Flashcards in Micro 2- Diagnostic Micro Deck (31)
what is a plasmid?
self-replicating circular pieces of DNA
-often code for proteins that enhance the pathogenicity of a bacterium
carries genes for sex pili and transfer of the plasmid
encode enzymes for the catabolism of unusual compounds
resistance factors (R factors)
encode antibiotic resistance
what are transposons?
segments of DNA that can move one region of DNA to another
insertion sequences (IS) that code for transposes that cuts and reseals DNA
what is special about complex transposons
they carry other genes (e.g. in antibiotic resistance)
what are morphological characteristics?
useful for identifying eukaryotes, tell little about phylogenic relationships
what is differential staining used for?
gram staining, acid-fast staining, not useful for bacteria without cell walls
what can biochemical tests identify about microorganisms?
determine presence of bacterial enzymes
a fermentation test shows
bacteria that catabolize carbohydrate or potion produce acid, causing the pH indicator to change color
oxidase tests for
identifies bacteria that have cytochrome oxidase (e.g. Neisseria gonorrhoeae, pseudomonas)
what are rapid identification methods?
perform several biochemical tests simultaneously
-results of each test are assigned a number
what is serology
the science that studies serum and immune responses in serum
what does "microorganisms are antigenic" mean?
they stimulate the body to form antibodies
a solution of antibodies is tested against an unknown bacterium
what occurs in a slide agglutination test
bacteria agglutinate when mixed with antiserum-containing antibodies produced in response to that species/strain
enzyme linked immunosorbent assay (ELISA)
known antibodies and an unknown type of bacterium are added to a well
-a reaction identifies the bacteria
identifies antibodies in a patient's serum, confirms HIV infection
what is phage typing?
test for determining which phages a bacterium is susceptible to
procedure of phage typing
-stain in question is grown over entire plate
-a drop of different phage type is placed on bacteria
-clearning called plaques appear where phages infect and lyse bacterial cells
example of how phage typing can be used- specific genus/family
used to distinguish S. enterica serotypes and S. aureus types
nucleic acid analysis via DNA base composition tests for
-percentage of guanine + cytosine
-two organisms that are closely related have similar amounts of various bases
nucleic acid analysis via DNA fingerprint tests for
-electrophoresis of restriction enzymes digests an organism's DNA
-comparing fragments from different organisms provides information on genetic similarities and differences
how do nucleic acid amplification tests work
use of PCR to amplify DNA of an unknown microorganism that cannot be cultured
how does nucleic acid hybridization work
measures the ability of DNA strands from one organism to hybridize with DNA strands of another organism
(greater degree of hybridization, greater degree of relatedness)
southern blotting uses
uses nucleic acid hybridization to identify unknown microorganisms using DNA probes
what does a DNA chip (microarray) contain, and what is its function
contains DNA probes and detects pathogens by hybridization between the probe and DNA in the sample
two types of DNA chip (microarray)
-fluorescent in situ hybridization (FISH)