Respiratory Tract Infections Flashcards
What is pneumonia?
Infection involving the distal airspaces (gas exchange region) of the lungs usually with inflammatory exudation and cellular infiltration.
These fluid filled spaces lead to consolidation.
What is an exudate?
Any fluid that filters from the circulatory system into lesions or areas of inflammation
What are the physical signs of consolidation within the lungs?
Changes in percussion
Changes in oscillation
What are the classifications of a pneumonia?
- By clinical setting
- By organism
- By morphology
What are the clinical settings that can define a pneumonia?
Hospital acquired pneumonia
Community acquired pneumonia
Which organisms can cause pneumonia?
Viruses - influenza, measles, COVID, RSV
Bacteria
Chlamydia, mycoplasma
Fungi
What can COVID cause in patients?
Adult Respiratory Distress Syndrome (ARDS) - acute lung injury with epithelial damage.
It can also affect non-respiratory related organs, especially the heart.
What is lobar pneumonia?
This is confluent consolidation involving a complete lung lobe.
What is the most common pathogen causing lobar pneumonia?
Streptococcus Pneumoniae. Other organisms include Klebsiella and Legionella.
Who is most likely to get community aquired pneumonia?
It is classically seen in otherwise healthy young adults
What is the classic acute inflammatory response seen in pneumonia?
Exudation of fibrin rich fluid
Neutrophil infiltration
Macrophage infiltration
Resolution
What is the ideal role of the immune system in pneumonia?
Antibodies lead to opsonisation and further phagocytosis of bacteria.
What are some complications associated with pulmonary fibrosis?
Fibrosis
Abscess formation
Bronchiectasis
Empyema
What is bronchopneumonia?
This is when an infection starting in the airways (bronchi/bronchioles) spreads to adjacent alveolar lung (lobules).
This is most often seen in patients with pre-existing disease.
What are the most common causes of bronchopneumonia?
Patients with - COPD Cardiac Failure Complications of Viral Infaction Aspiration of gastric contents
What is the most common pathogen causing bronchopneumonia?
The pathogens are more varied. Strep. Pneumoniae Haemophilus influenza Staphylococcus anaerobes Coliforms
What is a lung abscess?
This is a tumour-like collection of pus. (severe localised suppuration). This can be viewed on a CXR or CT to show a fluid level
What are the symptoms of a lung abscess?
Swinging fever
Malaise
Weightloss
What are the causes of a lung abscess?
Aspiration pneumonia
TB
Klebsiella pneumoniae
Staphylococcus aureus
What is bronchiectasis?
This is an irreversible widening of the the bronchi
What are some of the causes of bronchiectasis?
This is usually due to fibrous scarring following infection. Tumours Pneumonia Cystic fibrosis tuberculosis sarcoidosis Immune deficiency etc.
What are some of the symptoms of bronchiectasis?
Recurrent infection Airway damage Chronic suppuration Persistent cough sputum production breathlessness pleuritic chest pain coarse crackles clubbing haemoptysis
What is tuberculosis?
This is a myobacterial infection where there is chronic infection in many sites including the lungs, gut, kidneys, lymph nodes and skin.
Which pathogen causes TB?
Mycobacterium tuberculosis- This is an aerobic, intracellular pathogen. It is airborne and spread by respiratory droplets.
What is the pathological characterisation of TB?
Delayed type IV hypersensitivity and granulomas with necrosis.
Who is most likely to be infected with tuberculosis?
People from high incidence countries.
Immunocompromised patients.
People in prison, homeless or drug addicts.
What is primary TB?
This is the first infection a patient has with TB
Describe the process of primary TB infection.
- Inhaled pathogens are phagocytosed.
- They are then carried to the hilar lymph nodes.
- This activates the immune system after a few weeks.
- This leads to a granulomatous response in the nodes and lung.
- This will eventually kill the organism
But is a few cases the infection will overwhelm and spread.
What is reactivation TB?
This is when there is a reinfection or reactivation of disease in a person with some immunity. This disease tends to remain fairly localised, often in the apices of the lung. But it can progress to spread by the airways or blood stream
Why does it take a while for reactivation TB to develop?
The immune system contains the initial infection and the patient develops cell-mediated immune memory of the bacteria - latent TB. This latent TB will then be reactiveated years later.
What are the tissue changes in primary TB?
Small focuses called GHON FOCUSES in the periphery of the mid zone of the lung. Large Hilar nodes
What is a ghon focus?
