Impact of Performing a Rapid Antibiotic Susceptibility Test on Antibiotic Therapy Adaptation in Adult Patients with Enterobacterales Bacteremia

Bacteremia is defined as the presence of bacteria in the blood. They can potentially lead to life-threatening septic shock.

Effective probabilistic antibiotic therapy must therefore be initiated immediately after blood cultures have been taken.

To diagnose bacteremia, blood culture bottles must first be incubated, which allows bacterial growth and early detection. Then, as soon as the sample is positive, an antibiogram of the incriminated bacterium is carried out by inoculation on MH (Mueller Hinton) medium. This diffusion antibiogram is the reference method and is obtained 24 hours after the vial is positive, i.e. around 48 hours after blood cultures are taken.

American recommendations agree that it is crucial to use rapid diagnostic tests to obtain the antibiogram. Antibiotic susceptibility test data can be used to broaden the spectrum of antibiotics in the event of ineffective therapy. They can also be used to reduce the spectrum of broad-spectrum antibiotics. This is part of the proper use of antibiotics and the reduction of multi-resistant bacteria (MRB) or highly resistant bacteria (HRB). Finally, it is also possible to carry out an early oral relay, thus avoiding intravenous infusions and their complications, and potentially reducing hospitalization times.

The investigators have evaluated a rapid antibiogram by diffusion on MHR-SIR (Mueller-Hinton Rapid-SIR) medium from the blood culture bottle. The investigators were able to obtain antibiogram results 7 hours after blood culture positivity, with excellent correlation compared with the standard method after 24 hours incubation on MH (Mueller-Hinton). The antibiotics tested were the same as with the standard method.

Secondly, The investigators were able to evaluate prospectively the impact of diffusion antibiotic susceptibility testing on MHR-SIR medium on early modification of antibiotic therapy in bacteremia, on 167 patients Antibiotic susceptibility test data on MHR-SIR enabled us to adapt antibiotic therapy 8 hours after blood culture positivity for 74 patients (44%). Antibiotic therapy was ineffective for 30 patients (18%) and was therefore extended. It also enabled us to reduce the spectrum of antibiotic therapy, in particular through early oral relay, for 44 patients (26%).

The aim of this multicenter trial is to validate on a large scale this strategy for obtaining rapid antibiotic susceptibility test results, with significant consequences in terms of optimizing antibiotic therapy.