PowerPoint Contents

Author: Rebecca Buxton ​

Citation: Rebecca Buxton. 2007.

Sputum–gram-negative diplococci and coccobacilli.​

Publication Date: February 2007​

Haemophilus influenzae (Enlarged view)​
Slide 1. Haemophilus influenzae​
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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​
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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​
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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​
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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.​