Moraxella catarrhalis
📚 Related Subjects:
| Listeriosis
| Moraxella catarrhalis
| Leptospira interrogans
| Lactobacillus acidophilus
| Helicobacter pylori
| Haemophilus parainfluenzae
| Haemophilus influenzae
🦠 About
- Moraxella catarrhalis is an important cause of respiratory infections, especially in patients with COPD 🫁, chronic bronchitis, or immunosuppression.
- Also a recognised cause of otitis media 👂 in children and sinusitis 🤧 in adults.
🔬 Characteristics
- Aerobic, Gram-negative diplococcus 🧫 (resembles Neisseria).
- Grows best at 37°C 🌡️ on complex media with 5% CO₂.
- Oxidase-positive ✅, catalase-positive ✅, DNAse-positive 🧪.
- Hockey puck sign 🏒: Colonies easily pushed across agar with a loop.
🌍 Source
- Spread via respiratory droplets 💨 from colonised or infected individuals.
- Common coloniser of the upper respiratory tract 👃, becoming pathogenic in susceptible hosts.
⚔️ Virulence Factors
- Fimbriae → adherence to respiratory epithelium 🫁.
- Lipooligosaccharide (LOS): endotoxin → inflammation + immune evasion 🔥.
- Beta-lactamase production 🧬: confers resistance to amoxicillin/ampicillin.
🤒 Pathogenicity
- Respiratory infections: acute exacerbations of COPD 🚬.
- Community-acquired pneumonia (CAP): especially in those with lung disease 🫁.
- ENT infections: otitis media 👂, sinusitis 🤧, conjunctivitis 👀.
- Rare systemic disease: bacteraemia/sepsis in immunocompromised 🧍♂️.
🧪 Investigations
- Culture: “Hockey puck” colonies 🏒, smooth and movable.
- Biochemical tests: Nitrate reduction, oxidase +, catalase +, DNAse +.
- Butyrate esterase test 🧬: confirms M. catarrhalis (distinguishes from Neisseria).
💊 Sensitivity
- Most strains produce beta-lactamase ⚠️ → resistant to amoxicillin alone.
- Usually sensitive to:
- Co-amoxiclav 💊
- 2nd/3rd gen cephalosporins (e.g., cefuroxime, cefotaxime) 💉
- Macrolides (azithromycin, clarithromycin) 📈
- Fluoroquinolones (ciprofloxacin, levofloxacin) 🧪
🩺 Management
- Underlying disease: Optimise COPD management (bronchodilators, steroids, smoking cessation 🚭).
- Antibiotics: Co-amoxiclav first line; cefotaxime/macrolides/fluoroquinolones if resistant or in severe cases.
- Supportive care: Oxygen, fluids, symptom management where indicated.
