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Differences in genetic diversity of nonecapsulated Haemophilus influenzae from various diseases
Loek van Alphen1, Dominique A Caugant2, Birgitta Duim1
1Academic Medical Center, Department of Medical Microbiology, Meibergdreef 15, NL-1105 AZ Amsterdam, The Netherlands.
Abstract:
Genetic relationships among 80 isolates of nonencapsulated Haemophilus influenzae recovered from different disease types were determined by multilocus enzyme electrophoresis (MEE) at 13 enzyme loci in an attempt to assess the association between multilocus genotype and disease. The isolates were obtained from 15 patients with meningitis, 10 with otitis media, 19 with chronic bronchitis, 20 with cystic fibrosis, and 16 were obtained from healthy carriers. The 80 isolates were assigned to 69 electrophoretic types (ETs) falling into 5 groups. Isolates from each disease entity were represented by a variety of genotypes; however, cluster analysis from a matrix of genetic distances between ETs revealed that the ETs of the otitis media and meningitis isolates were all clustered within a genetic distance of 0.55 (group I). In addition, no genotypes were shared between H. influenzae carrier isolates and isolates from cases of disease, H. influenzae isolates from healthy individuals were distributed significantly differently from those from chronic bronchitis meningitis and otitis media patients. The genetic diversity (H) of carrier strains was greatest, although not statistically different from that of isolates from patients with disease. It was concluded that the genetic distribution of acute disease isolates is not random over the five ET groups, although the genetic diversity within the groups is not different. The effect of bacterial persistence in the host on the genetic diversity of H. influenzae is discussed.
Insights
Genetic analysis of non-encapsulated Haemophilus influenzae reveals distinct clustering for meningitis and otitis media strains. Healthy carrier strains show greater genetic diversity and differ significantly from disease-causing isolates.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Non-encapsulated Haemophilus influenzae (non-iE H. influenzae) is a significant pathogen causing various infections.
- Understanding the genetic diversity and population structure of non-iE H. influenzae is crucial for infection control and treatment.
Purpose of the Study:
- To investigate the genetic relationships among non-iE H. influenzae isolates from different disease types and healthy carriers.
- To determine if specific multilocus genotypes are associated with particular diseases.
Main Methods:
- Multilocus enzyme electrophoresis (MEE) was used to analyze 13 enzyme loci in 80 non-iE H. influenzae isolates.
- Isolates were obtained from patients with meningitis, otitis media, chronic bronchitis, cystic fibrosis, and from healthy carriers.
- Cluster analysis was performed on a matrix of genetic distances between electrophoretic types (ETs).
Main Results:
- Eighty isolates yielded 69 distinct electrophoretic types (ETs), grouped into 5 clusters.
- Isolates from otitis media and meningitis clustered together (genetic distance < 0.55, group I).
- No genotypes were shared between carrier and disease isolates; carrier strains exhibited greater genetic diversity.
Conclusions:
- The genetic distribution of acute disease isolates is non-random across ET groups.
- Distinct genetic profiles exist for isolates associated with different clinical presentations.
- Bacterial persistence may influence the genetic diversity of H. influenzae within hosts.