The present invention is directed to a method for separating, characterizing and/or identifying microorganisms in a test sample. The method of the invention comprises an optional lysis step for lysing non-microorganism cells that may be present in a test sample, followed by a subsequent separation step. The method may be useful for the separation, characterization and/or identification of microorganisms from complex samples such as blood-containing culture media. The invention further provides for Raman spectroscopic interrogation of the separated microorganism sample to produce measurements of the microorganism and characterizing and/or identifying the microorganism in the sample using said Raman spectroscopic measurements.