Chlamydial, Mycoplasmal, Rickettsial, and Ehrlichial Diseases

Lower respiratory tract infection and inflammatory consolidation caused by Mycoplasma pneumoniae

One of the most common community-acquired pneumonias

A fatal outcome is rare

Highest incidence in 5- to 20-year-olds

9% of community-acquired pneumonia isolates in patients younger than 5 years, 51% in 5- to 9-year-olds, 74% in 9- to 15-year-olds, and 3.3% to 18% in adults; in university students, 11% of clinically diagnosed pneumonias and 22% of radiologically confirmed pneumonias

Gradual onset of headache, malaise, fever, sore throat, and cough

Mycoplasma tracheobronchitis occurs 30 times more frequently than pneumonia

Similar incidence of productive cough, rales, and diarrhea as community-acquired pneumococcal or Legionella pneumonia, but with more frequent upper respiratory symptoms, normal leukocyte count, and younger age

Bronchopneumonia usually involving a single lobe, subsegmental atelectasis, peribronchial thickening, and streaky interstitial densities

High-resolution computerized tomography shows centrilobular consolidation, acinar shadows less than 1 cm in diameter, air bronchograms and bronchiolograms, and thickening of the bronchovascular bundle

Usually self-limited

The duration of illness, but not Mycoplasma carriage, is shortened by oral ambulatory treatment with doxycycline, erythromycin, clarithromycin, or azithromycin for 5 days; levofloxacin or moxifloxacin for 14 to 21 days

Because Mycoplasma pneumonia is rarely fatal, the gross pathologic lesions are not well described

Limited human autopsy and biopsy materials and similar observations in a hamster model show peribronchial, peribronchiolar, and interstitial infiltrates of macrophages, CD4 and CD8 T-lymphocytes, B-lymphocytes, and plasma cells

Airway lumens contain mucus, fibrin, polymorphonuclear leukocytes, and detached respiratory epithelial cells, which frequently cause obstruction leading to segmental and subsegmental atelectasis

In some cases, combinations of bronchiolitis obliterans, organizing pneumonia, and interstitial fibrosis occur rather than resolution

An immunohistochemical method for detection of Mycoplasma pneumoniae has been developed

Experimental studies of animals have demonstrated attachment of M. pneumoniae to the cell surface of respiratory epithelial cells between cilia by a specialized tip structure

Cilia are shed, intercellular junctions are disrupted, and the respiratory epithelial cells detach from the basement membrane

Influenza A and B, parainfluenza 1–4 pneumonia, respiratory syncytial virus pneumonia, and chlamydial pneumonias (C. trachomatis, C. pneumoniae, C. psittaci)

Lower respiratory tract infection and inflammatory consolidation caused by Chlamydia trachomatis

C. trachomatis is the etiologic agent of 25% to 36% of the cases of pneumonia requiring hospitalization in 1- to 3-month-old infants

Of infants born to mothers harboring C. trachomatis genital infection, 17% to 22% develop chlamydial pneumonia

Usually a prolonged self-limited illness, C. trachomatis can cause severe pneumonia in low-birth-weight neonates

Infection is usually acquired intrapartum, with onset of symptoms at 4 to 12 weeks of age

Pneumonia caused by C. trachomatis is rare in adults, even immunocompromised persons

Typical onset is characterized by afebrile, staccato cough, tachypnea, rales, hypoxemia, and mild peripheral eosinophilia

Chlamydial conjunctivitis is present in only 50% at the presentation with pneumonia

Chest radiographs reveal hyperexpansion and diffuse or patchy interstitial infiltrates

Rarely fatal

Infants are treated with erythromycin (12.5 mg/kg four times daily for 2 weeks), azithromycin (20 mg/kg once daily for 3 days), or trimethoprim-sulfamethoxazole (5 mg/kg two times daily for 2 weeks).

Lower respiratory tract infection and inflammatory consolidation caused by Chlamydia pneumoniae

C. pneumoniae is the fourth most common cause of infectious pneumonia, responsible for 6% to 12% of cases

Based on the detection of antibodies in half of the adult population, C. pneumoniae infection is likely nearly universal with frequent reinfections

Generally a mild or asymptomatic infection (90%), it is more severe in older patients

Rarely fatal

Persons of all ages greater than 5 years may become infected

Infected children younger than 11 years of age are more likely to develop bronchitis, otitis media, and rhinitis than asymptomatic infection, pneumonia, pharyngitis, laryngitis, tonsillitis, or croup

Initially presenting with pharyngitis, infection gradually proceeds to cough and pneumonia over days to a week

Adults manifest cough (61%) that is productive of sputum (44%), rales (61%), and fever (56%)

Primary C. pneumoniae pneumonia in adults causes alveolar infiltrates on admission more frequently than interstitial infiltrates, but interstitial infiltrates occur more often with reinfection

More than half of cases develop pleural effusions

Infection is self-limited

Doxycycline (tetracycline), erythromycin for 14 days, azithromycin for 5 days, or clarithromycin for 10 days or levofloxacin moxifloxacin for 7 days

Lower respiratory tract infection and inflammatory consolidation caused by Chlamydia psittaci

Although more than 813 cases of psittacosis were reported to the Centers for Disease Control and Prevention from 1988–1998, only 10 to 24 cases were registered annually in 2001–2004