Microorganism characterization using ATR–FTIR on an ultrathin polystyrene layer

An ultrathin polystyrene layer on a diamond ATR was used for solid-phase microextraction of Escherichia coli, Klebsiella pneumoniae and Enterobacter aerogenes. The polymer provides a recognition layer that capitalizes on the tendency of many bacteria to adhere to hydrophobic surfaces. When coupled with FTIR spectroscopy this method allowed for discrimination of the three bacteria investigated by direct application of the liquid suspensions followed by washing. A drying step was not necessary, since both the contributions of the polystyrene and that of water were effectively removed by weighted subtraction. Under conditions where the film was exposed to phosphate buffered saline, cell adhesion was essentially irreversible. However, the bound cells could be cleaned from the polymer layer by washing with sodium dodecyl sulfate. Moreover, when the recognition layer was first blocked with casein or bovine serum albumin, cell adhesion was not observed. This work demonstrates the potential of polymer coated ATR–FTIR for rapid (<15 min) bacterial detection and identification in liquids with little or no sample preparation.