Pq210011614p

The osmolyte xylitol reduces the salt concentration of
airway surface liquid and may enhance
bacterial killing
Joseph Zabner*†, Michael P. Seiler*, Janice L. Launspach*, Philip H. Karp*, William R. Kearney‡, Dwight C. Look§,
Jeffrey J. Smith¶, and Michael J. Welsh*ʈ**
ʈHoward Hughes Medical Institute, Departments of *Internal Medicine, ¶Pediatrics, and **Physiology and Biophysics, and ‡Nuclear Magnetic ResonanceFacility, University of Iowa College of Medicine, Iowa City, IA 52242; and §Department of Medicine, Washington University, St. Louis, MO 63110 Contributed by Michael J. Welsh, August 7, 2000 The thin layer of airway surface liquid (ASL) contains antimicrobial
an effect could be of value in preventing airway infections, substances that kill the small numbers of bacteria that are con-
irrespective of the absolute salt concentration in ASL or of stantly being deposited in the lungs. An increase in ASL salt
differences between CF and non-CF. We considered several concentration inhibits the activity of airway antimicrobial factors
factors. First, the airway epithelium is water permeable (17).
and may partially explain the pathogenesis of cystic fibrosis (CF).
Consistent with this finding, when large volumes of liquid are We tested the hypothesis that an osmolyte with a low transepi-
placed on the apical surface, liquid absorption is isotonic (9, 15).
thelial permeability may lower the ASL salt concentration, thereby
Thus, if water were simply added to the airway surface, electro- enhancing innate immunity. We found that the five-carbon sugar
lyte concentrations would rapidly return to starting values.
xylitol has a low transepithelial permeability, is poorly metabolized
However, if an osmolyte that has a low transepithelial perme- by several bacteria, and can lower the ASL salt concentration in
ability were added to ASL, it might serve to lower the salt both CF and non-CF airway epithelia in vitro. Furthermore, in a
concentration. Somewhat analogous to this effect, the relatively double-blind, randomized, crossover study, xylitol sprayed for 4
impermeable osmolyte lactose allows the water-permeable days into each nostril of normal volunteers significantly decreased
mammary gland duct epithelium to maintain the luminal NaCl the number of nasal coagulase-negative Staphylococcus compared
concentration at 5–10 mM (18). Second, an osmolyte that is with saline control. Xylitol may be of value in decreasing ASL salt
nonionic would be required, because it is ionic strength that concentration and enhancing the innate antimicrobial defense at
the airway surface.
inhibits antimicrobial activity, not osmolarity (19, 20). Third, the osmolyte should not provide a ready carbon source for bacterial A thin layer of liquid covering the airway surface (ASL) growth. Fourth, the osmolyte should be safe in humans. Fifth,
contains many antimicrobial substances, including ly- because many endogenous antimicrobials kill very quickly, even sozyme, lactoferrin, secretory leukoproteinase inhibitor, human a transient decrease in ionic strength might be effective. Finally, ␤ defensins 1 and 2, secretory phospholipase A2, and the a small reduction in the salt concentration, perhaps only 10 mM, cathelicidin LL-37 (for reviews see refs. 1–4). These agents might be beneficial because there is no unique relationship acting alone and synergistically form part of the local pulmonary between antimicrobial activity and ionic strength; the lower the host defense system, killing the small numbers of bacteria that ionic strength, the greater the bacterial killing (20–22).
are constantly being deposited on the airway surface. The A promising osmolyte for lowering ASL ionic strength is the antibacterial activity of most of these agents is salt-sensitive; an five-carbon sugar, xylitol, which is poorly metabolized by some increase in salt concentration inhibits the activity of individual bacteria (23). Interestingly, when incorporated into chewing factors and attenuates synergy between agents.
gum, xylitol is reported to prevent dental caries (24). Moreover, We recently proposed that disruption of this innate defense in chewing gum, lozenges, or syrup, xylitol decreases the inci- system causes, in part, the well-known propensity of cystic dence of acute otitis media by 20–40% (25). Therefore, we tested fibrosis (CF) airways for bacterial infection (5). CF lung disease the hypothesis that xylitol applied to the apical surface of human is initially characterized by infection with a variety of bacteria, airway epithelia would lower the ASL salt concentration. We and as the disease progresses Staphylococcus aureus and Pseudo- also examined the effect of xylitol on bacteria in vitro and in vivo.
