ch. 15 - diagnosing infections Flashcards
1
Q
what are the symptoms of a microbial infection?
A
- fever
- wound exudate
- mucus production
- abnormal lesions
2
Q
what are the 3 types of specimen collection lab techniques?
A
direct testing using:
- microscopic
- immunologic
- genetic
3
Q
what are the analysis method in lab techniques?
A
- cultivation
- isolation
- identification
…. of pathogens
4
Q
what is presumptive data?
A
place the isolated microbe into a preliminary category
5
Q
what is confirmatory data?
A
pinpoint the microbe’s identity
6
Q
what is the name of the technique used to collect specimens?
A
aseptic technique (sterile technique)
- sterile sample containers + other tools prevent contamination from the environment
7
Q
what is the phenotypic method for identifying specimens?
A
- considers macroscopic + microscopic morphology, physiology + biochemistry
- uses: microscope + staining
- 90% accuracy
8
Q
what is the immunologic method for identifying specimens?
A
- serological analysis –> blood work
- unknown (-) no binding (antibody) + known (+) binding (antigen)
- 95% accuracy
- takes hours
- $$
9
Q
what is the genetic method for identifying specimens?
A
- genetic techniques increasingly being used as a sole resource for identifying bacteria
- only done when patient is unconscious (super expensive-cannot be told symptoms)
- unknown (DNA) + known (DNA) –> no binding (-) or binding (+)
- $$$$
- 100% accuracy
- takes minutes, rapid testing
10
Q
what is macroscopic morphology?
A
traits that can be assessed with the naked eye:
- appearance of colonies: texture, size, shape + pigment
- speed of growth
- patterns of growth in broth + gelatin media
11
Q
what are the types of isolation media used in morphological testing?
A
- specialized media
- selective media
- differential media
12
Q
what is specialized media?
A
- used to enrich a pathogen present in small numbers or is easily grown
13
Q
what is selective media?
A
- use for nonsterile specimens containing a diversity of bacterial species to encourage the growth of only the suspected pathogen
- kills all other pathogens except the wanted one
14
Q
what is differential media?
A
- used to identify definitive characteristics + fermentation patterns
- different colors
15
Q
why must pure cultures be obtained from isolation media?
A
- pure cultures must be obtained from isolation media so that subsequent steps in identification will be accurate
16
Q
what two types of microscopy is used in microscopic morphology?
A
1) light microscopy
2) electron microscopy
17
Q
what does light microscopy help observe in microscopic morphology?
A
- cell shape, size + arrangement
- gram stain reaction + acid-fast reaction
- endospores, granules, + capsules
18
Q
what does electron microscopy help observe in microscopic morphology?
A
helps pinpoint additional structural features:
- cell wall (lipid or protein)
- flagella
- pili
- fimbriae
19
Q
what is immediate direct examination of a specimen (phenotypic)?
A
- direct observation of fresh or stained specimen is a rapid method of determining presumptive + sometimes confirmatory microbial characteristics
stain used most often:
- gram stain
- acid-fast stain (TB)
20
Q
what is done in the catalase test?
A
drop hydrogen peroxide in bacteria:
- bubbles = catalase (+)
- no bubbles = catalase (-)
21
Q
what are the physiological + biochemical characteristics in phenotypic identification?
A
- most traditional
- dozens of diagnostic tests exist for determining the presence of enzymes + to assess nutritional + metabolic activities:
- fermentation of sugars
- capacity to digest complex polymers
- production of gas
- sensitivity to antibiotics
22
Q
what is chemical analysis in identifying infections (phenotypic)?
A
analysis of specific structural substances can aid in microbial identification:
- peptide composition of the cell wall
- membrane + lipid profiles
23
Q
what are the advantages of using genotypic identification?
A
- culturing of microorganisms is NOT always necessary
- are increasingly automated, producing rapid results that are often more precise than phenotypic methods
DNA/genetics:
- A always binds to T
- G always binds to C
24
Q
what is viable noncultured (VNC) mean?
A
- microbes that can’t be grown in the lab that are identified by genotypic methods
25
what is a DNA analysis using genetic probes?
- probes can be labeled w/ chemically luminescent materials that can be measured by "light meters"
- avoids use of radioactivity
binding = reaction
no binding = no reaction
26
what is polymerase chain reaction (PCR)?
- amplifies minute quantities of DNA in samples - down to one DNA
- used in identification of a wide variety of microorganisms
-----------------------------------
- high-risk HIV patients using in-office PCR bc of rapidity
- hospitals use PCR to quickly diagnose MRSA
27
what do immunologic methods use to identify infections?
- uses blood
- antibody response is exploited when sample is tested for specific antibodies to a suspected pathogen (easier than testing for the microbe)
- characteristics of antibodies --> their quantity or specificity can reveal the patient's history of contact with microorganisms or other antigens
28
what is serology (immunologic)?
