittaci infection is tetracycline 500 mg every 6 hours given orally for 10 to 14 days.2 Alternatively, tetracycline can be given parenterally if the oral medication cannot be given. Clinical improvement occurs in 48 to 72 hours, and treatment should continue for at least 10 to 14 days after the fever resolves to avoid relapse. Erythromycin is recommended for children less than 8 years of age and for pregnant women. Azithromycin, clarithromycin, and chloramphenicol are also effective.
The incidence of psitticosis has decreased since the implementation of importation controls of parrots and other exotic birds into the United States. Confirmed cases of psitticosis should be reported to the local or state health department.2 Standard precautions are appropriate for infection control.2,10
Chlamydia pneumoniae, or the proposed new name, Chlamydophila pneumoniae, is a common respiratory pathogen worldwide.11 The organism is antigenically distinct from the other two Chlamydia species of Chlamydia trachomatis and Chlamydia psittaci and has been classified as a separate and third species under the name Chlamydia pneumoniae or Chlamydophilia pneumoniae.11
Over the past 2 decades with improvements in diagnostics and epidemiologic studies, C pneumoniae was found to be a common and important cause of community-acquired pneumonia in children and adults.11 It is transmitted by aerosolized respiratory secretions from person-to-person contact. The average incubation period is 21 days.11
In the United States, about 50% of adults have evidence of past infection with C pneumoniae by age 20.11 Hospital-based studies have shown that C pneumoniae is responsible for 2% to 10% of community-acquired pneumonia in adults.13 In children, studies using the microimmunofluorescence method show increasing C pneumoniae antibody prevalence rates beginning in school-age children which reach 30% to 45% in adolescents.14 Small epidemics have also been described in colleges and among military recruits.13,15
C pneumoniae can cause upper and lower respiratory tract infections; the most common clinical manifestations of C pneumoniae include pneumonia and bronchitis.16 In studies examining the etiology of pediatric community acquired pneumonia worldwide, C pneumoniae was found in 3% to 14% of cases.17-20 In addition to pneumonia, acute otitis media, rhinitis, sinusitis, and pharyngitis can also be seen.
The most common symptoms include cough, rhinitis, fever, and sore throat, followed by headache, dyspnea, and earache (eTable 259.1 ).15 Clinical findings may resemble influenza. The initial rhinitis and pharyngitis are followed by the development of a chronic cough with bronchitis or pneumonia that can last for several weeks. In addition to a prominent cough, the patient may have rales, rhonchi, or wheezing. A radiograph of the chest typically shows patchy infiltrates. The overall nature of this infection is typically nonspecific and resembles other etiologic agents of atypical pneumonia such as Legionella or Mycoplasma pneumoniae (see Chapters 264 and 273).
C pneumoniae may be identified by culture, polymerase chain reaction (PCR), antigen detection, and serologic testing; however, no reliable commercial diagnostic tests have been approved by the US Food and Drug Administration for clinical use.11 In the clinical setting, serology is the testing of choice. The microimmunofluorescence (MIF) antibody test is the most sensitive and specific serologic test for acute infection.11 IgM antibodies appear within 2 to 3 weeks after onset of illness followed by IgG antibodies, which peak 6 to 8 weeks after onset.11 A confirmatory test will show an IgM titer of 1:16 or greater or a 4-fold rise in IgG titer when comparing acute to convalescent titers.
TREATMENT AND PREVENTION
Macrolides (erythromycin, azithromycin, and clarithromycin) and tetracyclines are effective for treatment of C pneumoniae and are therefore recommended as first-line treatment options.11 One study showed a 79% eradication rate of C pneumoniae from the nasopharynx after a 10-day course of clarithromycin and an 86% eradication rate with a 10-day course of erythromycin.23 The newer fluoroquinolones such as levofloxacin and moxifloxacin which have been shown to be effective.24 A duration of 5 to 10 days may be effective, but given the tendency for prolonged symptoms and recurrence of symptoms, treatment of 14 to 21 days is suggested.11
Chlamydia trachomatis is the leading bacterial pathogen of sexually transmitted infections worldwide. Sexually transmitted infections are discussed in Chapter 233, including a detailed discussion of the diagnosis and management of nongonococcal urethritis, epididymitis, and endocervitis due to Chlamydia trachomatis. Lymphogranuloma venereum, a sexually transmitted disease, and other disorders caused by Chlamydia trachomatis are discussed below.
