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Microbiology Exam 2 (Modules 3-5) > Module 5: Chapter 15 > Flashcards

Module 5: Chapter 15 Flashcards

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1
Q

tests that can be performed at the bedside, meaning samples do not have to be sent out and patient care can continue without delay

A

point-of-care testing/diagnosis

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2
Q

scans often used to diagnose peritonsillar abscesses

A

computerized tomography (CT) scans

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3
Q

scan used to find areas of deep tissue infection

A

magnetic resonance imaging (MRI) scan

position emission tomography (PET) scan

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4
Q

refers to the traits that an organism is expressing in the present

A

phenotype

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5
Q

method of microbial identification:

observation of microbe’s microscopic and macroscopic morphology, physiology, and biochemical properties; involves examining their appearance and behavior ( behavior = enzymatic activities they carry out, what kind of physical conditions they thrive in, what antibiotics it is susceptible to, and the chemical composition of its walls and/or membrane)

A

phenotypic methods

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6
Q

method of microbial identification:

the nature of the antibody response is exploited for diagnostic purposes when a patient sample is tested for the presence of specific antibodies to a suspected pathogen (antigen)

analysis of microbe using antibodies, or of patients’ antibodies using prepackaged antigens

alternatively, microbial antigens in the patient’s tissues can be tested with antibodies “off the shelf” (these methods can be easier than trying to isolate the microbes itself.

A

immunologic methods

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7
Q

methods of microbial identification:

analysis of microbe’s DNA or RNA

ie. numerous viable nonculturable (VNC) microbes are currently being identified in this manner through studies such as the Human Microbiome Project

A

genotypic methods

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8
Q

primary advantages of genotypic methods over phenotypic methods

A

culturing of the microorganisms is not always necessary

genotypic methods are increasingly automated, producing rapid results that are often more precise than with phenotypic methods

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9
Q

15.1 outcome

list the three major categories of microbial identification and a one sentence description for each

A
  1. Phenotypic methods: examining the appearance and behavior (enzymatic activities, physical conditions it thrives in, antibiotics its susceptible to, chemical comp of walls/membranes)
  2. Immunologic methods: examining the antibodies present in a patient’s sample, to see if the antibodies link to the suspected antigens; antigens in the patients tissues can be tested with antibodies “off the shelf”
  3. Genotypic methods: examining a microbes genetic material (RNA or DNA
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10
Q

15.2 First Steps: Specimen Collection

A
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11
Q

the success of identification and treatment depends on how specimens are:

A

collected, handles, stored, and cultured

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12
Q

in specimen collection it is important that general _______ procedures be used, including sterile sample containers and other tools to prevent contamination from the environment or patient.

A

aseptic

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13
Q

throat and nasopharyngeal swabs should not touch the cheeks, tongue, or _____.

A

saliva (saliva contains millions of bacteria per milliliter, most of which is normal biota)

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14
Q

mucus secretion that coats the lower resp surfaced, especially the lungs; is discharged by coughing or taken by a thin tube called a catheter to avoid contamination with saliva

A

sputum

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15
Q

saliva samples may be needed for dental diagnosis and are obtained how?

A

having the pt spit or drool into a container

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16
Q

the mucous lining of the urethra, vagina, or cervix can be sampled with a swab or _______

A

applicator

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17
Q

depending on the nature of a skin lesion, skin can be swabbed or scaped with a scalpel to expose deeper layers; wounds are sampled either by _______ or by using a __________

A

swabbing or a punch biopsy tool

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18
Q

fluids such as blood, cerebrospinal fluid, and tissue fluids must be taken by _______ _______ _______

; antisepsis of the puncture site is extremely important in these cases

A

sterile needle aspiration

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19
Q

name some additional sources of specimen besides urine, blood, CSF, mucous secretions, and sputum

A

eye, ear canal, synovial fluid (joint fluid), nasal cavity (all by swab), and diseased tissue that has been surgically removed (biopsied)

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20
Q

nonsterile samples such as urine, feces, and sputum, are especially prone to deterioration at

A

room temperature

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21
Q

nonnutritive maintenance media

A

a media used to maintain specimens in stable conditions for several hours, but will but grow them

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22
Q

before collecting a specimen, what should your analyze a patient for?

