serology exam 2

What is the primary and secondary line of body defense against microbial pathogens?

Primary (natural innate)= non specific, no memory, skin, mucous membranes, NK, phagocytosis

secondary(acquired)= specific, memory, t cell, b cell

What infection is caused by Mycoplasma pneumoniae, why is it called that?

Atypical (not treated with penicillin) and walking (individuals don't stay home) pneumonia

What do mycoplasma colonies resemble?

Fried eggs, lack cell wall and wont stain w/ gram

How is primary atypical pneumonia usually diagnosed here in the USA?

Check for antibodies to M. pneumoniae IgM are for recent infections, IgG for possible reinfections, or by molecular panel

What are cold agglutinins?

autoantibodies against I antigens found in surface of RBC, they are present in some M. pneumoniae infections

What is the main reason testing for cold agglutinins is no longer recommended to diagnose infection with M.pneumoniae?

it is not specific enough for only infections with M. pneumoniae

What are rickettisae (be specific)?

Intracellular gram negative bacteria that are pleomorphic, are transmitted by ticks, mites, lice, or fleas 

What is the most common rickettsial infection in the U.S. that causes serious illness or fatal if left untreated?

Rocky mountain spotted fever 

What organism causes Rocky Mountain spotted fever (RMSF) and how is it transmitted?

Bite of american dog tick, caused by R. rickettsia

The pathogenesis of Rocky Mountain spotted fever involves:

tick to dog then human but can also be directly tick to human

How are rickettsial infections usually diagnosed?

Weil-felix test= antigens (ox-19,2,k) used to detect rickettsial antibody (not used) also can use indirect fluorescent antibody (IFA) or enzyme immunoassay (EIA)

Where is rickettsia most commonly reported (geographical location in the USA)?

east (central USA to the east coast)

Vector for RMSF

american dog tick (Dermacentor variabilis)

epidemic typhus

• Rickettsia prowazekii 

• Lice 

• Vector defecates while biting and rickettsia enters the body 

• Increased in natural disasters 

• Wash clothes in hot water or get rid of them

endemic typhus

• Rickettsia typhi 

• Flea (carried by rats, opossums, cats, dogs) 

• Vector defecates while biting and rickettsia enters the body

What is the Weil-Felix reaction, is it commonly used in the USA?

Proteus OX-19, OX-2, OX-K used as antigens to detect rickettsial antibody, not commonly used 

Which of the following are bacterial: spirochetes, mycoplasmas, rickettsiae?

all three are bacterial

Which of the following do not grow on ordinary lab media: spirochetes, mycoplasma, rickettsiae

rickettsia and spirochetes do not grow on ordinary lab media but mycoplasma can be grown on enriched media

A child complaining of fever and sore throat is examined in a physician’s office. A rapid group A serological streptococcal antigen test is performed in the office and the result negative. Control results were acceptable. What should be done and why?

A culture on sheep blood agar (beta hemolysis), the rapid assay might not be sensitive enough

What is the advantage of performing a serological test vs bacterial culture for the detection of Strep A infection, what about molecular testing?

The serological test will be significantly faster than a culture, molecular would be the most sensitive but also the more expensive option

What is the most common cause of bacterial pharyngitis?

strep A

Which organism causes scarlet fever, flesh eating bacteria, erysipelas, and impetigo?

strep A (pyogenes)

What is the sequelae to untreated Strep A infection? know mechanism.

Acute rheumatic fever, poststreptococcal glomerulonephritis- these are immunologically mediated and do not involve actively growing bacteria

Strep A is also called

strep pyogenes

Discuss antibodies such as anti-streptolysin O test (ASO), anti-DNAsae B, anti-streptokinase, anti-hyaluronidase, and why they may be useful to demonstrate prior streptococcal infection in patients. 

serological testing is needed because streptococcal bacteria are unlikely to be seen when signs and symptoms of sequelae appear, used to diagnose rheumatic fever

What is virulence and how may virulence by transferred among bacteria (like for antibiotic resistance)

is the extent of pathology caused by an organism when it infects a host. degree of damage is mediated by specific virulence factors

beta hemolysis

complete cell lysis

gamma hemolysis

no effect

alpha hemolysis

partial cell lysis

What is the hemolytic pattern seen in sheeps blood agar for Strep A

complete cell lysis (beta)

Which organism is thought to be the causative agent of some cases of gastric ulcers?

