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Description
A 76-year-old male patient with diabetes mellitus presented with a 4-day history of productive cough and fever. He was a former smoker, with a history of smoking 30 packs of cigarettes per year. Physical examination revealed the following: body temperature, 38.6°C (101.5°F); heart rate, 115 beats/min; blood pressure, 136/82 mm Hg; respiratory rate, 22 breaths/min and oxygen saturation, 96% on room air. Slight crackles were detected by auscultation over the right lower zone of the lung. CT showed mixed interstitial-alveolar infiltration of the right lower lung without emphysema. A sputum Gram stain revealed abundant, Gram-negative diplococci (figure 1A), and empiric therapy with ceftriaxone was begun. On hospitalisation day 2, the culture grew round colonies on blood agar and chocolate agar which slid across the agar surface without disruption (ie, the hockey puck sign, figure 1B and video 1). Based on these clinical and microbiological findings, ceftriaxone was continued, and the symptoms quickly resolved. Subsequently, the organisms were identified as Moraxella catarrhalis using the VITEK 2 system (BioMérieux, France).
(A) Sputum Gram stain showed neutrophils and Gram-negative diplococci resembling Moraxella sp or Neisseria sp. (B) The colonies were able to be slid across the agar surface without disruption, a feature known as the ‘hockey puck sign’.
M. catarrhalis is a common pathogen in respiratory tract infections. In adults, M. catarrhalis pneumonia occurs most frequently in elderly patients with an underlying illness, such as cardiopulmonary disease, chronic kidney disease and diabetes mellitus.1 2 To treat M. catarrhalis infections, extended-spectrum cephalosporins, ampicillin/sulbactam or amoxicillin/clavulanic acid are recommended because M. catarrhalis often produces beta-lactamase and may be resistant to penicillin, ampicillin and amoxicillin. Prompt identification of the causative organism is essential for pneumonia management, for which the findings of the sputum Gram stains and culture can provide practical data. However, M. catarrhalis morphologically resembles Neisseria spp, which are also part of the normal, upper airway flora. The hockey puck sign is therefore useful in distinguishing M. catarrhalis from Neisseria spp.3
Learning points
Moraxella catarrhalis is a common, bacterial cause of pneumonia most frequently occurring in elderly patients with an underlying illness.
A characteristic feature of M. catarrhalis colonies is their ability to be slid across the agar surface without disruption, known as the ‘hockey puck sign’.
A combination of sputum Gram stain examination and the hockey puck sign leads to prompt diagnosis and treatment of M. catarrhalis infection in patients with pneumonia.
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Acknowledgments
The author thanks James R. Valera and Kei Karakida for their assistance with editing the manuscript.
Footnotes
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.