monas aeruginosa predominate (5, 6). We hypothesized that the loss of cystic fibrosis transmembrane conductance ClϪ channels leads to a higher ASL salt concentration, which reduces antimi- Materials and Methods
crobial potency and thereby impairs the innate immune system Human Airway Epithelia. Airway epithelial cells were isolated from
(7, 8). Several studies using in vitro model systems of the human tracheal and bronchial tissue, grown on semipermeable mem- airway have reported that salt concentrations are lower in ASL branes at the air-liquid interface, and studied at least 14 days than in serum and are elevated in CF (8–11). However, the after seeding when they had differentiated and developed a applicability of these observations to the in vivo human airway ciliated apical surface (26, 27). Transepithelial resistance was has not been established with certainty. Some in vivo studies have 588 Ϯ 33 ⍀⅐cm2 (n ϭ 9) for non-CF and 493 Ϯ 24 ⍀⅐cm2 (n ϭ reported low NaCl concentrations in non-CF and higher values in CF ASL (12), whereas other reports have concluded that the ASL NaCl is similar to that of serum in both non-CF and CF (13, 14). The difficulty in measuring ASL electrolyte concentrations is due to its tiny volume (9, 15), to liquid application to the airway Abbreviations: ASL, airway surface liquid; CF, cystic fibrosis; cfu, colony-forming units.
surface followed by measurements before a steady state is †To whom reprint requests should be addressed at: University of Iowa College of Medicine, achieved (15), and to artifacts associated with the use of filter 500 Eckstein Medical Research Building, Iowa City, IA 52242. E-mail: [email protected].
We hypothesized that lowering the ASL NaCl concentration The publication costs of this article were defrayed in part by page charge payment. Thisarticle must therefore be hereby marked “advertisement” in accordance with 18 U.S.C.
could increase the activity of endogenous antimicrobials. Such §1734 solely to indicate this fact.
11614 –11619 ͉ PNAS ͉ October 10, 2000 ͉ vol. 97 ͉ no. 21
Measurement of Xylitol Fluxes. To the apical surface we applied 60
to 103) in the presence or absence of 100 mM xylitol and ␮l of a xylitol solution containing (in mM) 138 xylitol, 53 NaCl, 4 KCl, 29 NaHCO3, 1.2 CaCl2, 0.6 MgCl2, and 1 NaH2PO4. The To test the effect of xylitol on the growth of normal nasal flora osmolality of the submucosal solution was adjusted to equal that in a carbon-starved medium, we obtained nasal swabs from three of the mucosal solution with a vapor pressure osmometer normal volunteers and inoculated the swabs into M9 medium (Wescor, Logan, UT). To the apical and basolateral solutions we alone, M9 with 100 mM xylitol, or LB medium. Bacteria were added 1 ϫ 106 cpm͞ml of 3H2O. The apical solution also received incubated at 37°C for 72 h, and the ODs were recorded.
1 ϫ 106 cpm͞ml of 14C-labeled xylitol (Moravek Biochemicals, Brea, CA). After incubation at 37°C for 1–12 h, both solutions Administration of Xylitol to the Nasal Mucosa. The study was
were collected and the volume and xylitol concentrations were approved by the University of Iowa Institutional Review Board.
determined; the methods have been described (9).
Subjects were more than 18 years old and provided written informed consent. Individuals were excluded from participation Measurement of Liquid Absorption and Xylitol. Liquid absorption
if they had a seasonal allergic rhinitis or nasal polyps, or current was measured using methods similar to those previously de- treatment with any antibiotic, steroid, or topical intranasal scribed (9). To the apical surface we applied 60 ␮l of a saline preparation. Twenty-one normal healthy subjects (10 male and solution, a xylitol solution, or a mixture of the two. The saline 11 female, ages 20–52 years) participated.
solution contained (in mM) 138 NaCl, 4 KCl, 29 NaHCO3, 1.2 The design was a double-blind, randomized, cross-over study.
CaCl2, 0.6 MgCl2, and 1 NaH2PO4. The xylitol solution con- Subjects were randomized to one of two groups: xylitol followed tained (in mM) 244 xylitol, 4 KCl, 29 NaHCO3, 1.2 CaCl2, 0.6 by saline or saline followed by xylitol. A culture of both anterior MgCl2, and 1 NaH2PO4. The osmolality of the submucosal nares was obtained on day 0. Subjects then sprayed each nostril solution was adjusted to equal that of the mucosal (300-310 with a prefilled syringe of solution four times per day for 4 days.
