Moraxella catarrhalis

Introduction

-Moraxella catarrhalis are gram-negative cocci that pair as kidney-shaped diplococci and thus morphologically similar to Neisseria 

-In contrast to pathogenic Neisseria, Moraxella lacks antiphagocytic capsules and IgA proteases.

-It is found only in humans and is transmitted by respiratory aerosol.

Symptoms & Signs

-It causes otitis media and sinusitis primarily in children

-it causes bronchitis and pneumonia, primarily in older people with chronic obstructive pulmonary disease

Diagnosis 

-in culture, it grows as round, opaque colonies on blood and chocolate agar, which typically turn pink after 48 hours

-A characteristic feature of M. catarrhalis: its colonies slide across agar without disruption (hockey puck sign) 

Treatment 

-Antibiotics: amoxicillin-clavulanate, ampicillin-sulbactam, trimethoprim-sulfamethoxazole, macrolides (azithromycin, clarithromycin) fluoroquinolones (ciprofloxacin), and cephalosporins

-M.catarrhalis produces a β-lactamase and is resistant to ampicillin.

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