L10 - Lower Respiratory Tract Infections Flashcards
Is the LRT sterile?
YES
How is the LRT sterile?
Mucociliary escalator
Phagocytosis
What is the virulence of LRT pathogens partly dependent on?
ability to evade phagocytosis
What are the 3 ways infectious agent gain entry into LRT by?
Inhalation of aerosolised material
aspriation of URT commensals - lose gag reflex when drunk
hametogenous spread
what are the 3 types of pneumonia?
community-acquired pneumonia
hospital-acquired pneumonia
ventilator-associated pneumonia
What is community acquired pneumonia?
2 subtypes
- acute lobar pneumonia
- aytpical penumonia
What is hospital-acquired pneumonia?
pneumonia when patients are hospitalised for more than 72h
What is ventilator-associated pneumonia?
mechaniclly ventilated for more than 48 h
What bacteria infections lead to CA pneumonia in NEONATES?
Group B strep
L. monocytogenes
What bacteria infections lead to CA pneumonia in infants?
Encapsulated bacteria
C. trachomatis (abuse)
What bacteria infection lead to CA pneumonia in children/young adults?
S. pneumoniae
M. pneumoniae
C. pneumoniae
What bacteria infections lead to CA pneumonia in older adults?
S. pneumoniae
Legionella spp. (sick building syndrome)
What bacteria cause HA pneumonia?
P.aeurginosa
Gram-neg bacilli, MRSA
What bacteria cause HA pneumonia in CF patients?
P. aeruginosa
Burkholderia cepacia complex
S. aureus ( unusual nasty version )
What bacteria cause HA pneumonia in AIDS patients?
Pneumocystis Jiroveci
What is lobar pneumonia ALMOST always caused by?
S. pneumoniae
What are features of S. pneumoniae?
Gram-pos coccus
fastidious
a-haemolysis on FBA
What is the main cause of Bronchopneumonia?
S. aureus
What is bronchopneumonia?
secondary infection
‘plums and custard’ sputum
What are other causes of bronchopneumonia?
K. pneumoniae
Coliforms
P. aeruginosa
What is necrotising pneumonia caused by?
S.aureus elaborating Panton-Valentine Leukocidin
What does Panton-Valentine leukocidin do?
beta-barrel toxin
inserts in membrane, produces holes in membrane
What is Legionnaire’s disease?
Legionellla pneumonia - poor staining gram-neg
symptoms resemble flu
can progress systemic
Where does legionella thrive?
lakes
rivers
ponds
WARM STAGNANT WATER
What is atypical pneumonia also called?
walking pneumonia
non-cultivable pneumonia
What is used to treat atypical pneumonia?
Erythromycin
How is pneumonia diagnosed CLINICALLY?
CURB65 score of severity in CAP
^ score above 3 get admitted to hospital
X-ray
Ultrasound (make sure it’s not empyema)
What do pneumonia diagnosis CLINICAL results inform on?
EMPIRICAL THERAPY
How is pneumonia diagnosed in the lab?
sputum
broncho-alveolar lavage
blood culture
urine
NAAT
immunoassay
What do results from lab diagnosis inform on?
DIRECTED THERAPY
What classes as a good sputum?
lack of squames
one organism dominates
What us chronic bronchitis?
overproduction of mucus
typically H. influenzae
secondary bacterial infections complicate reovery
What causes Whooping cough?
Bordetella pertussis
What are the 2 toxins associated with Bordetella pertussis?
Pertussis toxin (PT)
Adenylate cyclase toxin (AC)
symptoms of whooping cough?
adheres to trachea
interferes with mucociliary escalator
paroxysmal coughing
high-pitched inspiration
How does PT toxin act?
BINARY (AB)
A-subunit binds G proteins
stops cyclicAMP production
blocks recruitment of immune cells
How does AC toxin act?
BIFUNCTIONAL
Ac domain - produce greater amounts of cAMP = immune evasion
RTX domain - pore within host cell = leakage
What is respiratory Tb caused by?
M. tuberculosis
M. bovis
M. MAC (immunocompromised)
M. kansasii
Where does Tb cause disease?
upper lobes
obligate aerobes
Symptoms of Tb?
night sweats
fever
weight loss
How does the immune system restrict spread of Tb?
granuloma
How is Tb diagnosed in the lab?
observe in sputum/BAL
culture
MGIT - see fluorescence when oxygen gets scavenged
NAAT - sensitivity issues
IFN-y release assay - doesn’t distinguish latent from active
