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Infectious Disease and Microbiology > Diagnosis of Infectious Diseases > Flashcards

Diagnosis of Infectious Diseases Flashcards

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Biology 101 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
Q

Blood agar

A
  • 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
Q

Why do selective and differential media have bile salts?

A

Toxic for gram negative bacteria other than coliforms

27
Q

EMB distiguishes

A

lactose fermenters from non-lactomse fermenting gram negative organisms

28
Q

The__________ is definitive for lactone fermenters

A

green metallic sheen

29
Q

How much blood should be collected from an adult (>16), child under 10 and over 10?

A

20ml (10 ml per bottle), 1-5 ml in pediatric bottles, 5 to 8 ml

30
Q

Bacteria and fungemia

A

Presence of bacteria and fungi respectively

31
Q

Septicemia or sepsis

A

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
Q

Specimens should be processed ______ after they are collected

A

immediately

33
Q

MacConkey agar contains

A

bile salts and dye crystal violet

-inhibit growth of Gram-positive bacteria

34
Q

Control strip measures abnormal levels of

A

glucose, billirubin, ketones, specific density, blood, pH, proteins, urobilinogen, nitrite, leukocytes in a urine sample

35
Q

What is diagnostic for gonorrhea?

A

Gram negative stain of urethral, vaginal or cervical smear of diplococci

36
Q

VCN inhibitor

A

Vancomycin (inhibts most gram + bacteria)
Colistin (inhibits most gram- bacteria besides neisseria)
Nystatin/Anisomycin (inhibits yeast)

37
Q

Regan Lowe Agar

A

selective media which consists of charcoal agar

  • supplemented with defibrinated horse blood
  • diagnostic of bordetella pertussis
38
Q

Simmons citrate agar

A

measurement of citrate utilization by salmonella

-citrate test detects ability of an organism to use citrate as sole source of carbon and energy

39
Q

IMViC test

A

Indole, Methyl red, Voges-Proskauer, Citrate

  • identifies coliform organisms
  • used to differentiace enterobacteriaceae
40
Q

Standard procedure for assessing antimicrobial activity

A

disc diffusion test

41
Q

antibiograms

A

define suseptibility of clinically isolated microorganisms to the ATB in current use

42
Q

minimum inhibitory concentration (MIC)

A

procedure for antibiotic susceptibility testing employs antibiotic dilution assay in agar, culture tubes or wells of microtiter plate

43
Q

Etest

A

nondiffusion based technique that employs a preformed and predefined gradient of an antimicrobial agent immobilized on a plastic strip

44
Q

Lower MIC value indicates

A

less of drug is required to inhibit growth of organism

-more effective antimicrobial agents

45
Q

many immunoassays utilize

A

antibodies

-specific for pathogens or their products for “in vitro” test

46
Q

It’s possible to identify an infection by measuring the patients

A

antibody titer (quantity) against antigen produced by pathogen

47
Q

____ and ______ are commonly used tests

A

Agglutination and EIA

48
Q

Delayed type hypersensitiviy reactions response is mediated by

A

TH1 cells

49
Q

Antibodies can be chemically modified with

A

fluorescent dyes to help detect antigens on intact cells

50
Q

Two common fluorescent dyes

A

Rhodamine B (red) and Fluorescein Isothiocyanate (green)

51
Q

Direct method

A

antibody targeted against surface antigen is covalently linked to fluorescent dye

52
Q

indirect method

A

presence of non fluorescent antibody on surface of cell is detected by use of fluorescent antibody directed against the non fluorescent antibody

53
Q

Enznyme immunoassay (EIA) or Enzyme Linked Immunosorbent Assay (ELISA)

A
  • very sensitive immunological assay
  • widely used in clinical diagnostic and research applications
  • allow detection of antigen-antibody complexes
54
Q

Direct EIA

A

detection of antigen

55
Q

Indirect EIA

A

detection of antibody

56
Q

Sandwich EIA

A

Detection of antibody

57
Q

Combination EIA

A

combination of direct EIA and sandwich EIA

58
Q

Rapid tests

A
  • reagents are absorbed to support material
  • body fluid is applied to support matrix
  • color forms when concentration of chromophore gets high enough
59
Q

Immunoblot (western blot)

A

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
Q

polymerase chain reaction (PCR)

A

presence of amplified gene segement confirms presence of pathogen

61
Q

Reverse transcriptase PCR (RT-PCR)

A

uses pathogen-specific RNA to make cDNA

62
Q

quantitative real-time PCR (qPCR)

A

uses fluorescently labeled PCR products

-almost immediate results

Infectious Disease and Microbiology (9 decks)

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