mOsm) solution. After incubation for 4 h, apical solutions were On the morning of day 5, subjects sprayed the final application collected under mineral oil, and the volume was measured as into each nostril at breakfast time, then a nasal swab was obtained 2 h later. No treatment was administered for the next 7 days. Then subjects repeated the protocol with the opposite Measurement of ASL Cl؊ Concentration. The ASL ClϪ concentra-
solution. The saline solution was 0.9% NaCl in water (Baxter tion was measured as described (9). To the apical surface we Health Care, Mundelein, IL); the xylitol solution was 5% xylitol applied 5 ␮l of a saline solution or a xylitol solution. The xylitol (304 mM) in water. The solutions (250 ␮l) were nebulized by solution contained (in mM) 290 xylitol, 1.2 CaCl2, and 0.6 MgCl2.
using an Accuspray syringe (Becton Dickinson Pharmaceutical The saline solution contained (in mM) 145 NaCl, 1.2 CaCl2, and Systems, Franklin Lakes, NJ). Xylitol and saline syringes were 0.6 MgCl2. To the basolateral medium (500 ␮l) we added 2.5 ϫ identical. The mass medium diameter of the particles was ϳ60 104 cpm of 3H2O and 36Cl. ASL ClϪ concentration and volume ␮m. It was impossible to disguise the sweet taste of the xylitol.
Fifteen of the 21 subjects were able to recognize the sweet taste of the xylitol; the other six subjects could not distinguish between Evaluation of the Effect of Xylitol on Bacterial Growth. Procedures
were approved by the Human Subjects Review Board of the Cultures were obtained with sterile rayon swabs (Culturette University of Iowa. Nasal lavage fluid was collected from normal Collection and Transport System; Becton Dickinson Microbiol- volunteers. A flexible catheter (18-gauge; Jelco, Tampa, FL) was ogy Systems, Sparks, MD). A swab was rotated firmly five times inserted into each nostril, and the area was flushed four times in each nostril. Swabs were collected by the same individual with 4 ml of sterile water. Cells were removed by centrifugation, throughout the study. Swabs were directly inoculated into 1 ml and the fluid was filtered with a sequential 0.8͞0.2 ␮m Supor of PBS and vortexed for 5 s, and 50 ␮l was plated by using an Acrodisc PF (Gelman). To study the effect of xylitol on bacterial automated spiral plater (Spiral Biotech, Bethesda, MD) onto killing by endogenous antimicrobial factors, we used a lumines- sheep blood agar (Remel, Lenexa, KS), and mannitol salt agar PHYSIOLOGY
cence assay of bacterial viability in which Escherichia coli (Becton Dickinson, Sparks, MD). Plates were incubated at 37°C expresses the genes from Photorhabdus luminescens (20). Bac- for 24 h, and colonies of coagulase-negative Staphylococcus teria (106) were incubated with 50 ␮l of nasal lavage fluid in colonies were identified and counted by using a Cling-On Grid serial dilutions of 300 mM xylitol or 150 mM NaCl in a 96-well (Spiral Biotech). Samples were routinely sent to the Clinical plate. Luminescence was measured after incubation at 30°C Microbiology Laboratory (University of Iowa Hospitals and Clinics) to confirm the identity of the bacteria.
To test the effect of xylitol on the growth of bacteria in a In a preliminary study in eight non-CF subjects, we found that carbon-starved medium, we grew P. aeruginosa, S. aureus, and the number of coagulase-negative Staphylococcus cultured from coagulase-negative Staphylococcus overnight in LB medium.
the nasal epithelium remained relatively stable over 4 days. A Bacteria were centrifuged; resuspended in M9 medium contain- power analysis (28) suggested that 39 independent nostrils would ing 100 mM of succinate, mannitol, or sucrose; and grown be required to show a 50% difference in the reduction in overnight at 37°C. The bacteria were centrifuged and resus- coagulase-negative Staphylococcus between treatments (power pended in M9 medium alone, M9 medium containing 100 mM of 0.84 and an f value of 0.5, assuming that the nostrils are xylitol, or 100 mM indicated metabolizable sugar as a positive independent). In contrast to non-CF subjects, we found that the control and studied in midlog phase. OD was measured after 0, numbers of bacteria cultured from the CF nasal surface were To test the antibiotic effect of xylitol, P. aeruginosa, S. aureus, and coagulase-negative Staphylococcus were grown overnight in LB medium, centrifuged, and resuspended in LB medium with Xylitol Permeability of Airway Epithelia. To examine the effect of
and without 100 mM xylitol. As a positive control, antibiotics xylitol on ASL, we used primary cultures of well-differentiated with activity to each of the bacteria were added to the medium airway epithelia (26, 27). Because airway epithelia are water (40 ␮g͞ml tobramycin or 40 ␮g͞ml levofloxacin). To test the permeable (17), lowering ASL salt concentration will require an antibiotic effect of xylitol on lower concentrations of coagulase- osmolyte with a relatively low transepithelial permeability. We negative Staphylococcus saprophyticus (ATCC 15305) over tested the xylitol permeability by applying it to the apical surface longer periods of time, we incubated log dilutions of bacteria (108 and measuring its disappearance over time. The amount of PNAS ͉ October 10, 2000 ͉ vol. 97 ͉ no. 21 ͉ 11615
Effect of apical xylitol on the rate of liquid absorption by non-CF and CF epithelia. Sixty microliters of saline solution, xylitol solution, or indicatedmixtures of the two was applied to the apical solution. Four hours later thesolution was removed to measure the rate of liquid absorption. A shortincubation period was chosen to avoid secondary changes in the epitheliumdue to the large volume of apical liquid. Data are mean Ϯ SEM (n ϭ 15) fromthree different experiments. Some SEM bars are hidden by symbols.
