The Source of Infection in the Intrafamilial Transfer of Streptococcus mutans

Abstract

Two approximal plaque samples were collected from each member of 32 families. <i>Streptococcus mutans</i> strains obtained from the samples were then characterized by bacteriocin typing. Only one <i>S. mutans</i> type was found in 15 (∼ 50%) of the families. In 10 of these, all members were infected with a single common type and in the remaining 5 families, all but 1 or 2 subjects harboured the organism. More than one <i>S. mutans</i> type was found in 12 (∼ 40%) of families; no individual harboured more than one type and usually no more than 1 member was <i>S. mutans</i>-free. In 4 of these families, maternal transfer was indicated, and in another 3, paternal transfer seemed likely; in 1, neither parent seemed to be the source of infection and in the remaining 4, the situation was not clear-cut. Overall, in 28 (88%) of the families, a common <i>S. mutans</i> type was shared by at least 2 members, 1 of them a parent. Thus, intrafamilial transmission of some strains of <i>S. mutans</i> can occur; the source of infection may vary from family to family and it was suggested that further investigation into the vehicle(s) responsible for indirect salivary transfer of the organism seems warranted.