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Updated: Aug 11, 2026
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
[PCR-based capsular typing of Haemophilus influenzae isolates non-typeable by agglutination]
G Weltman1, M S Fossati, C Correa
1Instituto Nacional de Enfermedades Infecciosas-ANLIS Dr. Carlos Malbrian Vélez Sarsfield 563, (1281) Ciudad Autónoma de Buenos Aires, Argentina.
Insights
Polymerase chain reaction (PCR) effectively identified non-capsulate Haemophilus influenzae strains. This molecular method is crucial for distinguishing non-encapsulated bacteria and capsule-deficient mutants, aiding in infection control.
Area of Science:
- Clinical microbiology
- Molecular biology
- Infectious diseases
Background:
- Haemophilus influenzae causes localized and systemic infections.
- Traditional slide agglutination is limited to six capsular types (a-f) and cannot identify non-encapsulated strains.
- Conjugate vaccines have reduced invasive diseases caused by H. influenzae type b.
Purpose of the Study:
- To evaluate polymerase chain reaction (PCR) for capsular typing of non-typeable Haemophilus influenzae (NTHi).
- To distinguish non-encapsulated strains from capsule-deficient type b mutants.
- To identify strains not detectable by slide agglutination.
Main Methods:
- Capsular genotyping of 38 NTHi isolates using PCR.
- Isolates were collected between 2002-2004 from blood cultures, primarily associated with respiratory infections.
- PCR was used to determine the capsular genotype of each isolate.
Main Results:
- PCR identified 100% of the isolates as non-encapsulate H. influenzae.
- The capsule deficient type b (b-) genotype was not detected in any of the isolates.
- PCR proved effective for characterizing NTHi, with most isolates originating from blood cultures linked to respiratory infections.
Conclusions:
- PCR is a highly effective method for capsular typing of Haemophilus influenzae, especially for non-encapsulated strains.
- This molecular technique is essential for differentiating non-encapsulated strains from capsule-deficient mutants and other serotypes.
- The study confirmed the utility of PCR in identifying non-encapsulate H. influenzae in clinical settings.
Abstract:
Haemophilus influenzae is recognized as a pathogenic agent responsible of localized and systemic infections. Six antigenically different capsular polysaccharide types have been described (a, b, c, d, e, and f ) which can be identified by slide agglutination with specific antisera. Besides there are non capsulated strains that cannot be typed by slide agglutination. The introduction of the conjugated vaccine produced an important reduction of invasive diseases caused by H. influenzae type b. Capsular typing by PCR is the most appropriated method for distinguishing non capsulated strains from capsule deficient type b mutants (b-) and for detecting strains of other serotypes that cannot be detected by slide agglutination. Capsular genotype was studied in 38 isolates of non-typeable Haemophilus influenzae received at INE-ANLIS "Dr. Carlos G. Malbrán" between 2002-2004. Of the isolates included in this study 78.9% of them were recovered from blood cultures and most of them were associated with a respiratory focus. By PCR technique 100% of the isolates were identified as non-capsulate H. influenzae and genotype b-was not detected.
