Lab Techniques Flashcards
What samples can be used for culture
Blood
Swabs
Fluids - pleural, ascetic or CSF
Tissue
How can culture results be used
Identify the organism
Test which antibiotic they are susceptible to
How are blood cultures carried out
The tubes are placed in a machine which can flag them if bacteria is present
Positive tubes are then plated and incubated as normal
When is the only time you should send urine cultures
If the patient has symptoms of a UTI
Why are skin/ulcer swabs not helpful
They usually just grow commensals and so hard to identify the causative organism
What does serology measure
Level of antibody or antigen
What does a positive IgM serology result suggest
The patient has had recent exposure to the pathogen
May cross react so makes it more difficult to identify the pathogen
What does a positive IgG serology result suggest
Patient has been exposed to the pathogen at some point - may have been years ago
What infections is serology useful for detecting
Viruses
Spirochetes
Protozoa
Which diseases are caused by spirochetes
Lyme disease
Syphilis
What is the main test for virus detection
PCR
Which samples can PCR be done on
Blood - for bloodborne infection Swabs - throat for viral infection Fluid - CSF (HSV, meningitis) Stool - norovirus Sputum - TB
What type of results can PCR give you
If the organism is present or not
Quantify the organism - how much is there
Which bloodborne viruses is PCR good for monitoring
HIV
Hep B
Hep C
Can indicate if condition is under control
How does MALDI-TOF work
Sample is placed onto target plate
The laser heats the organism and ionises the proteins
These ions travel up the tube and are detected by the mass spectrometer
Produces a fingerprint which can be compared to database to identify organism
