title: Xylitol and capsular gene expression in Streptococcus pneumoniae.
abstract: Xylitol is a sugar alcohol that inhibits the growth and adherence of Streptococcus pneumoniae. In clinical trials, xylitol has been shown to decrease the occurrence of acute otitis media in day-care children but did not decrease nasopharyngeal carriage of the pneumococci. It has also been shown that xylitol affects the ultrastructure of the pneumococcal capsule. Here, it was hypothesized that xylitol might affect the expression of pneumococcal capsular genes. Capsule gene expression levels were studied in 24 clinical pneumococcal isolates and one ATCC strain (49619) by using a real-time RT-PCR method targeting the mRNA of the second gene of the pneumococcal capsular locus, the cpsB gene. The isolates were exposed to 5 % glucose, 5 % xylitol and control medium (brain heart infusion medium containing 10 % fetal bovine serum) for 2 h. cpsB gene expression levels were measured by using a relative quantification method with calibrator normalization where the 16S rRNA gene of pneumococcus was used as a reference. Exposure to xylitol lowered cpsB gene expression levels significantly compared with those in the control (P=0.035) and glucose (P=0.011) media. This finding supports previous results where exposure to xylitol changed the ultrastructure of the pneumococcal capsule and could explain further the high clinical efficacy of xylitol in preventing otitis media.
authors: National Institute for Health and Welfare, Oulu, Finland.
authors: Paula
authors: P
authors: Kurola
authors: University of Oulu Department of Pediatrics, Oulu, Finland.
authors: Terhi
authors: T
authors: Tapiainen
authors: National Institute for Health and Welfare, Oulu, Finland.
authors: Tarja
authors: T
authors: Kaijalainen
authors: University of Oulu Department of Pediatrics, Oulu, Finland.
authors: Matti
authors: M
authors: Uhari
authors: National Institute for Health and Welfare, Oulu, Finland.
authors: Annika
authors: A
authors: Saukkoriipi
mesh_terms: D016667:Bacterial Capsules / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D002986:Clinical Trials as Topic; D003470:Culture Media; D015536:Down-Regulation; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D010033:Otitis Media / Q000382:microbiology / Q000517:prevention & control; D010034:Otitis Media with Effusion / Q000382:microbiology; D017027:Protein Tyrosine Phosphatases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D014993:Xylitol / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; C500440:CpsB protein, Streptococcus pneumoniae; D017027:Protein Tyrosine Phosphatases; D014993:Xylitol