101 CHLAMYDIAL INFECTIONS
Harrison’s Manual of Medicine
C. Trachomatis Genital Infections and Lymphogranuloma Venereum
Trachoma and Adult Inclusion Conjunctivitis
C. pneumoniae Infections
The genus Chlamydia contains three species: C. psittaci, C. trachomatis, and C. pneumoniae (formerly called TWAR). Chlamydiae are obligate intracellular bacteria. Different serovars are associated with different clinical syndromes. Chlamydiae cause conjunctival, genital, and respiratory infections.
C. TRACHOMATIS GENITAL INFECTIONS AND LYMPHOGRANULOMA VENEREUM
See Chap. 83.
TRACHOMA AND ADULT INCLUSION CONJUNCTIVITIS
EPIDEMIOLOGY In trachoma-endemic areas, C. trachomatis (usually serovar A, B, Ba, or C) is the major preventable cause of blindness. Transmission is from eye to eye via hands, flies, or fomites. In nonendemic areas, disease is usually confined to inclusion conjunctivitis and is caused by serovars D–K, which are transmitted via infected secretions from the genital tract to the eye.
CLINICAL MANIFESTATIONS Endemic trachoma usually begins as conjunctivitis with small lymphoid follicles in children <2 years old. It progresses to corneal involvement with inflammatory leukocytic infiltrations and superficial vascularization (pannus formation). Conjunctival scarring leads to distortion of the eyelids, inturned lashes that abrade and ulcerate the corneal epithelium, and subsequently corneal scarring and blindness. Eye infection with genital strains usually causes an acute onset of unilateral follicular conjunctivitis and preauricular lymphadenopathy in sexually active young adults.
DIAGNOSIS Classic trachoma is usually diagnosed clinically if two of the following signs are present: (1) lymphoid follicles on the upper tarsal conjunctiva, (2) typical conjunctival scarring, (3) vascular pannus, and (4) limbal follicles. The most sensitive laboratory tests are isolation of the organism in cell culture, newer antigen detection tests, and chlamydial polymerase chain reaction. Intracytoplasmic inclusions on Giemsa-stained conjunctival smears are diagnostic but are less sensitive. For adult inclusion conjunctivitis, culture or Giemsa or immunofluorescent staining of conjunctival smears is used and should be accompanied by genital examinations and cultures. Serum antibody tests are not diagnostic.
Therapy includes the topical application of tetracycline or erythromycin ointment for 21–60 d. Alternatively, tetracycline or erythromycin (500 mg qid PO for 3 weeks) may be used in adults and erythromycin (50 mg/kg PO daily for 3 weeks) in children. Treatment of sexual partners is important in genitally acquired infection. Topical therapy is not necessary if oral antibiotics are used.
EPIDEMIOLOGY Psittacosis (infection with C. psittaci) is transmitted via the respiratory route from many avian species, including psittacine birds (parrots, parakeets), pigeons, ducks, turkeys, chickens, and other birds. Occasionally, infection has resulted from contact with the environment previously occupied by an infected bird rather than from direct exposure to birds. Infected birds may not manifest symptoms. The incubation period is 7–14 d or longer.
CLINICAL MANIFESTATIONS Prominent headache, fevers increasing over a 3- to 4-d period, and a dry hacking cough occurring as late as 5 d after fevers begin are the most common manifestations. Pulmonary symptoms are usually more prominent than signs. Other symptoms may include myalgias, lethargy, agitation, mental depression (progressing to stupor or coma in severe cases), and GI symptoms such as abdominal pain, vomiting, and diarrhea. Splenomegaly is found in 10–70% of cases. Psittacosis should be considered strongly in pts with acute pneumonitis and splenomegaly.
DIAGNOSIS CXRs usually show diffuse, patchy infiltrates but may yield a variety of findings. The WBC count, ESR, and LFTs are usually normal. The diagnosis can be made only by isolating the organism (which is difficult in the laboratory) or by demonstrating a fourfold rise in CF antibody. Early antibiotic treatment may delay the convalescent antibody response by weeks or months.
C. psittaci, C. pneumoniae, and C. trachomatis share a genus-specific “group” antigen; a cross-reaction due to this antigen is the basis of the CF test. If there is doubt as to the interpretation, a micro-IF test can be used to distinguish the organisms based on different outer-membrane proteins.
Tetracycline (500 mg qid) usually leads to defervescence and alleviation of symptoms in 24–48 h. Treatment should be continued for at least 7–14 d after fever abates to avoid relapse. Erythromycin can be used for pts allergic to or intolerant of tetracycline.
C. PNEUMONIAE INFECTIONS
EPIDEMIOLOGY Serologic studies indicate that C. pneumoniae infections are ubiquitous. Seroprevalence rates in adult populations exceed 40%. The route of transmission appears to be from person to person. Primary infection seems to occur in young adults, with less severe reinfection episodes in older adults. Epidemiologic studies have demonstrated an association between serologic evidence of C. pneumoniae infection and atherosclerotic disease of the coronary and other arteries. C. pneumoniae has been identified in atherosclerotic plaques by several techniques. Antimicrobial treatment of infected animals has been shown to reduce the increased risk of atherosclerosis. Larger trials in humans are needed to determine more definitively whether antibiotics affect the risk of atherosclerosis.
CLINICAL MANIFESTATIONS The clinical spectrum includes acute pharyngitis, sinusitis, bronchitis, and pneumonitis. Upper respiratory tract symptoms usually precede fever and nonproductive cough. The pneumonitis often resembles Mycoplasma pneumoniae pneumonia. Pulmonary findings generally are minimal. Leukocytosis is typically absent. CXRs generally show small segmental infiltrates.
DIAGNOSIS Diagnosis is difficult because culture and antigen detection techniques are not available. A rise in CF antibody between acute- and convalescent-phase serum samples can allow a retrospective diagnosis but does not distinguish C. pneumoniae from C. trachomatis and C. psittaci. The micro-IF test can be used to make these distinctions.
The recommended therapy consists of erythromycin or tetracycline (500 mg qid PO) for 10–14 d. Other macrolides, such as azithromycin, and some fluoroquinolones, such as levofloxacin, also appear to be effective.
For a more detailed discussion, see Stamm WE: Chlamydial Infections, Chap. 179, p. 1075, in HPIM-15.