respiratory tract infection

Question 1

potential evolution line of a resp tract infection?

Answer 1

upper respiratory tract infection → lower resp tract infection → pneumonia

Question 2

which is worse - upper or lower tract infections?

Answer 2

lower → among the leading causes of death in the world

Question 3

what factor has a significant effect on mortality burden?

Answer 3

age

Question 4

risk factors for pneumonia?

Answer 4

• demographic/lifestyleage under 2 or 65+cigarette smoking, excess alcohol
• social factorsclose contact with children <15 and overcrowding, poverty
• medicationsinhaled corticosteroidsimmunosuppressantsPPIs
• medical historyCOPD, asthma, DM, heart/liver diseaseHIV, malignancy, hyposplenismcomplement/Ig deficienciesaspiration risk factorsprevious pneumonia

geographical variation,animal contect,healthcare contact

Question 5

common causative agents for resp infections?

Answer 5

• bacterialstreptococcus pneumoniaemycoplasma pneumoniaehaemophilus influenzaemycobacterium tuberculosis
• viralinfluenza A/Brespiratory syncytial virushuman metapneumovirusrhinoviruscold viruses

Question 6

differences in common causative agents in CAP and HAP?

Answer 6

community acquired → strep pneumoniae, mycoplasma pneumoniae,haemophilus influenza,staph.aureus,chlamydia pneumonia

hospital acquired → staph aureus, pseudomonas aeruginosa,klebsiella species,E coli,acinetobacter spp,enterobacter spp

Question 7

subtypes of acquired pneumonia?

Answer 7

typical vs atypical
typical → common bacterial species eg streptococcus pneumonia,haemophillus influenza and moraxella catarrhalis

atypical → more distinct species, slower onset of symptoms, milder eg mycoplasma pneumonia,chlamydia pneumonia,legionella pneumophilia

Question 8

what is the difference in treatment? pneumoonia subtypes

Answer 8

typical = often penicillin eg amoxicilin beta lactams that bind protein in the bacterial cell wall to prevent transpeptidation

atypical = often penicillin + macrolides eg clarithromycin bind to bacterial ribosomes to prevent protein synthesis

Question 9

what does pneumonia cause?

Answer 9

lung injury → arterial hypoxemia → possibly ARDS

bacteremia → possibly sepsis

inflammation → possibly lung function deterioration

Question 10

how is potential bacterial pneumonia graded?

Answer 10

use CRB-65 / CURB-65 scoring

1 point for each of:

confusion, resp rate > 30, blood pressure under 90 syst and/or 60 dias, 65 yo or older

in hospital: urea over 7 mmol/L

Question 11

CURB-65 scoring boundaries

Answer 11

0 = low severity, 1-2 = moderate severity (consider hospital), 3-4 = high severity (urgent hospital, empirical antibiotics if life threatening)

Question 12

bacterial pneumonia treatment?

Answer 12

supportive therapy → oxygen, fluids, analgesia

antibiotics → penicillins, macrolides

Question 13

what is an opportunistic pathogen?

Answer 13

microbe that takes advantage of a change in conditions e.g. immunosuppression to cause infection

Question 14

what is a pathobiont?

Answer 14

microbe that is normally commensal but can cause illness if found in the wrong place

Question 15

factors that can cause variable disease outcomes?

Answer 15

specific strains of causative agent, absence/presence of prior host immunity, predisposing illnesses and conditions

Question 16

where in the respiratory tract do viruses tend to infect?

Answer 16

if virus has existed in humans for a long time → adapt to preferentially target cells in upper resp tract

Question 17

defence mechanisms of the respiratory epithelium?

Answer 17

tight junctions

mucous lining and cilial clearance

antimicrobials, pathogen recognition receptors, interferon pathways

Question 18

what are serotypes?

Answer 18

different serotypes = can’t be recognised by same serum/antibody

Question 19

antibody distribution in respiratory tract?

Answer 19

upper → high frequency of IgA plasma cells

lower → enriched for IgG - thin alveolar walls allows transfer of plasma IgG into alveolar space

Question 20

what is RSV?

Answer 20

respiratory syncytial virus

Question 21

characteristics of infection?

Answer 21

repeated infection by similar strains possible

Question 22

in what subset of the population is it particularly prevalent?

Answer 22

babies → almost all children have had it by age 3

Question 23

what does RSV cause

Answer 23

1% - severe bronchiolitis

croupy cough, hypoxemia and cyanosis, expiratory wheeze, tachypnea with apneic episodes, chest wall retraction

Question 24

risk factors of rsv

Answer 24

premature birth, congenital heart and lung disease

Question 25

SARS-CoV-2 treatment options?

Answer 25

supportive → oxygen, fluids, analgesia

prophylactic → vaccine

therapeutic → anti-inflammatory e.g. dexamethasone

antivirals → remdesivir broad spectrum, monoclonal antibodies possible

Question 26

features of interplay between bacterial, viral and chronic lung diseases?

Answer 26

viral bronchiolitis → asthma development association

rhinoviruses (and other transient infections) can cause exacerbations of chronic disease like COPD, asthma

high likelihood of secondary bacterial pneumonia after viral resp infection

Question 27

signs and symptoms of resp infection

Answer 27

upper-cough,sneezing,runny/stuffy nose/sore throat/headache

lower-productive cough,muscle aches, wheezing,breathlessness,fever,fatigue

pneumonia-chest pain,blue tinge,severe fatigue,high fever

Question 28

ventilator associated pneumonia

Answer 28

pseudomonas aeruginosa
staphylococcus aureus
enterobacter

Question 29

why do viral infections cause disease

Answer 29

epithelial damage leads to loss of cilia,reduced barrier integrity,bacterial growth

Question 30

serotypes

Answer 30

viruses which cant be recognised by serum that recognise another virus-implications for protective immunity

Question 31

IFN-I

Answer 31

important role in viral infection
inhibits viral replicstion and activates antiviral state

Question 32

innate immunity

Answer 32

alveolar macrophages-phagocytosis,tissue homeostasis and pathogen sensing

resident dendritic cells-respond to inflammation and take up and present foreign antigen driving adaptive immune response

neutrophils-main cell type recrutied upon infection,can cause inflammatory damage

NK cells-provide innate antiviral immunity against infected cells

monocytes-resukts into site to provide mediators and macrophage sources

Question 33

antibody mediated immunity

Answer 33

humoral immunity
adaptive so dependant on prior exposure
b cells activated to differentiate into antibody secreting plasma cells
different antibody classes provide different biochemical properties and function