Effect of xylitol and other carbon sources on Streptococcus pneumoniae biofilm formation and gene expression invitro

Abstract number: P1900

Kurola P., Tapiainen T., Sevander J., Kaijalainen T., Leinonen M., Uhari M., Saukkoriipi A.

Objectives: Xylitol inhibits the growth and adherence of Streptococcus pneumoniae. In clinical trials, xylitol decreases the occurrence of acute otitis media but does not affect nasopharyngeal carriage of pneumococci. We hypothesized that xylitol inhibits biofilm formation of S. pneumoniae and measured pneumococcal biofilm formation and gene expression levels of the capsule gene cpsB and two other genes, autolysin encoding gene lytA and competence gene comA in different growth media in vitro.

Methods: Twenty pneumococcal isolates were grown on polystyrene plates for 18 hours in test media containing 0.5% xylitol, 0.5% glucose, 0.5% xylitol and 0.5% glucose, 0.5% fructose, 0.5% xylitol and 0.5% fructose or BHI medium supplemented with 10% horse serum. The polystyrene plates were made in duplicate; one set for RNA extraction and another set for crystal violet staining.

Results: The means of the OD values were 0.04, 0.03, 0.16, 0.15, 0.12 and 0.13 for BHI, xylitol, glucose, glucose supplemented with xylitol, fructose and fructose medium supplemented with xylitol, respectively (Figure). The results differed significantly between the test media (P < 0.001). The OD values were significantly lower in xylitol compared with BHI medium with a mean difference of -0.015 [95% confidence interval (CI) -0.028 to -0.002, P = 0.03]. Xylitol also decreased the expression levels of the cpsB and lytA genes. When the medium was supplemented with glucose or fructose, biofilm formation was enhanced and the inhibitory effect of xylitol on biofilm formation was not observed.

Conclusion: We found that xylitol inhibits the biofilm formation of S. pneumoniae whereas other extra carbon sources such as fructose and glucose enhance biofilm formation. The decrease in biofilm formation may further explain the efficacy of xylitol in preventing acute otitis media in previous clinical trials.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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