Diagnostic Microbiology Flashcards
Ziehl-Neelson and Kinyoun stains are used to identify what kind of bacteria?
mycobacteria
what is the most nutritious agar available?
chocolate agar - made of RBC that have been lysed, so their nutrients are available
coagulase tubes and catalase test are examples of what type of bacterial identification?
a. rapid bench assay
b. biochemical
c. antigen detection
d. molecular
e. mass spectrometry
a. rapid bench assay
coagulase tubes tests if sample coagulates, catalase test determines +/- for catalase enzyme
API strips identify bacterial species based on their specific biochemical profiles. What type of bacteria does this work best for?
works well for bacteria that grow in ambient air or CO2
does not work great for anaerobes or bacteria that require special environment to grow
what is the use of MALDI-TOF
type of mass spectrometry for bacterial identification
[matrix assisted laser desorption ionization-time of flight spectrometry]
fast, can be applied to all bacteria, cheap
what is the use of anti microbial susceptibility testing
predict the outcome of a therapy
can also confirm current treatment, provide choices of optimal treatment (cost, administration), provide alternatives when treatment is ineffective or patient develops adverse drug reactions
in vitro tests to approximate in vivo function
Broth dilution, disk diffusion, and the E-tests are all examples of what kind of test?
antimicrobial susceptibility testing (to determine or confirm best treatment option) - approximates minimum inhibitory concentration (MIC)
broth dilution: put in tubes of broth
disk diffusion: drug is added to culture plate and zone of inhibition is measured
E-test (gradient diffusion test): drug is added to strip in gradient and measure where bacterial growth intercepts strip
what does “therapeutic breakpoint” mean in interpretation of antimicrobial susceptibility results?
refers to concentration of antimicrobial at site of infection
comparing MIC (minimum inhibitory concentration) to breakpoint determines whether the microbe is rated as susceptible, intermediate, or resistant
(basically, MIC must be lower than breakpoint for drug to be effective)
what are antibiograms used for?
published by hospitals yearly, tell you the likelihood of susceptibility of microbes to certain drugs
helps inform what therapies are appropriate and tracks antibiotic resistance
what kind of tests are rapid influenza, strep, or covid tests?
enzyme immunoassays (EIAs, aka ELISA): detect antigens or antibodies by producing an enzyme-triggered color change
empiric vs specific therapy
empiric therapy is designed to treat everything (aka broad spectrum therapy, used until it is determined which specific therapy should be used)
specific therapy is specific (obviously) - reduces resistance rates, more effective
clinical relevance of urine cultures is judged by what?
Number of organisms (bacterial load)
NAAT molecular diagnostic testing
Nucleic acid amplification tests (NAAT): PCR, TMA, NASBA, etc
MRSA screening typically uses what kind of specimen?
upper respiratory specimen
what kind of stains (2) does mycobacteriology require?
study of acid fast organisms
requires Kinyoun and fluorescent stain, 6 week incubation
susceptibility testing usually done with small panel of first-line drugs with just one drug concentration
