16- Chapter 28 Flashcards
How are microorganisms clinically identified? (Flow chart slide 3)
Okay
How is identification of anaerobic bacteria complicated?
Specimen contamination
Challenge of maintaining anoxic conditions during collection, transport and culture
What plates are placed in a sealed jar which is made anoxic
What is general purpose media and enriched media?
General purpose media- support growth of most aerobic and facultatively aerobic organisms
Enriched media- contain specific growth factors that enhance growth of certain fastidious pathogens
What is selective media and differential media?
Selective media- inhibits growth of some bacteria while inhibiting others
Differential media- allow identification based on growth, colour and appearance
These specialized media are often available as kits containing several distinct tests
What is the disc diffusion test?
Method for assessing antimicrobial susceptibility
Specified agar medium is inoculated with culture of bacteria
Inhibition zones are measured and interpreted
What is minimum inhibitory concentration (MIC)?
Uses antibiotic dilution assay
Wells contain serial dilutions of antibiotics are inoculated with a standard amount of a test organism
Standard inoculum is prepared and agar is inoculated
Slide 14
What are nucleus acid based tests? (2 types of PCR)
Polymerase chain reaction
Presence of amplified gene segment confirms presence of pathogen
Quantitative and reverse transcriptase PCR uses pathogen specific rna
Qualitative real time PCR uses fluorescent labeled products
Slide 16-17
What is the dipstick assay in nucleus acid probes?
Reporter and capture probes used
Capture probe has poly A tail which hybridizes to Poly T oligo attaches to dipstick
Binding of target DNA to reporter seen as a colour change
Slide 18
What is serology?
What is test sensitivity and test specificity?
Study of antigen antibody reactions in vitro
Serological reactions used for many diagnostic immunology tests
Test sensitivity- probability of having a positive test when patient is infected
Test specificity- probability of having a negative test if patient is not infected
How can an infection be identified using antibody titer and antigens of pathogen?
Infection can be identified by measuring the patients antibody titer (quantity) against antigens produced by the pathogen
Skin testing can be used to determine exposure to a pathogen delayed hypersensitivity
What are polyclonal and monoclonal antibodies?
Polyclonal antibodies- multiple antibodies bind to an antigen with multiple epitopes (epitopes are where antibody binds to antigen)
Monoclonal antibodies bind to single epitope
Slide 23
What is agglutination?
The visible clumping of a particulate antigen when mixed with antibodies specific for the particulate antigens
Agglutination tests are typically more sensitive than precipitation tests
What is direct agglutination vs passive (indirect) agglutination?
Direct- soluble antibody causing clumping due to interaction with an antigen that is an integral part of the surface of a cell or other insoluble particle
Indirect- agglutination of soluble antigens or antibodies adsorbed or chemically couple to cells or insoluble particles
Slide 29
What is the direct and indirect fluorescent method?
Direct method- antibody targeted against the surface antigen is covalently linked to the fluorescent dye
Indirect method- the presence of a nonfluorescent antibody on the surface of a cell is detected by use of fluorescent antibody directed against the nonfluorescent antibody
Slide 31
What is immunofluorescence?
Antibodies can be chemically modified with fluorescent dyes to help detect antigens ok intact cells
If pathogen contains surface antigens reactive with the antibody, the pathogen cells fluoresce
Two common dyes are rhodamine B (red) and fluorescein isothiocyanate (yellow-green)
