Chlamydia Pneumoniae

Description of Medical Condition

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. Numbers do not necessarily apply to all areas. Incidence of subclinical infection much greater.

Predominant age: Less common in children under 5 years. Pneumonia more common in elderly.

Predominant sex: Male > Female (10-25% more)

Medical Symptoms and Signs of Disease

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
Retropharyngeal lymphoid granulation

What Causes Disease?

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.
Serologic evidence of acute and chronic C. pneumoniae infection found in approximately 1/3 of patients admitted to hospital with acute COPD exacerbation, often together with other concurrent bacterial infection
Associated with acute respiratory exacerbation in children with cystic fibrosis

Diagnosis of Disease

Differential Diagnosis

Consider other common bacterial respiratory pathogens, including Streptococcus, Bordetella, Haemophilus. Klebsiella, Mycoplasma and Legionella species

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

C. pneumoniae can be identified from clinical specimens (not sputum) by culture in HL or HEp2 and by polymerase chain reaction (PCR). Both culture and PCR require a sophisticated laboratory and are not widely available.
Serologic testing with microimmunofluorescence (MIF) antibody and enzyme immunoassay (EIA) antibody are both commercially available. Testing with MIF is recommended by the CDC. EIA is less specific. Testing acute and convalescent (at least 3 weeks after disease onset) sera is preferable.

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 of acute infection requires a positive culture or PCR or a four-fold rise in antibody titer. Very high antibody titer or antibody in the IGM fraction suggests a recent infection.

Treatment (Medical Therapy)

Appropriate Health Care

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

General Measures

No specific general measures

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

Medications (Drugs, Medicines)

Drug(s) of Choice

Azithromycin (Zithromax) 500 mg on day 1, then 250 mg a day on days 2 through 5
Clarithromycin (Biaxin) 500 mg po every 12 hours for 10-14 days
Tetracycline 500 mg po qid for at least 14 days
Doxycycline 100 mg po q 12 hours for at least 14 days

Contraindications:

Tetracycline not for use in pregnancy or children < 8 years.

Precautions:

Tetracycline may cause photosensi-tivity; sunscreen recommended.

Significant possible interactions:

Tetracyclines may increase the anticoagulant effect of warfarin
Broad-spectrum antibiotics may reduce the effectiveness of oral contraceptives; barrier method recommended.

Alternative Drugs

Erythromycin base 250-500 mg qid for 14-21 days
Levofloxacin 250-500 mg qd PO or IV
Beta-lactam (penicillin based) antibiotics and sulfisoxa-zole not effective

Patient Monitoring

Weekly until well for response to treatment and resolution of radio-graphic abnormalities

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/encephalitis
Reactive arthritis
Acute chest syndrome in sickle cell disease

Expected Course / 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

Associated with atherosclerotic disease-effect of treatment unknown

Pregnancy

No known special risks
Tetracyclines contraindicated

Synonyms

TWAR

International Classification of Diseases

078.88 Other specified diseases due to Chlamydiae

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 Ml and stroke in seroepidemiologic studies. Role in athero-genesis in humans not established. Clinical significance not known.
Associated with atherosclerotic disease — effect of treatment unknown