Method for treating a sample from a blood culture, or a sterile bodily fluid sample likely to contain one or more microorganisms of interest, comprising a decomplexification step, said decomplexification step comprising the following steps: - Optionally, performing a sample enrichment step by incubation, preferably in the presence of a culture medium, - introducing all or part of this sample into a first inlet orifice (1330a, 1430a) of a device of acoustophoresis (1300, 1400, 2000, 3000), - introducing a buffer into a second inlet orifice of the acoustophoresis device - the said inlet orifices being fluidically connected to at least two outlet orifices (1360a, 1360b, 1360b', 1460a, 1460b, 1460b') by at least one separation channel (1350, 1350', 1450, 1450'), - the buffer and the sample being introduced at respective flow rates capable of generating a laminar flow in the separation channel, - the performance of a step of separating said biological sample by acoustophoresis so as to promote the concentration of non-specific particles present in the sample in at least one of the outlet orifices of said acoustophoresis device - optionally and following the decomplexification step, the performance of a step for determination of the presence and advantageously of identification, of one or more biological species in the said sample, - optionally and following the decomplexification step and an identification step of biological species, performing a step of determining the antibiogram profile of the identified biological species, the method comprising a second step of decomplexification comprising carrying out a second step of separation of said sample decomplexified by acoustophoresis by introduction of a buffer in a third inlet (1330b', 1430b') of acoustophoresis device so as to favor a greater rate of recovery of biological species still present in the decomplexified sample in at least one orifices (1360a, 1360b, 1360b', 1460a, 1460b, 1460b') of said acoustophoresis device, wherein the first step of separation is carried out with a first buffer and wherein the second step of separation is carried out with a second buffer having a density different from the one of the first buffer. - Optionally, performing a sample enrichment step by incubation, preferably in the presence of a culture medium, - introducing all or part of this sample into a first inlet orifice (1330a, 1430a) of a device of acoustophoresis (1300, 1400, 2000, 3000), - introducing a buffer into a second inlet orifice of the acoustophoresis device - the said inlet orifices being fluidically connected to at least two outlet orifices (1360a, 1360b, 1360b', 1460a, 1460b, 1460b') by at least one separation channel (1350, 1350', 1450, 1450'), - the buffer and the sample being introduced at respective flow rates capable of generating a laminar flow in the separation channel, - the performance of a step of separating said biological sample by acoustophoresis so as to promote the concentration of non-specific particles present in the sample in at least one of the outlet orifices of said acoustophoresis device - optionally and following the decomplexification step, the performance of a step for determination of the presence and advantageously of identification, of one or more biological species in the said sample, - optionally and following the decomplexification step and an identification step of biological species, performing a step of determining the antibiogram profile of the identified biological species,