Analysis of volatile fingerprints for monitoring anti-fungal efficacy against the primary and opportunistic pathogen Aspergillus fumigatus.

The aims of this study were to use qualitative volatile fingerprints obtained using a hybrid sensor array system to screen anti-fungals for controlling the important lung infecting fungus, Aspergillus fumigatus, especially in immunocompromised patients. SIFT-MS was also used to try and identify key volatiles produced by A. fumigatus. Initial studies were carried out to identify the ED(50) and ED(90) (effective dose) for inhibiting growth of A. fumigatus using three anti-fungal compounds, benomyl, tebuconazole and fluconazole. Subsequent studies involved inoculation of malt extract agar plates with spores of A. fumigatus (25 and 37°C) over periods of 24-72 h to examine the headspace volatile fingerprints generated from the sample treatments using the hybrid sensor array system to compare controls and ED(50)/ED(90) concentrations. The sensor responses showed discrimination between treatments after 48-h incubation when benomyl and tebuconazole were used against A. fumigatus at 37°C using Principal Components Analysis and Cluster Analysis. SIFT-MS analysis showed that methyl pentadiene, ethanol, isoprene and methanol were key biomarker volatiles produced by A. fumigatus in the presence of anti-fungal compounds. This may also be a good approach for the development of rapid screening of anti-microbial compounds and potentially useful for monitoring the possible build up of resistance to specific drug types. Volatile fingerprints produced by patient samples could also be used to evaluate whether lung infections are caused by bacteria or specific fungi to facilitate early diagnosis and enable the right drug treatment to be prescribed.

Electronic nose analysis of bronchoalveolar lavage fluid.

BACKGROUND: Electronic nose (E-nose) technology has been successfully used to diagnose a number of microbial infections. We have investigated the potential use of an E-nose for the diagnosis of ventilator-associated pneumonia (VAP) by detecting micro-organisms in bronchoalveolar lavage (BAL) fluid in a prospective comparative study of E-nose analysis and microbiology. MATERIALS AND METHODS: BAL samples were collected using a blind technique from 44 patients following a minimum of 72 h mechanical ventilation. Control samples were collected from six patients mechanically ventilated on the intensive care unit (ICU) immediately following elective surgery. Quantitative microbiological culture and E-nose headspace analysis of the BAL samples were undertaken. Multivariate analysis was applied to correlate E-nose response with microbiological growth. RESULTS: E-nose fingerprints correctly classified 77% of the BAL samples, with and without microbiological growth from patients not on antibiotics. Inclusion of patients on antibiotics resulted in 68% correct classification. Seventy per cent of isolates, cultured in the laboratory from the clinical samples, were accurately discriminated into four clinically significant groups. CONCLUSIONS: E-nose technology can accurately discriminate between different microbial species in BAL samples from ventilated patients on ICU at risk of developing VAP with accuracy comparable with accepted microbiological techniques.

Detection and discrimination between ochratoxin producer and non-producer strains of Penicillium nordicum on a ham-based medium using an electronic nose.

The aim of this work was to evaluate the potential use of qualitative volatile patterns produced by Penicillium nordicum to discriminate between ochratoxin A (OTA) producers and non-producer strains on a ham-based medium. Experiments were carried out on a 3% ham medium at two water activities (aw ; 0.995, 0.95) inoculated with P. nordicum spores and incubated at 25°C for up to 14 days. Growing colonies were sampled after 1, 2, 3, 7 and 14 days, placed in 30-ml vials, sealed and the head space analysed using a hybrid sensor electronic nose device. The effect of environmental conditions on growth and OTA production was evaluated based on the qualitative response. However, after 7 days, it was possible to discriminate between strains grown at 0.995 aw, and after 14 days, the OTA producer and non-producer strain and the controls could be discriminated at both aw levels. This study suggests that volatile patterns produced by P. nordicum strains may differ and be used to predict the presence of toxigenic contaminants in ham. This approach could be utilised in ham production as part of a quality assurance system for preventing OTA contamination.