W6 27 respiratory infections including tuberculosis Flashcards
What can we split the respiratory tract into?
Upper and lower respiratory tracts
Upper - nasal and oral cavities, pharynx, epiglottis, larynx
Lower - trachea, bronchus, lungs, diaphragm
What is the normal state of the upper and lower RTs?
Upper usually has many bacteria and viruses present at all time but not causing infection
Lower is normally sterile
What defence mechanisms are in the respiratory tract?
Cilia, mucus production, cough, swallow mechanisms, immunoglobulins
When do URTI require antibiotics?
When bacterial aetiology is known or suspected (usually tends to worsen rather than resolve)
Systemically unwell
Features or high risk of complications
Are URTIs common?
Common, short lived, rarely serious, viral aetiology
What is acute coryza?
Nasal discharge, sneezing and cough (prolonged night cough with post-nasal drip)
What happens when there is pharyngeal compared with laryngeal involvement?
Pharyngeal involvement - sore throat
Laryngeal involvement - hoarse/lost voice
What is tracheitis/bronchitis?
Wheeze
When should we be worried about wheezing?
Wheezing upon breathing in = stridor, should prompt rapid investigation/treatment
What should nasal congestion, facial pain/pressure raise the possibility of?
Sinusitis
What are the common infections of the Nasopharynx, oropharynx, ear and larynx and trachea caused by?
(Don’t learn just be aware)
Nasopharynx - rhinoviruses (common cold), S. aureus
Oropharynx - Group A Strep (sore throat)
Ear - haemophilus
Larynx & trachea - parainfluenza
What is an important bacteria of the epiglottis, and what does it cause?
Haemophilus influenza type B
Causes acute onset of fever, sore throat, respiratory diseases
Is Haemophilus influenzae type B still around?
Nearly completely disappeared due to vaccine
What are worrying signs of Haemophilus influenzae type B?
Severe throat infection, with massive oedema of the epiglottis. Illness develops rapidly with high fever and difficult swallowing. AVOID MANIPULATION OF THROAT (call for help - ENT). Drooling and stridor should raise red flags
What is sinusitis and what causes it?
Inflammation of the lining of the sinuses
S. aureus, H. influenzae, and anaerobes (mainly gram +ve)
What is pharyngitis (sore throat/tonsillitis) caused by?
Can be viral or bacterial - difficult to differentiate
Streptococcus pyogenes: Group A streptococcal are most common bacterial cause
What is pharyngitis characterised by?
Inflammation, exudate, fever, tender cervical lymph nodes, red tender sore throat
What are some complications of pharyngitis?
Scarlet fever (characteristic red rash all over body)
Rheumatic fever
Post-strep Glomerulonephritis
What are the types of influenza?
A B and C
Type A and B cause most of the disease burden
The influenza virus is antigenically unstable and constantly changing. Describe what an antigenic drift is?
Antigenic DRIFT = minor changes to the amino acid sequence of the haemagglutinin (HA).
Happens fairly frequently, and people might still have some protection.
The influenza virus is antigenically unstable and constantly changing. Describe what an antigenic shift is?
Antigenic SHIFT = more major changes in the haemagglutinin or the Neuraminidase resulting in a large change in the virus. Shifts in the virus are associated with outbreaks of flu, with the population having little or no protective immunity.
Who are offered the flu vaccine?
Risk groups are offered it each year (eg over 65s, pregnant, at risk groups)
It is altered each year to reflect the most likely circulating strains but it is not always reactive.
How do you diagnose flu and what should you do if you suspect flu clinically?
Diagnose via a throat swab detection by PCR (but mainly just clinical)
If detected clinically - isolation precautions. Antivirals usually not necessary.
What is RSV?
Respiratory syncytial virus (RSV). It is transmitted by large droplets and secretions. It is a generally mild virus that occurs regularly each year, but can be severe in children (potentially developing bronchiolitis and pneumonia). Infection control in hospitals is critical to stop it. Disease in childhood does not give lifelong protection.
What is novel coronavirus?
Cause respiratory infections of varying severity in humans and animals
What are some lower respiratory tract infections (LRTI)?
Pneumonia - infection of lung tissues
Acute bronchitis/bronchiolitis - inflammation of bronchi
Primary difference is pneumonia has radiological changes ie abnormal CXR
Tuberculosis
What are the different types of pneumonia?
