Clinical Microbiology Flashcards
Marker of acute infection
IgM
Marker of recent or old infection
IgG
Immune-diagnosis of an acute infection
Draw acute serum within first week, then draw convalescent serum 3-6 weeks later.
Look for 4x or greater Ab titer increase due to IgG
Exceptions to making a presumptive diagnosis based on only convalescent titer.
Chronic infection:
- Lyme disease
- HIV
- Hepatitis
Testing for congenital infection
Test at birth
Test again after 3-4 months:
If baby is negative for infection, IgM should NOT be present, and IgG titer from mom will drop 1/2 every month and never go back up
If baby is positive, IgM will be present and the IgG titers eventually go up.
Dx of chikungunya and dengue
Day 2-6 of illness: PCR bc it detects circulation virus in the blood
Day 7-14: ELISA- tests for IgM in blood.
Days 6-8: both tests are ok
Organisms requiring prompt culture
Haemophilus ducreyi
Anaerobes in regular tubes
N. gonorrhea in joint fluid
Blood culture collection
Blood is taken from multiple sites, 2 bottles from each site though (one aerobic, one anaerobic)
4mL taken for children, 10mL for adults
For a single episode of sepsis:
2 sets of samples is minimum
5 sets is maximum
Blood cultures shouldn’t be collected from femoral vv. or venous catheters.
Urine preservatives
Boric acid based, Used when refrigeration isn’t available.
Hospital acquired diarrhea
C. difficile toxin. Occurs in patients in hospital of >3days, and in patients with recent antibiotics and/or chemotherapy.
Routine stool culture
Salmonella spp.
Shigella spp.
Campylobacter spp.
STEC
N. gonorrhea culture
Genital swab placed in transport medium, but NOT refrigerated.
Good for 6-12hrs at 20C
Rectal swabs are placed on selective Thayer Martin medium.
