Nitrous oxide production in sputum from cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection.
Chronic lung infection by Pseudomonas aeruginosa is the major severe complication in cystic fibrosis (CF) patients, where P. aeruginosa persists and grows in biofilms in the endobronchial mucus under hypoxic conditions. Numerous polymorphonuclear leukocytes (PMNs) surround the biofilms and create local anoxia by consuming the majority of O2 for production of reactive oxygen species (ROS). We hypothesized that P. aeruginosa acquires energy for growth in anaerobic endobronchial mucus by denitrification, which can be demonstrated by production of nitrous oxide (N2O), an intermediate in the denitrification pathway. We measured N2O and O2 with electrochemical microsensors in 8 freshly expectorated sputum samples from 7 CF patients with chronic P. aeruginosa infection. The concentrations of NO3(-) and NO2(-) in sputum were estimated by the Griess reagent. We found a maximum median concentration of 41.8 µM N2O (range 1.4-157.9 µM N2O). The concentration of N2O in the sputum was higher below the oxygenated layers. In 4 samples the N2O concentration increased during the initial 6 h of measurements before decreasing for approximately 6 h. Concomitantly, the concentration of NO3(-) decreased in sputum during 24 hours of incubation. We demonstrate for the first time production of N2O in clinical material from infected human airways indicating pathogenic metabolism based on denitrification. Therefore, P. aeruginosa may acquire energy for growth by denitrification in anoxic endobronchial mucus in CF patients. Such ability for anaerobic growth may be a hitherto ignored key aspect of chronic P. aeruginosa infections that can inform new strategies for treatment and prevention.
Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark ; Department of International Health, Immunology and Microbiology, Faculty of Health Sciences University of Copenhagen, Copenhagen, Denmark.
Mette
M
Kolpen
Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark ; Plant Functional Biology and Climate Change Cluster, University of Technology Sydney, Sydney, Australia ; Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.
Michael
M
Kühl
Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark ; Department of International Health, Immunology and Microbiology, Faculty of Health Sciences University of Copenhagen, Copenhagen, Denmark.
Thomas
T
Bjarnsholt
Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.
Claus
C
Moser
Copenhagen CF Centre, Rigshospitalet, Copenhagen, Denmark.
Christine Rønne
CR
Hansen
Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark.
Lars
L
Liengaard
Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.
Arsalan
A
Kharazmi
Copenhagen CF Centre, Rigshospitalet, Copenhagen, Denmark.
Tanja
T
Pressler
Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark ; Department of International Health, Immunology and Microbiology, Faculty of Health Sciences University of Copenhagen, Copenhagen, Denmark.
Niels
N
Høiby
Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.
Peter Østrup
PØ
Jensen
D000328:Adult; D015374:Biosensing Techniques; D002908:Chronic Disease; D003550:Cystic Fibrosis / Q000150:complications* / Q000382:microbiology*; D003710:Demography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011552:Pseudomonas Infections / Q000150:complications* / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000502:physiology*; D013183:Sputum / Q000378:metabolism*; D055815:Young Adult
D009566:Nitrates; D009573:Nitrites; D009609:Nitrous Oxide; D010100:Oxygen