Infectious Disease #1 Flashcards by Korey koper

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

antigen and ABS

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Latex agglutination can either be coated with what?

ABS and antigens

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

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

RBCs

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What amplifies low levels of DNA or RNA?

PCR

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

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

PCR

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Steps in PCR?

Denaturation
Annealing
Extension

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PCR: Denaturation?

1 min , 94 degrees

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PCR: Annealing?

45 sec , 54 degrees

*forward and reverse primers**

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PCR: Extension?

2 min , 72 degrees

*only dNTPs**

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Direct Fluorescent Antibody (DFA)?

ABS leveled with fluorescent dye

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Indirect Immunofluorescence Assay (IFA)?

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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Other Methods of Identification?

Culture

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

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

positive : TRUE positive

D-dimer is not sensitive

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

negative : TRUE negative

ESR is not specific

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Sensitivity avoids false _________?

negatives

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Specificity avoids false _________?

positives

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Clostridium organisms?

Clostridium botulinum

Clostridium tetani

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Indications of clostridium testing?

Suspicion of tetanus or botulism

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

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What type of organism is Clostridium? (background?)

Anaerobic, gram +, spore-forming rod

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Clostridium testing contraindications?

Do not delay care with suspicion of clostridium infection

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Clostridium tetani diagnosis is primarily ________?

clinical

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Clostridium tetani culture can be obtained from?

wound / umbilical stump

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

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Clostridium botulinum
, Botulism, Toxin Identification?

can do a wound culture too

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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Leptospirosis screening ?

1. Leptospira IgM (ELISA) | 2. Leptospira DNA PCR - more time consuming and expensive

Leptospirosis Conformation?

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 **

Leptospirosis is found mostly in ?

cow urine

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

gram-negative safety-pin appearance (polar staining)

What is the Bubonic Plague organism?

Yersinia Pestis

Where can you obtain cultures for Bubonic Plague?

Lymph node aspirates Blood Sputum - if pulmonic involvement Bronchial/trachial washing Post-mortem cultures from spleen, lung, liver, or bone marrow (DFA or PCR)

Bubonic Plague blood culture?

septicemia, early may be negative

Bubonic Plague sputum culture?

pneumonic involvement but usually blood cultures are positive by that time if pulmonic involvement

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

Serologic testing can be sent to the CDC: 1. One acute sample 2. One convalescent sample (4-6 weeks after disease onset)

When do you begin Abx treatment with Bubonic Plague?

ASAP *necrosis of extremities **

What is treatment for Bubonic Plague?

Streptomycin | Gentamycin

Indications for Tularemia testing?

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 **

Tularemia test used to detect AB to Fransicella tularensis?

Agglutination ( micro- and tube) GS

Tularemia test mostly used in ulceroglandular disease ?

PCR

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

Culture

Positive Tularemia test if single titer of?

greater to or equal to 1:160 OR 4-fold increase in titer collected 2-3 weeks apart

Tularemia considerations?

Many labs refuse to test because of high infectivity ↑ biosafety measures with handling specimens

What is the Lyme Disease organism?

Borellia burgdorferi

How is Borellia burgdorferi | , the organism that causes Lyme, transmitted?

Borellia burgdorferi is transmitted by Ixodes (deer tick)

What test is useful EARLY in Lyme disease?

Skin Culture of the risk ( Erythema migrans) Bx of EM *early on and they have a rash = most reliable**

What Lyme test determines levels of IgG & IgM?

1. ELISA ( GS)

In Lyme disease when does IgG peak?

4-6 months

In Lyme disease when does IgM peak?

3-6 weeks after onset of sxs

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

Western Blot

What Lyme test uses CSF or Urine?

PCR

Negative interpretation of Lyme Ab?

< 0.9 = negative

Equivocal interpretation of Lyme Ab?

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

Positive interpretation of Lyme Ab?

>1.10 = positive

Positive IgG Ab western blot?

>5 different IgG Ab = positive

Positive IgM Ab western blot?

>2 different IgM Ab = positive

Interpretation of PCR?

negative is normal

Interfering factors causing FALSE positives in Lyme disease Testing?

Previous infxn with Lyme Other spirochetal infections

RMSF organism?

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

RMSF testing?

1. Indirect Immunofluorescence Assay | 2. PCR

RMSF Indirect Immunofluorescence Assay incubation period?

7-10 days after onset

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

1:64

RMSF Indirect Immunofluorescence Assay sensitivity is?

94-100%

RMSF Indirect Immunofluorescence Assay specificity is ?

100%

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

PCR

RMSF PCR sensitivity?

70%

RMSF PCR specificity?

100%

Syphillis organism?

Spirochete -Treponema pallidum

What are the 4 stages of Syphillis?

Acute Secondary Latent Tertiary

Syphillis does not grow on __________ medium?

artificial

Syphillis -  Dark field microscopy, what to look for?

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**

Syphillis -  Dark field microscopy, advantage?

definite immediate diagnosis rapid results

Syphillis -  Dark field microscopy, disadvantages?

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 **

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

reagin

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

phospholipids similar to those of T.pallidum

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

screening and are nonspecific

Syphillis - Non-Treponemal tests?

VDRL - vanerial disease research lab RPR - rapid plasma reagent test RPR first

Syphillis - Treponemal tests detects __ against treponema organism ?

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

life confirmatory tests

Syphillis -Treponemal tests?

FTA-ABS MHA-TP

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

100

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

FTA-ABS

Leprosy organism?

Mycobacterium leprae acid-fast bacilli

Leprosy incubation period?

5-7 years

Types of Leprosy?

Polar tuberculoid (TT) - less severe Borderline tuberculoid (BT) Mid-borderline tuberculoid (BB) Borderline lepromatous (BL) Polar lepromatous (LL) - more severe

Leprosy studies?

Skin Bx Serums Lepromin skin test - not in USA

Leprosy skin bx uses what stain?

acid fast stain histopathology PCR on skin bx

Leprosy serums?

IgM Ab to PGL-1

What Leprosy stain is the acid fast stain and culture?

Ziehl-Neelsen Stain (Wade-Fite)

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

lepromatous leprosy In other types, the organisms may be more scarce and PCR may be helpful. Excludes other acid fast bacilli (TB) infection

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

lepromatous leprosy

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

tuberculoid leprosy Tuberculoid leprosy only about 60% have abs.

What does M. leprae have in its cell wall?

phenolic glycolipid

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

Lepromin skin test

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

read at 48 hours and 21 days

Positive response to lepromin skin test = ?

tuberculoid lepro

Negative response to lepromin skin test = ?

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