CLONAL DIVERSITY OF STREPTOCOCCUS-MITIS BIOVAR-1 ISOLATES FROM THE ORAL CAVITY OF HUMAN NEONATES

The clonal diversity of 101 isolates of the pioneer bacterium Streptoc occus mitis biovar I obtained from the oral cavities of 40 human neona tes 1 to 3 days, 2 weeks, and 1 month postpartum was examined by using rRNA gene restriction patterns, There was a high degree of genetic di versity, with the 101 isolates comprising 93 unique PvuII ribotypes, T here were eight identical pairs of ribotype patterns, and seven of the eight pairs were obtained from individual neonates, Only one identica l pair comprised isolates obtained from different neonates. In all but two cases, isolates with matching ribotypes were obtained at one visi t, Two pairs of isolates with matching ribotype patterns were obtained from neonates on successive visits, The ribotype patterns of the isol ates were examined by cluster analysis. The isolates forming each clus ter were very similar, yet each cluster was well separated from its ne ighbors, When several isolates were obtained from individual neonates at a particular visit, in some instances they were contained in a sing le cluster, whereas in other cases each isolate was contained in a sep arate cluster, Isolates obtained from individual neonates on successiv e visits tended to be contained in different clusters, This high degre e of diversity, which has been observed in other mucosal commensal bac teria, may serve as a mechanism for avoiding immune elimination of the se bacteria.