Detection and discrimination of coliform bacteria with gas sensor arrays

Electronic noses, which are used for characterizing complex vapors and aromas, may be useful for detection of bacterial contamination or diagnosis of infections, if minimal standards of selectivity and sensitivity can be met. A culture of Enterobacter aerogenes is readily discriminated from an Escherichia coli strain using principal components analysis (PCA) of data generated by an array of eight quartz microbalance (QMB), eight metal oxide semiconductor (MOX), and four electrochemical gas sensors. Two strains of E. coli were not discriminated under identical conditions. Retaining headspace air in a sealed vial containing growing bacteria results in an enhancement of sensitivity, so that a concentration of bacteria of about 5×108/ml may be both detected and distinguished from other species. Improvements in sensitivity to levels useful for practical applications will require enhancement of sensors, sampling system, and pattern classification.