乳児のMutans Streptococciの初期獲得：感染性の窓があることの証拠

Initial acquisition of mutans streptococci by infants: evidence for a discrete window of infectivity.

抄録

46組の母子の口腔内細菌量を，乳児の出生時から5歳までモニターし，小児によるMutans Streptococci（MS）の獲得について調査した．38人の小児が最初にMSを獲得したのは，中央値で生後26カ月であり，我々が「感染性の窓」と呼ぶ個別の時期であった．8人の小児（17％）は研究期間終了時（中央値56カ月）までMSが検出されないままであった。MSの有無にかかわらず，母親の唾液中のMSおよび乳酸菌の濃度に有意差はなかった．MSが検出された齲蝕活動中の集団（38人中9人）と検出されなかった小児の比較では、抗生物質の使用、妊娠年齢、出生時体重の点で類似した履歴が認められた。興味深いことに、MSに汚染されていない1歳から2歳の小児の半数は母親以外の介護者が世話をしたのに対し、同時期の齲蝕活動中の小児は全員が母親の世話をし、その差は統計的に有意であった。本研究では、MSが乳児の個体発生における特定の時期に獲得されることを初めて報告した。このような感染可能な時期があるという考え方は、動物モデルを含む他の情報源からも支持されている。

Oral bacterial levels of 46 mother-child pairs were monitored from infant birth up to five years of age so that the acquisition of mutans streptococci (MS) by children could be studied. The initial acquisition of MS occurred in 38 children at the median age of 26 months during a discrete period we designated as the "window of infectivity". MS remained undetected in eight children (17%) until the end of the study period (median age of 56 mo). The levels of both MS and lactobacilli in saliva of mothers of children with and without MS were not significantly different. Comparisons between a caries-active cohort colonized by MS (nine of 38) and children without detectable MS revealed similar histories in terms of antibiotic usage, gestational age, and birth weight. Interestingly, half of the children between the ages of one and two years who were not colonized by MS were attended by caretakers other than the mother, while all of the caries-active children during this same time period were cared for by their mothers; the difference was statistically significant. Here we report for the first time that MS is acquired by infants during a defined period in the ontogeny of a child. Support for the notion of a discrete window of infectivity comes from other sources, including animal models.