Microbiology of Respiratory Tract Infection 2 Flashcards
describe the 3 main routes of transmission
contact (touch)
airborne;
small particles
travels long distances
limited indications - multi-drug resistant TB, some viruses, respiratory tract infection undergoing aerosol generating procedures
precautions - standard infection control and filtering face place
droplet;
large molecules
spread via direct contact of droplets with mucous membranes (droplet, surface, contact spread)
precautions - patient in a single room
describe defences of the upper respiratory tract
host defences;
nasopharynx - nasal hairs, ciliated epithelia, IgA
oropharynx - saliva, sloughing, cough
describe colonisers of upper respiratroy tract
gram postive;
alpha-haemolytic streptococci - strep pneumoniae
beta-haemolytic streptococci - strep pyogenes
staphylococcus aureus
gram negative;
haemophilus influenzae (blood loving species)
moraxella catarrhalis
describe conducting airways defences
includes the trachea and bronchi; mucociliary escalator cough AMPs cellular and humoral immunity infections can occur when there are changes; trauma/intubation of airway abnormalities of defence e.g. ciliary escalator and others as occurs COPD, changes during CF virulent pathogen/large inoculum
describe CF
inefficient clearance and build-up of mucus
repeated chest infections and chronic colonisation;
staph aureus, haemophilus influenzae, strep pneumoniae, pseudomonas aeruginosa, burkholderia cepacia (plus more)
describe acute bronchitis
90%
preceded by upper respiratory tract infection (‘the cold in the chest’)
no antibiotics
describe COPD
30% viral
50% bacterial
20%?
haemophilus influenzae and moraxella catarrhalis, streptococcus pneumoniae, gram negatives (plus more)
describe defences of lower respiratory tract
lung defences;
normally relatively sterile
no ciliary escalator
alveolar lining fluid - surfactant, Ig, complement, FFA, AMP
alveolar macrophages and neutrophils (phagocytosis causing an inflammatory response)
describe community acquired pneumonia
organism reaches the lung
systemic response - immune activation and infiltration
fluid and cellular build up in alveoli leading to impaired gas exchange
microbiology; streptococcus pneumoniae - most common, 70% atypicals/viruses - 20% haemophilus influenzae - 5% staphylococcus aureus - 4% other bacteria - 1%
diagnosed via sputum culture and viral PCR
describe infections that can be caused by streptococcus pneumoniae
noninvasive pneumococcal disease; ear infection sinus infection upper respiratory tract infection pneumonia without spread to bloodstream
invasive pneumococcal disease;
meningitis
pneumonia with spread to bloodstream
bloodstream infection
describe structure and virulence of streptococcus pneumoniae
capsule; key virulence factor anti-phagocytic for sero-typing basis for vaccination rough strains (avirulent)
surface adhesions pneumolysin (cytotoxin) sIgA protease teichoic acid H2O2
describe types of pneumonia
typical - streptococcus pneumoniae
atypical - mycoplasma pneumoniae, legionella pneumonia, chlamoydophila pneumonia, chlamydia psitacci, viruses
hospital acquired (including ventilator associated)
aspiration
immunosuppressed/special population - pneumocystis jiroveci, aspergillus sp., endemic mycoses, TB
describe legionella pneumonia
atypical
gram negative (unusual cell wall structure)
obligate intracellular organism - resides with water amoeba (provides nutrients and protection)
pathogenesis - invades alveolar macrophages and replicates
transmitted via inhalation of contaminated water droplet (risk factor - contaminated aerosolised water)
describe walking pneumonia
non productive cough
rash
organism has no cell wall - no amoxicillin
describe staphylcoccus pneumonia
post influenza
haematogenous spread of staphylococcus aureus (cardiovascular infection)
