Effect of xylitol on growth of nasopharyngeal bacteria in vitro

Abstract

Xylitol is known to reduce caries by inhibiting the growth of Streptococcus mutans. We hypothesized that xylitol could also affect the growth of other nasopharyngeal bacterial flora, which could be important when considering respiratory infections caused by these bacteria. We studied this in vitro by adding xylitol to the medium and observed that 1 and 5% xylitol reduced markedly the growth of alpha-hemolytic streptococci, including S. pneumoniae. It reduced slightly the growth of beta-hemolytic streptococci but not that of Haemophilus influenzae or Moraxella catarrhalis. The inhibitory growth pattern was similar to that previously seen with S. mutans, which may indicate a similarity in the enzymatic processing of five-carbon sugars such as xylitol. This sugar alcohol is a widely used sweetener, and the concentrations used in our experiments are easily achieved in the oral cavity. If xylitol reduces the growth of S. pneumoniae in the nasopharynx, it could also reduce the carriage of this pathogen and thus have clinical significance in the prevention of pneumococcal diseases.Being a five-carbon sugar alcohol, xylitol is not fermented by most oral microorganisms, such as Streptococcus mutans (3), although most S. mutans strains are able to transport xylitol into the cell via the fructose phosphotransferase system (1a). Once in the cell, it is phosphorylated to xylitol-5-phosphate, which then has to be expelled from the cell (16). This futile energy-consuming xylitol cycle is thought to be responsible for the inhibition of S. mutans growth observed both in vitro and in vivo when the bacteria are exposed to xylitol (16).It has been shown on several occasions that regular consumption of xylitol reduces the incidence of caries, although the mechanisms are not clearly understood (2,6,9,14,15). The most significant effect so far demonstrated is its ability to reduce the growth and acid production of S. mutans. Research into caries has not shown any other major changes in the oral flora, except occasionally a reduction in other oral streptococci (1a, 10, 13, 18).We hypothesized that xylitol could also affect the growth of other bacteria in the nasopharyngeal flora, which could be important when considering respiratory infections caused by these bacteria. S. pneumoniae, in particular, could make use of xylitol in a manner similar to that of S. mutans. To test our hypothesis, we evaluated the growth of some strains of nasopharyngeal bacteria when xylitol was added to the medium. MATERIALS AND METHODSBacterial strains. Ten strains of S. pneumoniae and Haemophilus influenzae and five strains of Moraxella (Branhamella) catarrhalis were isolated from consecutive routine patient middle ear effusion samples or maxillary sinus aspirates. Five strains of S. pyogenes and S. mitis and four strains of group G streptococci were isolated from throat samples of asymptomatic children. Pneumococci, H. influenzae, M. catarrhalis, and beta-hemolytic streptococci were selected because of their ability to cause upper respiratory tract infecti...

Tolerability of oral xylitol solution in young children: Implications for otitis media prophylaxis

“…regimen of 1.67 grams five times-a-day as a chewing gum or 2 grams five times-a-day as a solution reduces the incidence of acute otitis media (AOM) by 35-40% in young children, (5,6) presumably because of its antibacterial effects against Streptococcus pneumoniae and Haemophilus influenzae. (7)(8)(9) In dosages used in foods and candies, xylitol and other sugar alcohols appear to have few side effects. The main limitation of the use of sugar alcohols is a dose-dependent osmotic laxative effect, and in adults, xylitol is well tolerated in doses up to 100 grams per day.…”

Ameliorating Effect of Dietary Xylitol on Human Respiratory Syncytial Virus (hRSV) Infection

“…Moreover, xylitol has a strong antimicrobial effect against Streptococcus pneumonia and an anti-adhesive effect against Streptococcus pneumonia and Haemophilus influenza in vitro. 14,15) Because chewing 8.4 g of xylitol per day reduced the incidence of ostitis media up to 50% it was proposed as a prophylactic against otitis media, 16) and most studies have focused on its anti-bacterial actions.…”

Effects and Safety of Xylitol on Middle Ear Epithelial Cells

“…Xylitol inhibits the growth of S. pneumoniae and reduces the adherence of S. pneumoniae and Haemophilus influenzae to nasopharyngeal cells [9,18] . In addition, xylitol can lower the airway surface salt concentration and enhance innate immunity in airway epithelia in vitro [19] .…”

“…Several studies in children demonstrated the preventive effects of xylitol on AOM [4][5][6][7][8] . In addition, 5% xylitol was shown to inhibit the growth of Streptococcus pneumoniae and addition of xylitol to the medium had some inhibitory effects against other bacteria in vitro [9] . To our knowledge, however, there have been no studies regarding the safety of xylitol for the prevention of AOM.…”