Flashcards in L29_ Diagnosis of Infectious Diseases by Laboratory Methods Deck (11)
How long does it take to get results from a normal culture method with a normal growing bacteria?
Day 1: specimen processing, plating and staining
Day 2: Culture examination(gram results and shape), Identification and sensitivity tests setup
Day 3: Identification and sensitivity Tests Read
Day 4: Physician Review of Culture Results
Name 3 examples of cultures that take longer than the normal 4 days?
Fastidious bacteria 2-4 weeks
Fungi up to 4-6 weeks
Mycobacteria (Tb) up to 8 weeks
Name two antigen detection formats?
ELISA and Immunochromatographic assay
What is the major disadvantage of serological tests?
They take time
How long after infection does IgM show up in serum, how long does it persist for? what is its temporal relationship with infections?
Appears in serum 1-2 weeks, persists for 2-3 months, consistent with current or recent infection
How long after infection does IgG show up in serum, how long does it persist for? what is its temporal relationship with infections?
Appears 2-3 weeks after infection, may persist for life, may represent somewhat recent infection or immunity.
What is the difference between a acute and convalescent titer, and what is the rule of thumb for diagnostic significance?
Acute titer is taken after exposure. Convalescent titer is taken 2-4 weeks later. Look for minimum of 4 fold increase to signify recent infection...this is for IgG.
What is some of the limitations of Molecular testing methods?
There are only a handful of approved tests. Relatively expensive, could be detecting dead organisms, risk of contamination.
What are some advantages of molecular testing?
Rapid results, can look at difficult to culture or dangerous to culture organism. Increased sensitivity. Possible to quantitate viral load (Real Time PCR)
Why is culturing viruses different than bacteria?
You need a cell to grow the virus in --> cell culture.
Long period for results, poor sensitivity, susceptible to contamination, not all viruses will grow in cell culture.