A

signs of microbial infection such as fever, wound exudate, mucus production, abnormal lesions

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23
Q

the time required for testing _______

ie. a few minutes for rapid strep testing to several weeks for tuberculosis testing

A

varies

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24
Q
  1. 2 outcomes
  2. identify factors that may affect the identification of an infectious agent from a sample
  3. compare the types of tests performed on microbial isolates versus those performed on patients themselves
A

1.

  • improper collection technique
  • collection, transport, storage, labeling
  1. Microbes: analysis involves
  2. Direct testing using microscope, immunologic or genetic methods that provide clues to identify the microbes.
  3. Cultivation, isolation, and identification of pathogens using a wide variety of general and specific tests.

Patients: tests on patient serum provide indirect evidence for specific pathogens though analysis of the antibody response. Skin testing can be used or some pathogens can be identified solely on the patient’s signs and symptoms

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25
Q

15.3 Phenotypic Methods

A
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26
Q

most used stains for bacterial identification

A

Gram stain and acid-fast stain

but as useful as these stains are they can identify only a few organisms on their own

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27
Q

direct microscopic observation of a fresh or stained specimen is one of the most ______ methods of determining presumptive and sometimes confirmatory microbial characteristics

A

rapid

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28
Q

in cases where the suspected pathogen is present in small amounts or is easily overgrown by normal biota, the specimen can be initially enriched with ____________ media.

A

specialized

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29
Q

nonsterile specimens containing a diversity of bacterial species, such as urine and feces, are cultured on _______ media to encourage the growth of only the suspected pathogen

A

selective

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30
Q

specimens are often inoculated into _________ media to identify definitive characteristics, such as reactions in blood (blood agar) and fermentation patters (mannitol salt and MacConkey agar)

A

differential media

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31
Q

dichotomous key

A

a graphic method that is essentially a flowchart leading to the identification of specimens

“di” refers to the fact that at each branch of the flowchart there are two (di) possible outcomes

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32
Q

a straightforward way to phenotypically identify specimens is to combine the results of tests such as gram staining (neg or pos?), growth on different media, and simple enzymatic tests —–> this can form the starting point for what

A

dichotomous key

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33
Q

cocci —>
gram + or gram - —>
gram + = Catalase + (irregular clusters, tetrads) or catalase - (pairs, chain arrangement) —>
catalase - = Streptococcus
catalase + = strictly aerobic or facultative anaerobic
strictly aerobic = micrococcus
facultative anaerobic = Staphylococcus/Planococcus

A

example of gram + dichotomous key

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34
Q

what technique in this chapter do most home pregnancy test kits utilize?

A

the lateral-flow test, which is an immunochromatographic method

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35
Q

Biochemical testing:

the physiological reactions of bacteria to nutrients and other substrates provide excellent evidence of the types of ______ systems present in a particular species;

knowing which ____ an isolate has can often leas to its identity

A

enzyme

enzymes

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36
Q

many biochemical testing are based on ________-mediated metabolic reactions that are visualized by a color change

A

enzyme

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37
Q

in enzyme-mediated biochemical testing the microbe is cultured in a medium with a special substrate and then tested for a particular end product.

microbial expression of the enzyme is made visible by a colored dye, no coloration means it ________ the enzyme for utilizing the substrate in that particular way

A

lacks

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38
Q

Mycobacterial Growth Indicator Tube (MGIT)

A

a type of phenotypic test used to detect the growth of slow-growing Mycobacterium tuberculosis

—> this system monitors oxygen levels in a tube that has been inoculated with a patient specimen (blood, sputum), tube contains medium that encourages growth of the tuberculosis bacterium; ***there is a silicon chip at the bottom of the tube that is impregnated with a fluorescent substance that is sensitive to oxygen

