Respiratory tract infection Flashcards
what level of resp tract is called the conducting zone?
what is the transitional zone
what is the resp zone?
the conducting zone is from trachea up to terminal bronchioles - this is about the 16th generation
the respiratory bronchioles take over from that point (17th)
at level 20 the alveolar ducts exist.
the alveolar sacs make up the 23rd generation
what is the definition of bronchitis or tracheitis
this is an infection of the conducting zone of the resp tract
in immunocompetent people these are usually self-resolving
what are the “atypical pneumonia” pathogens?
these are historical terms used to describe pathogens that weren’t particularly responsive to penicillins. They are also assoc with abnormal LFTs and GIT Sx
there are non-zoonotic
- chlamydia pneumophila
- mycoplasma
- legionella
zoonotic
- coxiella burnetti (q fever)
- chlamydia psittaci (psittacosis)
what would you do for a patient with pneumonia with S. pneumoniae, that had been treated with penicillin, was improving, BUT resistances came back showing intermediate (or even high) resistance?
if the patient is improving, you can continue the medication
this is only true for pneumonia, where there is good penetration into the alveolar fluid.
for some reason, with pneumococcus and pneumonia, penicillin seem to disobey the MIC readings
this is NOT the case for meningitis, and the patient should be switched (BBB means poor drug delivery)
what is the difference between the two vaccines that we see in Australia?
the childhood 7 valent is conjugated to diptheria toxin, and leads to good immunogenic response
it has lead to massive improvement in infection rates
the adult vaccine is called 23 valent, and is NON-CONJUGATED. Therefore it is less immunogenic
it is associated with decreased rates of invasive disease, but does not decrease rates of pneumonia
this is possibly because of the decreased level of Igs in elderly, COPD, immunosuppressed?
how does oseltamivir work?
it is a neuraminidase inhibitor
once the virus has been all packaged up from an infected cell, it needs to use neuraminidiase to cleave off the cell. It works on a Sialic acid receptor to cleave off.
Tamiflu inhibits this. So in fact, there are completely formed viruses just stuck - unreleased from the infected cell
what are the risks associated with antibiotics for an URTI?
25% get diarrhoea with AB
2% chance of skin reaction
1/5000 chance of anaphylaxis
what is the use of CURB65, SMARTCOP, PSI?
CURB and PSI are used to determine who to send home from ED
SMARTCOP is for admitted patients, and tries to predict need for intubation or vasopressor support
how good is the urinary antigen for penumococcus?
not perfect
sens 75%
spec 94%
what is the recommended duration of antibiotics for most lung infections?
5 - 7 days
the exception is Pseudomonas which is 10 - 14 days
what are some peculiar Australia only conditions?
Burkholderia pseudomallei (melioidosis) Acinetobacter baumanni
Who are the at risk groups for melioidosis?
What is melioidosis causative organism and what type of bug is it, and when/how do people get it
It is a soil dwelling Gram neg
it is the MOST common cause of septic death in Darwin
Most deaths are in alcoholics/renal/diabetics
It occurs mostly during the wet season
how do we determine melioidosis?
You can use Ashdown solution
this is a colistin containing solution, which is an antibiotic that melioid is intrinsically resistant to.
Do a throat swab, and then wash it in the solution. The colistin will kill everything else, but the melioid will grow
what is the empirical treatment for pneumonia in tropical Australia in monsoon season?
CTX 2g + gent (covers the acinetobacter baumanni - a soil dwelling pathogen from the tropics)
What does PVL mean with respect to CA-MRSA?
this is an increased virulence factor - Panton-Valentine Leukocidin
What is the common 2ndary infection after influenza pneumonitis?
S. aureus
and it’s bad, causes empyema early.
what is the role of the Mantoux tuberculin skin test?
when is it positive, and when is it negative?
when is it not possible to interpret it?
The TST is a test to determine latent TB infection
after injection of the “purified protein derivative”, read it in 48 - 72 hours
if HIV, 5 mm = pos
if RF, 10mm = pos
if no RF, 15mm = pos
if the patient has had bCG < 10 years previously, you can not do the test
what about the QuantiFERON?
what is the benefit vs Mantoux?
The QuantiFERON is also know as an interferon-gamma release assay (IGRA)
this test can be performed in patients with previous BCG vaccination
it also has an inbuilt mitogen control (they also ensure there is a response to a thing called “mitogen”, which should always cause a positive reaction)
this mitogen control is particularly important when there is co-existant AIDS.
if the mitogen is negative, then we can’t interpret the test, and all we can tell is that the LLs aren’t working
What is the role of QuantiFERON gold?
this is a screening test for LATENT TB infection in populations with low pre-test prob
it is not a diagnostic test.
What microorganism is “branching Gram positive bacilli” consistent with?
what stain do you need to use for this?
This is a catch phrase for Nocardia
the stain is a modified Ziehl-Neelson stain
In a myelosuppressed patient, what is the most common cause of a “Halo sign” on Ct chest?
this is from Aspergillus
this is a discrete nodule of inflammation with surrounding coagulation necrosis
in Australia, what would be the most common causes for a small focal consolidation?
what about if HIV?
HSCT?
pneumococcus
if HIV: cryptococcus
possibly TB
if HSCT - consider Aspergillus (not the most common, but might be the most likely if the patient had been on broad spectrums for a while)
what are some of the serum tests that you can do to diagnose fungal infections?
the first one is Serum Galactomannan
- this is a component of Aspergillus cell wall
- useful for early diagnosis of Aspergillus
- Can be done on serum, but also BAL fluid
- fairly specific for aspergillus
There is another fungal marker called “B-D-glucan” (beta-D-glucan)
- this is a polysaccharide located in cell membranes of most fungi
- has high sens and spec
- can test for PJP
HOWEVER - it does NOT EXCLUDE CRYPTOCOCCUS OR MUCORMYCOSES
what is the Gold standard for diagnosis of pleural TB?
pleural biopsy is the gold standard
sputum 20 - 40% sens
pleural fluid - about 10%
ADA - this is useful to exclude the disease in the appropriate population
How useful is the Legionella antigen?
it is reasonable for picking up L. pneumophilia
however, it does not test for L. longbeachii - this is a disease that gardeners get (associated with soil)
is egg anaphylaxis an absolute contraindication to influenza vaccination?
it is not. the amount of antigen is widely accepted to be below the level required for anaphylaxis.
however it should be done in strictly controlled environment, such as immunology clinic
what is the treatment for Legionella - why does this work, and what won’t work?
CTX or moxifloxacin are good choice
it is an intracellular pathogen, and things like gentamicin won’t work
