Oral bacteria--the missing link to ambiguous findings of exhaled nitrogen oxides in cystic fibrosis.
BACKGROUND
Nitrite in exhaled breath condensate (EBC) has been shown to be elevated in cystic fibrosis (CF), while exhaled nitric oxide (FENO) is paradoxically low. This has been argued to reflect increased metabolism of NO while its diffusion is obstructed by mucus. However, we wanted to study the possible influence of salivary nitrite and bacterial nitrate reduction on these parameters in CF patients by the intervention of an anti-bacterial mouthwash.


METHODS
EBC and saliva were collected from 15 CF patients (10-43 years) and 15 controls (9-44 years) before and 5 min after a 30s chlorhexidine mouthwash, in parallel with measurements of FENO. Nitrite and nitrate concentrations were measured fluorometrically.


RESULTS
EBC nitrite, but not nitrate, was significantly higher in the CF patients (median 3.6 vs 1.3 microM in controls, p<0.05) and decreased after mouthwash in both groups (3.6-1.4 microM, p<0.01; 1.3-0.5 microM, p<0.01). Salivary nitrite correlated significantly to EBC nitrite (r=0.60, p<0.001) and decreased correspondingly after chlorhexidine, whereas salivary nitrate increased. FENO was lower in CF and the difference between patients and controls was accentuated after mouthwash (5.4 vs 8.4 ppb in controls, p<0.05).


CONCLUSIONS
EBC nitrite mainly originates in the pharyngo-oral tract and its increase in CF is possibly explained by a regional change in bacterial activity. The limited lower airway contribution supports the view of a genuinely impaired formation and metabolism of NO in CF, rather than poor diffusion of the molecule.
Zetterquist
Wilhelm
W
Department of Woman and Child Health, Karolinska Institutet, Stockholm S-171 76, Sweden. wilhelm.zetterquist@ki.se
Marteus
Helena
H
Kalm-Stephens
Pia
P
Näs
Elisabeth
E
Nordvall
Lennart
L
Johannesson
Marie
M
Alving
Kjell
K
D000293:Adolescent; D000328:Adult; D001419:Bacteria / Q000378:metabolism*; D001944:Breath Tests / Q000379:methods; D002648:Child; D002710:Chlorhexidine; D003550:Cystic Fibrosis / Q000378:metabolism* / Q000382:microbiology / Q000503:physiopathology; D045853:Exhalation; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D009067:Mouthwashes; D009566:Nitrates / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D012463:Saliva / Q000378:metabolism*; D055815:Young Adult
D009067:Mouthwashes; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D002710:Chlorhexidine