Pneumonia Variants

Pneumonia Variants: Excerpt from Field Guide to Bedside Diagnosis

Differential Overview

❑ Streptococcus pneumoniae

❑ Mycoplasma pneumoniae

❑ Haemophilus influenzae

❑ Chlamydia pneumoniae

❑ Influenza virus

❑ Staphylococcus aureus

❑ Mycobacterium tuberculosis

❑ Legionella pneumophila

❑ Klebsiella pneumoniae

❑ Pneumocystis carinii

❑ Chlamydia psittaci

❑ Severe Acute Respiratory Syndrome (SARS)

❑ Hantavirus

Diagnostic Approach

Although the current consensus recommendations call for the use of broad spectrum empiric antibiotics without determining the cause of the pneumonia, clinical findings combined with low-tech bedside diagnostics, such as sputum Gram stain, can be surprisingly informative. As an example, in smokers with chronic bronchitis consider H. influenzae, S. pneumoniae, and
B. catarrhalis.

Clinical Findings

Streptococcus pneumoniae  Osler’s triad of rigor, pleuritic chest pain, and rust-colored sputum still applies in a febrile patient with acute cough. The patient appears ill, and fever may exceed 40˚C. A sputum Gram stain showing sheets of neutrophils and encapsulated gram-positive diplococci will confirm the diagnosis.

Mycoplasma pneumoniae  The onset is subacute, with thin mucoid sputum and low-grade fever. The typical patient will be a young adult who has had contact with others with bronchitis or pneumonia within the incubation time of 2 to 3 weeks. Sputum Gram stain shows sheets of neutrophils but no associated organisms (a pattern also common to atypical pneumonias caused by viruses, C. pneumoniae and Legionella). Bedside cold agglutinins provide a neat confirmation. Collect blood in an oxalated tube, and immerse it in wet ice for 1 to 2 minutes. Agglutination that occurs on the side of the tube and that disappears upon rewarming to body temperature indicates a positive test (at least 1:64 titer). Repeated agglutination on re-immersion helps differentiate mycoplasma from viral cold agglutinins.

Haemophilus influenzae  Usually occurring in a smoker, H. influenzae is marked by rales without consolidative findings on examination. The sputum Gram stain will show a background of small, pleomorphic, gram-negative coccobacilli.

Chlamydia pneumoniae  It presents similarly to mycoplasma but with a greater degree of upper respiratory signs such as laryngitis or sinusitis.

Influenza virus  Flu-like symptoms will be prominent, with myalgias, sore throat, and malaise. The cough will produce scant sputum, and a specimen for Gram stain will usually be unavailable.

Staphylococcus aureus  Abrupt in onset, this pneumonia makes the patient seriously ill, producing hectic fevers, chills, and productive cough. Hematogenous spread from endocarditis may be a source, so look for a murmur, splinter hemorrhages, or petechiae. The sputum Gram stain shows large gram-positive cocci in clusters.

Mycobacterium tuberculosis  The onset is subacute, associated with fatigue, anorexia, fever, and weight loss. Hemoptysis is a common presenting symptom. Look for upper lobe consolidative findings. Suspect this illness when the patient is HIV-infected, homeless, or institutionalized.

Legionella pneumophila  Cough is not prominent, but mental status changes, fever with relative bradycardia, and abdominal pain are. Sputum Gram stain will show the “atypical pneumonia” pattern, but the patient has more toxicity than does one with mycoplasma or influenza.

Klebsiella pneumoniae  “Currant-jelly” sputum is a classic finding in this necrotizing pneumonia. Suspect it in alcoholics and other patients at risk of aspiration.

Pneumocystis carinii  Consider it when there is insidious onset of dyspnea and dry cough in an HIV-infected patient.

Chlamydia psittaci  Suspect when there is a history of bird exposure.

Severe Acute Respiratory Syndrome (SARS)  Fever and cough are common, but shortness of breath, tachypnea, and pleurisy only occur later in the illness. Unlike other atypical pneumonias, SARS less commonly has upper respiratory symptoms like rhinorrhea or sore throat. Suspect when a patient has travelled from a region in which an outbreak has been reported.

Hantavirus A prodrome of fever and myalgia leads rapidly to pulmonary edema and hypotension, in a patient with a history of rodent exposure.

Pictures

Book Source Details

• Book Title: Field Guide to Bedside Diagnosis
• Author(s): David S. Smith
• Year of Publication: 2007
• Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.

More About Psittacosis

• Back to disease: Psittacosis: Introduction
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Field Guide to Bedside Diagnosis Authors: David S. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-78178-165-5

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