L11 Lab diagnosis Flashcards
what is lab diagnosis for
rapid accurate results advise on diagnosis, treatment and infection management infection control surveillance teaching
how many diagnostic lab specimens are there a year
900,000
what are sample examples that labs test
hospital
community - GP
environmental
public health
what are the microbiological tests
microscopy
culture
serology
molecular techniques
what are the pros of microscopy
cheap
rapid results
examples of unstained microscopy samples
urine
examples of stained microscopy samples
gram of CSF
ziehl neilsen sputa
why is microscopy limited
if negative stain doesnt mean no infection
what microscopy is used for faeces rotavirus
electron microscopy
what replaced electron microscopy for rotavirus diagnostic
EIA tests
now PCR look for specific rotavirus sequence
what sample is used for lung infection pneumonia
need from chest pneumococcal pneumonia
as sputum in lungs non sterile through respiratory tract
what is used for quick identification system
MALDI TOF
how is bacteria cultured
grows on solid or liquid media
agar added with nutrients
different oxygen and co2 levels
what are the types of cultures
enrichment
selective
indicator
what is chocolate agar
blood added that has been heated
what is a positive CSF detection
growth as CSF is sterile
what is enrichment
encourage growth of fastidious organisms
by adding host nutrients
how are blood infections detected
infection in blood stream not many bacteria/ml
need to detect small numbers - wont grow on agar too little
grow in bottles with nutrients in an/aerobic conditions
if co2 made - growth
what is an indicator culture
identify colonies of pathogens from mixtures
help identification of bacteria
examples of indicator methods
macconkey
API
what is selective culture
obtain pathogen from sample likely to contain other commensal bacteria e.g. stool sample
what can grow on deoxycholate agar
salmonella
cons of microscopy
operator dependent
sensitivity only positive if 100,000 organism/ml
rarely diagnostic
cons of culture
time = can take weeks, worsen patient
non-viable organisms wont grow on agar
what are the antibiotic sensitivity test methods
stokes/BSAC zones
breakpoint
MIC
what gives evidence for virus growth
cytopathic effect
haemadsorption
antigen detection
electron microscopy
what has replaced tissue culture for testing
PCR or serological testing
why is tissue culture not used for detection
hard to keep virus alive
cant process lots of samples
what is used for organisms hard/cant grow
serology
antigen-AB binding detect AB/antigen
