Loss of Genomic Diversity in a Neisseria meningitidis Clone Through a Colonization Bottleneck

Area of Science:

• Microbiology
• Epidemiology
• Genomics

Background:

• Neisseria meningitidis is a primary cause of epidemic meningitis in Africa's meningitis belt.
• Meningococcal populations diversify through mutations and gene exchange during clonal spread.
• High genomic diversity may be an evolutionary strategy for meningococci to fix successful genotypes.

Purpose of the Study:

• To investigate meningococcal population dynamics and genomic diversity during clonal replacement events in northern Ghana.
• To compare the genomic makeup of Neisseria meningitidis A:ST-2859 before and after a W:ST-2881 clone's dominance.

Main Methods:

• Longitudinal study of meningococcal carriage and disease in northern Ghana.
• Analysis of cerebrospinal fluid from meningitis cases.
• Twice-yearly colonization surveys.
• Whole genome sequencing of Neisseria meningitidis isolates.

Main Results:

• Observed complete replacement of an A:ST-2859 clone by a W:ST-2881 clone.
• A:ST-2859 meningococci re-emerged after a one-year gap as both colonizers and disease agents.
• Whole genome sequencing revealed the re-emerging A:ST-2859 clone differed by only one nonsynonymous SNP from the original population.
• The W clone's dominance caused a significant reduction in the genomic diversity of the A meningococcal population.

Conclusions:

• Colonization bottlenecks, like that caused by competing meningococcal clones, can drastically reduce bacterial genomic diversity.
• Neisseria meningitidis populations exhibit resilience, with previously dominant clones capable of re-emergence after competitive exclusion.
• Understanding these population dynamics is crucial for managing meningitis epidemics in endemic regions.