Abstract 965

Introduction: Orally administered xylitol prevents acute otitis media. According to in vitro experiments the mechanism might be antimicrobial effect against S. pneumoniae. Yet pneumococcal carriage is not reduced. To study this further we evaluated quantitatively the effect of nasal and oral dosing of xylitol on the nasopharyngeal colonization of S. pneumoniae in rats.

Methods: The nostrils of eighty rats were inoculated with 20µl of S. pneumoniae suspension either with 104 bacteria of serotype 19F or with mixture of 106 bacteria of serotypes 6B, 19F and 23F. Two intervention groups (n=20) got either xylitol diet (20 % of the dry weight of the food) or 5 % xylitol nasal spray 5 times per day. Two control groups (n=20) got either normal diet or saline nasal spray 5 times per day. After three days rats were decapitated. The nasoturbinates and nasal mucosa were removed and quantitative bacterial culture was done. Semiquantitative PCR detection for pneumococcal DNA was done from the suspensions.

Results: Serotypes 19F and 23F colonized the nasal mucosa, but type 6B was not found. Eight (40 %) rats in control diet group and 12 (60 %) in xylitol group had positive pneumococcal culture. Thirteen (65 %) rats in saline spray group and 12 (60 %) in xylitol spray group were colonized with pneumococci. The corresponding mean bacterial counts were 24 vs. 33 colony-forming units per tissue gram (cfu/g) in diet groups and 115 vs. 68 cfu/g in spray groups. PCR was positive in 9 (45 %) of the control rats on normal diet and 11 (55 %) of the xylitol diet rats while 14 (70 %) of both saline and xylitol spray rats had positive PCR. None of the differences between the groups were statistically significant.

Conclusion: Xylitol had no significant effect on pneumococcal colonization irrespective of the mode of administration.

This study was supported by the grants of Maud Kuistila foundation.