Ziehl-Neelsen (ZN) staining for the diagnosis of tuberculosis (TB) is time-consuming and operator dependent and lacks sensitivity. A new method is urgently needed. We investigated the potential of an electronic nose (EN) (gas sensor array) comprising 14 conducting polymers to detect different Mycobacterium spp. and Pseudomonas aeruginosa in the headspaces of cultures, spiked sputa, and sputum samples from 330 cultureproven and human immunodeficiency virus-tested TB and non-TB patients. The data were analyzed using principal-component analysis, discriminant function analysis, and artificial neural networks. The EN differentiated between different Mycobacterium spp. and between mycobacteria and other lung pathogens both in culture and in spiked sputum samples. The detection limit in culture and spiked sputa was found to be 1 ؋ 10 4 mycobacteria ml ؊1 . After training of the neural network with 196 sputum samples, 134 samples (55 M. tuberculosis culture-positive samples and 79 culture-negative samples) were used to challenge the model. The EN correctly predicted 89% of culture-positive patients; the six false negatives were the four ZN-negative and two ZN-positive patients. The specificity and sensitivity of the described method were 91% and 89%, respectively, compared to culture. At present, the reasons for the false negatives and false positives are unknown, but they could well be due to the nonoptimized system used here. This study has shown the ability of an electronic nose to detect M. tuberculosis in clinical specimens and opens the way to making this method a rapid and automated system for the early diagnosis of respiratory infections.

A number of rapid identification methods have been developed to improve the accuracy for diagnosis of tuberculosis and to speed up the presumptive identification of Mycobacterium species. Most of these methods have been validated for a limited group of microorganisms only. Here, Raman spectroscopy was compared to 16S rRNA sequencing for the identification of Mycobacterium tuberculosis complex strains and the most frequently found strains of nontuberculous mycobacteria (NTM). A total of 63 strains, belonging to eight distinct species, were analyzed. The sensitivity of Raman spectroscopy for the identification of Mycobacterium species was 95.2%. All M. tuberculosis strains were correctly identified (7 of 7; 100%), as were 54 of 57 NTM strains (94%). The differentiation between M. tuberculosis and NTM was invariably correct for all strains. Moreover, the reproducibility of Raman spectroscopy was evaluated for killed mycobacteria (by heat and formalin) versus viable mycobacteria. The spectra of the heat-inactivated bacteria showed minimal differences compared to the spectra of viable mycobacteria. Therefore, the identification of mycobacteria appears possible without biosafety level 3 precautions. Raman spectroscopy provides a novel answer to the need for rapid species identification of cultured mycobacteria in a clinical diagnostic setting.Mycobacteria cause a variety of infections in humans. Classically defined lung tuberculosis (TB) is predominantly caused by M. tuberculosis complex. The number of new cases is estimated at nine million per year worldwide, and the disease causes more than two millions deaths annually (17). In addition, the incidence of pulmonary disease caused by nontuberculous mycobacteria (NTM) appears to be increasing worldwide (1, 6). The clinical features of NTM-derived pulmonary disease are in some cases indistinguishable from those of tuberculosis. Because the treatment and the epidemiology of NTM-derived infections differ significantly from TB caused by M. tuberculosis complex bacteria, the timely and correct identification of causative organisms is mandatory for diagnosis, therapy, and control.Conventional approaches to the diagnosis of mycobacterial infection rely on tests that are far from optimal. For example, sputum smear microscopy is insensitive, laborious, and timeconsuming. Culture is technically complex and time-consuming, has a sensitivity of only 80 to 85%, and is scarcely available in high-prevalence settings. Chest radiography is nonspecific and not widely implemented either. Tuberculin skin testing is imprecise, and the results are often nonspecific (3). In the last decade, a number of rapid diagnostic tests have been developed in an effort to improve the diagnostic accuracy for TB and to speed up presumptive identification. PCR and other molecular amplification techniques are the most prominent among these new tools. Although promising, none are more than adjunctive to the diagnosis of TB, since the sensitivities of these tests vary widely. The most reliable results are fou...

Clinical relevance of nontuberculous mycobacteria (NTM) isolated from 180 chronically ill patients and 385 healthy controls in Zambia was evaluated to examine the contribution of these isolates to tuberculosis (TB)-like disease. The proportion of NTM-positive sputum samples was signifi cantly higher in the patient group than in controls; 11% and 6%, respectively (p<0.05). NTM-associated lung disease was diagnosed for 1 patient, and a probable diagnosis was made for 3 patients. NTM-positive patients and controls were more likely to report vomiting and diarrhea and were more frequently underweight than the NTM-negative patients and controls. Chest radiographs of NTM-positive patients showed deviations consistent with TB more frequently than those of controls. The most frequently isolated NTM was Mycobacterium avium complex. Multiple, not previously identifi ed mycobacteria (55 of 171 NTM) were isolated from both groups. NTM probably play an important role in the etiology of TB-like diseases in Zambia.

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