Glossary of 5. Bacterial serology
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- What's the other name for Group strep A?
- Strep pyogenes
- What are the cellular antgens on Strep A?
- -M protein
- What extracellular products does Strep A produce?
- -Streptolysin O
- What are suppurative strep infections?
- ones producing pus;
ones not producing pus
- What are the suppurative strep infections?
- -pharyngitis/tonsilitis/strep throat
- what are the nonsuppurative strep infections?
- -Rheumatic fever
- why are some infections better tested serologically?
- if the infectious organism is not obtainable on a specimen.
- which infections may be better tested with serologic methods?
- cellulitis/skin infections
finish this one
- what are 4 serological tests for strep A?
- 1. Antistreptolysin O (ASO)
2. ASO Latex agglutntion-rapid
3. Anti-DNAse B (ADN-B)
4. Anti-Hyaluronidase (AHT)
- What type of specimen is best for any of them?
- Paired sera, 3 weeks apart
- what if no paired sera is available?
- Compare the convalescent specimen to a reference range.
- How does the ASO classic test work?
- 1. Serum + Streptolysin O added, incubate 15 min at 37'C.
2. Add 5% RBC suspension, incubate 30 min at 37'C.
3. Centrifuge, look for hemolysis
- In the classic ASO, what is:
- Pos = no hemolysis
Neg = hemolysis; no ASO was present to neutralize the antigen added, so it bound to RBCs and caused lysis.
- What type of RBCs are used in the ASO test?
- -Human group Oneg
- How is the titer reported in the ASO test?
- The reciprocal of the highest dilution showing NO HEMOLYSIS.
- What is the ref range for ASO?
- <166 Todd units
- What controls are run with the ASO?
- 1. RBC control - only cells, to make sure not auto-hemolysis.
2. ASO control - Buffer, reagent, and RBCs to make sure hemolysis CAN occur.
3. Standard - to see what 166 Todd units looks like.
- What are 3 sources of error in the classic ASO test?
- 1. Oxidation of reagent from shaking/aerating vial
2. Reconstituted reagent older than 10 minutes.
3. Lipoprotein, cholesterol, bacterial contamination.
- How does the rapid ASO test work?
- 1. Latex beads coated with antigen (streptolysin O).
2. Add serum; look for agglutination.
- What should occur if the rapid ASO is positive?
- The lab tech should do a quantitative test.
- What is the ref range for the rapid aso test?
- <200 U/ml
- What are 4 sources of error in the rapid ASO?
- 1. Bacterial contamination
2. Reaction read beyond 3 min
3. Lipemic serum - nonspecific
4. Subjective readings
- Along with the classic/rapid ASO tests, what is used for Strep A?
- ADN-B test
- What type of test is the ADN-B test?
- Neutralization test
- What is the ADN-B principle?
- -Serum and Strep DNAse B are incubated 20 min at body temp.
-Inc w/ DNA-methyl grn overnite
Clear = neg; DNAse worked
Green = pos; the strep's DNAse beat the added to substrate.
- How do you report the titer of the ADN-B test?
- Reciprocal of highest dilution showing 3+ green.
- What is the ADN-B ref range for
- Preschool: <120
- What mainly causes error in the ADN-B test?
- dnase from organisms other than StrepA
- What is one other test that can be used but is uncommon?
- AHT - anti-hyaluronidase test
- What is the advantage of the ASO test?
- -ASO titer rises within 7 days of disease onset.
- What are disadvantages of the ASO test?
- -Many people have low titers already, b/c of freq. exposure.
-Strep skin infections may produce low titers, undetected
-False + from rising titer in rheumatic fever.
-Only half of glomeruloneph. patients show high titer.
- What is the advantage of the ADN-B test?
What is its limitation?
- -Most reliable test for Strep A
Titer rises later than ASO.
- What disease is Mycoplasma pneumoniae responsible for?
- walking pneumonia
- How is M. pneumoniae tested for?
- -Culture but it takes up to a month to grow!
- What 3 serological methods are used for mycoplasma?
- 1. Complement fixation
3. Cold agglutinins
- What is the principle of the cold agglutinins test?
- M. pneumoniae agglutinates human group O RBCs in the cold.
- What are limitations of the cold agglutinins test?
- -The agglutinins are only in 50% of cases.
-Other viral resp diseases can also stimulate cold agglutinins.
- what diseases are assoc. with Helicobacter pylori?
- What 4 specimen types are tested for H. pylori? How?
- 1. Mucosa - Endoscopic biopsy
2. Serum - Serology
3. Stool - EIA for Ag in
4. Breath - Urea tests
- What is the CLO test?
- a urease test done on endoscopic biopsies for h. pylori.
- What do serological H. pylori tests look for?
- Antibody in serum to the bug.
- What are adantages and disadvntg of serological methods for h. pylori?
- Advntg: less invasive than endoscopic biopsy
Disadvntg: less specific and sensitive.
- which test for h pylori is best? why?
- Urea breath tests - have the highest combined sens./specificty.
- What is febrile agglutinins testing used for?
- Identifying hard-to-grow microorganisms that often cause fever of unknown origin.
- What 4 bacterial diseases are included in a febrile agglutinin panel?
- 1. Salmonella somatic/flagellar antigens (typhi/paratyphi)
2. Brucella abortus
3. Francisella tularensis
- What is the Weil-felix test?
- A presumptive test for Rickettsial antibodies
- What is the principle of the Weil-felix test?
- Rickettsia antibodies cause positive reaction
- what is the major limitation of the weil-felix test?
- -Antibody detected is heterophilic and nonspecific.
-If Proteus is causing the infection, will get a false pos.
- what is the lab's role in diagnosing lymes disease?
- -Culture impractical - time
-Serology is most used method.
- What are the problems with serological methods for lymes?
- -Tests/reagents not standardizd.
-Tests have low sensitivity
- Which seroloical methods are used for screening lymes?
- IFA - lo volume
Elisa - hi volume
- What confirms lymes diagnosis?
- -Four fold paired sera titer
- what type of fluid can PCR be used on for lymes? What is the problem with this test type?
- -Synovial fluid
-Can detect both viable and nonviable lymes.
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