Diagnosis of Infectious Diseases by Lab Methods Flashcards
What must clinicians have an understanding of?
The lab test menu
Specimen collection and transport guideline
Testing policies
What are the goals of clinical microbiologist?
*ID the presence of pathogenic organisms in Tissues Body Fluids Excretion Secretions *Predict response to antimicrobial therapy *Epidemiological Investigations *Hospital Infection Control
What are the FIVE general approaches used to detect cause of infection?
Microscopy - biochemical method
Culture - specific antisera
Detection of bacterial Ag
Demonstration of specific nucleic acids - molecular tech
Detection of Abs directed against the organism or virus
–Each vary in sensitivity and specificity
What are some microscopic methods in detection of infection?
Differential stains (Gram/acid-fast/Giemsa)
Fluorescent stains
Fluorescent Ab stains
Contrast technique
About Direct Microscopy?
Rapid
But typically insensitive and nonspecific
About the Gram stain
Can tell us if infection by Gram + or -
Can tell us if organism is a rod or coccus
About culturing bacteria
Much of what we know about bacteria is based on the ability to grow them in vitro
Most of the commonly encountered clinically sig bacteria are recovered with 48-72hrs
May require additional 24hrs for ID and antimicrobial testing (AST)
Detection of Bacterial Ag advantages?
Rapidly performed
Inexpensive
Detection of Bacterial Ag disadvantages?
Some assays poor sensitivity
Limited availability of some assays
What are the most common type of antigen detection platforms?
Immunochromatographi Assays
Latex Agglutination Test
ELISA Tests
About nucleic acid-based test for detection of infectious disease
Most sensitive test
Restricted to large clinical/reference labs
What are nucleic acid-based test subdivided into? (2)
Non-amplified assays
Amplified assays
What do Non-amplified test detect?
Ribosomal RNA using hybridization based assays
What do amplified test do?
Derive their increased SENSITIVITY by ampifing the target nucleic acid seq
