Lower Respiratory Tract Infection

Acute bronchitis
Acute Exacerbation of COPD (AECOPD)
Pneumonia

ACUTE BRONCHITIS

Definition
Self‐limited inflammatory process involving large and mid‐sized airways

Common aetiologies

• Respiratory viruses (> 90%)
  • Influenza
  • Parainfluenza 3
  • Respiratory syncytial virus
  • Human metapneumovirus
• Non-­viral (<10%)
  • Suspect if prolonged cough, longer incubation period, local  outbreaks
    • Mycoplasma pneumoniae
    • Chlamydia pneumoniae
    • Bordetella pertussis
  • No association with S. pneumoniae or H. influenzae in  patients without evidence of underlying lung disease

Tests
No investigations are required in the vast majority of cases:

• Gram stain not recommended
• Nasopharyngeal swab for influenza PCR not recommended for uncomplicated influenza­‐like illness

Diagnosis and management

 

*Chest X-­‐rays are not necessarily indicated for all patients with acute bronchitis and should be performed only if likely to influence management

ACUTE EXACERBATION OF COPD (AECOPD)

Definition

Acute increase in baseline dyspnoea, cough and/or sputum above the normal day­‐to‐day variations, requiring a change in medication. Up to 80% of AECOPD have an infectious aetiology.

Common aetiologies

• Viral (up to 50%) – more common in winter months
  • Rhinoviruses
  • Parainfluenza
  • Coronavirus
  • Influenza (in non-­‐vaccinated)
  • RSV
• Bacterial
  • H. influenzae
  • S. pneumoniae
  • M. catarrhalis
  • Enterobacteriaceae (frequent hospitalisation and antibiotic use)
• Atypical bacteria are not implicated in AECOPD

Tests

Mild	Moderate (Requiring hospitalisation)	Severe (Requiring high care/ICU)
Sputum culture not routine CRP or PCT (if available) Withhold antibiotics if negative	Sputum culture if frequent admissions or poor response to antibiotics CRP or PCT (if available) Withhold antibiotics if negative	Sputum culture Blood culture if pyrexial Nasopharyngeal swab for influenza PCR in flu season

 

Diagnosis and management

Prevention

• Annual influenza vaccine recommended for all patients with COPD
• Pneumococcal polysaccharide (PPSV23) vaccine is recommended for all individuals over 65 years of age and anyone with COPD
• Antiviral chemoprophylaxis is not recommended

PNEUMONIA

Definition
Pneumonia is acute infection of lung parenchyma distal to the terminal bronchiole and causes consolidation.

Common aetiologies of community acquired or health care associated pneumonia

CAP		HCAP
Agent	Comments	Increased risk for infection with MDR pathogens Similar organisms to CAP Uncommonly legionella or viruses Gram negative bacilli P. aeruginosa A. baumanii Enterobacteriaciae S. aureus (including MRSA)
S. pneumoniae	Most common cause
H. influenzae	More common in COPD
Tuberculosis	More common in HIV
‘Atypical organisms’ M. pneumoniae Chlamydophilia  Legionella spp.	Not cultured  No specific clinical/ radiological features Suspect if risk factors or non-­‐response to beta-­‐ lactams
Oral anaerobes	Risk factors: alcoholism, aspiration, lung abscess
P. jirovecii	HIV, bilateral infiltrates, desaturation on minimal exertion, poor response  to beta-­‐lactams
Respiratory viruses	Seasonal  Risk factors: pregnancy, elderly, co-­‐morbidities

Tests

CAP	HCAP
Only perform if likely to influence empiric management decisions   Mild (CRB-­65 score ≤ 2) Sputum culture and Xpert MTB/Rif if failed outpatient Abx therapy  Severe (CRB­‐65 ≥ 3) or co-­‐morbidities* Sputum Gram stain and culture Blood culture Sputum for P. jirovecii DFAT if HIV +ve Urine Legionella antigen testing  NP swab for influenza PCR if flu season	Always send specimens prior to initiation of empiric antibiotics   In all cases Blood culture  Sputum Gram stain and culture

NP = Nasopharyngeal, DFAT = direct fluorescent antibody test

*Chronic cardio­‐pulmonary disease, alcohol abuse, immune suppression (excluding HIV), CKD, cirrhosis

Diagnosis and management

 

SPECIAL CIRCUMSTANCES

2. Health care associated pneumonia

• Send blood and sputum cultures prior to initiating broad spectrum antibiotics
• Consult microbiologist or infectious diseases specialist about choice of appropriate empiric antibiotic

3. Penicillin allergy

• Moxifloxacin  400  mg  po/IV  daily  or  levofloxacin  500mg  po  12­‐hourly (750mg IV 12‐hourly in severe pneumonia)