–> when first inoculated, there will be a lot of free oxygen in the medium because even if the bacteria are present, there will not be many of them
BUT, if the bacteria grow, they begin using the oxygen, and the decreased levels of O2 allow the silicon compound to fluoresce

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39
Q

antimicrobial susceptibility testing and phenotypic methods

A

most of the automated phenotypic systems incorporate a panel of commonly used antimicrobials for the particular infection site; and simultaneously test susceptibility while IDENTIFYING the pathogen;

*** commonly completed using an adaptation of the tube-dilation method (chapter 12)

–> these tests themselves can identify some species like Streptococcus, Clostridium, and Pseudomonas

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40
Q

miscellaneous tests:

Phage Typing

A

relies on bacteriophages (viruses that attack bacteria in a very species-specific and strain-specific way

—> useful in identifying some bacteria, primarily Salmonella, and is often used for tracing bacterial strains in epidemics

  • –> phage typing involves: inoculating a lawn of bacterial species onto agar, mapping it off into blocks, and applying a different PHAGE to each sectioned area of growth
    so: CLEARED AREAS corresponding to lysed cells indicate sensitivity to the PHAGE, and a bacterial identification may be determined from this pattern
41
Q

__________ __________ are needed to cultivate bacteria such as Mycobacterium leprae and significant quantities of Treponema pallidum;
whereas __________ _________ and cell cultures can be used to grow host cell-dependent rickettsias, chlamydias, and viruses

A

susceptible animals

avian embryos

42
Q

what are some clinically significant features of cultures?

A
  • the number of microbes present ie. a few colonies of E. coli in a urine specimen can simply indicate normal biota, several hundred colonies can indicate active infection
  • the presence of a single colony of a true pathogen, such as Mycobacterium tuberculosis in a sputum culture or an opportunist in sterile sites such as in CSF or blood, is highly suggestive of its role in disease
43
Q

the repeated isolation of a relatively pure culture of any microorganism can mean it is an agent of _______.

A

disease

44
Q

two major drawbacks of phenotypic methods

A

(1) when the microbe has to be cultured, it takes a minimum of 18 to 24 hours, and often longer
(2) we are learning that many infectious conditions may be caused by nonculturable organisms, leaving open the possibility that the organism that we do culture is simply a bystander

45
Q

phenotypic Dx methods summary

A

Direct Examination: microscopy of patient specimens, usually after staining (does not require cultivation)

Biochemical Testing: growth of microbe in media that detects the presence of microbe’s enzymes, creating a metabolic “fingerprint” (requires cultivation)

Susceptibility Testing: in some cases a particular patter or antimicrobial susceptibilities can lead to the identity of a microbe (requires cultivation)

Miscellaneous: Phage Typing, Animal inoculation, cell culture growth (requires cultivation)

Selective/Differential Growth: use of specialized media that reveal identifying characteristics such as colony appearance, motility, and gas requirements (requires cultivation)

46
Q
  1. 3 Outcomes
  2. List at least three tests that fall in the direct identification category.
  3. Explain the main principle behind biochemical testing, and identify an example of such tests.
  4. Discuss two major drawbacks of phenotypic testing methods that require culturing the pathogen
A

1.

  • Direct observation of fresh of stained specimen
  • Biochemical testing
  • Isolation media and morphological testing (when pathogen numbers are small, pathogen can be isolated and grown with enriched media)
  1. Physical reactions of bacteria to nutrients and other substrates provides excellent evidence of the types of enzyme systems present in a particular species. Most of these tests are based on enzymatic reactions visible by a color change.

ie. Production of acid and/or gas=carbohydrate fermentation
Hydrolysis of gelatin, starch, and fats
Actions of enzymes: catalase, oxidase, coagulose, lipase
Various by-products of metabolism

  1. Takes a longer time to get results, possibility of errors in storage, transportation, and culturing
47
Q

15.4 Immunologic Methods

A
48
Q

branch of immunology that traditionally deals with in vitro diagnostic testing of serum

A

serology

49
Q

serological testing is based on the principle that

A

antibodies have extreme specificity for antigens, so when a particular antigen is exposed to its specific antibody, it will fit like a hand in a glove

50
Q

what other fluids are tested in serology now a days?