Acute - hospital and community - typicals and atypicals
Chronic - pulmonary TB, fungal pneumonia
What are atypicals?
They have an inability to grow on normal laboratory media
What are the symptoms and signs of typical and atypical community acquired pneumonia?
Typical - fever, chest pain, purulent sputum
Atypical - dyspnoea and cough, minimal sputum production, more systemic upset
On a chest radiograph what is the difference between lobar and bronchopneumonia?
Lobar/multilobar/segmental - one or more lung lobes affected
Bronchopneumonia - diffuse/patchy/bilaterally, assymetric usually affects both lower lobes
What can cause atypical pneumonias?
Legionella pneumophila - contaminated water sources - can cause fever and diarrhoea from changes in electrolytes eg lower sodium
Mycoplasma pneumoniae
What is TB?
Tuberculosis is an airborne disease caused by the bacterium Mycobacterium tuberculosis.
How is TB transmitted?
M. tb spread via airborne particles called droplet nuclei, expelled when a person infected coughs, sneezes shouts etc. Transmission occurs when droplet nuclei inhaled and reach the alveoli of the lungs.
What is the probability that TB will be transmitted?
Susceptibility of the exposed person
Infectiousness of person with TB
Environmental factors that affect concentration of M tb organisms, ventilation and air circulation
Proximity, frequency and duration of exposure
What happens when someone gets the TB bacterium?
Tubercle bacilli multiply in the alveoli. A small number of tubercle bacilli enter the bloodstream and spread throughout the body. The tubercle bacilli may reach any part of the body.
Within 2-8 weeks, macrophages ingest and surround the tubercle bacilli. The cells form a barrier shell called a granulomas that keep the bacilli contained and under control (LTBI). You are latent and not infectious.
What happens if the immune system cannot keep the tubercle bacilli under control?
The bacilli begin to multiply rapidly (active TB disease)l this process can occur in different areas of the body eg lungs, kidneys, brain or bone. You are infectious.
What is LTBI?
Latent TB infection
Granulomas may persist (LTBI) or break down to produce TB disease
2-8 weeks after infection, LTBI can be detected via TST (tuberculum skin test) or interferon-y release assay (IGRA)
The immune system is usually able to stop multiplication of bacilli.
Persons with LTBI are not infectious and do not spread organisms to others.
What is occurring in active TB disease?
In some, the granulomas break down, bacilli escape and multiply, resulting in TB. Can occur soon after the infection, or heard later. Persons with TB a disease are usually infectious and can spread bacteria to others. Positive M tb culture confirms TB diagnosis.
Where are the sites of disease for TB?
Lungs (pulmonary) - most common and usually infectious
Miliary - occurs when bacilli spread to all parts of the body; rare but fatal if untreated
CNS - usually occurs as meningitis, but can occur in brain or spine
Outside lungs (extra-pulmonary) - usually not infectious unless a person has:
- concomitant pulmonary disease
- extra pulmonary disease in oral cavity or larynx or
- extra-pulmonary disease with open site, especially with aerosolised fluid
What is the risk of developing TB?
Low for people with normal immune system
Increased risk of progressing to TB with a weak immunity, eg untreated HIV or children <5
What groups are most at risk of TB?
Under-served populations = don’t seek out healthcare and hard to follow up on, eg prison populations, IV drug users, high alcohol intake
When do you consider TB and what do you do?
Cough (more than 3 weeks)
Fever (more than 3 weeks)
Unexplained weight loss
Night sweats
Take sputum for AFB (bacteria) smear and culture, do a chest x-ray and follow up
How do you diagnose TB?
Clinical awareness
Microbiology of pathological samples - discharged pus or biopsy material eg by direct staining and culture
Histopathology patterns of inflammation
Tuberculin skin testing
Interferon gamma release assays
Radiographic appearance (pg310/311 for examples)
How do you treat TB?
Requires multiple antibiotic regime to guard against the development of antibiotic resistance, it must be prolonged. Dormant bacteria are hard to kill. Minimum 6 months. Highly effective in eliminating infection and less effective in restoring function.
What are the problems with TB treatment?
Non compliance, drug resistance, side effects
