Introduction to Respiratory Infections Flashcards
most common site of infection
respiratory tract
how many rti in children per year
2-5
how many rti in adult per year
1-2
common reasons for medical consultations and time off work
inappropriate antibiotic prescription driving resistance
winter pressure on hospital beds
economic costs
tonsilitis
infection of tonsils
pharyngitis
“sore throat”
infection of pharynx
laryngitis
infection of larynx
tracheitis
infection of trachea
pleurisy
inflammation of pleura often caused by infection
bronchiolitis
infection of bronchioles (small airways)
bronchitis
infection of bronchi (large airways)
pneumonia
infection of alveoli and surrounding lung
protection - colonisation
commensal flora and colonisation resistance
normal swallowing reflex, epiglottis
protection - swallowing
neurological and anatomical factors
protection - lung anatomy
mucus and ciliated epithelium - mucociliary escalator
cough reflex
protection - immunity
innate and adaptive
soluble factors - IgA, defensins, collectin, lysozyme
alveolar macrophages
B and T cells
susceptibility to RTI
swallowing
colonisation of upper airway
altered lung physiology
immune dysfunction
co-morbidities
upper respiratory tract illness
viral - rhinovirus, influenza A, coronaviruses, adenoviruses, respiratory syncytial viruses, parainfluenza viruses
usually transient
complications of upper RTI
sinusitis, pharyngitis, otitis media, bronchitis, rarely pneumonia
may lead to bacterial super infection
influenza A causes systemic symptoms
rhinoviruses
common cold
bronchitis
sinusitis
coronaviruses
colds but occasionally severe resp illnesses
adenoviruses
upper RTI
pharyngitis
bronchitis
occasional pneumonia
resp syncytial viruses
bronchiolitis in small children
severe illness in care home residents
pneumonia in immunocompromised
parainfluenza viruses
croup
influenza A
flu
sars-cov-2
covid 19
severe resp illness with resp failure
emerged as cause of major global pandemic in 2019
high mortality and major economic impact
sars-cov
severe acute resp syndrome associated coronavirus
outbreak spread from china in 2002
severe resp illness with resp failure
middle eastern resp syndrome novel coronavirus (mers-ncv)
individual cases spread from middle east in 2012
similar to sars but low person to person spread
avian influenza
novel forms of influenza A
occasional human cases with severe illness
south-east asia
associated with exposure to poultry
low person to person spread
aetiology of pharyngitis
β-hemolytic streptococci (10-30%)
viral (70-80%) - rhino/adenovirus etc
glandular fever - epstein barr virus
acute hiv infection
aetiology of sinusitis
usually viral
bacterial - unilateral pain, purulent discharge, fever of >10 days/presenting acutely or with complications
microorganisms
streptococcus pneumoniae (40%)
haemophilus influenzae (30-35%)
other moraxella catarrhalis, streptococci
complications - brain abcess, sinus vein thrombosis, orbital cellulitis
acute epiglottitis
formerly children 2-4, fever, dysphagia, drooling and stridor
haemophilus influenzae type B - now rare due to Hib vaccine
adults can also have - most severe from Hib, also from causes of pharyngitis, other bacterial airway infections, additional pathogens in immunocompromised - e.g. AIDS
bordatella pertussis
acellular vaccine may not give lifelong immunity and vaccination may have reduced boosting from natural infections
adults - chronic cough, paroxyms of coughing and 50% post-ptussive vomitting
complications - pneumonia, encephalopathy, subconjunctival haemorrhage
croup
acute laryngo-tracheobronchitis
disease of children up to 6 (mostly 3mo-3yo)
mainly due to parainfluenza (also RSV, IAV and other resp viruses)
bronchiolitis infection and inflammation
infection due to resp syncytial virus (RSV) (80%) - rarely other viruses
inflammation of bronchioles and mucus production cause airway obstruction
bronchitis clinical features
cough may be productive or non-productive
SOB and often wheeze
may be fever by not systemic features of infection
wheeze but no signs of focal consolidation
bronchitis investigations
ABG/oximetry for those with chronic lung disease - determines need for hospitalisation
CXR shows no features of pneumonia - usually normal
bronchitis treatment
usually none especially if viral - sometimes antimicrobials
manage exacerbation of COPD/asthma with steroids and increased inhalers
bronchiectasis
abnormal dilation of airways and suppurative infection
chronic scarring of lung with excessive sputum production - bronchoohoea
bronchiectasis aetiology
congenital - CF, ciliary dysfunction, hypogammaglubulinemia
post-infectious - TB, suppurative pneumonia measles, whooping cough
other - foreign body
bronchiectasis symptoms
chronic cough
coius sputum
recurrent pneumonia
weight loss
pneumonia aetiology
mainly streptococcus pneumoniae (40%)
mycoplasma pneumoniae (~10%)
chlamydophila pneumoniae (~10%)
legionella pneumoniae and other spp. (<5%)
haemophilus influenzae (<5%)
klebsiella pneumoniae (rare, homeless and in hospital)
staphylococcus aureus (low % in community but increased after influenza and in hospital)
viruses (>10%)
people at risk of pneumonia
infants and elderly
copd and other chronic lung diseases
immunocompromised
nursing home
impaired swallow
diabetes
congestive heart disease
alcoholics and drug users
community acquired pneumonia (CAP)
incidence 5-11 per 1000
20-50% hospitalised, 5-10% require ITU
mortality 1% community, 10% hospital, 30% ITU
hospitalisation 6-8 days
significant short and long term mortality from other causes after pneumonia
key decisions
does the patient need antimicrobials
how sick? hospital?
alternative diagnosis? - heart failure, PE, cancer, TB, interstitial lung disease
pneumonia in immunocompromised
bacterial - all common causes but may be atypical presentation
fungal - pneumocystis pneumoniae (PCP), moulds
viruses - cytomegalovirus (CMV), adenovirus, RSV
pneumonia treatment
prompt but appropriate initiation of antimicrobials
use narrowest spectrum to stop spread of resistance
mild severity in community - oral antimicrobial, e.g. amoxicillin for short duration
severe - IV combination - e.g. co-amoxiclav and oral clarithromycin. duration 7d mild-moderate, 7-10d severe
tuberculosis
chronic resp tract infection - can be extrapulmonary - usually due to reactivation of latent infection
at risk - exposed, born in country of high incidence, homeless, alcoholic HIV infection
TB clinical features
cough
haemoptysis
SOB
weight loss
fever
night sweats
swollen lymph nodes/other extrapulmonary features
TB radiological appearances
upper lobe disease with cavities
pleural disease
multiple tiny nodules
lymphadenopathy
