21. Lower respiratory tract infections Flashcards Preview

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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
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
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