Infect Immun, June 1998, p. 2595-2600, Vol. 66, No. 6
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Department of Pedodontics and
Orthodontics1 and
Institute of
Dentistry,
Received 31 July 1997/Returned for modification 26 September
1997/Accepted 3 March 1998
The production of bacteriocin-like inhibitory substances, mutacins,
by mutans streptococci varies among isolates. To find if the
degree of mutacin activity of an isolate was related to its
transmission between mother and her child, 19 mothers and their
18-month- to 3-year-old children were sampled for their oral
mutans streptococci. In addition, the
stability of mutacin activity was studied with isolates from the
mothers and with isolates from five unrelated 5-year-old
children in 5- to 7-year follow-up studies. A total of 145 oral mutans
streptococcal isolates were serotyped by immunodiffusion, ribotyped,
and mutacin typed by the stab culture technique.
Mutacin was produced by 88% of the strains against more than 1 of
the 14 indicator strains, representing mutans streptococci,
Streptococcus sanguis, Streptococcus
salivarius, Streptococcus oralis, Streptococcus
gordonii, and Streptococcus pyogenes. Streptococcus
mutans isolates showed more inhibitory activity than did
Streptococcus sobrinus isolates. Identical ribotypes had similar mutacin activity profiles within a subject,
initially and in the follow-up studies, in all but two cases. The
mothers harbored a total of 37 different mutans streptococcal
ribotypes. Six children were negative for mutans streptococci.
Transmission was probable in 9 of 20 mother-child pairs on the
basis of the presence of identical strains, as determined by ribotyping
and bacteriocin (mutacin) typing. S. mutans
strains shared between a mother and her child showed a broader spectrum
of inhibitory activity than did nontransmitted strains. In conclusion,
the mutacin activity of clinical isolates is reasonably stable, and
this virulence factor seems to be of clinical importance in early
colonization by S. mutans.
*
Corresponding author. Mailing address: Department of
Pedodontics and Orthodontics, University of Helsinki, P.O. Box 41, Mannerheimintie 172, 00014 University of Helsinki, Finland. Phone:
358-9-19127312. Fax: 358-9-19127266. E-mail:
Lisa.Gronroos{at}Helsinki.fi.
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