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Journal of Clinical Microbiology, January 2000, p. 79-84, Vol. 38, No. 1
Institute of Dentistry, University of
Helsinki,1 HUCH Diagnostics, Helsinki
University Central Hospital,2 and
Anaerobe Reference Laboratory, National Public Health
Institute,3 Helsinki, Finland
Received 7 June 1999/Returned for modification 4 August
1999/Accepted 2 September 1999
Actinobacillus actinomycetemcomitans, an oral pathogen,
only occasionally causes nonoral infections. In this study 52 A. actinomycetemcomitans strains from 51 subjects with nonoral
infections were serotyped and genotyped by arbitrarily primed PCR
(AP-PCR) to determine whether a certain clone(s) is specifically
associated with nonoral infections or particular in vitro antimicrobial
susceptibility patterns. The promoter structure of leukotoxin genes was
additionally investigated to find the deletion characteristic of highly
leukotoxic A. actinomycetemcomitans strains. The nonoral
A. actinomycetemcomitans strains included all five known
serotypes and nonserotypeable strains, the most common serotypes being
b (40%) and c (31%). AP-PCR distinguished 10 different genotypes.
A. actinomycetemcomitans serotype b strains were more
frequently found in blood samples of patients with bacteremia or
endocarditis than in patients with focal infections. One AP-PCR
genotype was significantly more frequently found among strains
originating in focal infections than in blood samples. Resistance to
benzylpenicillin was significantly more frequent among A. actinomycetemcomitans serotype b strains than among strains of
other serotypes. No differences in the leukotoxin gene promoter region
or benzylpenicillin resistance between nonoral and oral A. actinomycetemcomitans strains were observed. Nonoral A. actinomycetemcomitans strains showed great similarity to the oral
strains, confirming that the oral cavity is the likely source of
nonoral A. actinomycetemcomitans infections. The
predominance of serotype b strains in endocarditis and bacteremia
supports the hypothesis of a relationship between certain A. actinomycetemcomitans clones and some nonoral infections. The
mechanisms behind the exceptionally high rate of occurrence of
benzylpenicillin resistance among A. actinomycetemcomitans
serotype b strains are to be elucidated in further studies.
0095-1137/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Heterogeneity of Actinobacillus
actinomycetemcomitans Strains in Various Human Infections and
Relationships between Serotype, Genotype, and Antimicrobial
Susceptibility
*
Corresponding author. Mailing address: Institute of
Dentistry, P.O. Box 41, University of Helsinki, Helsinki, FIN-00014
Finland. Phone: 358-9-19127365. Fax: 358-9-19127365. E-mail:
Susanna.Paju{at}helsinki.fi.
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