CLINICAL FEATURES, TREATMENT, AND PREVENTION BY SITE
Lymphogranuloma venereum is a sexually transmitted chlamydial disease caused by serovars L1 to L3. The incidence of this disease has declined in the United States, but it is still quite prevalent in tropical and subtropical areas.32Tender, unilateral inguinal or femoral lymphadenopathy is the most common clinical manifestation of LGV among heterosexual men.30,32 Women and homosexually active men may have proctocolitis or involvement of perirectal or perianal lymphatic tissues resulting in fistulas and strictures.32 The disease is rare in children and infrequently seen in adolescents.
LGV can manifest as acute or chronic disease because it is a disease of the lymphatic tissue.33 First, there is a primary lesion, which is transient and clinically mild, usually appears as a papule or a shallow ulcer on the penis or vaginal wall, and generally heals without scar formation (eFig. 259.1 ). Systemic manifestations can include fever, chills, and anorexia. In the secondary stage, occurring 2 to 6 weeks after the primary lesion, there is pronounced lymphadenitis or lymphadenopathy in the inguinal area (Fig. 259-1). The nodes are large and often fluctuant, forming buboes. This stage of disease is found predominantly in males. In the tertiary stage, which is not necessarily preceded by lymphadenopathy, there is a chronic inflammatory response with fibrosis which can result as strictures in the anal, rectal, and vaginal areas. Once suspected, the diagnosis can be best confirmed by complement-fixation or microimmunofluorescence tests, using the specific antigens. The treatment of choice is doxycycline 100 mg orally twice a day for 21 days (eTable 259.2 ).30 For children less than 8 years of age, erythromycin base (2 grams per day in 4 divided doses for 21 days) is recommended.32 Some experts recommend a 1 gram dose of azithromycin weekly for 3 weeks; however, there are minimal data using this regimen.32
Perinatally Transmitted Infections
C trachomatis can be transmitted to newborns and can cause purulent conjunctivitis and pneumonia. Notably, 50% to 75% of infants born to infected mothers become infected at one or more sites including the conjunctiva, nasopharynx, vagina, and rectum.33-35 The most frequent site of perinatally acquired chlamydia infection in neonates is the nasopharynx with rates as high as 70% in exposed infants. Furthermore, in those with nasopharyngeal infection, chlamydia pneumonia develops in 30% of infants.35
Newborn Inclusion Conjunctivitis
Acute purulent conjunctivitis in the newborn, also known as inclusion blenorrhea, has an incubation period from 5 to 12 days.32 There is a watery discharge from the eyes that becomes progressively more purulent, with swelling of the eyelids. Left untreated, lymphoid follicles and a membranous conjunctivitis can develop and persist for weeks or months. The conjunctivitis should be distinguished from other pyogenic bacterial infections (N gonorrhoeae and S aureus,) and from chemical conjunctivitis resulting from silver nitrate prophylaxis. N gonorrhoeae conjunctivitis typically occurs in the first 2 to 5 days after birth, whereas chlamydia conjunctivitis occurs later. It may be difficult to distinguish between the two clinically.
FIGURE 259-1. Lymphogranuloma venereum: striking tender lymphadenopathy occurring at the femoral and inguinal lymph nodes, separated by a groove made by Poupart’s ligament. This “sign-of-the-groove” is not considered specific for LGV; for example, lymphomas may present with this sign. (From Fauci AS, Braunwald E, Kasper DL et al (eds). Harrison’s Principles of Internal Medicine. 17th ed. New York: McGraw-Hill, 2008.)
Conjunctival cultures on blood and chocolate agar media will identify bacterial pathogens. The most useful diagnostic method is examination of Giemsa-stained conjunctival scrapings for inclusion bodies. Because chlamydia are obligate intracellular agents, the conjunctivae must be scraped rather than swabbed to obtain an adequate specimen. The infection can also be diagnosed by culture, immunofluorescence, or enzyme-linked immunosorbent assay (ELISA).