- study of antigen-antibody interactions
- involves in vitro testing of serum
- based on the principle that antibodies have an extreme specificity for antigens
- visualization of the interaction of antigens + antibodies macroscopically or microscopically provides a powerful tool for ---> detecting, identifying + quantifying antibodies and antigens
29
what is an antibody?
- binds to, and destroys pathogen (antigen)
30
what are the basic principles of serological testing using antibodies + antigens?
- known w/ unknown
- binding = antibodies
- no binding = no antibodies to that antigen
--------------------------------------------
- symptomatic --> making large amounts of antibodies = current infection
- small amount of antibodies = past or not current infection
31
what is specificity in immune testing?
- specific --> attaches to specific antibodies
32
what is sensitivity in immune testing?
- can detect small amounts
33
what are polyclonal antibodies?
- many antibodies to 1 antigen
34
what are monoclonal antibodies?
- 1 antibody against 1 antigen (breast cell - Brac 1/2)
- in the lab --> antibodies recognizing one epitope (monoclonal antibodies [mAb]) are produced using myelomas
- myelomas cells are fused to an activated B cell to form a hybridoma
- mAb can be used in
- disease prevention
- immunomodulation (controlling overactive inflammatory responses)
35
what is titration?
- dilution of antigen or antibody solution to the most favorable concentration
36
what is a titer?
- the last in tube in which there was a reaction during titration
- a rise in the titer ratio (antibody:serum) indicates disease
ex.) 1/10,000 is the titer --> 10,000 antibodies/ ml
- never had Ebola = 0 antibodies
- vaccine or previous = 1-100 antibodies
- currently infected = >100 antibodies
37
what is agglutination?
- clumping reaction of antigens
38
what is hemagglutination?
- determines blood type
- detect viruses that cause agglutination of red blood cells
39
what is the order that ALL immunologic tests follow?
1) known antigen
2) unknown antibody attaches to the known antigen (patient's, primary, 1)
3) the detecting antibody attaches to the unknown antibody (secondary, 2)
40
what are the tests that can used as the detecting antibody in ALL immunologic tests?
- Western blot - color
- immunofluorescence testing - fluorescence
- RIA/RAST - radiation
- ELISA - enzymes
41
what are the steps in the Western blot procedure?
- proteins within cell lysates are separated via electrical charge within a gel
- proteins in the gel are transferred to a special filter
- filter is incubated w/antibody solutions labeled w/radioactive, fluorescent, or luminescent molecules
- sites of specific Ag-Ab binding will appear as a pattern of bands that can be compared to known positive + negative controls
- verifies microbial-specific antigens or antibodies in a patient sample
42
what is immunochromatography?
ex.) lateral flow test found in drugstore pregnancy tests and rapid strep tests in doctor's offices
- fluid (patient's sample) will encounter antibodies along its route of flow
- if the sample contains the correct antigen, it will bind the antibodies + continue on to the next "station"
- next stage contains a third molecule that induces color changes in a strip pattern
43
what are fluorescent antibodies (Fabs)?
- monoclonal antibodies labeled by a fluorescent dye
44
what are the steps for direct immunofluorescence testing?
- unknown test specimen or antigen is fixed to a slide and exposed to a FAb solution
- if Ag-Ab complexes form, they will remain bound to the sample + will be visualized by fluorescence microscopy
- valuable for identifying + locating microbial antigens on cell surfaces or tissues
- also identifies ---> causative agents of syphilis, gonorrhea, + meningitis
45
what are the steps for indirect immunofluorescence testing?
- FAbs recognize the Fc region of antibodies in patient serum
- known antigen is added to the test serum
- binding of the fluorescent antibody is visualized through fluorescent microscopy
- fluorescing aggregates or cells indicates the FAbs have complexed w/ microbe -specific antibodies
- used to diagnose syphilis + various viral infections
46
what are immunoassays?
- alternative methods that employ monoclonal antibodies + permit rapid, accurate measurement of trace antigen or antibody levels
47
what is radioimmunoassay (RIA)?
- antibodies or antigens labeled with a radioactive isotope used to pinpoint minute quantities of a corresponding antigen or antibody
- extremely sensitive
- used to detect hormone levels in samples + diagnose allergies
48
what is radioallergosorbent test (RAST)?
- uses radioactive antiglobulin antibodies
- if the person is making the antibody, it will bind to antigen
49
what is enzyme-linked immunosorbent assay (ELISA)?
- uses an enzyme-linked indicator antibody to visualize Ag-Ab reactions
- relies on a solid support such as a microtiter plate that can absorb the reactions
ex.) often used to detect antibodies against HIV
50
what are enzymes?
- catalysts --> speed things up
51
what is the best way to detect a virus?
- relying on genotypic + immunologic tests
- phenotypic testing --> need electron microscope (they are not cells + are more labor intensive to culture)
