Text Box: 11:50 AM Text Box: MICROBIOLOGY Text Box: Identification of Pseudomonas spp. Using Fourier Transform Infrared (FT-IR) Spectroscopy and Cluster Analysis Text Box: Michele Manuzon, N. Kocaoglu-Vurma, Dr. Rodriguez-Saona, and Dr. Harper Text Box: Pseudomonas spp. are among the most common spoilage organisms in milk and other dairy products. They are usually found as part of surface-associated communities called biofilms in food processing environments. The rapid detection and enumeration of these organisms could prove useful for the identification of specific contamination sources in dairy plants, thereby facilitating the early implementation of corrective actions during routine equipment cleaning processes. In this study, the use of Fourier transform infrared (FT-IR) spectroscopy for the rapid identification of 15 strains of Pseudomonas belonging to seven species was evaluated. The isolates were grown in tryptic soy broth (TSB) overnight at 30°C, serially diluted in the same culture medium and filtered using hydrophobic grid membranes (HGM). The membrane filters were incubated in tryptic soy agar (TSA) for 24-48 h at 30°C and vacuum-dried. The bacterial colonies were analyzed directly using attenuated total reflectance (ATR) FT-IR microspectroscopy, and the spectra from 4000 to 700 cm-1 of the colonies were collected. Results indicated that different species of Pseudomonas had unique, reproducible infrared spectra in the fingerprint region (1200 to 900 cm-1). Multivariate analysis of the derivatized spectra, using soft independent modeling of class analogy (SIMCA), showed that the different species of Pseudomonas formed distinct clusters from each other presumably due to differences in cell wall components. FT-IR coupled with multivariate data analysis offers a rapid, non-destructive, and reliable approach for identifying and discriminating different Pseudomonas at the species and strain levels.