Apical xylitol and volume after the addition of xylitol to the apical after the addition of saline (Fig. 3A). This value is approximately surface of non-CF airway epithelia. Xylitol (138 mM in 60 ␮l) was added to the double that in non-CF epithelia and is consistent with our earlier apical surface of differentiated airway epithelia at time 0. Then, at the times measurements (9). However, with xylitol application, the ClϪ indicated, the apical liquid was removed and the quantity of xylitol (A), the concentration fell to values observed in non-CF epithelia. Xylitol liquid volume (B), and the xylitol concentration (C) were determined. Data are also increased the estimated ASL volume in both non-CF and CF mean Ϯ SEM (n ϭ 6). Some SEM bars are hidden by symbols. The asterisk epithelia (Fig. 3B). Thus, adding xylitol to the CF epithelial indicates P Ͻ 0.01 compared with time 0.
surface allowed a reduction in ClϪ concentration that was likely due to a combination of active transepithelial salt transport, ASL xylitol progressively decreased; after 12 h, 40% of the applied dilution, and the osmotic pressure generated by xylitol.
sugar had diffused to the basolateral surface (Fig. 1). Because the volume decreased with time, the xylitol concentration in- Xylitol Does Not Affect Bacterial Growth and Does Not Interfere with
creased. We obtained similar results when we measured the Killing by Endogenous Antimicrobial Factors. Earlier data showed
concentration of xylitol by NMR (not shown). Thus the xylitol that increased ionic strength, not increased osmolarity, inhibited permeability was not high, and the increase in concentration bacterial killing by endogenous airway antimicrobial factors (20).
suggested that xylitol could temporarily hold liquid on the apical To test the effect of xylitol, we collected nasal lavage fluid, which contains multiple antimicrobial factors, and examined killing of To test this hypothesis directly, we asked whether xylitol E. coli with a luminescence assay. Fig. 4 shows that nasal lavage reduces the rate of liquid absorption. We applied 60 ␮l of a saline solution, a xylitol solution, or a mixture of the two to the apical surface. The apical solution always had the same osmolarity as the basolateral solution; thus as the xylitol concentration in- creased, the NaCl concentration decreased. Four hours later, we removed the liquid and determined the rate of liquid absorption.
Fig. 2 shows that during a 4-h incubation with apical saline, both non-CF and CF epithelia absorbed liquid, and consistent with our previous report the rate of liquid absorption was greater in non-CF than in CF epithelia (9). In both non-CF and CF epithelia, increasing the xylitol concentration reduced the rate of liquid absorption (Fig. 2). Like the data in Fig. 1, these results indicate that xylitol is relatively nonpermeable because it re- duced the absorption rate and held liquid on the apical surface.
Xylitol Added to the Apical Surface Decreases ASL Cl؊ Concentration
in CF Epithelia in Vitro. We tested the ability of xylitol to reduce the
ASL salt concentration by applying a small volume (5 ␮l) of saline or xylitol to the apical surface. Twenty-four hours after the saline was applied (138 mM ClϪ), non-CF epithelia reduced the ASL ClϪ concentration to 45.3 Ϯ 1.3 mM (Fig. 3A). This value Effect of apical xylitol on non-CF and CF ASL ClϪ concentration and agrees with earlier measurements of ASL ClϪ concentration (9).
volume. Isosmotic xylitol or saline (5 ␮l) was applied to the apical surface.
