Not all infectious agents have the same epidemic potential, and this can vary widely within the same species. Rapid determination of this potential is essential to optimize control of infectious diseases. It is now accepted that identification with the species is clearly insufficient to identify an epidemic and to carry out epidemiological analyzes. Indeed, if the same bacterial species can present a great diversity of strains, it is organized in clonal complexes having strong variations of clinical and epidemiological expression.

More specifically, on a bio-epidemiological level, the clonal identification of the bacterial agent is a real asset because it can make it possible to identify the highly virulent strains or known to be resistant, the clones associated with nosocomial infections, the source of the infection. an epidemic and to follow its spatio-temporal extension, to know the epidemiological antiquity of the clone, to follow or rebuild a chain of transmission, to discover epidemic clusters.

There are rapid identification techniques, for example by polymerase chain reaction (PCR), but which are targeted at particular genomic compositions previously identified.

Routine bacterial identification now rests on the determination of the protein composition by mass spectrometry (MALDI-TOF). The bacterial spectrum is compared to a reference library of protein composition, thus obtaining an identification equivalent to that based on the 16s RNA (ribonucleic acid 16s) and can descend to an infra-species level.

The aim of this work is to use the proteome part of the MALDI-TOF spectrum to identify peaks that signal clonality and to determine proteomic fingerprintings that can be used for epidemiological and clinical purposes.

Instead of relying on expensive genomic methods, the identification of the clonal characteristics of the strains will rely on the bacterial proteome present on the MALDI-TOF spectrum that is produced during the routine identification of the bacterium.

The results are intended to feed a complementary knowledge base

Inclusion Criteria:

• bacterial identification by Matrix Assisted Laser Desorption Ionisation - Time of Flight (MALDI-TOF)

Exclusion Criteria:

• Unidentified strain or noisy spectrum

Bacterial identification of patients taken as part of the care