Infectious DiseasesTier 1Disease (DEADMAN)

Lower respiratory tract infections, such as pneumonia

Description

Infection of the lung parenchyma - classified by setting (CAP community-acquired, HAP hospital-acquired >=48h post-admission, VAP ventilator-associated, aspiration) - setting determines likely organism and empirical therapy

CAP - one of the commonest reasons for hospital admission and a leading infectious cause of death, particularly in older adults
Incidence rises with age, smoking, chronic lung/cardiac disease, immunosuppression
HAP/VAP carry higher mortality, reflecting both host factors and more resistant organisms

CAP

Streptococcus pneumoniae - commonest bacterial cause
Atypicals: Mycoplasma pneumoniae (younger patients), Legionella (severe disease, exposure to contaminated water sources), Chlamydophila pneumoniae
Haemophilus influenzae (COPD), Staphylococcus aureus (post-influenza, IV drug use), respiratory viruses (influenza, RSV, SARS-CoV-2) as primary or co-pathogens

HAP/VAP

Gram-negative bacilli (Pseudomonas, Klebsiella, E. coli), S. aureus (including MRSA) - broader and more resistant organism profile than CAP

Aspiration pneumonia/pneumonitis

Polymicrobial - oral anaerobes plus the organisms above; risk with impaired swallow, reduced consciousness, oesophageal disease

Clinical

Fever, cough (+/- purulent sputum), pleuritic chest pain, dyspnoea, tachypnoea; focal crackles/bronchial breathing
CXR - new infiltrate required for radiological confirmation of pneumonia (vs bronchitis)

Severity assessment - drives disposition and empirical antibiotic choice

CORB / SMART-COP / CURB-65 - Australian guidance favours SMART-COP for predicting need for intensive respiratory/vasopressor support; CURB-65 widely used and simpler (Confusion, Urea>7, RR>=30, BP<90/60, Age>=65)
Low severity - outpatient management; moderate - ward admission; high severity - HDU/ICU consideration

Microbiological work-up (higher-severity or specific risk factors, not every mild case)

Sputum culture, blood cultures (moderate-severe), urinary antigen tests (pneumococcal, Legionella) in severe CAP
Respiratory virus PCR (influenza, SARS-CoV-2) as relevant to presentation and season
CT chest if diagnosis unclear, complication suspected (empyema, abscess), or failure to resolve

A. CAP - empirical therapy by severity (Australian eTG-based)

Low severity (outpatient): oral amoxicillin, +/- doxycycline added/substituted if atypical cover wanted or penicillin allergic
Moderate severity (ward): IV benzylpenicillin (or amoxicillin) + doxycycline (or a macrolide) for atypical cover; step down to oral once improving
Severe (ICU/HDU): broader empirical cover - e.g. a beta-lactam/beta-lactamase inhibitor or third-generation cephalosporin + azithromycin, covering pneumococcus, Legionella, and other atypicals; add specific cover if Pseudomonas/MRSA risk factors present
Confirmed pathogen: narrow to targeted therapy (e.g. benzylpenicillin for confirmed pneumococcal CAP)
Duration - typically 5 days for uncomplicated CAP responding well, longer for severe disease, bacteraemia, or complications

B. HAP/VAP

Empirical cover reflecting local resistance patterns - broader Gram-negative (including antipseudomonal) and consider MRSA cover especially with risk factors or local prevalence
De-escalate promptly once culture/sensitivity data available

C. Aspiration pneumonia

Anaerobic cover generally not required for community aspiration events without periodontal disease/lung abscess per updated evidence - standard CAP regimen often sufficient; reserve anaerobic cover (e.g. amoxicillin-clavulanate) for aspiration with poor dentition, lung abscess, or empyema
Address the underlying swallow/aspiration risk (speech pathology assessment)

D. Supportive care

Oxygen to target saturation, fluid management, early mobilisation
Vaccination review (pneumococcal, influenza) as secondary prevention before discharge
Smoking cessation counselling

Most uncomplicated CAP resolves with appropriate therapy within 1-2 weeks clinically (radiological resolution lags, especially in older adults - repeat CXR at 6 weeks mainly to exclude underlying malignancy in smokers/high-risk patients, not to confirm clinical cure)
Complications: parapneumonic effusion/empyema (requires drainage if complicated), lung abscess, respiratory failure, sepsis
Mortality significantly higher in severe CAP, HAP/VAP, and in frail/comorbid patients
Recurrent pneumonia - consider underlying structural lung disease, immunodeficiency, or aspiration risk requiring further work-up

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