EMQ practice - Causes of pneumonia

Causes of pneumonia:

• 80 year old male, bilateral cavitating bronchopneumonia after an influenza infection
• Staphylococcus aureus
• Not common pathogen in community acquired pneumonia
• May cause secondary infection in elderly recovering from influenza
• IV drug users
• Flucloxacillin is the treatment of choice for staphylococcal infection
• 24 year old student, severe headache, fever, dry cough and arthralgia. Recently bought several parrots and was previously fit and well
• Chlamydia psittaci
• Rare cause of community acquired pneumonia
• Lower respiratory tract symptoms and signs with exposure to birds
• No acute diagnostic tests are available and diagnosis is made in retrospect by demonstrating a rising titre of complement-fixing antibody (same as other atypical cases like Legionella pneumophila
• Macrolide antibiotic
• 40 year old male, HIV, fever, dry cough, weight loss, exertional dyspnoea
• Pneumocystis carinii
• Common complication of HIV infection (AIDS-defining illness)
• Opportunistic infection in other immunocompromised patients such as  those receiving immunosuppressive drugs and cancer chemotherapy
• 75 year old male, headache, dry cough, anaemia, skin rash, blood tests detect cold agglutinins
• Mycoplasma pneumoniae
• Most common atypical cause of community-acquired pneumonia
• Cases usually occur during an epidemic, which may give a clue to diagnosis
• Characteristic feature of is the autoimmune haemolytic anaemia caused by the presence of cold agglutinins
• Erythema multiforme, myopericarditis, and meningoencephalitis
• Diagnosis often made in retrospect via detection of a rising antibody titre
• Macrolide should be commenced if suspected
• 25 year old air conditioning technician, flu-like symptoms, dry cough, radiograph shows multilobar shadowing, blood tests show hyponatraemia and lymphopenia, urinalysis reveals haematuria
• Legionella pneumophila
• Rare cause of atypical community pneumonia
• Hyponatraemia and lymphopenia may assist in diagnosis
• This can be performed rapidly by testing for the presence of legionella antigen in the urine (high sensitivity and specificity)
• Adequate chlorination of water supply