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Moraxella catarrhalis

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Moraxella catarrhalis

Metal-axe Cats
Moraxella catarrhalis is a gram-negative diplococci, which is oxidase-positive and catalase-positive. It can lead to otitis media in children, along with sinusitis. It is the second most common bacterial cause of COPD exacerbation in adults, and can lead to bronchitis. This bacterium is also responsible for laryngitis in patients. Moraxella catarrhalis can be treated with amoxicillin-clavulanate, trimethoprim-sulfamethoxazole, extended-spectrum cephalosporins, macrolides, like azithromycin and clarithromycin, along with tetracyclines, and fluoroquinolones.
Graham-cracker Negative-devil

Moraxella Catarrhalis is gram negative, meaning it does not retain crystal violet stain. This is because it has a thin peptidoglycan layer, which is sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.


Under microscopy, Moraxella catarrhalis exists as diplococci, or round bacteria (cocci) that typically occur in the form of two joined cells.

Positive Ox-daisy

This bacterium is oxidase-positive, meaning it can produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain. This means Moraxella catarrhalis can use oxygen as a terminal electron acceptor in respiration.


Moraxella is catalase-positive. This means that it catalyzes the decomposition of hydrogen peroxide to water and oxygen, which is important for preventing oxidative damage by reactive oxygen species.

Otitis Media

This bacterium is a common cause of otitis media in children.


Adults and children may be colonized with Moraxella catarrhalis, and can develop sinusitis because of this bacteria. This is more commonly seen in children.

Chronic Obstructive Pulmonary Disease (COPD)
Crone Lungs Diseased

Moraxella catarrhalis is the second most common cause of bacteria-induced COPD exacerbation. The most common cause is H. influenzae.


One type of COPD caused by Moraxella infection is bronchitis. Acute inflammation of the bronchial airways decreases expiratory airflow, leading to COPD in patients.


Patients can also develop laryngitis due to Moraxella catarrhalis infection, which is one of the most common bacterial causes of laryngitis. This is more common in adults, but children can also be affected.


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