A

not just sera, we also test urine, CSF, whole tissues, and saliva.

51
Q

immunologic Dx methods

A

Agglutination/Precipitation: A- antibody-mediated clumping of whole cells
P- smaller complexes of antibody-antigen

Immuno-chromatography: most common for is a lateral-flow system, supplied in prepackaged cartridges that produce a colored stripe

Western Blot: electrophoresis separates proteins (either antigens or antibodies) and then labeled antibodies or antigens are used for detection

Fluorescent Antibodies:
Direct- unknown specimen is exposed to known fluorescent Ab
Indirect- patient’s antibody (its Fc portion) probed with fluorescent Ab

ELISA: sandwiching technique using Ag, Ab, and a secondary Ab to produce a color change

In vivo Tests: antigen introduced into a patient to elicit a reaction, such as a TB skin test

52
Q

Agglutination and Precipitation + their differences

A

differences are in size, solubility, and location of the antigen

A- antigens are whole cells or organisms such as RBCs, bacteria, or viruses displaying whole surface antigens
-> easily seen because it forms visible clumps of cells, such as in the Weil-Felix reaction used in dx-ing rickettsial infections

P- (smaller clumps) the antigen is examined is a soluble molecule

—> in both reactions, when antigen and antibody concentrations are optimal, one antigen is interlinked by several antibodies to form insoluble aggregates that settle out in solution

53
Q

Agglutination is also used to determine blood ________.

A

compatibility

54
Q

immunochromatography

A

“lateral-flow test”

can be found in drugstore pregnancy tests, and rapid strep tests in the doctor’s office

55
Q

an antigen-antibody reaction in liquid is read as a ________, or the concentration of antibodies in the sample

A

titer

56
Q

define titer
; it is determined by serially diluting patient serum into test tubes or wells of a microtiter plate, all of which contain equal amounts of bacterial cells (antigens)

A

defined as the highest dilution of serum that still produces agglutination

-> in general, the more serum a sample can be diluted and still react with antigen, the greater the concentration of antibodies, and thus its titer

57
Q

antibody titers are often used to diagnose autoimmune disorders such as _____ and _____, and also to determine past exposure to certain diseases such as rubella.

A

rheumatoid arthritis, and lupus

58
Q

antigen-antibody technique for identifying, classifying, and subgrouping certain bacteria into categories called serotypes

  • –> this method of immunologic dx employs antisera against cell antigens such as the capsule, flagellum, and cell wall.
  • widely used in identifying Salmonella species and strains, and is the basis for differentiating the numerous pneumococcal and streptococcal serotypes
A

serotyping

59
Q

immunologic methods widely used in identifying Salmonella species

A

serotyping

60
Q

involves the separating of proteins by electrophoresis, and then using antibodies to detect the proteins

  1. A sample of proteins is obtained from cells after lysing them is separated via electrical charge within a gel = the proteins embedded in the gel are transferred and immobilized to a special filter
  2. The filter is incubated with antibody solutions, some of which have been labeled with radioactive, fluorescent, or luminescent molecules
  3. After incubation, sites of specific antigen-antibody binding will soon appear as a pattern of bands that can be compared with known pos and neg controls

this is a HIGHLY specific and sensitive way to identify or verify the presence of microbial-specific antigens or antibodies in a patient sample

A

Western Blot Test

61
Q

fundamental tool in testing is a fluorescent antibody, a monoclonal antibody labeled by a fluorescent dye

Direct testing- an unknown specimen or antigen is fixed to a slide and exposed to FAb solution of known composition- if antibody-antigen complexes form, they will remain bound to the sample and will be visualized by fluorescent microscopy = positive result

valuable in identifying causative agents of syphilis, gonorrhea, meningitis, etc.

