Respiratory Tract Infections and Immunity Flashcards
What are the signs and symptoms of an upper respiratory tract infection?
A cough Sneezing A runny or stuffy nose A sore throat Headache
What are the signs and symptoms of a lower respiratory tract infection?
A “productive” cough - phlegm Muscle aches Wheezing Breathlessness Fever Fatigue
What are the signs and symptoms of pneumonia?
Chest pain
Blue tinting of the lips
Severe fatigue
High Fever
What are DALYs?
DALY – Disability-adjusted Life Year
A sum of Years of Life Lost (YLL) and Years Lost to Disability (YLP)
What demographic and lifestyle factors increase risk of pneumonia?
Age <2 years or >65 years
Cigarette smoking
Excess alcohol consumption
What social factors increase risk of pneumonia?
Contact with children aged <15 years
Poverty
Overcrowding
What medications increase risk of pneumonia?
Inhaled corticosteroids
Immunosuppresants (e.g steroids)
Proton pump inhibitors
What medical history increases risk of pneumonia?
COPD, Asthma Heart disease Liver disease Diabetes mellitus HIV, Malignancy, Hyposplenism Complement or Ig deficiencies Risk factors for aspiration Previous pneumonia
What specific risk factors for certain
pathogens are there?
Geographical variations
Animal contact
Healthcare contacts
What are causative Agents of respiratory infection?
Bacterial Streptococcus pneumoniae Myxoplasma pneumoniae Haemophilus Influenzae Mycobacterium tuberculosis
Viral Influenza A or B virus Respiratory Syncytial Virus Human metapneumovirus Human rhinovirus Coronaviruses
Define bronchitis, bronchiolitis and pneumonia
Bronchitis - inflammation and swelling of the bronchi
Bronchiolitis - inflammation and swelling of the bronchioles
Pneumonia - Inflammation and swelling of the alveoli
What are the mechanisms of damage in acute bacterial pneumonia?
Lung injury results in arterial hypoxemia causing acute respiratory distress syndrome. Bacteremia causes organ infection resulting in organ injury or dysfunction which lung injury also contributes to. This leads to sepsis and deterioration. Pneumonia causes systemic inflammation and organ injury + dysfunction.
Deterioration refers to decrement in pulmonary, cardiovascular, neuromuscular, haematologic, cognitive, psychological and other functions.
How is potential bacterial pneumonia graded?
CRB/CURB-65 scoring (1 point per item) Confusion Respiratory rate – >30 breaths/min Blood pressure - < 90 systolic and/or 60 mmHg diastolic 65 - 65 years old or older In hospital add Urea - 7 mmol/L
What is the treatment plan based on CRB scoring?
If 0, low severity so antibiotics and home treatment
If 1-2, moderate severity so consider hospital referral
If 3-4, severe and urgent hospital admission + empirical antibitiotics
What are supportive treatments for bacterial pneumonia?
Oxygen (for hypoxia) Fluids (for dehydration) Analgesia (for pain) Nebulised saline (may help expectoration) Chest physiotherapy?
What antibiotics are prescribed for bacterial pneumonia?
Penicillins e.g. amoxicillin – beta lactams that bind proteins in the bacterial cell wall to prevent transpeptidation
Macrolides e.g. clarithromycin – bind to the bacterial ribosome to prevent protein synthesis
Define opportunistic pathogen and pathobiont
Opportunistic Pathogen: A microbe that takes advantage of a change in conditions (often immuno-suppression).
Pathobiont: A microbe that is normally commensal, but if found in the wrong environment (e.g. anatomical site) can cause pathology.
Why do viral infections result in disease?
Cause mediator release, cellular inflammation and epithelial damage. Epithelial damage results in loss of cilia, bacterial growth, poor barrier to antigen and loss of chemoreceptors.
What factors cause severe disease?
- Highly pathogenic strains (zoonotic)
- Absence of prior immunity
Innate immunodeficiency (e.g. IFITM3 gene variant)
B cells (antibody- presumably local)
T cells (correlate with peripheral levels?) - Predisposing illness/conditions
Frail elderly
COPD/asthma
Diabetes, obesity, pregnancy etc.
Describe viral binding
Most respiratory viruses can infect cells throughout the respiratory tract, but tend to preferentially adapt to bind cells of the upper respiratory tract if they have existed in humans for a prolonged time
What defence mechanisms does the respiratory epithelium have?
Tight junctions – prevents systemic infection
Mucous lining and cilial clearance – prevents attachment, clears particulates
Antimicrobials – recognise, neutralize and/or degrade microbes and their products
Pathogen recognition receptors – recognise pathogens either outside or inside a cell.
Interferon pathways – activated by viral infection. Promotes upregulation of anti-viral proteins and apoptosis.
Contrast antibodies in oropharynx as compared to lower resp tract
Oropharynx has high frequency of IgA-plasma cells
ECs express poly IgA receptor, allowing export of IgA to the mucosal surface. Homodimer is extremely stable in protease rich environment.
LRT has thin-walled alveolar space which allow transfer of plasma IgGs into the alveolar space.
What are symptoms of RSV bronchiolitis
Chest wall retractions, nasal flaring, hypoxemia and cyanosis, croupy cough, expiratory wheezing, tachypnoea with apnoeic episodes
What are RSV risk factors
Premature birth
Congenital heart and lung disease
