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Sputum–Gram-Negative Diplococci and Coccobacilli Send Print

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Created: Tuesday, 06 February 2007
Last update: Tuesday, 27 September 2011
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Haemophilus influenzae (Enlarged view)
Slide 1. Haemophilus influenzae
These small, pleomorphic gram-negative bacteria range in shape from round (cocci) to short, thin rods (bacilli); hence the bacteria are called “coccobacilli.” In specimens from patients with pneumonia caused by Haemophilus influenzae, both neutrophils and bacteria are usually plentiful. However, if examination of the slide is not thorough, the coccobacilli may be inconspicuous in the background of pink-staining mucus. Other organisms, such as Eikenella corrodans or Bacteroides species, are also pleomorphic gram-negative coccobacilli; but they rarely cause pneumonia.
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Haemophilus influenzae (Enlarged view)

Slide 2. Haemophilus influenzae
Many coccobacilli are present in the cytoplasm of the neutrophils, a common site for Haemophilus influenzae in sputum stains. The examiner should always look carefully for organisms in white cells. (An alveolar macrophage is also present on this slide.)

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Neisseria meningitidis (Enlarged view)

Slide 3. Neisseria meningitidis
Numerous gram-negative diplococci are present, singly and in pairs. In patients with pneumonia, the respiratory pathogens most likely to have this appearance are Neisseria meningitidis or Moraxella (Branhamella) catarrhalis which look alike. Other gram-negative diplococci, such as commensal Neisseria species or Veillonella species, are rarely the sole or predominant organism in sputum smears of patients with pneumonia.

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Moraxella (Branhamella) catarrhalis (Enlarged view)

Slide 4. Moraxella (Branhamella) catarrhalis
Moraxella catarrhalis can cause pneumonia, especially in patients with alcoholism or chronic obstructive lung disease. This slide shows many gram-negative cocci, singly and in pairs. Like meningococci and Haemophilus influenzae, Moraxella catarrhalis is often visible within the cytoplasm of neutrophils.



These images are from the original published atlas: Tenover, F. C., and J. V. Hirschmann. 1990. Interpretation of Gram stains and other common microbiologic slide preparations. The UpJohn Company, Kalamazoo, Mich. Permission granted to the ASM MicrobeLibrary by Pfizer Inc.

This atlas was written to help clinicians, microbiologists, and laboratory personnel identify organisms in infected materials stained by techniques commonly used in most clinical laboratories. Please refer to the atlas' main page for more information and a guide to all of the images.
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