GENOTYPING SHOWS DIFFERENT STRAINS OF MUTANS STREPTOCOCCI BETWEEN FATHER AND CHILD AND WITHIN PARENTAL PAIRS IN SWEDISH FAMILIES

The purpose of this study was to investigate whether there was an intr afamilial similarity of mutans streptococcal strains in some Swedish f amilies using chromosomal DNA fingerprinting. Plaque samples were obta ined from buccal and occlusal surfaces of 25 three-year-old children, their mothers and 18 fathers. The colonization levels of mutans strept ococci were estimated with the ''Strip mutans'' test, and caries exper ience was scored by decayed, missing and filled teeth or decayed, extr acted and filled teeth. Interviews about medical history, diet regimes , breastfeeding and care of the child were performed. In 11 families i solates of mutans streptococci were detected in all three individuals. These isolates were serotyped by immunofluorescent technique and geno typed using the restriction endonuclease Hae III. The results showed t hat 5 children harbored mutans streptococci genotypes different from t heir parents. Six children showed genotypes identical to their mothers . None of the children harbored genotypes similar to their fathers, ev en though two thirds of the fathers had high or very high mutans strep tococci levels. No matching of genotypes was observed within the 11 pa rental pairs. Mothers as primary caregivers with high ''Strip mutans'' scores were more often observed in the group with identical genotypes within the mother-child pairs, the ''matching group'', than in the '' no-matching group''. These data indicate that the fathers and the chil dren had not acquired each others' strains of mutans streptococci nor had the spouses. The results suggest that the children acquired mutans streptococci both from outside and inside the family.