H. pylori

What is H. pylori? (be specific)

gram neg microaerophilic spiral bacteria

How is H.pylori believed to be transmitted

by fecal oral route

How is H. pylori diagnosed?

CLO test (rapid urease in stomach biopsy), urease breath test, best is ELISA

What is the most commonly reported tick-borne infection in the U.S?

lyme disease

How is Lyme disease transmitted?

Ixodes- black legged ticks, tick bites in the environment, tick has to be attached to feed for >24 hours

What are the symptoms of Lyme disease?

Localized rash in bullseye, early dissemination ( flu like, bell’s palsy, swollen knees, irregular heartbeat), late dissemination (rheumatological, neurological, cardiovascular) 

How is Lyme disease most commonly diagnosed?

difficult to diagnose, lab test to detect AB

Is Lyme disease easily curable and diagnosed?

no its both hard to diagnose and treat

Name some bacterial infections transmitted by arthropods

lyme, RMSF

Which organism causes syphilis?

treponema pallidum

primary syphilis stage

ulcers on genitalia, goes away spontaneously, organisms multiply and disseminate via blood or lymph systems

secondary syphilis stage

lymphadenopathy, malaise, fever, pharyngitis, RASH, most contagious

latent syphilis stage

asymptomatic usually begins after 2 year after untreated infection

tertiary syphilis stage

gummas (granulomas) cardiovascular enlargement, neurosyphilis, deformities

How are Treponema pallidum subspecies pallidum infections diagnosed?

through direct or serological tests

direct detection of syphilis

• Treponemes in active lesions 

• Dark field microscopy 

• Fluorescent antibody staining 

• ONLY FOR ACTIVE LESIONS 

non treponemal test VDRL

(detect IgG or IgM against cardiolipin (reagin) 

• VDRL = microscopic flocculation w/ microscope 

  • Antigen – cardiolipin w lecithin + cholesterol 

  • Antibody – reagin 

  • Needs heat 

  • Needs pos confirmation (NR, WR, or R) 

  • CSF or serum 

HAS FALSE POS TO MALARIA

non treponemal test RPR

• RPR= macroscopic floccution 

  • Antigen – cardiolipin + cholesterol 

  • Antigen – reagin 

  • Can be qualitative or semiquantitative  

  • Serum 

HAS FALSE POS TO MALARIA

treponemal

detect antibody to T pallidum 

• Fluorescent treponemal absorption (FTA-ABS) indirect 

• T pallidum particle agglutination (TP-PA) - pos will be clump in well in a smooth mat, neg will be button clump 

• ELISA 

• CLIA 

• MFI 

What is flocculation?

small particles that clump together

In syphilis testing, what are biological false positives?

malaria, autoimmune diseases (lupus)

What antigen is used in the RPR and VDRL?

cardiolipin

How are RPR and VDRL same/different?

RPR is macro, VDRL is micro 

When must the needle used in RPR be checked?

daily every shift

How is the delivery needle used in the RPR be checked, why do we check it?

you check that the amount is correctly dispensing 30 drops and that should be equal to 0.5 mL

How can the room temperature affect the RPR

it can falsely influence the sensitivity of the reaction

what is the speed of rotation for the RPR

100

How do the titers of nontreponemal tests for syphilis vary during the course of the infection

a decline is seen with patient treatment

Which serological test for syphilis is used to diagnose neurosyphilis

VDRL or ELISA

What is the absorbent in the FTA-ABS?

nonpathogenic treponemes

In the FTA, what is fixed to the slide?

