Microbial identification is a critical process aiming at identifying the species contained in a biological sample,- with applications in healthcare,- industry or even national security. Traditionally,- this process relies either on MALDI-TOF mass spectroscopy,- on biochemical tests and on the observation of the morphology of colonies after growth on a Petri dish. Here is presented an innovative method for label-free optical identification of pathogens,- based on the multispectral infrared imaging of colonies. This lensless imaging technique enables a high-throughput analysis and wide-field analysis of agar plates. It could yield very high correct identification rates as it relies on an optical fingerprint gathering both spectroscopic and morphologic features. The setup consists of a Quantum Cascade Lasers light source and an imager,- a square 2.72 by 2.72 mm uncooled bolometer array. Microorganisms to be analyzed are streaked on a porous growth support compatible with infrared imaging,- laid on top of an agar plate for incubation. When imaging is performed,- growth support is put in close contact with the imaging sensor and illuminated at different wavelengths. After acquisition,- an image descriptor based on spectral and morphological features is extracted for each microbial colony. Supervised classification is finally performed with a Support Vector Machine algorithm and tested with tenfold cross-validation. A first database collecting 1012 multispectral images of colonies belonging to five different species has already been acquired with this system,- resulting in a correct identification rate of 92%. For these experiments,- multispectral images are acquired at nine different wavelengths,- between 5.6 and 8 mum. Considering the optimization possibilities of the image descriptors currently used and the ongoing development of the uncooled bolometers technology,- these very first results are promising and could be dramatically improved with further experiments. Thereby,- mid-infrared multispectral lensless imaging has the potential to become a fast and precise Petri dish analysis technology. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.