Testing in the Diagnostic Microbiology Laboratory Flashcards
What is done during microbiology lab diagnostic testing?
Detection of pathogens Identification of pathogens Antimicrobial susceptibility testing
What is the emphasis of microbiological testing?
Quick diagnosis
What are the types of lab tests?
Microscopy Culture Detection of microbial components Serology
What are the types of microscopy?
Bright field Dark field Phase contrast Fluorescence Electron
What is bright field micrscopy?
Sample illumination is transmitted (i.e., illuminated from below and observed from above) white light, and contrast in the sample is caused by attenuation of the transmitted light in dense areas of the sample.
What kind of microscopy is used for gram stains?
bright field microscopy
What is dark field microscopy?
Using a dark background and allowing light to bend on the organism and into the eye piece making the organism show up on a black background
What is phase contrast microscopy?
Similar to bright field but 2 lights shine through with a phase difference of 1/4 wavelength
What is fluorescence microscopy?
Fluorescent light is shone onto labelled molecules to create a light image of the slide
How is the electron beam focused in electron microscopy?
Using magnets
How is the sample prepared on electron microscope?
It is prepared on a metal grid that is 3mm in diameter
What influences resolution in microscopy?
The wavelength
What is the purpose of culturing bacteria?
To determine if pathogens are present To provide enough of the organism to perform tests on To perform antibiotic susceptibility testing
How do lab staff determine which bacteria to culture for?
They use knowledge of the location that the specimen was taken from
How do lab staff determine which bacteria to culture for?
They use knowledge of the location that the specimen was taken from. (eg sputum: S.pneumoniae, h. influenzae) Doctors also make requests for ordering the tests. However, a particular set of conditions will not suit all pathogens. Instead particular culture conditions must be used.
What conditions must be accounted for when looking for pathogens using cultures?
Nutrition requirements Gaseous atmosphere Incubation time and temperature