infections of the lower respiratory tract Flashcards
10 general lower resp tract infections
1 - Bronchiolitis 2 - Bronchitis 3 - Acute exacerbations of COPD 4 - Bronchiectasis 5 - Community acquired pneumonia 6 - Healthcare acquired pneumonia 7 - Pulmonary tuberculosis 8 - Aspiration pneumonia 9 - Empyema 10- Lung abscesses
Many bacteria causing lower respiratory tract infections are part of normal upper respiratory flora. They cause infection due to reduced host defence e.g.
S. pneumoniae
H. influenzae
M. catarrhalis
what is Bronchiolitis
In infants especially first six months of life
Starts with cold-like symptoms e.g. nasal discharge
Followed by fever, cough, tachypnoea, expiratory wheeze, cyanosis, intercostal recession
Rapid deterioration & death in 1% that are hospitalised
Main pathogen is Respiratory syncytial virus - RSV
Transmission is by droplet spread or by contact with fomites
Annual winter epidemics
Hospital outbreaks
intercostal recession is very worrying
what can RSV cause
Rhinitis
Pharyngitis
Bronchiolitis
Pneumonia – in the elderly and immunocompromised
RSV – Laboratory diagnosis
Throat swab or nasopharyngeal aspirate
into viral culture
RSV - Prevention and Management
Admit to hospital if severe lower respiratory tract disease
Supportive treatment with oxygen therapy
Ribavirin by aerosol inhalation for severely ill or debilitated patients – but controversial
Source isolation and strict hand washing to prevent nosocomial transmission
Palivizumab- monoclonal RSV Ab for high risk infants
NO VACCINE (yet)
pneumonia definition
infection of the lung parenchyma
Various Classifications
Community versus hospital acquired
Acute versus chronic
Lobar & bronchopneumonia versus interstitial
Typical versus atypical
what is Community-acquired Pneumonia (CAP)
Pneumonia presenting in community or within 48hrs of attending hospital
Common cause of death worldwide (6th)
Leading cause of infectious death in the USA and UK
Caused mainly by bacteria but also by viruses (RSV leading cause 50%
bacterial causes of CAP
Bacterial causes
Streptococcus pneumoniae – “pneumococcus” Moraxella catarrhalis Haemophilus influenzae Staphylococcus aureus “The atypicals” Mycoplasma pneumoniae Legionella pneumophilia Chlamydia spp Coxiella burnetii
viral causes of CAP
Viral causes
Viral causes less common
RSV leading cause of CAP in the under 2 year old
Other viral pathogens associated with pneumonia include parainfluenza, influenza and human metapneumovirus
Very young, elderly and immunocompromised most at risk
Risk of secondary bacterial pneumonia
Symptoms and signs of acute (Typical) Pneumonia
Fever Cough Purulent sputum Haemoptysis Chest pain Shallow rapid breathing Reduced chest movements Dullness to percussion Bronchial breathing/coarse crepitations
what is streptococcus pneumoniae
Gram positive diplococcus
Grows with alpha haemolysis on blood agar
Has polysaccharide capsule
Part of the normal upper respiratory tract flora
> 84 different capsular types
Leading cause of CAP, AOM, acute exacerbations of COPD
Important cause of acute bacterial meningitis and septicaemia
diagnosis and treatment of strep pneumoniae
Diagnosis: culture or antigen detection
Treatment: Penicillins
Causes of Atypical Pneumonia
Mycoplasma pneumoniae Legionella pneumophilia serogroups 1 & 6 Chlamydia: pneumoniae trachomatis psittaci Coxiella burnetii Pneumocystis jiroveci (carinii) Respiratory viruses
Legionella pneumophilia presentation diagnosis and treatment
Commonly atypical presentation e.g. fever, confusion, myalgia, non productive cough, headache
BUT may present typically
May have few chest signs and patchy consolidation
BUT may have lobar pneumonia
Commonly affects middle aged males
More common in summer months
Need exposure to contaminated water e.g. showers, air conditioning, sprays
Diagnosis: antigen/serology
Treatment: macrolides +/- rifampicin
