1b// Respiratory infections Flashcards
What is the typical presentation of upper respiratory tract infections?
Cough Sneezing Runny/stuffy nose Sore throat Headache
What is the typical presentation of a lower respiratory tract infection?
Productive cough Muscle aches Wheezing Breathlessness Fever Fatigue
What is the typical presentation of pneumonia?
Chest pain
Blue tinge on lips
Severe fatigue
High grade fever
what are the main medical history risk factors for respiratory infection?
COPD, asthma heart disease liver disease diabetes mellitus HIV, malignancy, hypertension complement/Ig deficiencies aspiration risk fctors previous pneumonia
what are the demographic/lifestyle risk factors for respiratory infections?
under 2 yrs old, over 65
smoking cigarettes
excess alcohol consumption
what are the social risk factors for respiratory infections?
contact with children under 15
poverty
overcrowding
what are the medication risk factors for respiratory infections?
immunosuppressants e.g steriods
inhaled corticosteroids
proton pump inhibitors
what are the common bacterial causative agents? (in order)
streptococcus pneumoniae mycoplasma pneumoniae staphylococcus aureus haemophilus influenzae mycobacterium tuberculosis
what are the common viral causative agents? (in order)
human rhinovirus influenza A/B human metapneumovirus respiratory syncytial virus (infancy) coronaviruses
what sort of organism is streptococcus pneumoniae?
gram positive
extracellular
opportunistic
what organisms are most typical for ventilator associated pneumonia?
pseudomonas aerginosa
staphylococcus aureus
what organism represents 40-50% of community acquired pneumonia?
streptococcus pneumoniae
what are the mechanisms of damage from acute bacterial pneumonia?
inflammation and swelling of alveoli
cellular and extracellular infiltrate, type 1 cells damaged
therefore gas exchange barrier damaged & ineffective
how is bacterial pneumonia graded? in hospital
CURB 65 one point for each Confusion respiratory rate (>30/min) blood pressure (<90 sys/ 60 dia) 65 years or older urea - 7mmol/L 3+ points = aggressive treatment
how is a CURB 65 score of 0 treated?
in community - amoxicillin
in hospital - doxycycline PO
how is a CURB65 score of 1/2 treated?
community - amoxicillin + clarythromycin
how is a CURB65 score of 3-5 treated?
community - benzyl penicillin IV, clarythromycin oral
hospital - tazocin IV +/- gentamicin IV
how do penicillins treat pneumonial infections?
beta lactams
bind to proteins in bacterial cell wall to prevent transpeptidation
how do macrolides treat pneumonial infections?
bind to bacterial ribosome to prevent protein synthesis
how do you acquire pnuemonia?
mostly from own microbiome
skin, gastrointestinal tract, nose, oropharynx
opportunistic pathogens
what is the mechanism of damage for viral respiratory infections?
damage to epithelium - cilia loss, loss of barrier defence, chemoreceptors
mediator release
cellular inflammation
local immune memory
how do severe viral infections develop?
highly pathogenic strains
host absence of prior immunity - innate immunodeficiency, T cell, B cell memory
predisposing illnesses/conditions
how do respiratory epithelial cells protect against viral infection?
tight junctions - prevent systemic infection
mucous lining, cilial clearance - prevents attachment + promotes clearance
antimicrobials - recognise, neutralise, degrade pathogens and profucts
pathogen recognition receptors
interferon pathways - upregulation of anti-viral proteins and apoptosis
what are serotypes?
viruses which cannot be recognised by serum/antibodies that recognise another virus - implications for protective immunity
where in the respiratory tract is there a high frequency of IgA-plasma cells?
oronasopharynx
epithelial cells express poly IgA receptor allowing export of IgA to mucosal surface
where in the respiratory tract is enriched for IgG-plasma cells?
alveoli/bronchioles
thin walled alveolar space allows transfer of plasma IgGs into alveolar space
what is the immunity for influenza?
no reinfection by same strain
imperfect vaccines - vaccine induced immunity rapidly decreases, mainly homotypic, annual vacc required
what is the immunity for RSV like?
recurrent reinfection with similar strains (2 serotypes also)
no vaccine - poor immunogenicity, vaccine enhanced disease
what are the risk factors for RSV bronchiolitis in infancy?
premature birth
congenital heart and lung disease
what are the symptoms of RSV bronchiolitis in infancy?
nasal flaring hypoxemia and cyanosis croupy cough (barking) expiratory wheezing, prolonged expiration tachypnoea chest wall retractions
what are the supportive treatments used for viral and bacterial infections?
oxygen fluids analgesia nebulised saline chest physio
what are the prophylactic treatments for viral infection?
viral vector vaccines
mRNA vaccines
major surface antigen vaccines
what are the main therapeutic treatments for viral infections?
anti inflammatories - dexamethasone (steroid), toclizumab, sarilumab (anti IL-6R/ anti IL-6)
anti virals - remdesivir (broad spec), paxlovid, casirivimab
how does remdesivir act?
blocks RNA-dependent RNA polymerase activity
how does paxlovid act?
antiviral - protease inhibitor
how do infections and chronic lung disease interplay?
viral bronchiolitis associated with asthma development
rhinoviruses most common asthma and COPD exacerbations
high likelihood of secondary bacterial pneumonia after viral infection
