Pneumonia involves infection of the lung tissue, causing inflammation in the alveoli. Community-acquired pneumonia (CAP) develops in the community. Hospital-acquired pneumonia (HAP) develops after more than 48 hours in hospital.
Acute bronchitis refers to infection and inflammation in the bronchial tubes. Both pneumonia and acute bronchitis are lower respiratory tract infections.
Bronchiolitis refers to infection and inflammation in the bronchioles and occurs in children under 2 years, usually under 6 months. Bronchiolitis is most often caused by respiratory syncytial virus (RSV).
Upper respiratory tract infections, causing a blocked nose, sore throat and dry cough, are usually viral. As a general rule, the lower down the respiratory tract, the higher the probability of bacterial infection (as opposed to viral).
Causes
The top causes of bacterial pneumonia are:
- Streptococcus pneumoniae (most common)
- Haemophilus influenzae
Other bacterial causes include:
- Group A strep (e.g., Streptococcus pyogenes)
- Staphylococcus aureus
- Mycoplasma pneumoniae (atypical bacteria with extra-pulmonary manifestations, e.g., erythema multiforme)
Viral causes:
- Respiratory syncytial virus (RSV) is the most common viral cause
- Parainfluenza virus
- Influenza virus
In a neonate, the causative organism may originate from the birth canal:
- Group B streptococcus (GBS)
- Escherichia coli (E. coli)
- Listeria
- Klebsiella
In children with cystic fibrosis, the key causes are:
- Staphylococcus aureus
- Pseudomonas aeruginosa
In immunocompromised patients, such as those with end-stage HIV, consider:
- Pneumocystis jirovecii
- Cytomegalovirus
Presentation
Presenting symptoms may be non-specific, particularly in young infants. The only symptoms may be poor feeding, drowsiness, restlessness or abdominal pain.
Presenting symptoms include:
- Productive cough
- High fever
- Shortness of breath
- Lethargy
- Drowsiness or confusion
Signs on examination include:
- Fever (above 38.5ºC)
- Tachypnoea (raised respiratory rate)
- Tachycardia (raised heart rate)
- Signs of respiratory distress (e.g., recessions, nasal flaring and tracheal tug)
- Low oxygen saturation
- Hypotension (low blood pressure)
- Cyanosis (blue discolouration of the skin)
Chest Auscultation Findings
Bronchial breath sounds are harsh and equally loud on inspiration and expiration. They are caused by consolidation of the lung tissue around the airway, amplifying the airway sounds heard at the chest surface.
Focal coarse crackles are caused by air passing through fluid, similar to using a straw to blow into a drink.
Dullness to percussion over the affected area occurs due to lung tissue collapse or consolidation.
Investigations
In uncomplicated pneumonia, investigations are not routinely performed or helpful. The diagnosis can be made clinically, and treatment can be started empirically.
A chest x-ray may be helpful if there is diagnostic doubt or in severe or complicated cases. Pneumonia can be seen as a consolidation.
White blood cells and CRP are raised roughly in proportion to the severity of the infection.
Sputum culture for bacterial culture and viral PCR can establish the causative organism and guide treatment.
Blood cultures are required in patients with suspected sepsis.
Capillary blood gas analysis measures the lactate and pH and is used to identify acidosis in acutely unwell patients.
Management
The choice of oral antibiotic will depend on the local guidelines. Typical choices include:
- Amoxicillin (usually first-line)
- Co-amoxiclav (particularly with concurrent influenza or in cystic fibrosis, to cover Staph aureus)
- Clarithromycin (penicillin allergy)
Macrolide antibiotics (e.g., clarithromycin) may be added to cover atypical bacteria (e.g., Mycoplasma pneumoniae), particularly where there is no response to the initial antibiotic.
IV antibiotics can be used in sepsis, complicated pneumonia or reduced absorption of oral antibiotics (e.g., vomiting).
Oxygen is used as required to maintain saturations above 92%.
Recurrent Chest Infections
Further investigations may be required in children with recurrent hospital admissions for chest infections. Conditions to consider include:
- Cystic fibrosis
- Primary ciliary dyskinesia
- Bronchiectasis
- Immunodeficiency (e.g., HIV or selective IgA deficiency)
- Neurological disease (e.g., cerebral palsy)
- Congenital heart disease
Tests that may be considered include:
- Full blood count to check the levels of white blood cells
- Chest x-ray for any structural abnormalities or long-term scarring
- Serum immunoglobulins for selective IgA deficiency and other immunoglobulin disorders
- Immunoglobulin G to previous vaccines (pneumococcal and Haemophilus influenzae type b)
- Sweat test for cystic fibrosis
- HIV test
Testing for IgG to previous vaccines can detect immunoglobulin class-switch recombination deficiencies. Patients with these conditions are unable to convert IgM to IgG and, therefore, do not form long-term immunity to that pathogen.
Last updated February 2025
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