Respiratory tract infection

Question 1

what level of resp tract is called the conducting zone?

what is the transitional zone

what is the resp zone?

Answer 1

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

Question 2

what is the definition of bronchitis or tracheitis

Answer 2

this is an infection of the conducting zone of the resp tract

in immunocompetent people these are usually self-resolving

Question 3

what are the “atypical pneumonia” pathogens?

Answer 3

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)

Question 4

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?

Answer 4

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)

Question 5

what is the difference between the two vaccines that we see in Australia?

Answer 5

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?

Question 6

how does oseltamivir work?

Answer 6

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

Question 7

what are the risks associated with antibiotics for an URTI?

Answer 7

25% get diarrhoea with AB
2% chance of skin reaction

1/5000 chance of anaphylaxis

Question 8

what is the use of CURB65, SMARTCOP, PSI?

Answer 8

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

Question 9

how good is the urinary antigen for penumococcus?

Answer 9

not perfect

sens 75%
spec 94%

Question 10

what is the recommended duration of antibiotics for most lung infections?

Answer 10

5 - 7 days

the exception is Pseudomonas which is 10 - 14 days

Question 11

what are some peculiar Australia only conditions?

Answer 11

Burkholderia pseudomallei (melioidosis)
Acinetobacter baumanni

Question 12

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

Answer 12

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

Question 13

how do we determine melioidosis?

Answer 13

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

Question 14

what is the empirical treatment for pneumonia in tropical Australia in monsoon season?

Answer 14

CTX 2g + gent (covers the acinetobacter baumanni - a soil dwelling pathogen from the tropics)

Question 15

What does PVL mean with respect to CA-MRSA?

Answer 15

this is an increased virulence factor - Panton-Valentine Leukocidin

Question 16

What is the common 2ndary infection after influenza pneumonitis?

Answer 16

S. aureus

and it’s bad, causes empyema early.

Question 17

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?

Answer 17

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

Question 18

what about the QuantiFERON?

what is the benefit vs Mantoux?

Answer 18

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

Question 19

What is the role of QuantiFERON gold?

Answer 19

this is a screening test for LATENT TB infection in populations with low pre-test prob

it is not a diagnostic test.

Question 20

What microorganism is “branching Gram positive bacilli” consistent with?

what stain do you need to use for this?

Answer 20

This is a catch phrase for Nocardia

the stain is a modified Ziehl-Neelson stain

Question 21

In a myelosuppressed patient, what is the most common cause of a “Halo sign” on Ct chest?

Answer 21

this is from Aspergillus

this is a discrete nodule of inflammation with surrounding coagulation necrosis

Question 22

in Australia, what would be the most common causes for a small focal consolidation?

what about if HIV?

HSCT?

Answer 22

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)

Question 23

what are some of the serum tests that you can do to diagnose fungal infections?

Answer 23

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

Question 24

what is the Gold standard for diagnosis of pleural TB?

Answer 24

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

Question 25

How useful is the Legionella antigen?

Answer 25

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)

Question 26

is egg anaphylaxis an absolute contraindication to influenza vaccination?

Answer 26

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

Question 27

what is the treatment for Legionella - why does this work, and what won’t work?

Answer 27

CTX or moxifloxacin are good choice

it is an intracellular pathogen, and things like gentamicin won’t work