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Clinical Medicine LAB - Professor Sample > Infectious Disease #1 > Flashcards

Infectious Disease #1 Flashcards

1
Q

Most lab tests measure a reaction between an _______ and ________.

A

antigen and ABS

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2
Q

Latex agglutination can either be coated with what?

A

ABS and antigens

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3
Q

in agglutination inhibition clumping means there is a positive or negative result?

A

negative

if it was positive then it means there was the antigen in the serum and is binding to the Anti- HCG ABS and the HCG molecule…not allowing the two to bind and cause visible clumping

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4
Q

In Hemagglutination, instead of latex what is used that have antigens on the surface?

A

RBCs

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5
Q

What amplifies low levels of DNA or RNA?

A

PCR

90 (denature), 55 (add synthetic DNA pieces), 70 (DNAp binds & copies)

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6
Q

Used to amplify even a small amount of DNA or RNA to detectable amounts?

A

PCR

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7
Q

Steps in PCR?

A

Denaturation
Annealing
Extension

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8
Q

PCR: Denaturation?

A

1 min , 94 degrees

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9
Q

PCR: Annealing?

A

45 sec , 54 degrees

*forward and reverse primers**

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10
Q

PCR: Extension?

A

2 min , 72 degrees

*only dNTPs**

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11
Q

Direct Fluorescent Antibody (DFA)?

A

ABS leveled with fluorescent dye

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12
Q

Indirect Immunofluorescence Assay (IFA)?

A

substrate containing the antigen

if it is positive then the patients ABS is adhered already to the base ( cause it contains the antigen) and then the new added Anti_IgG ABS binds to the patients ABS.

The Anti-IgG ABS has fluorescein molecule then it is able to be detected

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13
Q

Other Methods of Identification?

A

Culture

Direct Exam/Gram Stain - can direct treatment before a true culture report

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14
Q

Sensitivity is the proportion of patients with the disease who test ________?

A

positive : TRUE positive

D-dimer is not sensitive

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15
Q

Specificity is the proportion of patients without the disease that test ________?

A

negative : TRUE negative

ESR is not specific

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16
Q

Sensitivity avoids false _________?

A

negatives

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17
Q

Specificity avoids false _________?

A

positives

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18
Q

Clostridium organisms?

A

Clostridium botulinum

Clostridium tetani

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19
Q

Indications of clostridium testing?

A

Suspicion of tetanus or botulism

*tetanus - dirty wound make sure they have updated tetanus**

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20
Q

What type of organism is Clostridium? (background?)

A

Anaerobic, gram +, spore-forming rod

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21
Q

Clostridium testing contraindications?

A

Do not delay care with suspicion of clostridium infection

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22
Q

Clostridium tetani diagnosis is primarily ________?

A

clinical

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23
Q

Clostridium tetani culture can be obtained from?

A

wound / umbilical stump

*culture and grow out bacteria but Dx is clinical **

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24
Q

Clostridium botulinum
, Botulism, Toxin Identification?

can do a wound culture too

A 
Vomit
NG secretions ( nasogastric)
Serum
Stool (late in the course)
Food samples

*Not routinely done. Treatment based on clinical suspicion and exposure.**

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25
Q

Leptospirosis screening ?

A
  1. Leptospira IgM (ELISA)

2. Leptospira DNA PCR - more time consuming and expensive

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26
Q

Leptospirosis Conformation?

A
  1. Microscopic agglutination testing (MAT)
  2. Serum titers (serial 1st and 4th week of illness)
  3. DNA PCR
  4. Leptospira cultures - hardly used, har to grow, not reliable
    * ELISA has replaced MAT for first line **
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27
Q

Leptospirosis is found mostly in ?

A

cow urine

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28
Q

Bubonic plague is a gram ________ organism with a _________ appearance?

A

gram-negative

safety-pin appearance (polar staining)

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29
Q

What is the Bubonic Plague organism?

A

Yersinia Pestis

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30
Q

Where can you obtain cultures for Bubonic Plague?

