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Journal of Clinical Microbiology, April 2000, p. 1615-1622, Vol. 38, No. 4
Biotechnology Centre of Oslo and Institute of
Pharmacy, University of Oslo, 0316 Oslo,1
Department of Bacteriology, National Institute of Public
Health, 0462 Oslo,2 and Department
of Oral Biology, University of Oslo, 0317 Oslo,3
Norway
Received 22 September 1999/Returned for modification 8 December
1999/Accepted 29 December 1999
The genetic diversity and relationships among 35 Bacillus
cereus and Bacillus thuringiensis isolates recovered
from marginal and apical periodontitis in humans and from various other
human infections were investigated using multilocus enzyme
electrophoresis. The strains were isolated in Norway, except for three
strains isolated from periodontitis patients in Brazil. The genetic
diversity of these strains was compared to that of 30 isolates from
dairies in Norway and Finland. Allelic variation in 13 structural gene loci encoding metabolic enzymes was analyzed. Twelve of the 13 loci
were polymorphic, and 48 unique electrophoretic types (ETs) were
identified, representing multilocus genotypes. The mean genetic diversity among the 48 genotypes was 0.508. The genetic diversity of
each source group of isolates varied from 0.241 (periodontal infection)
to 0.534 (dairy). Cluster analysis revealed two major groups separated
at a genetic distance of greater than 0.6. One cluster, ETs 1 to 13, included solely isolates from dairies, while the other cluster, ETs 14 to 49, included all of the human isolates as well as isolates from
dairies in Norway and Finland. The isolates were serotyped using
antiflagellar antiserum. A total of 14 distinct serotypes were
observed. However, little association between serotyping and genotyping
was seen. Most of the strains were also analyzed with pulsed-field gel
electrophoresis, showing the presence of extrachromosomal DNA in the
size range of 15 to 600 kb. Our results indicate a high degree of
heterogeneity among dairy strains. In contrast, strains isolated from
humans had their genotypes in one cluster. Most strains from patients
with periodontitis belonged to a single lineage, suggesting that
specific clones of B. cereus and B. thuringiensis are associated with oral infections.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Genetic Structure of Population of Bacillus
cereus and B. thuringiensis Isolates Associated
with Periodontitis and Other Human Infections
*
Corresponding author. Mailing address: Biotechnology
Centre of Oslo, University of Oslo, PB 1125, 0316 Oslo, Norway. Phone: 47 22958460. Fax: 47 22694130. E-mail:
annebko{at}biotek.uio.no.
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