Atypical organisms are generally associated with a milder form of pneumonia, the so-called "walking pneumonia." A feature that makes these organisms atypical is the inability to detect them on Gram stain or to cultivate them in standard bacteriologic media. In addition, they often produce several nonpulmonary related symptoms. Atypical organisms include the following:

• Mycoplasma species

• Chlamydophila species

• Legionella species

• Coxiella burnetii

• Bordetella pertussis

For more on the etiology of pneumonia, read here.

Examination findings that may indicate a specific etiology for consideration are as follows:

• Bradycardia may indicate a Legionella etiology;

• Periodontal disease may suggest an anaerobic and/or polymicrobial infection;

• Bullous myringitis may indicate M pneumoniae infection;

• Physical evidence of risk for aspiration may include a decreased gag reflex; and

• Cutaneous nodules, especially in the setting of central nervous system findings, may suggest Nocardia infection.

For more on the presentation of pneumonia, read here.

Recent interest has focused on developing PCR-based tests with single, multiplex, and real-time readings. These tests have sensitivity better than that of cultures. Nested PCR and RT-PCR are the most sensitive methods. They increase the detection rate of respiratory viruses in adults with hematologic cancers and pneumonia from 19% to 35%.

For more on workup in viral pneumonia, read here.

Aspiration pneumonia x-ray findings may be seen in the gravity-dependent portions of the lungs (affected by patient positioning). The classic finding is an infiltrate in the right lower lobe, but aspiration pneumonia also has characteristic distributions based on patient positioning at the time of the aspiration event. The right lung is affected twice as often as the left lung. In recumbent patients, the findings are in the posterior segments of the upper lobes; and, in upright patients, the basal segments of the lower lobes are often affected.

For more on the imaging of pneumonia, read here.

In otherwise healthy hosts, therapy does not need to cover Staphylococcus aureus, Klebsiella species, or P aeruginosa in CAP. (Most CAP regimens include Klebsiella pneumoniae coverage.) S aureus coverage should be included in patients with influenza who have focal infiltrates.

Most antibiotics used to treat CAP (eg, doxycycline, respiratory quinolones, beta lactams) are highly effective against oral anaerobes. Metronidazole and clindamycin are unnecessary unless anaerobic lung infection is suspected. For aerobic lung abscesses, clindamycin or moxifloxacin is preferable. Coverage should include the typical (Streptococcus pneumoniae, H influenzae, M catarrhalis) and atypical (Legionella and Mycoplasma species, Chlamydophila pneumoniae) pathogens.

For more on the treatment of CAP, read here.

Editor's Recommendations Bacterial Pneumonia Community-Acquired Pneumonia

 

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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.

Cite this article: Michael Stuart Bronze. Quiz: How Much Do You Know About Pneumonia? Medscape. Feb 16, 2016.