OBJECTIVETo find out horizontal transmission of oral Streptococcus mutas (S. mutans) in nursery children through analyzing the similarity of S. mutans genotypes.

METHODSThe study group included 24 nursery children between 3 and 4 years of age. Dental plaque samples were collected with sterile toothpick and cultured on MSB plates for 48 h. Individual Streptococcus mutans group colonies representative of the colonial morphologies were subcultured on TPY plates. These strains were identified to species level biochemically. AP-PCR fingerprinting was preformed after identification. S. mutans isolates from different children with very similar fingerprinting profiles were examined by chromosomal DNA fingerprinting analysis.

RESULTSStreptococcus mutans group were isolated in oral cavities of 66.7% children, 58.3% in caries-free and 75.0% in caries children. A total of 4' S. mutans isolates from 24 subjects were analyzed by AP-PCR, and 29 different amplitypes were identifyied, 45.8% carried tw. genotypes. There were 2 genotypes of S. mutans isolated repeatedly among 12 nursery children.

CONCLUSIONThe presence of matching genotypes of S. mutans among nursery children suggests horizontal transmission.