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Clinically significant cross-reactions with counterimmunoelectrophoresis between pneumococcus type 6 and Haemophilus
Abstract:
Biologically and clinically significant cross-reactions may occur between the immunochemically similar capsule antigens of Haemophilus influenzae type b and Streptococcus pneumoniae type 6 by using counterimmunoelectrophoresis (CIE). In three cases of culture-proven S. pneumoniae type 6 disease, a false-positive H. influenzae type b CIE result was detected in a body fluid. Two of three cases were also positive when tested by CIE with pneumococcal omnisera. However, in one of the culture-proven cases of pneumococcal type 6 disease, the omniserum was negative and only the burro 132 H. influenzae type b antiserum demonstrated a positive precipitant reaction. In addition to the three case isolates, we evaluated nine blood or cerebrospinal fluid isolates of pneumococcus type 6, using a variety of both species- and type-specific antisera, by CIE. Two burro antisera detected 12 of 12 (100%) of the S. pneumoniae type 6 strains. A rabbit H. influenzae type b antiserum did not detect any (0 of 12; 0%) of the S. pneumoniae type 6 strains evaluated. All (12 of 12; 100%) of the S. pneumoniae type 6 strains were detected with both rabbit omniserum (S. pneumoniae) and rabbit type 6 antiserum. Our data illustrate the importance of being aware of the immunologic cross-reactivity of the H. influenzae type b capsule with the pneumococcus type 6 capsule and the possibility of false-positive results with CIE when patient specimens are interpreted.
Insights
Immunochemical similarities between Haemophilus influenzae type b and Streptococcus pneumoniae type 6 capsule antigens can cause false-positive results in counterimmunoelectrophoresis (CIE) tests, impacting disease diagnosis.
Area of Science:
- Microbiology
- Immunology
- Clinical Diagnostics
Background:
- Cross-reactions between bacterial capsule antigens can complicate laboratory diagnostics.
- Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae type 6 share immunochemically similar capsule antigens.
Observation:
- False-positive CIE results for Hib were observed in three patients with culture-proven Spn6 disease.
- In one case, only an anti-Hib antiserum showed a positive reaction, while pneumococcal antisera were negative.
- Evaluation of 12 Spn6 isolates showed that while specific Spn6 antisera were effective, a Hib antiserum did not detect any Spn6 strains.
Findings:
- Significant cross-reactivity exists between Hib and Spn6 capsule antigens.
- This cross-reactivity can lead to false-positive CIE results when testing patient specimens.
- The study identified specific Hib antisera that can erroneously react with Spn6.
Implications:
- Clinicians and laboratorians must be aware of potential cross-reactions in CIE testing.
- Careful interpretation of CIE results is crucial, especially when results conflict with clinical presentation or other diagnostic data.
- This understanding is vital for accurate diagnosis and appropriate patient management of bacterial meningitis and other invasive diseases.