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Diagnosis of Neisseria infections by defined immunofluorescence. Methodologic aspects and applications
Abstract:
Defined IF techniques have been used in our laboratories for the past 15 years for diagnosing meningococcal and gonococcal infections. Conjugates against these bacteria give desired specific staining (DSS) but also undersired specific staining (USS) due to cross-reacting antigens. USS is controlled by absorption. Nonspecific staining (NSS) of protein A-containing S. aureus caused by the reaction with the Fc part of the IgG molecule is blocked by adding RB 200-labeled antiS. aureus globulins to diluted FITC conjugates against gonococci or menigococci. Nss is also avoided by using FITC-labeled F(ab')2 fragments of IgG. By optimal labeling and separation of unlabeled FITC and heavily labeled molecules on Sephadex G-25 at low ionic strength and low pH, nonspecific reactions with tissues are reduced to a minimum. Defined IF can be utilized for diagnosing pathogenic Neisseria by examination of smears prepared from clinical specimens, as confirmative tests of oxidase-positive colonies, and for demonstrating these bacteria in tissue efflorescences and tissue biopsies. It is stressed that this technique should always be used in conjunction with conventional methods.
Insights
Defined immunofluorescence (IF) techniques effectively diagnose Neisseria infections. Methods were optimized to control cross-reactivity and non-specific staining, improving diagnostic accuracy for meningococcal and gonococcal diseases.
Area of Science:
- Microbiology
- Immunology
- Diagnostic Pathology
Background:
- Immunofluorescence (IF) techniques are established for diagnosing Neisseria infections.
- Cross-reacting antigens can cause undesired specific staining (USS) in IF assays.
- Non-specific staining (NSS) can occur due to protein A from Staphylococcus aureus or non-optimal reagent preparation.
Purpose of the Study:
- To refine defined IF techniques for improved diagnosis of meningococcal and gonococcal infections.
- To minimize both undesired specific staining (USS) and non-specific staining (NSS).
- To enhance the reliability of IF for identifying pathogenic Neisseria in clinical samples.
Main Methods:
- Controlling USS through antigen absorption.
- Blocking NSS from Staphylococcus aureus using RB 200-labeled anti-S. aureus globulins.
- Utilizing FITC-labeled F(ab')2 fragments of IgG to avoid Fc-mediated NSS.
- Optimizing FITC labeling and purification using Sephadex G-25 chromatography under specific buffer conditions (low ionic strength, low pH).
Main Results:
- Optimized IF techniques significantly reduced non-specific reactions with tissues.
- The refined methods effectively controlled USS and NSS, leading to cleaner specific staining.
- Demonstrated the utility of defined IF for diagnosing Neisseria in various clinical contexts.
Conclusions:
- Defined IF techniques, when optimized, provide accurate and reliable diagnosis of meningococcal and gonococcal infections.
- The described methods effectively mitigate common sources of staining artifacts.
- Defined IF is a valuable tool for identifying pathogenic Neisseria in clinical specimens, colonies, and tissue biopsies, complementing conventional methods.