Theme 2: Advanced Microbiology Flashcards
(164 cards)
A person is described as being pyrexial when __?__
their temperature is over 38 degrees.
How does procalcitonin aid diagnosis in a patient with a suspected infection?
Differentiates between bacterial and viral
What is the most important investigation to confirm a clinical diagnosis of pneumonia?
CXR
What effect might a bacterial infection have on these lab results?
a) WCC
b) Lymphocytes
c) Neutrophils
a) WCC - raised
b) Lymphocytes - normal or low
c) Neutrophils - raised
What effect might a viral infection have on these lab results?
a) WCC
b) Lymphocytes
c) Neutrophils
a) WCC - normal
b) Lymphocytes - raised
c) Neutrophils - normal
What does sensitivity testing tell you in microbiology?
Pathogen resistance to specific antimicrobials.
Concentration of antimicrobial required to kill the organism.
What is meant by ‘empiric’ antimicrobial therapy?
Initial treatment of infection with broader spectrum antimicrobials.
What are the limitations and uses of blood cultures?
Uses: Establish presence of microorganism, determine, identify targeted therapy, provides typing information.
Limitation: Slower than direct detection, can only detect cultivable organisms, can only detect organisms at specific site.
Direct detection of microorganisms can detect either the whole organism (by __1__) or components of the organism (__2__ or __3__).
1) microscopy
2) antigen
3) nucleic acid (DNA or RNA)
What method is used to detect nucleic acid of an organism?
PCR
What method of microbial identification is usually the fastest?
Direct detection
__?__ is the transition from no antibody response to an antibody response. Identifiable as a change from a negative result on one test, to a positive result on the next.
Seroconversion
If a patient’s antibody concentration rises from 1/2 to 1/32, this would be called a __?__
‘fourfold rise in titre’
Why is antibody testing not usually able to help inform antimicrobial therapy decisions?
The convalescent sample is taken 10 days to 2-weeks after the event.
This is often too late to inform antimicrobial therapy decisions.
Describe the normal variation in temperature for a patient with fever
Fevers are usually associated with diurnal variation in temperature: increases during the early day and goes down at night.
How is fever useful in diagnostic testing?
Most commonly caused by infections.
Pyrogens secreted at sites of infection are detected by hypothalamus. Hypothalamus responds by sending signals for generating and retaining more heat.
Raised neutrophil count generally indicates ____
bacterial infection
Raised lymphocytes generally indicates ____
viral infection
True or false: raised monocytes may indicate a chronic infection.
True, though it is important to note they are also raised in acute infections
Raised eosinophil count generally indicates ____
parasitic infection
Raised basophils generally indicates ____
viral infection
Raised CRP/procalcitonin means what?
Indicates potential bacterial infection (but not definitely). Negative inflammatory markers suggest infection is less likely.
High sensitivity; low specificity.
Which of the following is true of inflammatory marker in a blood test:
a) high sensitivity; high specificity
b) low sensitivity; low specificity
c) high sensitivity; low specificity
d) low sensitivity; high specificity
c) high sensitivity; low specificity
Often picks up a bacterial infection if present (few false negatives); but also raised by a range of other things (many false positives)
How can lactate be useful as an infection test?
Raised lactate may indicate severe infections such as sepsis and meningitis.