When primary TB develops, there is formation of caseour granulomas surrounded by epithelioid cells and langhans giant cells. When the infection has passed the caseous areas heal can become calcified. Some of these calcified nodlues can contain bacteria which is contained by the immune system and can lay dormant for years. These nodules are called Ghon Focuses.
What are the tissue changes in reactivated TB?
Fibrosing and cavitating apical lesions. ( Cancer is an important differential diagnosis).
What is miliary TB?
This is a disease that occurs throught the haematogenous spread of bacilli to mulitple sites
Why does TB reactivate?
The patient has decreased T cell function due to -
Age
Coincident disease (HIV)
Immunosuppressive Therapy
The patient is reinfected at a high dose or with a more virulent organism.
How do we diagnose TB?
We can take microbiological samples to look for the presence of mycobacterium.
Biopsy using special stains
Name some upper respiratory tract conditions?
Common cold
Sore throat - pharyngitis
Sinusitis
Epiglottis
What infections does a viral throat swab look for?
Influenza A Influenza B RSV Metapnemovirus Rhinovirus Coronavirus Parainfluenza Adenovirus Enterovirus Parechovirus Mycoplasma pneumoniae - not a virus but it is detected
What is strep throat?
This is a streptococcal infection
It is a bacterial infection that causes swelling of the throat
What are the symptoms of strep throat infections?
Exudate Pus formation Sore throat Dysphagia Dysphonia
What is tonsilitis?
This is usually caused by bacterial infection, in particular, beta haemolytic streptococcus
What are some of the symptoms of tonisilitis?
Swollen tonsils Erythematous Dysphagia Dysphonia Recurrent Tonsilitis
What are some of the treatments for tonsilitis?
If it is betahaemolytic steptococcus, it can be treated with penicillin V
A tonsilectomy can be done in cases of recurrent tonsilitis
What is quinsy?
This is a complication of tonsilitis where there are peri-tonsillar abscesses filled with pus. They usually cross across the midline into the other side of the mouth. These can be drained.
What is epigoititis?
This is usually caused by a bacterial infection of the epiglottis mainly caused by HAEMOPHILUS INFLUENZAE TYPE B. This is a life threatening condition as it can lead to airway blockage.
What is the treatment for epiglotitis?
This requires immediate endotrachial intubation and intravenous antibiotics (CEFTAZIDIMINE)
What is the common cold (coryza)?
This is an acute VIRAL infection of the nasal passages often accompanied by a sore throat and occasional mild fever. It is spread by droplets and fomites.
What are some complications of coryza?
Sinusitis
Acute bronchitis
What are some caused of coryza?
Most commonly rhinovirus infection.
Also adenovirua, RSV and coronavirus
What is sinusitis?
This is an infection of the paranasal sinuses.
What are the causes of sinusitis?
Most commonly bacterial infection with streptococcus pneumoniae or haemophilus influenza. It can sometimes be caused by fungal infection.
What are some of the symptoms of sinusitis?
Frontal headache
Retro-orbital pain
Maxillary sinus pain
Tooth ache discharge
What is acute sinusitis?
This is normally preceeded by a common cold and has purulent nasal discharge. It has a mostly viral aetiology but some require antibiotics
What is diphtheria?
This is a life threatening condition caused by toxin production. There is a characteristic pseudo-membrane but this condition is not usually seen in the UK.
What are some lower respiratory tract infections?
Acute bronchitis
Acute exacerbation of COPD
What is acute bronchitis?
This is a bacterial infection often described as a cough that goes to the chest. There is often thickening of the bronchiole walls. It is often proceeded by a viral infection. It is more likely to occur in patients with COPD or in smokers.
What are some of the clinical features of acute bronchitis?
Productive cough Fever in the minority of cases Normal chest examination Normal chest X-ray Transistent wheeze
Which bacterium can cause acute bronchitis?
Streptococcus pneumoniae
Haemophilus influenzae
What is used to treat acute bronchitis?
It is usually self limiting and antibiotics arent required, however there are cases when amoxicillin is required in more serious illness.
What are symptoms of an acute exacerbation of COPD?
Increased sputum production Increased sputum purulence More wheezy Breathlessness These must be in excess of normal symptoms
What will we seen in patients on examination of a COPD exacerbation?
Respiratory distress Wheeze Coarse crackles Cyanosis Ankle oedema in advanced disease.
How do we manage a COPD exacerbation in primary care
We would prescribe -
An antibiotic - doxycycline or amoxicillin
Bronchodilator inhalers
In some cases a short course of steroids.
