Mass spectrometric methods and kits to identify a microorganism

A method for identifying a microorganism in a fluid comprising one or more interfering mammalian proteins, the method comprising:

• preparing a lysate from the fluid, the lysate comprising a microorganism protein and an interfering mammalian protein from the group consisting of hemoglobin, defensins and proteolysis products thereof;
• passing the lysate through an extraction cartridge, the extraction cartridge comprising:
• a column body having a reservoir portion, an extraction media portion, and a collar portion;
• wherein the reservoir portion includes an inlet and a reservoir;
• wherein the extraction media portion includes an elongated sleeve having an inner surface defining a cavity having a chromatography medium therein, said elongated sleeve further having an inlet end in fluid communication with the reservoir and an outlet end disposed remote from the inlet end, the chromatography medium extending substantially to the outlet end of the elongated sleeve;
• wherein the collar portion extends axially in a common direction with the elongated sleeve and has a terminal end which is spaced apart from the outlet end of the elongated sleeve and which extends axially at least to a plane defined by the outlet end of the elongated sleeve;
• and
• wherein the interfering mammalian protein and the microorganism protein bind to the chromatography medium;
• selectively eluting proteins bound to the chromatography medium to produce at least one eluted fraction, wherein the at least one eluted fraction is enriched in the microorganism protein and depleted in hemoglobin, defensins or proteolysis products thereof;
• and
• subjecting the at least one eluted fraction to protein mass spectrometry analysis and thereby identifying the microorganism in the fluid.