Blood culture samples from bacteremia patients positive for Gram-negative bacteria will be tested for antibacterial susceptibility using Resistell Phenotech device. The results will be compared with current AST gold standard tests to calculate sensitivity, specificity, and accuracy of Resistell Phenotech device.

NANO-RAST: Nano-motion based Resistell AST to determine the antibiotic susceptibility of bacteria causing bacteremia and sepsis.

Study population: patients admitted at the study site with bacteremia considered to be due to a pathogenic strain (E. coli or K. pneumoniae).

Study design: prospective, observational, single arm study.

Inclusion Criteria: The patients meeting all the following criteria can be recruited in the study:

• patients over the age of 18 years who sign, or their relatives / legal representatives sign the informed consent form;
• patients with bacteremia considered to be due to a pathogenic strain;
• patients hospitalized at CHUV at the time of blood culture inoculation;
• patients whose positive blood cultures were not older than 24 hours at the time of AST start.

Exclusion Criteria The patients meeting any of the following criteria will be excluded from the study:

• patient is diagnosed with polymicrobial bacteremia;
• samples can be excluded from the study during the processing of samples in case of technical errors e.g. failure with attachment of cells, technical problem with the device or sensor, operator's error, etc.

Note: in the event that the capacity of the Resistell instruments is reached for the day, no more ICFs will be obtained for the day.

Patients with bacteremia considered to be due to a pathogenic strain who have been hospitalized at CHUV at the time of blood culture inoculation