Maternal transmission of mutans Streptococci in severe-early childhood caries

Abstract

Purpose: This study utilized multiple genetic analyses to detect evidence of maternal MS acquisition in children with S-ECC.

Methods: Twenty-seven mother/child pairs were selected from children with 5-ECC preceding dental rehabilitation under general anesthesia. Plaque samples were collected from the mother, child, and the child's carious lesion. Arbitrarily primed-polymerase chain reaction (AP-PCR) genotyped 6-8 MS isolates from each plaque sample, and unique genotypes were identified. Representative MS isolates with unique genotypes were characterized by pulsed-field gel electrophoresis (PFGE). Cluster analysis using the Dice band-based similarity coefficient was used to generate dendrograms from gel bonding patterns. A Dice coefficient >70% indicated similarity or match among PFGE genotypes.

Results: In 26% (7/27) of mother/child pairs, all of the child's isolates matched the mother. In 15% (4/27), some of the child's genotypes matched the mother, and in 59% (16/27), no isolates matched the mother. Maternal transmission was a mode of MS acquisition in 41% (11/27) of mother/child pairs, while acquisition from non-maternal sources occurred in 74% (20/27).

Conclusions: MS genotypes that did not match maternal strains were identified in the majority of children (74%) within this S-ECC population. Evidence of maternal transmission was detected in 41% of mother/child pairs.

Figure 1

S. mutans Ingbritt C was used as the reference strain for PFGE gel comparisons. DNA fragment size is expressed in kilobases (kb) and compared to lambda (λ) phage.

Figure 2

Representative comparison of AP-PCR gel with PFGE gel for mother/child pair #17. (A) AP-PCR gel demonstrating maternal genotypes do not visually match genotypes from the child. (B) PFGE gel confirming representative genotypes from mother (M-1, M-2, M-3) and child (BP-1, BP-2, BP-3) do not match (DICE coefficient = 56.6%) -Dice coefficient greater than 70% indicates match.

Figure 3

Representative PFGE analysis where each genotype in child matches mother. (A) Mother/Child Pair #11 where all MS genotypes share at least 97.9% similarity. (B) Mother/Child Pair #18 where all MS genotypes share at least 96.3% similarity. -Dice coefficient greater than 70% indicates match.

Figure 4

Representative PFGE gels where genotypes in child partially match mother. Mother/Child Pair #26 where child’s MS genotype 26BP-2 does not match mother, while other child genotypes (26BP-1,5,BC-1) match maternal genotypes (26M-1,2,5). (B) Mother/Child Pair #27 where genotypes 27BP-1, 27BC-3 do not match maternal genotypes, while child’s 27BC-1 matches maternal genotypes (27M-5,6,7). -Dice coefficient greater than 70% indicates match.

Figure 5

Representative PFGE gels where child does not match mother. (A) Mother (1M) and child (1BP) share less than 49 percent similarity. (B) Mother (2M) and child (2BP) share less than 60 percent similarity. (C) Mother (28M) and child (28BP/28BC) share less than 44 percent similarity. -Dice coefficient greater than 70 percent indicates match.

Figure 6

PFGE gel from siblings (12BP/BC and 13BP/BC) who possess genotypes that match one another, but do not match maternal genotypes (12M). Sibling genotypes 12BC-1, 12BP-4, 13BP-2 and 13BP-3 share 100 percent match. Neither child matches maternal genotypes (DICE coefficient <45 percent). -Dice coefficient greater than 70 percent indicates match.

Figure 7

PFGE gel for siblings (20BP and 23BP) whose genotypes match one another and maternal genotypes (23M) (Dice coefficient >90 percent). -Dice coefficient greater than 70 percent indicates match.

Figure 8

95% confidence intervals for fidelity of reported maternal MS transmission. Reported transmission percentages are marked by •. Calculated confidence intervals are demarcated by error bars. Vertical bars indicate studies sharing 30% or 60% fidelity.