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Carried meningococci in the Czech Republic: a diverse recombining population
K A Jolley1, J Kalmusova, E J Feil
1Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, Oxford, OX1 3FY, United Kingdom.
Abstract:
Population and evolutionary analyses of pathogenic bacteria are frequently hindered by sampling strategies that concentrate on isolates from patients with invasive disease. This is especially so for the gram-negative diplococcus Neisseria meningitidis, a cause of septicemia and meningitis worldwide. Meningococcal isolate collections almost exclusively comprise organisms originating from patients with invasive meningococcal disease, although this bacterium is a commensal inhabitant of the human nasopharynx and very rarely causes pathological effects. In the present study, molecular biology-based techniques were used to establish the genetic relationships of 156 meningococci isolated from healthy young adults in the Czech Republic during 1993. None of the individuals sampled had known links to patients with invasive disease. Multilocus sequence typing (MLST) showed that the bacterial population was highly diverse, comprising 71 different sequence types (STs) which were assigned to 34 distinct complexes or lineages. Three previously identified hyperinvasive lineages were present: 26 isolates (17%) belonged to the ST-41 complex (lineage 3); 4 (2.6%) belonged to the ST-11 (electrophoretic type [ET-37]) complex, and 1 (0.6%) belonged to the ST-32 (ET-5) complex. The data were consistent with the view that most nucleotide sequence diversity resulted from the reassortment of alleles by horizontal genetic exchange.
Insights
Neisseria meningitidis, a common nasopharyngeal bacterium, shows high genetic diversity in healthy individuals. Most genetic variation arises from horizontal gene exchange, not just invasive strains.
Area of Science:
- Microbiology
- Bacterial genetics
- Evolutionary biology
Background:
- Population and evolutionary studies of pathogenic bacteria often overlook commensal strains.
- Neisseria meningitidis is a leading cause of bacterial meningitis and septicemia worldwide.
- Existing isolate collections primarily consist of disease-causing strains, not commensal ones.
Purpose of the Study:
- To genetically characterize Neisseria meningitidis isolates from healthy individuals.
- To understand the genetic diversity and evolutionary dynamics of meningococci in a commensal population.
- To compare the genetic makeup of commensal meningococci with those causing invasive disease.
Main Methods:
- Isolation and molecular characterization of 156 Neisseria meningitidis strains from healthy young adults in the Czech Republic.
- Multilocus sequence typing (MLST) to determine genetic relationships and diversity.
- Analysis of sequence types (STs) and their assignment to known complexes or lineages.
Main Results:
- High genetic diversity was observed, with 71 distinct sequence types (STs) identified among 156 isolates.
- These STs were grouped into 34 distinct complexes or lineages.
- Three known hyperinvasive lineages (ST-41, ST-11, and ST-32 complexes) were found, albeit at low frequencies.
- Nucleotide diversity was largely attributed to horizontal genetic exchange.
Conclusions:
- Commensal Neisseria meningitidis populations exhibit significant genetic diversity.
- Horizontal genetic exchange is a major driver of genetic variation in Neisseria meningitidis.
- Understanding the genetic diversity of commensal strains is crucial for tracking and controlling pathogenic strains.