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Clinical and Diagnostic Laboratory Immunology, October 2005, p. 1184-1190, Vol. 12, No. 10
1071-412X/05/$08.00+0 doi:10.1128/CDLI.12.10.1184-1190.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, D.C.,1 Department of Oral Biology, University of Manitoba, Winnipeg, Canada,2 Department of Pediatrics, Georgetown University Medical Center, Washington, D.C.,3 Department of Medicine, INOVA Fairfax Hospital, Fairfax, Virginia4
Received 11 May 2005/ Returned for modification 20 June 2005/ Accepted 14 July 2005
Streptococcus mitis bv. 1 is a pioneer colonizer of the human oral cavity. Studies of its population dynamics within parents and their infants and within neonates have shown extensive diversity within and between subjects. We examined the genetic diversity and clonal turnover of S. mitis bv. 1 isolated from the cheeks, tongue, and primary incisors of four infants from birth to 1 year of age. In addition, we compared the clonotypes of S. mitis bv. 1 isolated from their mothers' saliva collected in parallel to determine whether the mother was the origin of the clones colonizing her infant. Of 859 isolates obtained from the infants, 568 were unique clones. Each of the surfaces examined, whether shedding or nonshedding, displayed the same degree of diversity. Among the four infants it was rare to detect the same clone colonizing more than one surface at a given visit. There was little evidence for persistence of clones, but when clones were isolated on multiple visits they were not always found on the same surface. A similar degree of clonal diversity of S. mitis bv. 1 was observed in the mothers' saliva as in their infants' mouths. Clones common to both infant and mothers' saliva were found infrequently suggesting that this is not the origin of the infants' clones. It is unclear whether mucosal immunity exerts the environmental pressure driving the genetic diversity and clonal turnover of S. mitis bv. 1, which may be mechanisms employed by this bacterium to evade immune elimination.
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