A

Lymph node aspirates

Blood

Sputum - if pulmonic involvement

Bronchial/trachial washing

Post-mortem cultures from spleen, lung, liver, or bone marrow (DFA or PCR)

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31
Q

Bubonic Plague blood culture?

A

septicemia, early may be negative

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32
Q

Bubonic Plague sputum culture?

A

pneumonic involvement but usually blood cultures are positive by that time

if pulmonic involvement

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33
Q

If Bubonic Plague cultures are negative then who else can you do ?

A

Serologic testing can be sent to the CDC:

  1. One acute sample
  2. One convalescent sample (4-6 weeks after disease onset)
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34
Q

When do you begin Abx treatment with Bubonic Plague?

A

ASAP

*necrosis of extremities **

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35
Q

What is treatment for Bubonic Plague?

A

Streptomycin

Gentamycin

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36
Q

Indications for Tularemia testing?

A

r/o tularemia

Pts with fever, large ulcerative blisters, and large tender lymph nodes and risk factors

farmers that run over dead rabbit carcus and the bug is aerosolized

*Tests can be done off of serum, ulcer scrapings, lymph node bx, sputum, blood cultures **

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37
Q

Tularemia test used to detect AB to Fransicella tularensis?

A

Agglutination ( micro- and tube)

GS

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38
Q

Tularemia test mostly used in ulceroglandular disease ?

A

PCR

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39
Q

Tularemia test that is not useful, difficult to isolate and uses cysteine-glucose-blood agar plate?

A

Culture

40
Q

Positive Tularemia test if single titer of?

A

greater to or equal to 1:160

OR

4-fold increase in titer collected 2-3 weeks apart

41
Q

Tularemia considerations?

A

Many labs refuse to test because of high infectivity

↑ biosafety measures with handling specimens

42
Q

What is the Lyme Disease organism?

A

Borellia burgdorferi

43
Q

How is Borellia burgdorferi

, the organism that causes Lyme, transmitted?

A

Borellia burgdorferi is transmitted by Ixodes (deer tick)

44
Q

What test is useful EARLY in Lyme disease?

A

Skin Culture of the risk ( Erythema migrans)

Bx of EM

*early on and they have a rash = most reliable**

45
Q

What Lyme test determines levels of IgG & IgM?

A
  1. ELISA ( GS)
46
Q

In Lyme disease when does IgG peak?

A

4-6 months

47
Q

In Lyme disease when does IgM peak?

A

3-6 weeks after onset of sxs

48
Q

What Lyme test do all positive or indeterminate ELISA need to be confirmed with ?

A

Western Blot

49
Q

What Lyme test uses CSF or Urine?

A

PCR

50
Q

Negative interpretation of Lyme Ab?

A

< 0.9 = negative

51
Q

Equivocal interpretation of Lyme Ab?

A

0.91 - 1.09 = equivocal ( maybe run another Western Blot)

52
Q

Positive interpretation of Lyme Ab?

A

> 1.10 = positive

53
Q

Positive IgG Ab western blot?

A

> 5 different IgG Ab = positive

54
Q

Positive IgM Ab western blot?

A

> 2 different IgM Ab = positive

55
Q

Interpretation of PCR?

A

negative is normal

56
Q

Interfering factors causing FALSE positives in Lyme disease Testing?

A

Previous infxn with Lyme

Other spirochetal infections

57
Q

RMSF organism?

A

Rickettsia rickettsii

*starts on the wrist and ankles , end organ failure later one these people get very sick very fast**

58
Q

RMSF testing?

A
  1. Indirect Immunofluorescence Assay

2. PCR

59
Q

RMSF Indirect Immunofluorescence Assay incubation period?

A

7-10 days after onset

60
Q

RMSF Indirect Immunofluorescence Assay diagnostic titer is greater than or equal to ?

A

1:64

61
Q

RMSF Indirect Immunofluorescence Assay sensitivity is?

A

94-100%

62
Q

RMSF Indirect Immunofluorescence Assay specificity is ?

A

100%

63
Q

With RMSF testing, what is the only test useful in acute presentation ( uses skin bx of rash) - EARLY testing?

A

PCR

64
Q

RMSF PCR sensitivity?

