Respiratory Tract Infections Flashcards
What does rhinovirus cause?
Common cold
What does the influenza virus cause?
Flu
What causes meningitis?
Haemophilus influenza
What bacteria are present in >50% of normal people in the respiratory tract?
- Bacteroides spp
- Candida albicans
- Oral streptococci
- Haemophilus influenza
What bacteria are occasionally present in the respiatory tract (<10% normal people)?
- Streptococcus pyogenes
- Streptococcus pneumoniae
- Neisseria meningitidis
What are some of the host defenses in the RT?
- Saliva
- Mucus
- Cilia (muco-ciliary escalator/elevator)
- Nasal secretions
- ANtimicrobial peptides
What cells produce mucous?
Goblet cells
What bacteria causes whooping cough?
Bordetella pertussis
What demographic does whooping cough generally target?
<5 years old (90% of cases)
What does the catarrhal stage (1 week) of whooping cough include?
- Highly contagious
- Malaise
- Mucoid rhinorrhoea
- Conjunctivitis
What does the paroxysmal stage (1-4 weeks) of whooping cough include?
- Paroxysms of coughing with a classic inspiratory “whoop”
- Lumen of respiratory tract is compromised by mucus secretion and mucosal oedema
How is whooping cough diagnosed?
- By characteristic “whoop”
- Bacterial isolation from nasopharyngeal swabs
- NAAT
How is whooping cough treated?
- In catarrhal stage can be treated with erythromycin
- In paroxysmal stage, antibiotics have no effect
- Isolationn
- Supportive care (hospitalisation for infants)
What does bordetella pertussis attach to?
- Attaches and replicates in the ciliated respiratory epithelium, does not invade deeper structures
What kind of bacteria is bordetella pertussis?
Gram negative aerobic coccobacilus
What are the toxic factors produced by bordetella pertusis?
- Pertussis toxin (Ptx) (can paralyse cilia)
- Adenylate cyclase toxin (increases cAMP)
- Tracheal cytotoxin (kills tracheal cells)
- Endotoxin (damages cells)
What infections can cause acute bronchitis?
- Rhinovirus
- Coronovirus
- Adenovirus
- Mycoplasma pneumoniae
Secondary infections - Streptococcus pneumoniae
- Haemophilus influenzae
What is chronic bronchitis characterised by?
- Cough and excessive mucus secretion in tracheobronchial tree
What can cause chronic bronchitis?
Anatomical disturbances of the respiratory system
- Immune deficit: SCID
- Ciliary deficit: Kartenger syndrome, smoking
- Excessively thick mucus: CF
What is bronchiolitis?
- Infection of bronchioles
- Restricted to children <2 years
- Mainly caused by respiratory syncitial virus
What is the most common cause of infection-related death in the UK and USA?
Pneumonia
What can cause pneumonia in neonates/children?
- Mainly viral
- Streptococcus B
- E coli
- Chlamydia trachomatis
What can cause viral pneumonia?
- Influenza virus
- Measles
- Coronavirus
- Parainfluenza virus
- Respiratory syncytial virus (RSV)
- Cytomegalovirus (CMV)
- Adenovirus
What can cause bacterial pneumonia?
- Streptococcus pneumoniae
- Mycobacterium tuberculosis
- Haemophilus influenza
- Pseudomonas aeruginosa
- Staphylococcus aureus
What atypical pneumonias do not respond to penicillin?
- Mycoplasma pneumoniae
- Legionella pneumophillia
- Chlamydia psittaci
- Chlamydia pneumoniae
- Coxiella burnetii
What are the different anatomical classifications of pneumonia?
- Lobar pneumonia
- Bronchopneumonia
- Interstitial pneumonia
- Necrotising pneumonia
What is interstitial pneumonia usually a characteristic of?
Viral infection
What are the cinical features of streptococcus pneumoniae infection?
- Initially: Abrupt onset Rigors Fever Malaise Tachycardia Dry cough - Followed by: Productive cough with rusty sputum Spiky temperature Lobular consolidation
What are the clinical features of mycoplasma pneumoniae?
- Fever
- Dry cough
- Dyspnoea
- Lymphadenopathy
What are the clinical features of haemophilus influenza?
- Mainly occurs in children
- Consolidation or patchy bronchopneumonia
- Persistant purulent sputum and malaise
What bacteria causes Legionnaire’s disease?
Legionella pneumophila
How is legionella spread?
Through aerosols, but not person to person
What are the clinical features of legionnaire’s disease?