Indirect testing- FAbs used in this testing recognize the Fc region of Ab’s in patient sera, a known antigen (ie. bacterial cells) is added to the test serum, and binding of the fluorescent antibody is visualized through fluorescence microscopy = fluorescing aggregates or cells indicate that FAbs have complexed with the microbe specific antibodies in the test serum

frequently used to dx syphilis and various viral infections

A

Immunofluorescence Testing

62
Q

“sandwich technique”

uses an enzyme-linked indicator antibody to visualize antigen-antibody reactions; this technique also relies on solid support such as a plastic microtiter plate that can adsorb (attract on its surface) the reactants

indirect: known ANTIGEN is adsorbed to the surface of a well and mixed with unknown antibody; complex forms, and indicator Ab will bind and subsequent development will produce a color change = pos result
common test for HIV, Hep A and C, and Helicobacter, and rickettsial species

direct: sandwich test; a known ANTIBODY is adsorbed to bottom of well and incubated with an unknown antigen; if any antibody-antigen complex forms, it will attract the indicator antibody and color will develop in these walls = pos result

A

Enzyme-Linked Immunosorbent Assay (ELISA)

63
Q

A western blot may be needed to confirm what other type of test because of possible false positives?

A

ELISA indirect testing

64
Q

employ principles similar to serological tests, except in this testing an antigen is introduced into a patient to elicit some sort of visible reaction.

ie. TB skin test where a small amount of purified protein derivative (PPD) from Mycobacterium tuberculosis is injected into the skin

A

In vivo testing

65
Q

the property ff a test to focus on only a certain antibody or antigen and not to react with unrelated or distantly related ones;

ie. a test with high ________, will have a low false-POSITIVE rate.

A

specificity

66
Q

the most effective tests have a high degree of ________ and _______

A

specificity and sensitivity

67
Q

refers to the detection of minute quantities of antibodies or antigens in a specimen

ie. a test with high _________ will have a low false-NEGATIVE rate

A

sensitivity

68
Q
  1. 4 Outcomes
  2. Define the term serology and explain the immunologic principle behind serological tests
  3. Identify two immunologic diagnostic techniques that rely on a secondary antibody, and explain how they work
A
  1. branch of immunology that traditionally deals with in vitro diagnostic testing of serum; based on the principle that antibodies have extreme specificity for antigens, so when a particular antigen is exposed to its specific antibody, it will fit like hand and glove
  2. immunofluorescence testing: FAbs (fluorescent antibodies) recognize the Fc region of antibodies in patient sera. known antigen (i.e. bacterial cells) is added to the test serum, and binding of the fluorescent antibody is visualized through microscopy

enzyme-linked immunosorbent assay (ELISA): known antigen is adsorbed to well, serum samples with unknown antibodies applied, well is rinsed to remove unbound antibodies, indicator antibody outfitted with an enzyme attaches to Fc portion of any antibody, well rinsed to remove unbound indicator antibody (a colorless substrate for enzyme added), and enzymes linked to indicator Ab hydrolyze the substrate, which releases a dye. wells that develop color are (+) for the antibody

69
Q

15.5 Genotypic Methods

A
70
Q

the sequence of nitrogenous bases within DNA or RNA is

A

unique to every microorganism —> this is why genotypic methods have become a mainstay of microbial identification

71
Q

genotypic test useful for outbreak investigations

A

Pulsed-field gel electrophoresis

72
Q

test that results in the production of numerous identical copies of DNA or RNA molecules within hours; this method can amplify even minute quantities of nucleic acids present in a sample which greatly improved the sensitivity of these tests

can be performed on genetic material of bacteria, viruses, protozoa, and fungi

A

Polymerase Chain Reaction (PCR)

73
Q

uses fluorescent labeling during the amplification procedure and the level of fluorescence is measured in real time as the reaction is running; is fully automated and is faster than traditional PCR because analysis of the DNA after the reaction is finished is not necessary

these tests often assess the antimicrobial susceptibilities at the same time they are identifying the organism

A

Real-Time PCR “qPCR”

74
Q

Reverse-transcriptase PCR (RT-PCR)

A

involves the creation of DNA out of RNA (reversed, as usually RNA comes from DNA)

