IMMUNOLOGY PRACTICE TEST #5
QUESTIONS WITH COMPLETE
SOLUTIONS
Lyme disease confirmation - Answer-Positive or equivocal results with screening
tests are supplemented with Western blot. Nucleic acid probe and PCR have not be
standardized for routine diagnosis
Current Lyme disease interpretation - Answer-IgM antibody positive, IgG antibody
positive and positive Western blot
Late or previous Lyme disease interpretation - Answer-Negative IgM antibody, IgG
antibody positive, and Western blot positive
Negative Lyme disease or low level interpretation - Answer-Negative IgM, IgG, and
Western blot
Lyme Disease treatment - Answer-Antibiotic treatment includes Penicillin,
tetracycline, macrolides for adults, and Amoxicillibn and Cefuroxime axetil for
children
Streptococcus pyogenes (Group A) - Answer-Gram-positive cocci that causes acute
infections like strep throat and skin infections as well as non suppurative sequalae
like acute rheumatic fever and post-streptococcal glomerulonephritis
Suppurative diseases associated with Strep - Answer-Pharyngitis, skin infections,
Scarlet fever, erysipelas, impetigo
Diagnosis of Strep species - Answer-Culture and antigen testing
Nonsuppurative complications - Answer-Inflammation not at site of infection, throat
or skin infections, acute rheumatic fever and post streptococcal glomerulonephritis,
diagnosed by serology because there is no bacterial for culture
Pathogenic mechanism of Strep pyo - Answer-Exact is unknown, theory is infection
induces the formation of host antibodies against the cell wall, capsule, and cell
membrane. These antibodies cross-react with various host components that are
antigenically similar in heart, joint, muscle tissues, etc.
Exoantigen - Answer-Excreted by bacterial cells as it metabolizes and contributes to
virulence and includes Streptolysin, Deoxyribonuclease, Hyaluronidase,
Nicotinamide adenine dinucleotidase, and Streptokinase.
Streptolysins - Answer-Hemolysin produced by Streptococcus that destroys RBCs
and WBCs
,Streptolysin O - Answer-Oxygen labile, measured in chemistry to determine prior
infection of group A Strep in non-suppurative infections
Streptolysin S - Answer-Oxygen stable
Acute rheumatic fever - Answer-Systemic complication following untreated strep A
infections, clinical manifestations include joint pain,
endocarditis/pericarditis/myocarditis with murmurs and chorea, and occurs in 2-3%
of positive patients
Poststreptococcal glomerular nephritis - Answer-Kidney infection that occurs about
10 days after skin or pharyngeal infection, clinical manifestations include diffuse
glomerular lesions, hypertension, hematuria, and proteinuria
ASO test principle - Answer-Reagent SLO lyses RBC, if SLO antibody is present,
reagent SLO is neutralized and does not lyse RBC
ASO procedure - Answer-1. Prepare a serial dilution of patient serum
2. Add standard amount of reagent SLO
3. Incubate to allow interaction of reagent SLO and pt anti-SLO
4. Add RBCs, incubate, and centrifuge
5. Report highest dilution with no hemolysis (endpoint)
ASO latex aggultination - Answer-SLO is attached to latex beads and mixed with
serial diluted serum and examined for agglutination, clumping indicates ASO level of
>200 units/mL
ASO nephelometry - Answer-Measures the rate of increase in light scatter from
antibody-antigen interaction, replaces traditional ASO testing, requires less technical
expertise, automated thus less expensive
Brucella species - Answer-Slow growing intracellular gram negative bacillus, 4
species: abortus, suis, melitensis, and canis, cultures are often negative and take
weeks to grow, and antibodies with appear within 2-3 weeks of infection
Brucellosis - Answer-zoonotic disease caused by Brucella, vaccination program for
animals, usually seen in farmers, veterinarians, and slaughterhouse workers with a
gradual onset with nonspecific symptoms
Brucella laboratory detection - Answer-1. Serial dilutions of patient sample and
antigen (killed bacteria with blue dye tag) are mixed for 1 minutes and examined for
agglutination, used as initial screen test
2.Tube test is utilized to confirm positive slide test, patient sample and antigen are
combined, incubated at 37 degrees for 24-48 hours, tube is then examined for
agglutination
Brucella serology testing - Answer-Detects antibodies to B. abortus, suis, and
melitensis, significant titers are >/= 1:160 or a 4-fold increase in titers, ELISA and
IFA can also be done to detect both IgG and IgM
, Francisella tularensis - Answer-Intracellular gram negative bacillus that causes
tulerimia (rabbit fever) and humans become infected by contact with infected
animals, insect bites, or aerosols created when testing the sample in the lab
Tularemia diseases - Answer-1. Ulceroglandular disease - most common form seen
in US. Lesions at infection site become ulcer and be accompanied by fever and
lympadenopathy
2. Occuloglandular - eye involvement
3. Systemic and pulmonary forms
Tularemia diagnosis - Answer-Organism can be culture but is considered a lab
hazard because of aerosol infections (BSL 3/4) so serology is considered best
practice. Antibodies present within 2 weeks of illness with an initial slide agglutination
test being performed with a tube confirmation
Brucella false positive/negative results - Answer-May be caused by cross-reactivity
to F. tularensis and other organisms with higher titers seen with homologos antigens
Tularemia interpretation - Answer-Titers equal to or higher than 1:160 are considered
significant, as well as a 4-fold increase.
