Late Established Mutans Streptococci in Children over 3 Years Old

Abstract

Acquisition of mutans streptococci has been reported to most commonly occur at approximately 26 months of age. In the present study, we detectedStreptococcus mutansandS. sobrinususing polymerase chain reaction (PCR) assays in children, then re-examined the subjects to determine the time of acquisition of these bacteria over a 1-year period. The subjects were 57 children ranging in age from 3 to 5 years old, each with primary dentition. Plaque samples were collected from all erupted tooth sites using a sterile toothbrush. PCR assays were performed to detect the targeted mutans streptococci at the beginning of the study (baseline) and after 1 year. At the baseline examination, the prevalence ofS. mutansandS. sobrinuswas 61.4% and 54.4%, respectively, in all subjects, of whom 14 (24.6%) were positive forS. mutansalone, 10 (17.5%) forS. sobrinusalone, and 21 (36.8%) for bothS. mutansandS. sobrinus, with 12 (21.1%) negative for both. After 1 year, 4 of 22 (18.2%) subjects newly had acquiredS. mutansand 15 of 26 (57.7%) had aquiredS. sobrinus, while 5 (8.8%) remained negative for both bacteria. The age of the first positiveS. mutansfinding ranged from 49 to 71 months, while that forS. sobrinusranged from 49 to 81 months old. Our results suggest thatS. sobrinusbecomes established later thanS. mutansin the oral cavities of children over the age of 3 years old.