A

70%

65
Q

RMSF PCR specificity?

A

100%

66
Q

Syphillis organism?

A

Spirochete -Treponema pallidum

67
Q

What are the 4 stages of Syphillis?

A

Acute
Secondary
Latent
Tertiary

68
Q

Syphillis does not grow on __________ medium?

A

artificial

69
Q

Syphillis - 
Dark field microscopy, what to look for?

A

T. pallidum morphology and motility

*gram negative spiral shape, rotates about its axi, and 2-3 flagella at each end to allow corkscrew like motility**

70
Q

Syphillis - 
Dark field microscopy, advantage?

A

definite immediate diagnosis

rapid results

71
Q

Syphillis - 
Dark field microscopy, disadvantages?

A
  1. Requires specialized equipment and an experienced microscopist
  2. Possible confusion with other pathogenic and nonpathogenic spirochetes
  3. Must be performed immediately
  4. Possibility of false-negatives
    * DFM - not done that much , not readily available **
72
Q

Syphillis - Non-Treponemal tests don’t look for spirochete - it detects presence of a ______?

A

reagin

73
Q

Syphillis - Non-Treponemal tests reacts to _____________ in the body similar to those of _.________

A

phospholipids

similar to those of T.pallidum

74
Q

Syphillis - Non-Treponemal tests are used as ________ tests?

A

screening and are nonspecific

75
Q

Syphillis - Non-Treponemal tests?

A

VDRL - vanerial disease research lab

RPR - rapid plasma reagent test

RPR first

76
Q

Syphillis - Treponemal tests detects __ against treponema organism ?

A

Ab

77
Q

Syphillis - Treponemal tests are usually reactive for ____ and used as ____________ tests?

A

life

confirmatory tests

78
Q

Syphillis -Treponemal tests?

A

FTA-ABS

MHA-TP

79
Q

Sensitivity of all syphillis tests if the sphyillis is secondary is ?

A

100

80
Q

diffuse rash and suspect maybe secondary or tertiary or they have neurologic involvement then use what syphillis test?

A

FTA-ABS

81
Q

Leprosy organism?

A

Mycobacterium leprae

acid-fast bacilli

82
Q

Leprosy incubation period?

A

5-7 years

83
Q

Types of Leprosy?

A

Polar tuberculoid (TT) - less severe

Borderline tuberculoid (BT)

Mid-borderline tuberculoid (BB)

Borderline lepromatous (BL)

Polar lepromatous (LL) - more severe

84
Q

Leprosy studies?

A

Skin Bx
Serums
Lepromin skin test - not in USA

85
Q

Leprosy skin bx uses what stain?

A

acid fast stain

histopathology

PCR on skin bx

86
Q

Leprosy serums?

A

IgM Ab to PGL-1

87
Q

What Leprosy stain is the acid fast stain and culture?

A

Ziehl-Neelsen Stain (Wade-Fite)

88
Q

Ziehl-Neelsen Stain (Wade-Fite) (skin bx) makes it easier to identify _________________ than the other types.

A

lepromatous leprosy

In other types, the organisms may be more scarce and PCR may be helpful.

Excludes other acid fast bacilli (TB) infection

89
Q

Leprosy - IgM Ab to PGL-1 (serum) is found in 95% of patients with untreated _________________?

A

lepromatous leprosy

90
Q

Leprosy - IgM Ab to PGL-1 (serum) is not as great at detecting ___________________?

A

tuberculoid leprosy

Tuberculoid leprosy only about 60% have abs.

91
Q

What does M. leprae have in its cell wall?

A

phenolic glycolipid

92
Q

what leprosy test uses heat killed M.leprae (mycobacterium)?

A

Lepromin skin test

93
Q

When do you want to read the lepromin skin test for leprosy?

A

read at 48 hours and 21 days

94
Q

Positive response to lepromin skin test = ?

A

tuberculoid lepro

95
Q

Negative response to lepromin skin test = ?

A

possible lematous

*cause there is not enough cell-mediated immune response in the skin - “it may not react”**

Clinical Medicine LAB - Professor Sample (36 decks)

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