Twenty-four hours later, ASL ClϪ concentration (A) and volume (B) were When xylitol was applied instead of saline, the ASL ClϪ con- determined. The asterisk indicates a difference between the saline and the centration was even lower (34.2 Ϯ 4.3 mM).
xylitol solutions (P Ͻ 0.05; n ϭ 15–18) from three CF and three non-CF In CF epithelia, the ClϪ concentration was 98 Ϯ 12 mM 24 h 11616 ͉ www.pnas.org
Effect of modifying ionic strength and xylitol concentration on killing of E. coli by nasal lavage liquid. Nasal lavage liquid was diluted with increasingconcentrations of NaCl (bottom x axis) or xylitol (top x axis). SEMs are smallerthan the symbols.
fluid killed the bacteria. Although killing was inhibited as ionic strength increased, killing was not affected by an increase in xylitol concentration. We obtained similar results with P. aerugi- We asked whether xylitol would support the growth of the predominant colonizers in CF lungs, P. aeruginosa and S. aureus. P. aeruginosa was placed in M9 medium, which lacks a carbon source. Under these conditions, the bacteria showed no growth (Fig. 5A). Adding the energy source succinate allowed bacterial growth. In contrast, there was no growth of P. aeruginosa when M9 medium was supplemented with xylitol. Likewise, xylitol failed to support the growth of S. aureus or coagulase-negative Staphylococcus (Fig. 5 B and C). Xylitol also failed to support the growth of Staphylococcus saprophyticus, which ferments xylitol (34) (Fig. 5D). To learn whether bacteria from the nasal surface could use xylitol for growth, we obtained nasal swabs and inoculated them into medium. The bacteria grew in LB medium, whereas in M9 medium alone or M9 medium containing xylitol, there was no growth (Fig. 5H). Although xylitol did not support growth, it did not inhibit the growth of P. aeruginosa, S. aureus, or coagulase-negative Staphylococcus in rich medium (Fig. 5 Effect of xylitol on growth of several bacteria. Growth of P. aerugi- E–G). As a positive control, we added a pharmaceutical antibi- PHYSIOLOGY
nosa (A), S. aureus (B), and coagulase-negative Staphylococcus (C) was mea- otic to which the bacteria were sensitive.
sured as OD ‚, M9 medium alone. Xylitol (F) or succinate, mannitol, or sucrose These results suggest that xylitol is relatively inert in terms of (E) was added to M9 medium at 100 mM as indicated. (D) S. saprophyticus was CF pathogens and bacteria on the nasal surface. It did not inhibit grown in log phase in the presence (open symbols) and absence (closed the effect of endogenous antibiotics, it did not serve as a ready symbols) of xylitol for 18 h. Starting bacterial concentrations were 108 cfu carbon source for growth, and it did not have antibiotic effects (circles), 107 cfu (triangles), and 103 cfu (squares). P. aeruginosa (E), S. aureus (F), and coagulase-negative Staphylococcus (G) were cultured in LB mediumalone (‚), LB medium with 100 mM xylitol (F), and LB medium containingtobramycin or levofloxacin (E). (H) Nasal swabs were collected and cultured Xylitol Applied to Nasal Epithelia in Vivo Reduces the Number of
for 3 days in LB medium (E), in minimal M9 medium (ᮀ), or in M9 medium Coagulase-Negative Staphylococcus. The ability of xylitol to lower
supplemented with 100 mM xylitol (F).
ASL ClϪ concentration in vitro and its relatively inert behavior toward bacteria suggested the hypothesis that xylitol might lower ASL salt concentration, thereby enhancing bacterial killing by endogenous antimicrobial factors. However, as discussed above, istered xylitol or a NaCl solution to both nostrils four times a day.
methods to accurately measure ASL salt concentration in vivo After 4 days, the culture was repeated. After a 1-week recovery remain problematic. Therefore, to test the concept, we examined period, the study was repeated with the other treatment. The the effect of xylitol administration on bacteria cultured from the intervention (290 mM xylitol or 145 mM saline) for the first nasal mucosa of normal subjects. Because pathogens such as P. treatment was chosen at random. These agents were applied to aeruginosa and S. aureus are uncommon on normal nasal mu- both nostrils in 250 ␮l with a preloaded syringe spray device.