Nontreponemal false positive results - Answer-May be caused by infectious diseases
such as TB, HIV, measles, and Mono, or non-infectious states caused by drug
addiction, autoimmune diseases such as SLE, lymphoma, and pregnancy
VDRL - Answer-Venereal Disease Research Laboratory, uses serum or CSF as
specimen, qualitative and semi-quantitative slide test, reagent is cardiolipin, lecithin,
and cholesterol prepared daily.
Darkfield microscopy false negative results - Answer-may be cause by a delay in
examining the slide, poor specimen collection, antibiotic treatment or the organism
may be removed during the rinse stage
Darkfield microscopy false positive results - Answer-May be caused by
contamination of normal spirochete flora which can cause a cross-reactivity
VDRL procedure - Answer-1. Heat serum or CSF at 56 degrees for 30 minutes in
inactivate complement
2. Place specimen in well in special slide
3. Add antigen with special syringe and needle
4. Rotate slide for 4 minutes and read with 10x objective
VDRL qualitative interpretation - Answer-Nonreactive = no clumping
Weakly reactive = small clumping
Reactive = medium to large clumps
VDRL CSF interpretation - Answer-Reactive is diagnostic for neurosyphilis
VDRL semi-quantitative results - Answer-Serial dilute serum and report highest
dilution with reactive results. Used to follow response to therapy.
QUESTIONS WITH COMPLETE
SOLUTIONS
Lyme disease confirmation - Answer-Positive or equivocal results with screening
tests are supplemented with Western blot. Nucleic acid probe and PCR have not be
standardized for routine diagnosis
Current Lyme disease interpretation - Answer-IgM antibody positive, IgG antibody
positive and positive Western blot
Late or previous Lyme disease interpretation - Answer-Negative IgM antibody, IgG
antibody positive, and Western blot positive
Negative Lyme disease or low level interpretation - Answer-Negative IgM, IgG, and
Western blot
Lyme Disease treatment - Answer-Antibiotic treatment includes Penicillin,
tetracycline, macrolides for adults, and Amoxicillibn and Cefuroxime axetil for
children
Streptococcus pyogenes (Group A) - Answer-Gram-positive cocci that causes acute
infections like strep throat and skin infections as well as non suppurative sequalae
like acute rheumatic fever and post-streptococcal glomerulonephritis
Suppurative diseases associated with Strep - Answer-Pharyngitis, skin infections,
Scarlet fever, erysipelas, impetigo
Diagnosis of Strep species - Answer-Culture and antigen testing
Nonsuppurative complications - Answer-Inflammation not at site of infection, throat
or skin infections, acute rheumatic fever and post streptococcal glomerulonephritis,
diagnosed by serology because there is no bacterial for culture
Pathogenic mechanism of Strep pyo - Answer-Exact is unknown, theory is infection
induces the formation of host antibodies against the cell wall, capsule, and cell
membrane. These antibodies cross-react with various host components that are
antigenically similar in heart, joint, muscle tissues, etc.
Exoantigen - Answer-Excreted by bacterial cells as it metabolizes and contributes to
virulence and includes Streptolysin, Deoxyribonuclease, Hyaluronidase,
Nicotinamide adenine dinucleotidase, and Streptokinase.
