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Infectious Disease and Microbiology > Diagnosis of Infectious Diseases > Flashcards

Diagnosis of Infectious Diseases Flashcards

1
Q

A Clinical Microbiologist

A

detects, identifies, and characterizes the microorganisms that causes infectious diseases from a variety of samples collected from sick hosts

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2
Q

Direct Observation of pathogens

A

acquired from clinical specimens, which is a very important tool for many Infectious Diseases

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3
Q

Diagnostic Approaches

A

in Clinical Microbiology include evaluation of samples by: growth-dependent techniques, molecular biology techniques, immunoassays

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4
Q

The idea is to ______, _________ and _____ most pathogenic bacteria within ___-_____ hrs of sampling

A

grow, isolate, identify, 24-48

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5
Q

In general the usefulness of any diagnostic test depends on the test’s

A

Specificity and Sensitivity

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6
Q

Specificity

A

is the ability of the test to recognize a single pathogen, optimal specificity implies that the test is specific for a single pathogen, and will not identify any other

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7
Q

High specificity prevents

A

False positive results

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8
Q

Sensitivity

A

defines the lowest numbers of a pathogen or the lowest amount of a pathogen product that can be detected

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9
Q

High sensitivity prevents

A

False negative results

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10
Q

Clinical specimens or suspension of microorganisms can be placed on

A

glass slide and examine under the microscope

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11
Q

Direct examination

A

simplest methods for preparing samples for microscopic examination

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12
Q

Wet mount

A

The sample can be suspended in water or saline

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13
Q

India ink method

A

the ink darkens the background rather than the cell

-creates a clear halo around the cell

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14
Q

Differential Stains

A
  • gram stain (most widely used for bacteria)
  • acid fast stain
  • endospore stain
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15
Q

Immunoassays

A

used to measure patient immune response, indicating pathogen exposure, or can be used to directly identify the pathogen in host tissue or culture

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16
Q

Specimens should be obtained from

A

the actual site of infection

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17
Q

Samples must be taken _________ to avoid

contaminations with irrelevant microorganisms

A

Aeseptically

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18
Q

General-purpose growth media

A

nutrient agar, blood agar and chocolate agar

-Support the growth of most aerobic and facultative aerobic organisms

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19
Q

Enriched growth media

A

Thayer-Martin agar

-Contain specific growth factors that enhance growth of certain fastidious pathogens

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20
Q

Selective growth media

A

Oxford Agar media

-Allow for some organisms to grow while inhibiting the growth of others due to the presence of inhibitory agents

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21
Q

Differential growth media

A

eosin-methylene blue

-specialized media that allow identification of organisms based on their growth, color and appearance on the medium

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22
Q

The red color in blood agar is froms

A

blood suspended in Trypticase soy agar medium

  • can be from horse, rabbit, or sheep
  • Fibrin removed beforehand
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23
Q

The browncolor in chocolate agar is due to

A

heat-lysed blood in trypticase soy agar

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24
Q

Thayer-Martin Agar

A

used for the selective isolation of gonorrhoeae and Neisseria meningitidis

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25
Blood agar
- considered a general purpose growth media - shows three types of hemolysis - alpha hemolysis ( partial breakdown, greenish) - beta hemolysis (complete breakdown, clear zone) - gamma hemolysis (no breakdown, brownish)
26
Why do selective and differential media have bile salts?
Toxic for gram negative bacteria other than coliforms
27
EMB distiguishes
lactose fermenters from non-lactomse fermenting gram negative organisms
28
The__________ is definitive for lactone fermenters
green metallic sheen
29
How much blood should be collected from an adult (>16), child under 10 and over 10?
20ml (10 ml per bottle), 1-5 ml in pediatric bottles, 5 to 8 ml
30
Bacteria and fungemia
Presence of bacteria and fungi respectively
31
Septicemia or sepsis
blood infection by virulent organism that enters the blood from focus of infection, multiplies and travels to various body tissues to initiate new infections
32
Specimens should be processed ______ after they are collected
immediately
33
MacConkey agar contains
bile salts and dye crystal violet | -inhibit growth of Gram-positive bacteria
34
Control strip measures abnormal levels of
glucose, billirubin, ketones, specific density, blood, pH, proteins, urobilinogen, nitrite, leukocytes in a urine sample
35
What is diagnostic for gonorrhea?
Gram negative stain of urethral, vaginal or cervical smear of diplococci
36
VCN inhibitor
Vancomycin (inhibts most gram + bacteria) Colistin (inhibits most gram- bacteria besides neisseria) Nystatin/Anisomycin (inhibits yeast)
37
Regan Lowe Agar
selective media which consists of charcoal agar - supplemented with defibrinated horse blood - diagnostic of bordetella pertussis
38
Simmons citrate agar
measurement of citrate utilization by salmonella | -citrate test detects ability of an organism to use citrate as sole source of carbon and energy
39
IMViC test
Indole, Methyl red, Voges-Proskauer, Citrate - identifies coliform organisms - used to differentiace enterobacteriaceae
40
Standard procedure for assessing antimicrobial activity
disc diffusion test
41
antibiograms
define suseptibility of clinically isolated microorganisms to the ATB in current use
42
minimum inhibitory concentration (MIC)
procedure for antibiotic susceptibility testing employs antibiotic dilution assay in agar, culture tubes or wells of microtiter plate
43
Etest
nondiffusion based technique that employs a preformed and predefined gradient of an antimicrobial agent immobilized on a plastic strip
44
Lower MIC value indicates
less of drug is required to inhibit growth of organism | -more effective antimicrobial agents
45
many immunoassays utilize
antibodies | -specific for pathogens or their products for "in vitro" test
46
It's possible to identify an infection by measuring the patients
antibody titer (quantity) against antigen produced by pathogen
47
____ and ______ are commonly used tests
Agglutination and EIA
48
Delayed type hypersensitiviy reactions response is mediated by
TH1 cells
49
Antibodies can be chemically modified with
fluorescent dyes to help detect antigens on intact cells
50
Two common fluorescent dyes
Rhodamine B (red) and Fluorescein Isothiocyanate (green)
51
Direct method
antibody targeted against surface antigen is covalently linked to fluorescent dye
52
indirect method
presence of non fluorescent antibody on surface of cell is detected by use of fluorescent antibody directed against the non fluorescent antibody
53
Enznyme immunoassay (EIA) or Enzyme Linked Immunosorbent Assay (ELISA)
- very sensitive immunological assay - widely used in clinical diagnostic and research applications - allow detection of antigen-antibody complexes
54
Direct EIA
detection of antigen
55
Indirect EIA
detection of antibody
56
Sandwich EIA
Detection of antibody
57
Combination EIA
combination of direct EIA and sandwich EIA
58
Rapid tests
- reagents are absorbed to support material - body fluid is applied to support matrix - color forms when concentration of chromophore gets high enough
59
Immunoblot (western blot)
detects antibodies to specific antigens or antigens themselves - electrophoresis of proteins - followed by transfer to a membrane and detection by addition of specific antibodies
60
polymerase chain reaction (PCR)
presence of amplified gene segement confirms presence of pathogen
61
Reverse transcriptase PCR (RT-PCR)
uses pathogen-specific RNA to make cDNA
62
quantitative real-time PCR (qPCR)
uses fluorescently labeled PCR products | -almost immediate results

Infectious Disease and Microbiology (9 decks)

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