cosa, we counted the number of coagulase-negative Staphylo- Fig. 6 shows the median change in bacterial numbers after coccus, an organism commonly found on the nasal mucosa xylitol or saline administration. ANOVA for a crossover design was applied to the change in bacterial count from pretreatment We performed a randomized, double-blind, crossover study in to posttreatment. The factors included in the ANOVA model 21 subjects. The number of coagulase-negative Staphylococcus were treatment, sequence of treatment, and nostril side. Before was determined by culture of nasal swabs. Subjects then admin- the analysis a square root transformation (sign of change times PNAS ͉ October 10, 2000 ͉ vol. 97 ͉ no. 21 ͉ 11617
airway infections develop, they may exist as biofilms that are extremely resistant to antibiotics, including endogenous antimi- crobial factors (35). Second, endogenous antimicrobial factors are more important in the innate immune defense against small numbers of bacteria; once infections develop, phagocytes and the acquired immune system become more important. Third, there is a significant inoculum effect, such that with large numbers of bacteria the potency of endogenous antimicrobial factors is reduced (7, 36). Fourth, in established infections, it seems possible that bacteria might develop the ability to metab- olize xylitol (37). However, we do not know whether the growth of P. aeruginosa or other organisms is limited by the lack of metabolic substrate. Finally, once established, infection and inflammation alter the airway architecture, causing chronic bronchiectasis, a difficult therapeutic challenge, even in patients Effect of xylitol administration to nasal mucosa on coagulase- negative Staphylococcus. Data are the decrease in colony-forming units of coagulase-negative Staphylococcus after treatment with either saline or xy- None of the subjects reported adverse effects of xylitol or litol. Shown are median Ϯ one quartile. The asterisk indicates P ϭ 0.05.
saline. Although we have not rigorously tested for safety, we predict that xylitol should be relatively nontoxic; it is present in many foods, and it has been administered intravenously in large square root change) was used to normalize the data. The analysis doses to humans (38). In addition, other agents, including showed that there was no significant effect of the sequence or the hypertonic mannitol and hypertonic saline solutions, have been nostril. Thus the comparison of xylitol vs. saline was evaluated safely aerosolized to patients with bronchiectasis and CF to from the data of both nostrils and both sequences. The average improve cough and sputum clearance (39, 40).
reduction in the xylitol-treated nostrils was 597 Ϯ 242 colony- Previous reports indicated that xylitol could reduce the growth forming units (cfu) compared with 99 Ϯ 104 cfu for saline (P ϭ of ␣-hemolytic Streptococci, including S. pneumoniae and S. 0.05). The median change was 500 (interquartile range of 1,152 mutans; however, it had little or no effect on Hemophilus to 120) for xylitol and 89 (interquartile range of 540 to Ϫ53) for influenzae or Moraxella catarrhalis (34). Moreover, we showed saline (Fig. 6). Thus xylitol significantly reduced the number of that xylitol did not have antimicrobial activity on its own against coagulase-negative Staphylococcus on the nasal surface com- coagulase-negative Staphylococcus or S. saprophyticus, yet when administered to the surface of the nasal epithelium, it decreased the number of coagulase-negative Staphylococcus. These data, Discussion
plus the finding that xylitol lowered the ASL ClϪ concentration By lowering the ASL ionic strength and enhancing the effec- in vitro, suggest that the number of nasal bacteria decreased tiveness of endogenous antimicrobials, xylitol administration to because endogenous antimicrobial factors became more active.
the airway surface might be of value in preventing or delaying the However, we have not measured a lower salt concentration in onset of CF respiratory tract infections. Enhancing the activity vivo (see above). Consequently, we cannot exclude the possibility of endogenous ASL antibacterial factors could have significant that xylitol reduced the number of bacteria by some other advantages as a preventive strategy. These factors have broad- mechanism. Although it is possible that mucociliary clearance spectrum activity against Gram-positive and Gram-negative was improved, we think this unlikely to be entirely responsible, bacteria, including the organisms that are major CF pathogens because the saline solution we administered as a control had no (1–4). Because many of the factors kill very quickly (some within significant effect. Nevertheless, it has been hypothesized that minutes), conceivably even a transient enhancement of activity mucociliary clearance is defective in CF airways because of a might be of value. Importantly, most bacteria, even the major CF reduced ASL volume (15). If this is the case, apical application pathogens, do not show resistance to antibacterial peptides, of xylitol might be of value, because our data show that it was despite growth in the presence of subinhibitory concentrations.†† poorly permeable and increased ASL volume.
