21. Lower respiratory tract infections Flashcards
What is the significance of lower respiratory tract infections?
One of the three most important infective causes of death in children aged under 5
What are the causes of respiratory tract infections?
Bacteria - streptococcus pneumonia, haemophilius influenzae
Viruses - influenza, respiratory syncytial virus (RSV)
Fungi (in the immunocompromised) - Aspergillus spp
Protozoa (in the immunocompromised) - toxoplasma gondii
What is pneumonia?
Inflammatory condition of the lung primarily affecting the alveoli
Inflammation of the lung (pneumonitis) and also consolidation of the lung i.e. the alveoli fill with liquid rather than air as they should
Caused by a virus or bacaterium
What is community acquired pneumonia?
CAP - pneumonia acquired in the community, outside of healthcare facilities
Less likely to involve multi-drug resistant bacteria
Most frequently in the very young or the very old
Can be secondary to a viral respiratory tract infection
What are some typical bacterial causes of community acquired pneumonia and how does this present?
Streptococcus pneumoniae
Haemophilius influenza
Clinically presents with sudden onset of chills, fever, pleuritic chest pain and productive cough
The white blood cell count is greatly increased
Sputum is thick and purulent (containing pus)
Chest x-rays will show parenchymal involvement
What are some atypical bacterial causes of CAP and how does this present?
Myocplasma pneumoniae
Chamydia pneumoniae
Usually has an insidious onset
Patients have a non-productive cough, fever, headache
Chest x-ray shows very abnormal compared to the presentation
What is hospital acquired pneumonia?
Pneumonia acquired in a hospital, 48 hours following admission
Generally due to hospital acquired infections or multi-drug resistant pathogens - frequently due gram negative organisms
What complications can arise from pneumonia?
Pleural effusion - 3-5% - clear fluid in the pleural cavity and pus in the cells
Empysema - pus in the pleural space
Lung abscess - discharge of pus and destruction of lung parenchyma
How is pneumonia diagnosed?
History and clinical examination
Chest x-ray
HB, WBC, platelet counts
Blood cultures
Sputum sample - microscopy, culture and sensitivity
Serodiagnosis/antigen detection if aytpical pneumonia is suspected
How can the severity of pneumonia be determined?
CAP can progress rapidly from mild to death British thoracic CURB 65 score: C - confusion U - urea >7mmol R - respiratory rate >30 B - blood pressure <90mmHg 65 - age > 65
The risk of death increases as the score increases (1 point for each of them)
Explain the results of the CURB 65 score
Patients with a score of 0 are at a low risk of death and do not usually require hospitalisation
Patients with a score of 1 or 2 are at an increased risk of death and hospitalisation should be considered
Patients with a score of 3 or more are at a high risk of death and require urgent hospital admission
How is CAP generally treated?
Generally given beta-lactams e.g. amoxocillin, benzylpenicillin
BUT NB. these are ineffective against M.Pneumoniae as this does not have a cell wall
Pneumococcal vaccine - 56-81% effective against invasive disease
What is tuberculosis?
This is mainly a respiratory illness affecting the lungs but it can also affect almost any other organ
Caused by mycobacterium tuberculosis
Chronic infection
How is TB transmitted?
TB is a primary infection - via droplet infection i.e. cough or sneeze
What are the symptoms of TB?
Productive cough Night sweats Weakness Fever Dry cough Weight loss GI symptoms
Describe the important characteristics of the mycobacterium tuberculosis to know when treating
Waxy cell wall - resistant to drying, antibiotics, acids and alkalis, impermeable to standard stains, survives in macrophages
How can TB be identified?
Traditionally via biochemical properties e.g. nitrate reduction, pigmentation, urease production but these are time consuming
Now, molecular diagnosis e.g. nucleic acid probe and quantiferon (gold standard)
How can you diagnose TB?
Clinical diagnosis - compatible history, examination, radiology
Microscopy and culture from the affected site - sputum sample
Histology
Immunological tests
How can TB be treated?
Generally treated with anti-microbial therapy
Minimum of 6 months but this can be longer in complicated TB e.g. multi-drug resistant
What is the BCG vaccine and why is it relevant?
BCG - Bacille Calmette Guerin
Not part of the routine childhood immunisation
BUT advised for children with background/parental background of high prevalence areas and if traveling to high prevalence areas
What is meant by the lower respiratory tract?
Part of the respiratory system including the larynx, trachea, bronchi and the lungs
What is meant by the upper respiratory tract?
The part of the respiratory system including the nose and nasal passages, the paranasal sinuses, the pharynx and also the portion of the larynx above the vocal cords