75
Q

type of diagnostic PCR that contains primers for multiple organisms instead of just one single primer; as with biochemical panels, this test will contain primers for multiple organisms in the differential diagnosis for the patient’s symptoms

—> most often this test is also real-time PCR

*tests multiple organisms not just one

A

Multiplex PCR

76
Q

amplification method that, unlike PCR, does not require temperature changes; uses two enzymes, reverse transcriptase (to make DNA) and polymerase (to transcribe RNA)

A

Transcription-Mediated Amplification

77
Q

technique that makes it possible to identify microbes by analyzing segments of its genetic material; this requires small fragments of single-stranded RNA or DNA called PROBES that are known to be complementary to the specific sequences of nucleic acid isolated from a particular microbe

—> base pairing of the known probe to the nucleic acid can be observed, providing evidence of the microbe’s identity

*probes are typically fluorescently labeled or attached to an enzyme that triggers colorimetric change when __________ occurs

A

hybridization

78
Q

COVID-19 at home tests that detect viral RNA, are what time of PCR test?

A

RT-PCR

Reverse-transcriptase polymerase chain reaction test

79
Q

Hybridization

Fluorescence in situ hybridization (FISH) technique

A

involves the application of fluorescently labeled probes to intact cells within a patient specimen or an environmental sample
*microscopic analysis or automated processed are used to locate “glowing” cells and conclude the identity of the microbe

***used to identify the microbial components of a BIOFILM

—> often used to confirm diagnosis or identify a specific microbe; FISH is deceasing in use as PCR tests become more convenient and accurate but FISH is still used in cancer diagnosis especially in personalized medicine where a patient’s DNA is examined for particular characteristics that can make a drug a better choice for them

80
Q

_________ designed for infectious disease diagnosis are “chips” (absorbent plates) that contain gene sequences from potentially thousands of different possible infectious agents, selected based on the syndrome being investigated (such as resp infection or meningitis symptoms)

**matching sequences hybridize to the chip, and the label (most often fluorescence) is detected by a computer program which identifies the isolate or isolates

—> could include genes for fungal, bacterial, or viral all in one single test

A

Microarrays

81
Q

particularly useful for rapid analysis of outbreaks and drug resistant organisms; this method is generally low cost and low time of completion

a single genome can be scanned and analyzed multiple times in a process called “deep-sequencing”, which minimizes error

A

Whole-Genome Sequencing

82
Q

in chapter 8, ___________ was described as a method for analyzing short segments of DNA within a sample

A

fingerprinting

83
Q

similar to fingerprinting, but instead involves the separation of DNA fragments that are too large for conventional gel electrophoresis methods;

this is accomplished by slowly adding alternating voltage levels to the gel from three different directions, allowing even similarly sized DNA fragments to fully separate
—> because the DNA is subjected to restriction enzymes, single changes in the DNA sequence (from mutations) will result in fragments of different sizes

**often used in acute outbreaks of foodborne illness and other infections

A

Pulsed-Field Gel Electrophoresis: Microbial Fingerprints

84
Q
  1. 5 Outcomes
  2. Explain why amplification techniques are useful for infectious disease dx
  3. name two techniques that employ hybridization
  4. explain how whole-genome sequencing can be used for diagnosis
  5. identify the situations in which pulsed-field gel electrophoresis is most useful
A
  1. because amplified amounts of a pathogen can lead to more data for investigation and high specificity + sensitivity
  2. name two techniques that employ hybridization
    - FISH (fluorescent in situ hybridization)
    - Microarrays (matching sequences hybridize to the chip, and the label is detected by a computer program which identifies the isolate(s))
  3. it can be used for rapid analysis of outbreaks and drug-resistant organisms; a single genome can be scanned and analyzed multiple times in a process called “deep sequencing”
  4. when DNA fragments are too large for conventional gel electrophoresis methods
85
Q

a process that matches complememtary strands of nucleic acid

(DNA-DNA, RNA-DNA, RNA-RNA); used for locating specific sites or types of nucleic acid