In striking contrast, when currently available pharmaceutical Earlier reports have shown that xylitol used in chewing gum, antibiotics are administered to prevent or treat CF infections, in lozenges, or as syrup reduces the risk of caries and prevents resistance rapidly emerges (6). P. aeruginosa is notorious in this regard. Although in vitro acquired resistance to lysozyme has acute otitis media (24, 25). In these applications, it is possible been reported (32), it seems likely that resistance to the mixture that xylitol may have enhanced mechanical clearance of bacteria of endogenous factors will be uncommon, given the long period without providing an energy source. However, the mechanisms of coevolution of humans and bacteria. A recent report found could be more complex. The mouth and oral pharynx contain that aerosolized xylitol did not significantly reduce S. pneu- endogenous antimicrobial factors (31). If xylitol administration moniae nasal mucosal colonization in rats (33). This result is lowers the salt concentration, the activity of those factors might surprising because xylitol has been reported to have antimicro- increase. In the case of acute otitis media, a small decrease in the bial properties against this organism in vitro (34). Such results total number of bacteria at the opening of the eustachian tube highlight the need for human studies because the ASL antimi- might decrease the frequency of middle ear seeding and infec- crobial and electrolyte composition may vary significantly be- tion. Our results, plus these considerations, suggest that using xylitol to lower ASL salt concentrations could be of value for Although xylitol might be of value in preventing airway other applications, perhaps including prevention of ventilator- infections, for several reasons we think it unlikely that enhancing the activity of endogenous antimicrobials would be sufficient to In conclusion, our data suggest that xylitol delivered to the treat infections once they are established. First, when chronic airway surface may enhance the innate antibacterial defense system. These results suggest the hypothesis that xylitol or a related osmolyte could prevent or slow the onset of bacterial ††Fujii, C. A., Boggs, A. F., Hurst, M. A. & Mosca, D. A. (1999) Pediatr. Pulmonol. Suppl. 19,
infection in CF. Further studies will be required to test this 11618 ͉ www.pnas.org
We thank Pary Weber, Tom Moninger, Norma Anderson, Xuihui Liu, National Heart, Lung and Blood Institute; the Cystic Fibrosis Founda- Sam McLennan, David Welsh, and Theresa Mayhew for excellent tion; and the National Institutes of Diabetes and Digestive and Kidney assistance. We thank Drs. Barbara Conway, Pradeep Singh, and Sue Diseases) and the General Clinical Research Center (supported by Travis for helpful discussions. We thank Drs. Leon Burmeister and RR00059). This work was supported by the National Institutes of Health Miriam Zimmerman for the statistical analysis. We appreciate the help (HL42385, J.Z.), the Cystic Fibrosis Foundation, and the Howard of the Iowa Statewide Organ Procurement Organization. We thank the Hughes Medical Institute. J.Z. is supported by the Carver Charitable University of Iowa In Vitro Cell Models Core (supported in part by the Trust. M.J.W. is an Investigator of the Howard Hughes Medical Institute.
1. Lehrer, R. I. & Ganz, T. (1999) Curr. Opin. Immunol. 11, 23–27.
22. Bals, R., Wang, X., Wu, Z., Freeman, T., Bafna, V., Zasloff, M. & Wilson, J. M.
2. Huttner, K. M. & Bevins, C. L. (1999) Pediatr. Res. 45, 785–794.
(1998) J. Clin. Invest. 102, 874–880.
3. Bals, R., Weiner, D. J. & Wilson, J. M. (1999) J. Clin. Invest. 103, 303–307.
23. Holt, J. G., ed. (1984) Bergey’s Manual of Systemic Bacteriology (Lippincott, 4. Travis, S. M., Singh, P. K. & Welsh, M. J. (2000) Curr. Opin. Immunol., in press.
Philadelphia), Vol. 1, pp. 1016–1017.
5. Burns, J. L., Emerson, J., Stapp, J. R., Yim, D. L., Krzewinski, J., Louden, L., 24. Edgar, W. M. (1998) Br. Dent. J. 184, 29–32.
Ramsey, B. W. & Clausen, C. R. (1998) Clin. Infect. Dis. 27, 158–163.
25. Uhari, M., Kontiokari, T. & Niemela¨, M. (1998) Pediatrics 102, 879–884.
6. Welsh, M. J., Tsui, L. C., Boat, T. F. & Beaudet, A. L. (1995) in The Metabolic 26. Yamaya, M., Finkbeiner, W. E., Chun, S. Y. & Widdicombe, J. H. (1992) Am. J. and Molecular Basis of Inherited Disease, eds. Scriver, C. R., Beaudet, A. L., Sly, Physiol. 262, L713–L724.
W. S. & Valle, D. (McGraw-Hill, New York), pp. 3799–3876.
27. Zabner, J., Zeiher, B. G., Friedman, E. & Welsh, M. J. (1996) J. Virol. 70,
7. Smith, J. J., Travis, S. M., Greenberg, E. P. & Welsh, M. J. (1996) Cell 85,
8. Goldman, M. J., Anderson, G. M., Stolzenberg, E. D., Kari, U. P., Zasloff, M.
28. Cohen, J. (1988) Statistical Power Analysis for the Behavioral Sciences (Lawrence & Wilson, J. M. (1997) Cell 88, 553–560.
