title: Detection of Escherichia coli O157:H7 and Salmonella typhimurium using filtration followed by Fourier-transform infrared spectroscopy.
abstract: Fourier-transform infrared spectroscopy has been successfully used as a nondestructive method for identifying, distinguishing, and classifying pathogens. In this study, a less time-consuming Fourier-transform infrared procedure was developed to identify Escherichia coli O157:H7 and Salmonella Typhimurium. Samples containing 10(9) CFU/ml were prepared in tryptic soy broth and then serially diluted (up to eight times) to obtain bacterial solutions of 10(9) to 10 CFU/ml. These dilutions were incubated at 37 degrees C for 6 h, samples were filtered through a Metricel filter hourly (for 0 to 6 h), and spectra were obtained using a ZnSe contact attenuated total reflectance accessory on a Continu mum infrared microscope. Midinfrared spectra (4,000 to 700 cm(-1)) of Salmonella Typhimurium and E. coli O157:H7 were generated, and peak areas in the region of 1,589 to 1,493 cm(-1) were used to detect the pathogens. Initially, detection limits were between 10(6) and 10(7) CFU/ml without preenrichment, and samples starting with 500 CFU/ml were detectable following incubation for 6 h, when counts reached at least 10(6) CFU/ ml. Compared with results of previously published studies in which Fourier-transform infrared spectroscopy was used to identify select pathogens, this method is more rapid and less expensive for practical large-scale sample analysis.
authors.affiliation: Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, Indiana 47907-2009, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Burgula
authors.forename: D
authors.initials: D
authors.lastname: Khali
authors.forename: S
authors.initials: S
authors.lastname: Kim
authors.forename: S S
authors.initials: SS
authors.lastname: Krishnan
authors.forename: M A
authors.initials: MA
authors.lastname: Cousin
authors.forename: J P
authors.initials: JP
authors.lastname: Gore
authors.forename: B L
authors.initials: BL
authors.lastname: Reuhs
authors.forename: L J
authors.initials: LJ
authors.lastname: Mauer
mesh_terms: D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005374:Filtration; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D012486:Salmonella typhimurium / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013696:Temperature; D013997:Time Factors