Abstract
In this study a natural transmission model was employed to determine the role of sucrose as an ecological determinant in the colonisation of Streptococcus sobrinus. This experimental model was designed to resemble more closely the acquisition of mutans streptococci by human infants than is possible with artificial oral inoculation/superinfection invariably employed in rodent models. Sixty donor rats were infected intraorally with S. sobrinus 6715. Each infected donor was caged with an uninfected recipient rat. Five groups of 12 donor-recipient pairs were fed diets containing either 0, 01, 1, 5 or 56 per cent sucrose and their levels of colonisation with S. sobrinus were monitored daily. Transmission of S. sobrinus from donor to recipient rats occurred at all dietary sucrose concentrations including those recipients consuming no sucrose (56 per cent raw corn starch). With the single exception of recipient rats fed 56 per cent sucrose, colonisation and dental caries scores were independent of dietary sucrose.