diagnostics Flashcards
what are diagnostic tests
lab tests eg blood and urine
imaging tests eg ultrasound and ct scan
endoscopy eg colonoscopy and bronchoscopy
and history and clinical exam
how to identify an unknown pathogen in clinical specimens
culture based methods - bacteria, fungus, viruses
non-culture based methods - microscopic exam, molecular methods, antigen-antibody reactions, point of care tests
aseptic
procedure that is performed under sterile conditions to avoid contamination during sampling
principles for sample collection
- specimens must be obtained aseptically from a site that is representative of the disease process
- sufficient quality of material should be collected
- specimens must be collected prior to antimicrobial therapy to maximise pathogen recovery
- if cultures not immediately initiated after collection, specimens should be refrigerated.
cons of microscopic observation
cost effective and rapid
provides immediate info on presence/absence of bacteria, fungi and number of organisms
allows presumptive identification of bacteria
provides information on the host cellular response
difference between gram staining staphylococcus and streptococcus
straph = grape like
strep = twisted
aims of bacterial culture
isolation of organism in pure culture
identification of isolate by microscopic examination, biochemical reactions, state of art techniques
antimicrobial susceptibility testing
enrichment media
general purpose media supplemented by blood or other special nutrients to encourage growth of fastidious organisms.
differential media
distinguish between different groups of bacteria on the basis of their biological characteristics
selective media
favour the growth of particular microorganisms and inhibit the growth of others
characterising bacteria tests
oxidase test
catalse test
