Chlamydia Disease

BASICS

DESCRIPTION

Chlamydia pneumoniae, an obligate intracellular bacteria, has been established as an important cause of adult respiratory disease including pneumonia, bronchitis, sinusitis and pharyngitis. There is no animal reservoir.

System(s) affected: Pulmonary
Genetics: No known genetic predisposition
Incidence/Prevalence in USA: Estimated incidence of 100 to 200 cases of pneumonia/100,000/year. Accounts for 6 to 12% of pneumonias and 3 to 6% of bronchitis cases. Studies to date have included relatively few geographic areas. Numbers do not necessarily apply to all areas. Incidence of subclinical infection much greater.
Predominant age: Uncommon in children under 5 years. Pneumonia more common in elderly.
Predominant sex: Male > Female (10-25% more)

SIGNS AND SYMPTOMS

70% to 90% of infections are mild or subclinical
Onset often gradual with delayed presentation
Sore throat and hoarseness may precede cough by a week or more, giving biphasic appearance to illness
Cough (often prominent with scant sputum)
Fever (usually early in illness)
Sore throat
Rhinitis
Headache
Malaise
Hoarseness
Sinus congestion
Rales, rhonchi or wheezing
Pharyngeal erythema
Sinus tenderness

CAUSES

Infection with C. pneumoniae

RISK FACTORS

Outbreaks have occurred among groups of military recruits, university students, students and nursing home residents. Incubation period is approximately 30 days. Sporadic cases often have no apparent source of exposure. No known animal hosts.

DIAGNOSIS

LABORATORY

Leukocyte count usually normal or low
Sedimentation rate often moderately elevated
Sputum usually negative by gram stain and routine culture

Drugs that may alter lab results: Early treatment with tetracycline may blunt IgG antibody response
Disorders that may alter lab results: None known

PATHOLOGICAL FINDINGS

Not usually available

SPECIAL TESTS

Most easily cultured in HL or HEp2 cells
Complement fixation (CF) serology for Chlamydia widely available but cannot distinguish C. pneumoniae infection from C. psittaci
Microimmunofluorescence (MIF) test, which is specific for C. pneumoniae, is available at some research institutions or commercially (from American Medical Laboratories, MRL Diagnostics)
Every effort should be made to obtain paired sera. The convalescent sera should be obtained 3 weeks after disease onset.
Four-fold antibody rise diagnostic of acute infection
Presence of IgM antibody (³ 1:16) or of high IgG antibody titers (³ 1:512) by MIF suggests a recent or acute infection
Polymerase chain reaction (PCR) from pharyngeal swab or bronchoalveolar lavage specimen

IMAGING

Chest radiograph may be abnormal even in clinically mild disease
Variable radiographic abnormalities include unilateral and bilateral infiltrates and pleural effusions. Single, subsegmental infiltrate is common.

DIAGNOSTIC PROCEDURES

Definite diagnosis requires positive serology or culture

TREATMENT

APPROPRIATE HEALTH CARE

Usually outpatient
Patients with severe pneumonia or coexisting illness may require hospitalization

GENERAL MEASURES

No specific general measures

SURGICAL MEASURES

N/A

ACTIVITY

Usually reduced during illness

DIET

No special diet

PATIENT EDUCATION

Griffith HW: Instructions for Patients; Philadelphia, W.B. Saunders Co.
For a listing of sources for patient education materials favorably reviewed on this topic, physicians may contact: American Academy of Family Physicians Foundation, P.O. Box 8418, Kansas City, MO 64114, (800)274-2237, ext. 4400

FOLLOW UP

PREVENTION/AVOIDANCE

Transmission presumably via respiratory secretions. Avoid infected persons.
Hand washing

POSSIBLE COMPLICATIONS

Reactive airway disease
Erythema nodosum
Otitis media
Endocarditis
Myocarditis
Pericarditis
Sarcoidosis
Meningitis
Reactive arthritis
Mild bacterial infection
Associated with atherosclerotic disease (causal relationship is unknown)

EXPECTED COURSE AND PROGNOSIS

Resolution of cough and malaise often requires several weeks or longer
Chronic bronchospastic disease has been reported following acute infection
Persistent or relapsed symptoms may respond to second course of antibiotics

MISCELLANEOUS

ASSOCIATED CONDITIONS

Chronic obstructive pulmonary disease
HIV infection
Cystic fibrosis

AGE-RELATED FACTORS

Pediatric: Usually milder disease in children
Geriatric: Usually more severe in older adults
Others: None known

PREGNANCY

No known special risks
Tetracyclines contraindicated

OTHER NOTES

No significant seasonal variation
Most cases occur sporadically, though intrafamilial spread also occurs
Infection in debilitated or hospitalized patients can be severe
Reinfection is possible
Individuals have been reported who are persistently culture positive despite antibiotic treatment
Country-wide epidemics of C. pneumoniae infections have been documented in the Scandinavian countries
Found in atherosclerotic plaque in coronary arteries, carotid arteries and the aorta. Also associated with MI and stroke in seroepidemiologic studies. Role in atherogenesis in humans not established. Clinical significance not known.

ABBREVIATIONS

N/A

Clinical Investigations

ROLE OF HOMOEOPATHY

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