T. pallidum

What is the most sensitive test for the diagnosis of syphilis?

FTA-ABS

Which test is best at monitoring the effectiveness of syphilis treatment?

RPR

Interpret the following results: RPR - Reactive| FTA-ABS – nonreactive

biological false positive

May assays such as Chemiluminescent and Enzyme-linked immunosorbent assays be used for Syphilis testing?

yes

What is seroresistance 

failure of a patients serum to revert to nonreactive in non treponemal test following treatment for syphilis

Which organisms may be best visualized by darkfield microscopy

live organisms, best to visualize motile organisms from primary and secondary lesions

antibody response to Syphilis

Which of the following tests is used to confirm a syphilis infection after another method is positive?

TP-PA

Why are some parasitic infections chronic in nature? 

because parasites evade and suppress the hosts immune system while allow them to multiple over time

Examples of how parasites evade the immune system: 

• antigenic concealment - parasite antigens remain inside host cells

• antigenic variation - parasites vary their surface antigens

• antigenic shedding - parasites shed surface antigens which bind to the hosts antibodies and cells

• antigenic mimicry - parasites express epitopes that are similar or identical to to the hosts molecules

Name a flagellate that looks like an old man with glasses

giardia

Name the most common intestinal protozoan infection in the U.S. 

giardia

Name a flagellate that can be diagnosed from duodenal aspirates or the enterotest capsule 

giardi

Which parasite can be found in the blood? 

malaria - plasmodium

If I want to look for a parasite in a blood sample, what tube should I collect? 

EDTA

Name a parasite that lives inside erythrocytes 

malaria - plasmodium

How do we avoid blood transfusion transmitted malaria? 

patient history and screening

Which sporozoan causes malaria 

plasmodium

Which parasite has killed more people worldwide than any other? 

plasmodium - malaria

Name a parasite that requires the Anopheles mosquito for its sexual cycle

plasmodium (malaria)

Which species of plasmodium has sausage-shaped or crescent-shaped gametocytes?   

P. falciparum

Which species of plasmodium commonly has multiple ring forms within one RBC?

P. falciparum

Which species of plasmodium is most malignant?  

P. falciparum

With which species of plasmodium does one see rings and gametocytes only?  

P. falciparum

When is the best time to draw blood for malaria smears? 

shortly after shaking chills and fever (paroxysm) . blood should be taken at 6-8 hr intervals so different stages of the parasite can be studied to identify species

How is a thick malaria smear prepared? 

three drops of blood are placed on slide, allowed to dry, and placed in giemsa stain without fixation

Are blood donors typically screened for Malaria?

yes

Name a protozoan that can be found in municipal water supplies causes a profuse watery diarrhea, is a serious risk to immunocompromised patients, and appears as red spherical structures approximately 6 microns in diameter on a modified acid-fast stain. 

cryptosporidium

Which protozoan can be spread by infective oocyst in cat feces?  

Toxoplasma gondii

Which protozoan can cause neurologic problems if contacted by the fetus after the first trimester?

Toxoplasma gondii

Which protozoan is the major cause of encephalitis in AIDS patients?

toxoplasmosis

How is toxoplasmosis usually diagnosed? 

TORCH panel, tissue sample to check for live organism, avidity

What are low avidity vs high avidity anti-Toxoplasma antibodies?

• Low avidity= low avidity IgG mean infection within last 8 months (more recent)   

• high avidity= high IgG mean infection occurred 5 or more months before testing (past infection)

What is TORCH testing?

the serological test for toxoplasmosis, other infections, rubella, cytomegalovirus, herpes

Which antibody type may increase in parasitic infections?

IgE

Which WBC type may increase in parasitic infections and allergic reactions?

eosinophil

What is mycosis?

fungal infections

What is a yeast, how do they reproduce?

unicellular form that reproduces by budding