No abstract

We report here on a novel methodology in detecting Mycobacterium bovis (M. bovis) infection in cattle, based on identifying unique volatile organic compounds (VOCs) or a VOC profile in the breath of cattle. The study was conducted on an M. bovis-infected dairy located in southern Colorado, USA, and on two tuberculosis-free dairies from northern Colorado examined as negative controls. Gaschromatography/mass-spectrometry analysis revealed the presence of 2 VOCs associated with M. bovis infection and 2 other VOCs associated with the healthy state in the exhaled breath of M. bovis-infected and not infected animals, yielding distinctly different VOC patterns for the two study groups. Based on these results, a nanotechnology-based array of sensors was then tailored for detection of M. bovis-infected cattle via breath. Our system successfully identified all M. bovis-infected animals, while 21% of the not infected animals were classified as M. bovis-infected. This technique could form the basis for a real-time cattle monitoring system that allows efficient and non-invasive screening for new M. bovis infections on dairy farms.

Bovine tuberculosis, caused by Mycobacterium bovis, is a zoonotic disease of international public health importance. Ante-mortem surveillance is essential for control; however, current surveillance tests are hampered by limitations affecting ease of use or quality of results. There is an emerging interest in human and veterinary medicine in diagnosing disease via identification of volatile organic compounds produced by pathogens and host-pathogen interactions. The objective of this pilot study was to explore application of existing human breath collection and analysis methodologies to cattle as a means to identify M. bovis infection through detection of unique volatile organic compounds or changes in the volatile organic compound profiles present in breath. Breath samples from 23 male Holstein calves (7 non-infected and 16 M. bovis-infected) were collected onto commercially available sorbent cartridges using a mask system at 90 days post-inoculation with M. bovis. Samples were analyzed using gas chromatography-mass spectrometry, and chromatographic data were analyzed using standard analytical chemical and metabolomic analyses, principle components analysis, and a linear discriminant algorithm. The findings provide proof of concept that breath-derived volatile organic compound analysis can be used to differentiate between healthy and M. bovis-infected cattle.

Manganese oxides in soils may be sites for sorption of heavy‐metal cations, but the roles of pH‐dependent charge and oxide mineralogy remain unclear as controls on exchangeability of the metals. A model soil‐oxide system tested the effect of pH on the amount and form of Zn retained in exchangeable or nonexchangeable fractions on birnessite‐hausmannite‐coated sand or pyrolusite‐coated sand. Two Zn treatments, 250 and 2500 µmol/kg sand, were used to determine the effect of Zn concentration on the form of Zn retained. Surface charge for the birnessite‐hausmannite‐coated sand and pyrolusite‐coated sand increased across the pH range from 4 to 7.6, but surface charge was found to be a poor predictor of the amount and form of Zn retained even though the oxides increased Zn sorption by the sand. The distribution between the exchangeable and nonexchangeable Zn fractions changed from predominantly exchangeable to predominantly nonexchangeable Zn due to the oxide coatings and higher pHs. The difference in the exchangeable and nonexchangeable Zn retention by the two sands was attributed to mineralogical constraints on the type of surface functional groups. The mechanisms proposed to account for the nonexchangeable retention of Zn on both oxide‐coated sand surfaces were hydrolysis of the Zn followed by chemisorption to the oxide surface.