Topical treatment of neonatal conjunctivitis is not recommended because local eye treatment does not prevent or clear nasopharyngeal carriage and, thus, the further risk of developing pneumonia or repeated episodes of conjunctivitis.35
Optimal management is oral erythromycin, 50 mg/kg per day in 4 divided doses daily for 14 days.30 Because treatment is not 100% effective, a second course may be needed.32
Attempts to provide prophylaxis through antibiotic regimens administered topically to the eyes shortly after delivery has not been 100% effective with either erythromycin or tetracycline because neither eliminates nasopharyngeal colonization and further risk for pneumonia. Prevention can be achieved only by identifying and treating pregnant women prior to delivery.
Chlamydial Pneumonia of Infancy
C trachomatis pneumonia usually occurs during an infant’s first 4 months of life. Chlamydial pneumonia is seen in 30% of infants with nasopharyngeal infection.34,35 The classic symptoms of chlamydial pneumonia of infancy include a staccato cough that worsens over time; nasal obstruction; and a respiratory exam showing tachypnea or rales, but no wheezing.36 Fever is usually not present (eTable 259.3 ).37The infant may appear mildly to moderately ill. On chest radiological imaging, hyperinflation with bilateral interstitial infiltrates is the classic finding. The recommended treatment is azithromycin (20 mg/kg orally once daily for 3 days) or erythromycin base or ethylsuccinate (50 mg/kg per day in 4 divided doses) for 14 days.30,32 The diagnosis of chlamydial pneumonia (or conjunctivitis) in a neonate is clear evidence of maternal infection, and thus the mother and her partner should be treated.
Trachoma is responsible for about 3% of blindness worldwide along with cataracts, glaucoma, and diabetic retinopathy. Approximately 1.3 million people worldwide are blind from trachoma, and 84 million people have active trachoma infection.38,39 The global distribution is shown in eFigure 259.2 . Trachoma is caused by Chlamydia trachomatis which spreads through contact with eye discharge from the infected person (on towels, handkerchiefs, fingers, etc.) and through transmission by eye-seeking flies. It is associated with poverty and unsanitary living conditions. In hyperendemic areas active disease is most common in pre-school children with prevalence rates as high as 60–90%.
Active trachoma starts as the presence of follicles on the tarsal conjunctiva.40 The follicles heal with necrosis and cause severe conjunctival scarring. This in turn produces lacrimal stenosis, lid distortion, and entropion and trichiasis. The chronic keratoconjunctivitis then progresses to severe scarring of the cornea and finally to blindness. The end result occurs after many years of active disease. The World Health Organization (WHO) developed a grading system including at least 2 of the following 4 criteria to diagnose trachoma: lymphoid follicles on the upper tarsal conjunctiva, typical conjunctival scarring, vascular pannus, and limbal follicles.39,40 (See: http://www.who.int/ncd/vision2020_action plan/documents/Simplifiedgradingoftrachoma.PDF, accessed August 8, 2010.)
The diagnosis of trachoma is usually clinical but can be confirmed by examining conjunctival scrapings with a Giemsa stain or immunofluorescence demonstrating the infective particles. Chlamydia can also be cultured. Serologic tests are not very helpful, but they are important epidemiologic tools to assess prevalence.
The World Health Organization (WHO) has a goal of global elimination of blindness attributable to trachoma by 2020 by utilizing 4 prevention and treatment methods: surgery for trichiasis, antibiotics, face washing, and environmental improvement (SAFE). Antibiotic treatment is prolonged either with topical antibiotics or oral agents.32 Mass antibiotic treatment with azithromycin once or twice a year or topical tetracycline twice daily for 6 weeks are effective in treating large populations in areas of high endemicity.41 The treatment and control of trachoma are complex and involve important international health issues as outlined in the WHO trachoma control guide for program managers available at: http://www.who.int/blindness/publications/tcm%20who_pbd_get_06_1.pdf (accessed August 8, 2010).