Streptolysins - Answer-Hemolysin produced by Streptococcus that destroys RBCs
and WBCs
,Streptolysin O - Answer-Oxygen labile, measured in chemistry to determine prior
infection of group A Strep in non-suppurative infections
Streptolysin S - Answer-Oxygen stable
Acute rheumatic fever - Answer-Systemic complication following untreated strep A
infections, clinical manifestations include joint pain,
endocarditis/pericarditis/myocarditis with murmurs and chorea, and occurs in 2-3%
of positive patients
Poststreptococcal glomerular nephritis - Answer-Kidney infection that occurs about
10 days after skin or pharyngeal infection, clinical manifestations include diffuse
glomerular lesions, hypertension, hematuria, and proteinuria
ASO test principle - Answer-Reagent SLO lyses RBC, if SLO antibody is present,
reagent SLO is neutralized and does not lyse RBC
ASO procedure - Answer-1. Prepare a serial dilution of patient serum
2. Add standard amount of reagent SLO
3. Incubate to allow interaction of reagent SLO and pt anti-SLO
4. Add RBCs, incubate, and centrifuge
5. Report highest dilution with no hemolysis (endpoint)
ASO latex aggultination - Answer-SLO is attached to latex beads and mixed with
serial diluted serum and examined for agglutination, clumping indicates ASO level of
>200 units/mL
ASO nephelometry - Answer-Measures the rate of increase in light scatter from
antibody-antigen interaction, replaces traditional ASO testing, requires less technical
expertise, automated thus less expensive
Brucella species - Answer-Slow growing intracellular gram negative bacillus, 4
species: abortus, suis, melitensis, and canis, cultures are often negative and take
weeks to grow, and antibodies with appear within 2-3 weeks of infection
Brucellosis - Answer-zoonotic disease caused by Brucella, vaccination program for
animals, usually seen in farmers, veterinarians, and slaughterhouse workers with a
gradual onset with nonspecific symptoms
Brucella laboratory detection - Answer-1. Serial dilutions of patient sample and
antigen (killed bacteria with blue dye tag) are mixed for 1 minutes and examined for
agglutination, used as initial screen test
2.Tube test is utilized to confirm positive slide test, patient sample and antigen are
combined, incubated at 37 degrees for 24-48 hours, tube is then examined for
agglutination
Brucella serology testing - Answer-Detects antibodies to B. abortus, suis, and
melitensis, significant titers are >/= 1:160 or a 4-fold increase in titers, ELISA and
IFA can also be done to detect both IgG and IgM
, Francisella tularensis - Answer-Intracellular gram negative bacillus that causes
tulerimia (rabbit fever) and humans become infected by contact with infected
animals, insect bites, or aerosols created when testing the sample in the lab
Tularemia diseases - Answer-1. Ulceroglandular disease - most common form seen
in US. Lesions at infection site become ulcer and be accompanied by fever and
lympadenopathy
2. Occuloglandular - eye involvement
3. Systemic and pulmonary forms
Tularemia diagnosis - Answer-Organism can be culture but is considered a lab
hazard because of aerosol infections (BSL 3/4) so serology is considered best
practice. Antibodies present within 2 weeks of illness with an initial slide agglutination
test being performed with a tube confirmation
Brucella false positive/negative results - Answer-May be caused by cross-reactivity
to F. tularensis and other organisms with higher titers seen with homologos antigens
Tularemia interpretation - Answer-Titers equal to or higher than 1:160 are considered
significant, as well as a 4-fold increase.
Nontreponemal false positive results - Answer-May be caused by infectious diseases
such as TB, HIV, measles, and Mono, or non-infectious states caused by drug
addiction, autoimmune diseases such as SLE, lymphoma, and pregnancy
VDRL - Answer-Venereal Disease Research Laboratory, uses serum or CSF as
specimen, qualitative and semi-quantitative slide test, reagent is cardiolipin, lecithin,
and cholesterol prepared daily.
Darkfield microscopy false negative results - Answer-may be cause by a delay in
examining the slide, poor specimen collection, antibiotic treatment or the organism
may be removed during the rinse stage
Darkfield microscopy false positive results - Answer-May be caused by
contamination of normal spirochete flora which can cause a cross-reactivity
VDRL procedure - Answer-1. Heat serum or CSF at 56 degrees for 30 minutes in
inactivate complement
2. Place specimen in well in special slide
3. Add antigen with special syringe and needle
4. Rotate slide for 4 minutes and read with 10x objective
VDRL qualitative interpretation - Answer-Nonreactive = no clumping
Weakly reactive = small clumping
Reactive = medium to large clumps
VDRL CSF interpretation - Answer-Reactive is diagnostic for neurosyphilis
VDRL semi-quantitative results - Answer-Serial dilute serum and report highest
dilution with reactive results. Used to follow response to therapy.
