This study aims at determining within a short time (<3h) the susceptibility to clinical isolates of E. coli to the major antibiotics directly from positive blood cultures.

The resistance to antibiotic is a concern for the great majority of pathogenic bacteria. The proportion of antibiotic-resistant bacteria is particularly high in hospital settings. The accumulation of resistance mechanisms can lead to multidrug resistance, therapeutic impasses and a subsequent higher mortality of infected patients. The use of antibiotics in humans and animals creates a selection pressure that favors the dissemination of antibiotic resistant strains. It's necessary to optimize antibiotic consumption to limit the spread of these bacteria. It requires both the fast bacterial identification and the fast determination of their resistance profile in order to use narrower-spectrum compounds.

Usually antibiotic susceptibility testing usually takes 18-24 hours. Mass Spectrometry type Matrix-Assisted Laser Desorption Ionization Time-Of-Flight (MALDI-TOF MS) has become a valuable tool in clinical laboratories for pathogen identification. Preliminary data showed that susceptible and resistant bacteria can be differentiated within 1 or 2 hours with a new technology called 'MS-ASTRA' based on a lower global peak intensity in the presence of the antibiotic of interest (at a concentration corresponding to the susceptibility breakpoint defined by the EUCAST) than in its absence. The objective of this study is to evaluate the performances of this new MALDI-TOF MS method on a panel of wild-type and resistant clinical isolates.

This study aims to determine the resistance of Escherichia coli isolates to cefotaxime, piperacillin-tazobactam, amoxicillin and to implement the method to positive blood cultures. Minimal Inhibitory Concentrations will be determined the standard agar dilution method.

Results and full analyze are deliverable within 2 years. The data obtained with the MS-ASTRA technique will be compared with the resistance status of the clinical isolates. The shortest incubation time (1 or 2 hours) that gives the more accurate result will be evaluate.The antibiotic savings that the implementation of this new method could have allowed will be evaluate.

Inclusion Criteria:

• All patients hospitalized in the hospital of Besançon, with a sepsis with E. coli.

Exclusion Criteria:

• Patients without sepsis with E. coli

All patients hospitalized in the hospital of Besançon, with a sepsis with E. coli.