A

hybridization

86
Q

15.6 Additional Diagnostic Technologies

A
87
Q

Lab on a Chip - Infectious Disease Diagnosis

A

since the development of microarrays, many genetic tests have been miniaturized and placed on chips (integrated circuits) that are:

  • easy to use
  • require few supplies
  • require little technical training

—> they have been facilitated by the used of microfluidics, using miniscule amounts of reagents and fluids to perform reactions that were previously done in test tubes

  • PCR methods and DNA and RNA sequencing have been made available on “chips”

BUT: biggest impact on developed countries as in developing countries this form of diagnosis is not possible due to lack of supplies, expertise, or even refrigeration required to store an array of diagnostic reagents

88
Q

utilized for years to determine the structure and composition of various chemical compounds and biological molecules

  • –> used alone, and in combination with PCR to provide rapid and highly accurate microbial identification within just minutes
    • –> this method, called the MALDI-TOF can be used to analyze a protein fingerprint from pure culture isolates or directly from samples isolated from patient specimens
  • **WORKS by adding the pt sample to a metal plate and then striking it with a laser, this causes the sample to be ionized
  • > the ions from the sample are guided into a machine that separates them and identifies them according to their mass-to-charge ratio

used for bacteria, fungi, viruses, and is becoming a commonplace utility in clinical and research laboratories due to its ability to produce RAPID, PRECISE, and COST-EFFECTIVE results

A

Mass Spectrometry

89
Q

one distinct advantage of mass spectrometry

A

clinical laboratories can construct databases of local strains of microorganisms by running profiles of known microbes; this provides for an infinitely customizable and expandable database

-> can also be used to detect antibiotic susceptibilities

90
Q

diagnostic method that offers a pair of eyes to inaccessible places, and can save the patient an invasive biopsy

-> infections associated with hip implants may be difficult to access through blood samples; the bacteria may be growing in biofilms on the implanted materials, or they may be in an abscess deep in the hip joint, this method allows us to un-invasively investigate

; MRIs, Computerized tomography (CT) scans, PET scans, have been increasingly employed to find areas of localized infection in deep tissue, which can later be biopsied to aspirate samples for culture; or if no infection is found during imaging, the patient has been spared an invasive procedure

A

Imaging

91
Q

new strategy for identification involving seven genes

A

used blood from patient to check for the presence of seven genes that host cells express in response to BACTERIAL infection

  • > if the genes are active, then the prescriber knows to prescribe an antibiotic; if they are not active than the symptoms are caused by virus(es) and therefore are not going to be helped by antibiotics
  • *very important in a society where its estimated that many prescriptions are incorrectly prescribed for conditions that are not caused by bacteria
92
Q
  1. 6 OUTCOMES
  2. describe the benefits of “lab on a chip: tech for global public health
  3. identify an advantage presented by mass spectrometry and also by imaging techniques as diagnostic tools
A
  1. -easy to use
    - requires little to no training
    - requires few supplies
  2. imaging: is less invasive then biopsies; potentially avoids unnecessary invasive procedures

mass spectrometry:

  • rapid
  • highly accurate
  • rapid, precise, and cost-effective
  • can construct databases of local strains of micros by running profiles of known microbes
93
Q

mass spectrometry identifies microbes via

a. fluorescent antibodies
b. cell surface carbs
c. protein fingerprints
d. DNA profiling

A

c. protein fingerprints

94
Q

when using pulsed-field gel electrophoresis, mutations in a microbe’s genome will show up as

A

a different pattern of bands

95
Q

which category of dx is represented by studying a microbe’s utilization of nutrients?

A

phenotypic

96
Q

_______ diagnostic techniques are most likely to be affected by changes in growth conditions of the specimen

A

phenotypic

97
Q

which of the following techs is most likely to reveal that an infection is in biofilm form?

a. ELISA
b. Whole-genome sequencing
c. PFGE
d. imaging

A

d. imaging

98
Q

a test that results in a very large number of false POSITIVES probably has an unacceptable level of

A

sensitivity

*think ebola example in text

Microbiology Exam 2 (Modules 3-5) (13 decks)

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