RESPIRATORY TRACT INFECTIONS AND IMMUNITY Flashcards by Eric Lee

What symptoms are indicative of an upper respiratory tract infection?

Cough
Sneezing
Runny or stuffy nose
Sore throat
Headache

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What symptoms are indicative of a lower respiratory tract infection?

Phlegm from a cough
Muscle aches
Wheezing
Breathlessness
Fever
Fatigue

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What symptoms are indicative of pneumonia?

Chest pain
Blue tinting of lips
Severe fatigue
High fever

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What is the epidemiology for respiratory infections?

One of the leading causes of death in the world causing increased mortality in elderly

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What are some demographic and lifestyle risk factors for pneumonia?

Age < 2 years or > 65 years
Cigarette smoking
Excess alcohol

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What are some social risk factors for pneumonia?

Contact with children aged <15
Poverty
Overcrowding

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What are some medications that increase risk of pneumonia?

Inhaled corticosteroids
Immunosuppresants e.g. steroids
PPIs

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What are some previous diseases which could increase risk of pneumonia?

COPD, asthma
Heart disease
Liver disease
Diabetes mellitus
HIV
Malignancy
Hyposplenism
Previous pneumonia

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What are the 4 most common bacterial species that cause respiratory infections?

Streptococcus pneumoniae
Myxoplasma pneumoniae
Haemophilus influenzae
Mycobacterium tuberculosis

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What are the most common viruses that cause respiratory infections?

Influenza A/B
Respiratory syncytial virus
Human metapneumovirus
Human rhinovirus
Corona viruses

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How often do respiratory viral pandemics occur?

Almost one pandemic every decade

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What are some bacteria that are responsible for community acquired pneumonia?

Streptococcus pneumoniae (40-50%)
Myxoplasma pneumoniae
Staphylococcus aureus
Chlamydia pneumoniae
Haemophilus influenzae
Moraxella catarrhalis

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What are some bacteria that are responsible for hospital acquired pneumonia?

Staphylococcus aureus
Pseudomonas aeruginosa
Klebsiella species
E. coli
Acinetobacter spp.
Enterobacter spp.

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What are some bacteria that are responsible for ventilator associated pneumonia?

Pseudomonas aeruginosa (25%)
Staphylococcus aureus (20%)
Enterobacter

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What are some atypical bacterium causes of pneumonia?

Mycoplasma pneumoniae
Chlamydia pneumoniae
Legionella pneumophilia

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What is pneumonia?

Inflammation and swelling of alveoli

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How do you grade bacterial pneumonia?

CRB65 scoring (1 point per criteria)

Confusion
Respiratory rate > 30 breaths/min
Blood pressure < 90 systolic/ 60 mmHg diastolic

In hospital:
- Urea > 7 mmol/L

0 = home treatment
1-2 = consider hospital referral
3-4 = urgent hospital admission, empirical antibiotics if life-threatening

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What are the treatments for bacterial pneumonia

Oxygen
Fluids
Analgesia
Antibiotics

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What are the 2 types of antibiotics you can give patients with bacterial pneumonia?

Penicillins e.g. amoxicillin

Macrolides e.g. clarithromycin

How do penicillins work?

Beta-lactams that bind proteins in the bacterial cell wall to prevent transpeptidation

Typical CAPs may respond to these

How do macrolides work and give an example?

Antibiotics which bind to bacterial ribosome to prevent protein synthesis
E.g. clarithromycin

Atypical CAPs may respond these

Why can you catch pneumonia from yourself?

Many of the bacteria which can cause it are abundant in your microbiota

What are some bacteria that are present in your oropharynx microbiota and can cause pneumonia?

Haemophilus spp
Staph. aureus
Strep. pneumoniae

Haemophilus spp and staph. aureus also seen in nose but more commonly

What are some bacteria that are present in your nose microbiota and can cause pneumonia?

Strep. pneumoniae

What is a pathobiont?

A microbe which is normally commensal but if found in wrong environment (anatomical site) can cause pathology

What is an opportunistic pathogen?

A microbe that takes advantage of a change in conditions e.g. immunosuppression

What 3 things cause severe viral disease?

Highly pathogenic strains Absence of prior immunity Predisposing illness/conditions

What is viral tropism?

Depending on what the virus binds to, will decide where in the respiratory tract the virus tends to affect

Where does H1N1 influenza A tend to affect in the respiratory tract and why?

H1N1 influenza A haemogglutinin binds to alpha 2,6 sialic acids which are presented more in upper respiratory tract rather than lower

Where does H5N1 avian flu tend to affect in the respiratory tract and why?

H5N1 avian flu haemogglutinin binds to alpha 2,3 sialic acids which are presented more in lower respiratory tract rather than upper

Why do most viruses which have existed in humans for a prolonged time tend to infect cells of the upper respiratory tract?

Upper respiratory tract infections are easier to spread but cause less pathology/damage than lower respiratory tract infections

In what ways does the respiratory epithelium defend against infections?

Tight junctions (preventing systemic infection) Mucous lining + cilial clearance Antimicrobials Pathogen recognition receptors Interferon pathways (induces anti-viral state in cells)

Why do rhinoviruses account for 60% of all colds?

Over 100+ different serotypes

Which antibody is in greater numbers in the nasal cavity?

IgA as these bind to viruses and disable them | Lots of disulphide bridges so strong against protease rich extracellular environment

Which antibody is in greater numbers in the bronchi?

IgGs as the thin walled alveolar space allows transfer of plasma IgGs into alveolar space. Good at killing intracellular pathogens

How many serotypes does influenza have?

Lots of serotypes so vaccine-induced immunity rapidly wanes, annual vaccination required

How many serotypes does respiratory syncytial virus (RSV) have ?

Only 2 so causes recurrent re-infection with similar strains

Why does RSV currently not have a vaccine?

Poor immunogenicity of vaccine | Vaccine-enhanced disease

What is the leading cause of infant hospitalisation in the developed world?

RSV

Why is RSV notable in infants and what can it lead to?

50% of children infected in year 1 of life, all children by year 3 1% develop severe bronchiolitis Can repeatedly infect children

What are some symptoms of RSV in infants?

``` Nasal flaring Hypoxemia and cyanosis Expiratory wheezing, prolonged expiration Chest wall retractions Tachypnea with apneic episodes Croupy cough ```

What are the risk factors for RSV broncholitis in infants?

Premature birth | Congenital heart and lung disease

What are the treatment options for viral respiratory tract infections?

``` Oxygen Fluids Analgesia Vaccines Anti-inflammatory e.g. steroids Anti-virals e.g. remdesivir ```

What is the most common cause of developing asthma and COPD exacerbations?

Rhinoviruses

What does a viral respiratory tract infection increase the risk of?

Secondary bacterial pneumonia

What is viral bronchiolitis associated with?

Development of asthma