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Microevolution through DNA exchange among strains of Neisseria meningitidis isolated during an outbreak in the Czech
P Kriz1, D Giorgini, M Musilek
1National Reference Laboratory for Meningococcal Infections, NIPH, Prague, Czech Republic.
Abstract:
Neisseria meningitidis is a highly variable bacterium. Indeed, N. meningitidis is naturally competent for transformation, and horizontal DNA exchange between strains may lead to mosaic genetic loci in N. meningitidis. We studied such an exchange in nature during an epidemic provoked by N. meningitidis. This epidemic started in the Czech Republic in 1993 and the original epidemic clone was shown to have the antigenic formula (serogroup:serotype:serosubtype) C:2a:P1.2,5. We analysed 145 meningococcal strains isolated in the Czech Republic between 1993 and 1997 using serological and genetic typing methods (multilocus enzyme electrophoresis and polymorphism of pilA and pilD genes). This analysis showed that genetic exchange between epidemic and endemic strains had occurred. Exchanges involved mostly surface-exposed structures such as the capsule, giving rise to new meningococcal variants. The expansion of these variants should be kept under close surveillance.
Insights
Genetic exchange occurred between epidemic and endemic Neisseria meningitidis strains during a Czech Republic epidemic. This led to new variants with altered surface structures, requiring ongoing surveillance.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Neisseria meningitidis exhibits significant genetic variability.
- Natural competence and horizontal DNA exchange contribute to mosaic genetic structures.
- An epidemic in the Czech Republic (1993-1997) provided a unique opportunity to study these exchanges.
Purpose of the Study:
- To investigate genetic exchange between epidemic and endemic Neisseria meningitidis strains.
- To identify the genetic basis of new meningococcal variants during an epidemic.
Main Methods:
- Analysis of 145 meningococcal strains isolated between 1993 and 1997.
- Utilized serological typing methods.
- Employed genetic typing: multilocus enzyme electrophoresis and pilA/pilD gene polymorphism analysis.
Main Results:
- Confirmed genetic exchange between epidemic and endemic Neisseria meningitidis strains.
- Identified exchanges primarily involving surface-exposed structures, such as the capsule.
- Observed the emergence of novel meningococcal variants resulting from these exchanges.
Conclusions:
- Horizontal DNA exchange is a significant driver of Neisseria meningitidis evolution.
- The emergence of new variants with altered surface antigens poses a potential public health concern.
- Close surveillance of these expanding variants is crucial for effective disease control.