- Tachypnoea
- Purulent sputum
- CXR shows consolidation
What type of bacteria is legionnaire’s disease?
Gram negative bacillus
What does legionella pneumophila secrete?
protease causing lung damage
How is legionnaire’s disease diagnosed?
- Gram staining of sputum
- Recognition with stereotype-specific fluorescent antibody
- Culture of Legionella on cystine yeast extract agar
- Detection of antigen in urine
- 4-fold rise in antibody
What are the clinical features of measles?
- Fever
- Runny nose
- Koplik’s spots - clusters of white lesions
- Characteristic rash
- May result in neurological complications
- Can cause ‘giant cell’ (Hecht’s) pneumonia in the immunocompromised - usually fatal
How is measles spread?
Via aerosol
Where does measles replicate?
LRT
What kind of virus is measles?
Paramyxovirus
How long are people incubated for when they have measles?
10-14 days
How is measles diagnosed?
- Serology for measles-specific IgM
- Virus isolation
- Viral RNA detection
How is measles treated?
- If severe, ribavirin available
- Antibiotics for secondary bacterial infection
What is an endemic?
Present in the community at all times; at a relatively low to medium frequency but at a steady state
What is an epidemic?
Sudden severe outbreak within a region or group
What is a pandemic?
Occurs when an epidemic becomes widespread and affects a whole region, a continent, or the entire world
What are the three types of influenza virus?
- Type A: epidemics and pandemics, animal reservoir
- Type B: epidemics, no animal hosts
- Type C: minor respiratory illness
What are the type-specific antigens (spikes) on the influenza virus?
- Haemagglutinin (H)
- Neuraminidase (N)
What does the segemented single-stranded RNA allow for?
- Reassortment (“shuffling”) which gives rise to novel combinations of H and N antigens
How many segments of single-stranded RNA are there in the influenza virus?
8
What is antigenic drift?
- Small point mutations in the H and N antigens which occur constantly
- Allows the virus to multiply in individuals with immunity to preceding strains
- New subtype can re-infect community
- Occurs with all influenza types
What is antigenic shift?
- Sudden major change based on recombination between two different virus strains when they infect the same cell
- Produces a virus with novel surface glycoproteins
- New strain can spread through previously immune populations - new pandemic
What makes a pandemic?
- Antigenic shift
- Most people have no immunity
- Attack rate is high - it spreads rapidly
- Mortality can be high
What kind of virus was swine flu?
- H1N1 virus
- zoonotic
Who was affected mostly by swine flu?
<40 years as most older people had a degree of immunity against H1N1
How is influenza diagnosed?
- Nasopharyngeal apirate Direct immunofluorescence Culture NAAT detection - Serology
How is influenza treated?
- Amantadine
- Zanamavir
- Oseltamivir “Tamiflu”
How is influenza managed?
- Rest, warmth, hydration, analgesia
- Anti-viral treatment within 48hrs has some effect on the duration of fever
- Antibiotics not given unless secondary bacterial infection suspected
How are influenza viruses prevented?
- Killed vaccine has 70% efficacy
- Different strains of antigen used in different years in anticipation of latest strain toemerge
What is the influenza vaccine based on?
- The predicted strains
- Trivalent vaccine
- Based off of new recombinant methods
What does SARS stand for?
Severe Acute respiratory syndrome
What are the symptoms of SARS?
- Sudden onset of high fever
- Dry cough
- Chills and shivering
- Muscle aches
- Breathing difficulties
2002 - 10% fatality rate
How was SARS transmitted?
- Droplets
- Faeces
- Infected animals
How long are individuals with SARS incubated for?
2-7 days (10 days max)
What is the SARS-associated coronavirus identified by?
- Virus isolation in cell culture
- Electron microscopy
- Molecular techniques
What does SARS-associated coronovirus look like?
- Enveloped
- RNA virus
- Characteristic ‘halo’
- Receptor for spike protein is ACE2
What is given to treat SAR?
No specific anti-viral treatment available
- Ribavirin
- Corticosteroids
- Interferons
- Anti-retroviral therapies e.g protease inhibitors
Whole inactivated virus vaccine has now been developed
What fungal infections can cause respiratory infections?
- Apergillus fumigatus
- Pneumocystis jiroveci (asscciated with AIDS)
What parasitic infections can cause respiratory tract infections?
- Ascaris
- Strongyloides
- Schistosoma
- Echinococcus granulosus
