Methods for isolating microbial cells from a blood sample

A method for isolating bacterial cells from a blood sample containing or suspected of containing one or more bacteria, the method comprising:

• providing a blood sample from a mammal;
• adding a first selective lysis reagent and a second selective lysis reagent comprising a non-ionic detergent to the blood sample and incubating the blood sample for a time period sufficient to lyse most of the erythrocytes and release hemoglobin therefrom, and for the non-ionic detergent to lyse leukocytes in the blood sample and release mammalian DNA therefrom, wherein the integrity of at least most bacterial cells in the blood sample are preserved;
• separating and removing from the blood sampleat least a portion of the mammalian proteins, including hemoglobin, while preserving most or all of the bacterial cells;
• incubating the sample with an endonuclease, for a time period sufficient to lyse mammalian DNA;
• adding an insoluble solid surface, and at least one of a water soluble polymer and at least one inorganic salt in a quantity sufficient to cause blood plasma, blood cell components and bacteria to displace directly or indirectly onto the solid surface;
• separating bacterial cells displaced onto the solid surface;
• eluting bacterial cells from the solid surface by incubating the bacterial cells on the solid surface with a solution comprising at least one protease;
• and
• isolating released bacterial cells from the solid surface.