Chapter 15: Diagnosing Infections Flashcards
Light microscopy aids in the observation of these items.
cell shape, size, and arrangement; Gram stain reaction, acid-fast reaction; endospores, granules, and capsules
What can you use to pinpoint harder to see characteristics such as cell wall, flagella, pili, or fimbriae?
Electron Microscopy
Name the biochemical characteristics used to diagnose infectious agents. (5)
(1) Enzyme production, (2) fermentation of sugars, (3) capacity to digest complex polymers, (4) production of gas, (5) sensitivity to antibiotics
Which method produces more rapid results?
Genotypic (automated)
Viable Noncultured (VNC)
microbes that can’t be grown in the laboratory that are identified by genotypic methods
Immunological Methods
patient sample is tested for the presence of specific antibodies to a suspected pathogen
A Gram stain of a sputum sample from a patient is an example of a ______ method of microbial identification. A. genotypic B. immunologic C. phenotypic D. histologic E. None of the choices is correct.
A. phenotypic
“Clean Catch” Urine Sampling (describe the method)
taken by washing the external urethra and collecting the urine midstream
How to collect a skin sample
skin can be swabbed or scraped with a scalpel to expose deeper layers; wounds must be cleansed prior to swabbing
Sterile Material Sampling
blood, cerebrospinal fluid, and tissue fluids must be taken by STERILE NEEDLE ASPIRATION
Signs of microbial infections (4)
(1) fever, (2) wound exudate, (3) mucus production, and (4) abnormal lesions
Presumptive Data
place the isolated microbe into a preliminary category
Confirmatory Data
pinpoint the microbe’s identity
Results are entered into ______
a summary patient chart
Tests involved when starting with patient analysis: (3)
(1) immunologic and serologic tests on blood; (2) in vivo tests for reaction to microbe; (3) clinical signs and symptoms
Direct Testing (Microscopic) (4)
(1) Gram-stain; (2) Acid-fast stain; (3) Fluorescent Ab stain; (4) Gene probes
Direct Testing (Macroscopic) (2)
(1) Direct Antigen; (2) Gene probes
Tests on Isolates (6)
(1) Biochemical; (2) Serotyping; (3) Antimicrobial Sensitivity; (4) Gene probes; (5) Phage testing; (6) Animal inoculation
Care should be taken to avoid contamination with ______ when taking samples from a patient. air water droplet nuclei normal microbiota None of the choices is correct.
Normal Microbiota
Stains most often used when diagnosing
Gram-stain and Acid-fast
Specialized Media
used to enrich a pathogen present in small numbers or is easily overgrown
Selective Media
to encourage the growth of only the suspected pathogen
Differential Media
used to identify definitive characteristics and fermentation patterns
pure cultures must be obtained from___________so that subsequent steps in identification will be accurate
isolation media
Physiological reactions of bacteria to nutrients and other substrates indicates what?
Enzymes are present in bacteria
Enzyme-mediated metabolic reactions often visualized by what?
a color change
Carbohydrate Fermentation shows…?
production of acid and/or gas
Enzyme actions (biochemical tests):
catalase, oxidase, and coagulase
Dichotomous keys
Flow charts based on easily recognizable characteristics (motility, gram-stain, morphology) that helps identify bacteria
Phage Typing
Test used when morphological and biochemical tests are insufficient; infects bacteria with bacteriophage to identify certain kinds
Probes
small fragments of single-stranded DNA or RNA complementary to the specific DNA sequence of a particular microbe
Fluorescent in situ hybridization (FISH)
rapidly identifies 16s RNA sequences without first culturing the organism;
Ribosomal subunit suitable for identifying bacteria
16s rRNA (part of 30s)
Polymerase Chain Reaction
Amplifies minute quantities of DNA in samples into billion of copies & greatly improving the quality of the test
Kary Banks Mullis
Won a nobel prize for improving on the polymerase chain reaction
Fluorescent in situ hybridization (FISH) requires a pure culture of organisms obtained from a patient sample. True False
False
Serology
involves in vitro testing of serum based on the principle that antibodies have an extreme specificity for antigens
Specificity
property of a test to focus only on a certain antibody or antigen, and not react with an unrelated or distantly related antigen
Sensitivity
detection of even minute quantities of antibodies or antigens in a specimen;
These samples can be analyzed for the presence of specific & sensitivity antibodies
urine, cerebrospinal fluid, whole tissues, and saliva
Fluorescent Antibodies (Direct)
unknown test specimen or antigen is fixed to a slide and exposed to a Fluorescent antibodies (Fab) solution;
Antigen-Antibody (Ab-Ag)
Complexes that will remain bound to the Fab sample and will be visualized by fluorescence microscopy
Fluorescent Antibodies testing is used to…? (Direct)
valuable for identifying and locating microbial antigens on cell surfaces or tissues; also ID’s agents for syphilis, gonorrhea, and meningitis
Fluorescent Antibodies (Indirect)
In the indirect FAB method, known antigen is added to the test serum (not onto slide as direct method); binding of the antibody is seen under microscope
Fluorescent Antibodies testing is used to…? (Indirect)
used to diagnose syphilis and various viral infections
Radioimmunoassay (RIA)
antibodies or antigens labeled with a radioactive isotope used to pinpoint minute quantities of a corresponding antigen or antibody
RIA is used to…?
used to detect hormone levels in samples and diagnose allergies
Enzyme-Linked Immunosorbent Assay (ELISA)
uses an enzyme-linked indicator antibody to visualize Ag-Ab reactions
ELISA is used to…?
common test used for antibody screening for HIV, hepatitis A and C, and Helicobacter
Tuberculin test for Mycobacterium tuberculosis
small amount of purified protein derivative (PPD) from Mycobacterium tuberculosis is injected into the skin
Indicator of mycobacterium tuberculosis
appearance of a red, raised, thickened lesion in 48 to 72 hours can indicate previous exposure to tuberculosis