9. Zabner, J., Smith, J. J., Karp, P. H., Widdicombe, J. H. & Welsh, M. J. (1998) 29. Citron, D. M., Edelstein, M. A. C., Garcia, L. S., Roberts, G. D., Thomson, Mol. Cell 2, 397–403.
R. B. & Washington, J. A. (1994) in Bailey & Scott’s Diagnostic Microbiology, 10. Zhang, Y. & Engelhardt, J. F. (1999) Am. J. Physiol. 276, 469–476.
eds. Baron, E. J., Peterson, L. R. & Finegold, S. M. (Mosby, St. Louis), pp.
11. Baconnais, S., Tirouvanziam, R., Zahm, J.-M., de Bentzmann, S., Pe´ault, B., Balossier, G. & Puchelle, E. (1999) Am. J. Respir. Cell Mol. Biol. 20, 605–611.
30. Woods, G. L. & Washington, J. A. (1995) in Mandell, Douglas and Bennet’s 12. Joris, L., Dab, I. & Quinton, P. M. (1993) Am. Rev. Respir. Dis. 148, 1633–1637.
Principles and Practice of Infectious Diseases, eds. Mandell, G. L., Bennett, J. E.
13. Knowles, M. R., Robinson, J. M., Wood, R. E., Pue, C. A., Mentz, W. M., & Dolin, R. (Churchill Livingstone, New York), Vol. 1, pp. 169–175.
Wager, G. C., Gatzy, J. T. & Boucher, R. C. (1997) J. Clin. Invest. 100,
31. Tenovuo, J., Luminkari, M. & Soukka, T. (1991) Proc. Finn. Dent. Soc. 87,
14. Hull, J., Skinner, W., Robertson, C. & Phelan, P. (1998) Am. J. Respir. Crit. Care 32. Fleming, A. (1929) Lancet 5501, 217–220.
Med. 157, 10–14.
33. Kontiokari, T., Svanberg, M., Mattila, P., Leinonen, M. & Uhari, M. (1999) 15. Matsui, H., Grubb, B. R., Tarran, R., Randell, S. H., Gatzy, J. T., Davis, C. W.
FEMS Microbiol. Lett. 178, 313–317.
& Boucher, R. C. (1998) Cell 95, 1005–1015.
34. Kontiokari, T., Uhari, M. & Koskela, M. (1995) Antimicrob. Agents Chemother. 16. Erjefa¨lt, I. & Persson, C. G. A. (1990) Clin. Exp. Allergy 20, 193–197.
39, 1820–1823.
17. Folkesson, H. G., Matthay, M. A., Frigeri, A. & Verkman, A. S. (1996) J. Clin. 35. Singh, P. K., Schaefer, A. L., Parsek, M. R., Moninger, T. O., Welsh, M. J. & Invest. 97, 664–671.
Greenberg, E. P. (2000) Nature (London), in press.
18. Neville, M. C., Zhang, P. & Allen, J. C. (1995) in Handbook of Milk Composition, ed. Jensen, Robert G. (Academic, San Diego), pp. 577–675.
36. Thrupp, L. D. (1986) in Antibiotics in Laboratory Medicine, ed. Lorian, V.
19. Yamauchi, K., Tomita, M., Giehl, T. J. & Ellison, R. T. (1993) Infect. Immun. (Williams & Wilkins, Baltimore), pp. 93–149.
61, 719–728.
37. Doten, R. C. & Mortlock, R. P. (1985) J. Bacteriol. 161, 529–533.
20. Travis, S. M., Conway, B. A., Zabner, J., Smith, J. J., Anderson, N. N., Singh, 38. Spitz, I. M., Rubenstein, A. H., Bersohn, I. & Bassler, K. H. (1970) Metabolism P. K., Greenberg, E. P. & Welsh, M. J. (1999) Am. J. Respir. Cell Mol. Biol. 20,
19, 24–34.
39. Robinson, M., Regnis, J. A., Bailey, D. L., King, M., Bautovich, G. & Bye, 21. Singh, P. K., Jia, H. P., Wiles, K., Hesselberth, J., Liu, L., Conway, B. A., P. T. P. (1996) Am. J. Respir. Crit. Care Med. 153, 1503–1509.
Greenberg, E. P., Valore, E. V., Welsh, M. J., Ganz, T., et al. (1998) Proc. Natl. 40. Daviskas, E., Anderson, S. D., Eberl, S., Chan, H.-K. & Bautovich, G. (1999) Acad. Sci. USA 95, 14961–14966.
Am. J. Respir. Crit. Care Med. 159, 1843–1848.
PHYSIOLOGY
PNAS ͉ October 10, 2000 ͉ vol. 97 ͉ no. 21 ͉ 11619

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