title: 13[C]-urea breath test as a novel point-of-care biomarker for tuberculosis treatment and diagnosis.
abstract: BACKGROUND
  Pathogen-specific metabolic pathways may be detected by breath tests based on introduction of stable isotopically-labeled substrates and detection of labeled products in exhaled breath using portable infrared spectrometers.
  
  
  RESULTS
  We tested whether mycobacterial urease activity could be utilized in such a breath test format as the basis of a novel biomarker and diagnostic for pulmonary TB. Sensitized New-Zealand White Rabbits underwent bronchoscopic infection with either Mycobacterium bovis or Mycobacterium tuberculosis. Rabbits were treated with 25 mg/kg of isoniazid (INH) approximately 2 months after infection when significant cavitary lung pathology was present. [(13)C] urea was instilled directly into the lungs of intubated rabbits at selected time points, exhaled air samples analyzed, and the kinetics of delta(13)CO(2) formation were determined. Samples obtained prior to inoculation served as control samples for background (13)CO(2) conversion in the rabbit model. (13)CO(2), from metabolic conversion of [(13)C]-urea by mycobacterial urease activity, was readily detectable in the exhaled breath of infected rabbits within 15 minutes of administration. Analyses showed a rapid increase in the rate of (13)CO(2) formation both early in disease and prior to treatment with INH. Following INH treatment, all evaluable rabbits showed a decrease in the rate of (13)CO(2) formation.
  
  
  CONCLUSIONS
  Urea breath testing may provide a useful diagnostic and biomarker assay for tuberculosis and for treatment response. Future work will test specificity for M. tuberculosis using lung-targeted dry powder inhalation formulations, combined with co-administering oral urease inhibitors together with a saturating oral dose of unlabeled urea, which would prevent the delta(13)CO(2) signal from urease-positive gastrointestinal organisms.
authors.affiliation: Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Mandeep S
authors.initials: MS
authors.lastname: Jassal
authors.forename: Gueno G
authors.initials: GG
authors.lastname: Nedeltchev
authors.forename: Jong-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Seong Won
authors.initials: SW
authors.lastname: Choi
authors.forename: Viorel
authors.initials: V
authors.lastname: Atudorei
authors.forename: Zachary D
authors.initials: ZD
authors.lastname: Sharp
authors.forename: Vojo
authors.initials: V
authors.lastname: Deretic
authors.forename: Graham S
authors.initials: GS
authors.lastname: Timmins
authors.forename: William R
authors.initials: WR
authors.lastname: Bishai
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests / Q000379:methods*; D001999:Bronchoscopy; D002247:Carbon Isotopes; D007114:Immunization; D008168:Lung / Q000473:pathology; D009163:Mycobacterium bovis / Q000502:physiology; D010641:Phenotype; D019095:Point-of-Care Systems; D011817:Rabbits; D016896:Treatment Outcome; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D014508:Urea / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D002247:Carbon Isotopes; D014508:Urea
references.citation: J Clin Microbiol. 2010 Jan;48(1):229-37
references.pmid: 19864480
references.citation: Curr Opin Pulm Med. 2010 May;16(3):271-84
references.pmid: 20224410
references.citation: J Clin Microbiol. 1979 Aug;10(2):134-7
references.pmid: 389943
references.citation: Lancet Infect Dis. 2009 Mar;9(3):162-72
references.pmid: 19246020
references.citation: Infect Immun. 2009 Feb;77(2):598-603
references.pmid: 19064634
references.citation: J Gastroenterol. 2008;43(2):108-14
references.pmid: 18306984
references.citation: Int J Tuberc Lung Dis. 2008 Nov;12(11):1226-34
references.pmid: 18926032
references.citation: Gut. 1991 Aug;32(8):866-70
references.pmid: 1885067
references.citation: Science. 2005 Jan 14;307(5707):223-7
references.pmid: 15591164
references.citation: Am Rev Respir Dis. 1974 Jan;109(1):147-51
references.pmid: 4203284
references.citation: Expert Rev Med Devices. 2009 Mar;6(2):147-55
references.pmid: 19298162
references.citation: Eur J Gastroenterol Hepatol. 2002 Oct;14(10):1161-2
references.pmid: 12362109
references.citation: J Infect. 2008 Aug;57(2):103-9
references.pmid: 18649943
references.citation: Am Rev Respir Dis. 1961 May;83:757-61
references.pmid: 13777146
references.citation: Am J Respir Crit Care Med. 2003 May 15;167(10):1299-301
references.pmid: 12738594
references.citation: J Dig Dis. 2007 Nov;8(4):211-5
references.pmid: 17970879
references.citation: Lancet Infect Dis. 2007 Jul;7(7):481-90
references.pmid: 17524807
references.citation: Int J Syst Bacteriol. 1992 Apr;42(2):315-23
references.pmid: 1581193
references.citation: Am J Respir Crit Care Med. 2003 May 15;167(10):1348-54
references.pmid: 12519740
references.citation: J Exp Med. 1991 Oct 1;174(4):881-9
references.pmid: 1919441
references.citation: Int J Tuberc Lung Dis. 2008 Sep;12(9):1021-9
references.pmid: 18713499
references.citation: Lancet. 2007 Jun 16;369(9578):2042-2049
references.pmid: 17574096
references.citation: Lancet. 1987 Jun 13;1(8546):1367-8
references.pmid: 2884468
references.citation: PLoS One. 2008 Apr 09;3(4):e1933
references.pmid: 18398459
references.citation: Crit Rev Microbiol. 1984;11(1):1-12
references.pmid: 6373150
references.citation: Aliment Pharmacol Ther. 2002 Mar;16 Suppl 1:3-15
references.pmid: 11849122
references.citation: Curr Opin Infect Dis. 2008 Oct;21(5):454-61
references.pmid: 18725793
references.citation: J Clin Microbiol. 1975 May;1(5):465-8
references.pmid: 1176615
references.citation: J Clin Microbiol. 1977 Jun;5(6):656-7
references.pmid: 328530
references.citation: Am Rev Respir Dis. 1993 Apr;147(4):1062-3
references.pmid: 8466107
references.citation: Clin Biochem. 2005 Aug;38(8):731-4
references.pmid: 15963485
references.citation: Int J Tuberc Lung Dis. 2003 Jul;7(7):684-9
references.pmid: 12870691
references.citation: Tuberculosis (Edinb). 2008 Aug;88 Suppl 1:S75-83
references.pmid: 18762155
references.citation: J Clin Microbiol. 1982 Mar;15(3):478-80
references.pmid: 7042746
references.citation: Nature. 2000 Jun 22;405(6789):962-6
references.pmid: 10879539
references.citation: PLoS Med. 2006 Nov;3(11):e466
references.pmid: 17132069
references.citation: J Antimicrob Chemother. 1992 May;29(5):477-93
references.pmid: 1624388
references.citation: Am J Gastroenterol. 1999 Jul;94(7):1983-4
references.pmid: 10406282