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Serological Diagnosis of Bacterial Infection

Experiment six. Serological Diagnosis of Bacterial Infection. Serological Identification of Salmonella. Select the specimen. React with A-Z polyvalent antiserum. Agglutination reaction. ( ＋ ) ( － ).

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Serological Diagnosis of Bacterial Infection

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  1. Experiment six Serological Diagnosis of Bacterial Infection

  2. Serological Identification of Salmonella Select the specimen React with A-Z polyvalent antiserum Agglutination reaction (＋) (－) React with several individual types of anti-O and anti-H antiserum React with anti-Vi antiserum Identify its group and phage

  3. Serological diagnosis • Classification: agglutination precipitation • Samples: ASO test ------ Streptococcus Widal’s test ------ S. typhi and paratyphi Weil-Felix Test ------ Richettsia

  4. Widal’s test

  5. Introduction • It is a serological approach for the diagnosis of typhoid and paratyphoid fever in clinical laboratory. • This is a test for the measurement of H and O agglutinins of typhoid and paratyphoid bacilli in patient’s sera. • To assist to diagnosis typhoid fever or other salmonella infection.

  6. Materials • Antigens: • Suspension of S. typhi "O" antigen, O • Suspension of S. typhi "H" antigen; H • Suspension of S. paratyphi A "H" antigen, PA • Suspension of S. schottmuelleri "H" antigen, PB • Antibody: serum of suspected patient • Normal saline • Test tubes and pipettes

  7. PROCEDURE

  8. Saline 0.5 0. 5 0.5 0. 5 0. 5 0. 5 0. 5 Patient serum 0.5 0.5 0.5 0.5 0.5 0. 5 discard Serum dilution 1:20 1:40 1:80 1:160 1:320 1:640 - Bacteria suspension 0. 5 0. 5 0. 5 0. 5 0. 5 0. 5 0. 5 PROCEDURE • Make the mark • Add reagents as the following: Reagent (ml) 1 2 3 4 5 6 7 Final serum 1:40 1:80 1:160 1:320 1:640 1:1280 - dilution Bacteria suspension: O H PA PB • Shaking several times, put it in 370C water bath for 16-18 hours.Then let it stand at room temperature over night.

  9. Observation: 1. Control tube: no agglutination (-) 2. Lowest titer tube: absolutely agglutination (++++) 3. Other tubes: three quarters agglutination(+++) half agglutination (++) one quarter agglutination (+) no agglutination (-) Judgment: Agglutination titer: the highest dilution of serum which appears (++) bacteria agglutination.

  10. Interpretation of results

  11. Interpretation of results • Dynamic observation • – A gradual rise of antibody titers • – Titer of convalescence serum ≥4 times of that of early specimen • False negative • – Preantibiotic • – Immunosuppressed

  12. Conclusion 1 2 3 4 5 6 7 O ++++ ++ ++ + - - - H ++++ +++ ++ ++ - - - PA ++ + - - - - - PB - - - - - - - 1:40 1:80 1:160 1:320 1:640 1:1280 Negative control

  13. Precautions • Make the mark • Make sure the procedure • carefully use the pipettes • Correctly Judge the results

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