Flashcards in Infectious Disease #1 Deck (95):
Most lab tests measure a reaction between an _______ and ________.
antigen and ABS
Latex agglutination can either be coated with what?
ABS and antigens
in agglutination inhibition clumping means there is a positive or negative result?
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
In Hemagglutination, instead of latex what is used that have antigens on the surface?
What amplifies low levels of DNA or RNA?
90 (denature), 55 (add synthetic DNA pieces), 70 (DNAp binds & copies)
Used to amplify even a small amount of DNA or RNA to detectable amounts?
Steps in PCR?
1 min , 94 degrees
45 sec , 54 degrees
*forward and reverse primers**
2 min , 72 degrees
Direct Fluorescent Antibody (DFA)?
ABS leveled with fluorescent dye
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
Other Methods of Identification?
Direct Exam/Gram Stain - can direct treatment before a true culture report
Sensitivity is the proportion of patients with the disease who test ________?
positive : TRUE positive
D-dimer is not sensitive
Specificity is the proportion of patients without the disease that test ________?
negative : TRUE negative
ESR is not specific
Sensitivity avoids false _________?
Specificity avoids false _________?
Indications of clostridium testing?
Suspicion of tetanus or botulism
*tetanus - dirty wound make sure they have updated tetanus**
What type of organism is Clostridium? (background?)
Anaerobic, gram +, spore-forming rod
Clostridium testing contraindications?
Do not delay care with suspicion of clostridium infection
Clostridium tetani diagnosis is primarily ________?
Clostridium tetani culture can be obtained from?
wound / umbilical stump
*culture and grow out bacteria but Dx is clinical **
, Botulism, Toxin Identification?
can do a wound culture too
NG secretions ( nasogastric)
Stool (late in the course)
*Not routinely done. Treatment based on clinical suspicion and exposure.**
Leptospirosis screening ?
1. Leptospira IgM (ELISA)
2. Leptospira DNA PCR - more time consuming and expensive
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 ?
Bubonic plague is a gram ________ organism with a _________ appearance?
safety-pin appearance (polar staining)
What is the Bubonic Plague organism?
Where can you obtain cultures for Bubonic Plague?
Lymph node aspirates
Sputum - if pulmonic involvement
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?
*necrosis of extremities **
What is treatment for Bubonic Plague?
Indications for Tularemia testing?
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)
Tularemia test mostly used in ulceroglandular disease ?
Tularemia test that is not useful, difficult to isolate and uses cysteine-glucose-blood agar plate?
Positive Tularemia test if single titer of?
greater to or equal to 1:160
4-fold increase in titer collected 2-3 weeks apart
Many labs refuse to test because of high infectivity
↑ biosafety measures with handling specimens
What is the Lyme Disease organism?
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?
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 ?
What Lyme test uses CSF or Urine?
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
*starts on the wrist and ankles , end organ failure later one these people get very sick very fast**
1. Indirect Immunofluorescence Assay
RMSF Indirect Immunofluorescence Assay incubation period?
7-10 days after onset
RMSF Indirect Immunofluorescence Assay diagnostic titer is greater than or equal to ?
RMSF Indirect Immunofluorescence Assay sensitivity is?
RMSF Indirect Immunofluorescence Assay specificity is ?
With RMSF testing, what is the only test useful in acute presentation ( uses skin bx of rash) - EARLY testing?
RMSF PCR sensitivity?
RMSF PCR specificity?
Spirochete -Treponema pallidum
What are the 4 stages of Syphillis?
Syphillis does not grow on __________ medium?
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**
Dark field microscopy, advantage?
definite immediate diagnosis
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 ______?
Syphillis - Non-Treponemal tests reacts to _____________ in the body similar to those of _.________
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
Syphillis - Treponemal tests detects __ against treponema organism ?
Syphillis - Treponemal tests are usually reactive for ____ and used as ____________ tests?
Syphillis -Treponemal tests?
Sensitivity of all syphillis tests if the sphyillis is secondary is ?
diffuse rash and suspect maybe secondary or tertiary or they have neurologic involvement then use what syphillis test?
Leprosy incubation period?
Types of Leprosy?
Polar tuberculoid (TT) - less severe
Borderline tuberculoid (BT)
Mid-borderline tuberculoid (BB)
Borderline lepromatous (BL)
Polar lepromatous (LL) - more severe
Lepromin skin test - not in USA
Leprosy skin bx uses what stain?
acid fast stain
PCR on skin bx
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.
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 _________________?
Leprosy - IgM Ab to PGL-1 (serum) is not as great at detecting ___________________?
Tuberculoid leprosy only about 60% have abs.
What does M. leprae have in its cell wall?
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 = ?