Selective lysis of cells

A method for detecting the presence of micro-organisms contained or suspected to be contained within a mammalian blood sample, the method comprising the steps of:

• providing the mammalian blood sample containing or suspected to contain the micro-organisms, wherein:
• said mammalian blood sample comprises whole blood that has not been cultivated, said whole blood including blood plasma and eukaryotic blood cells,
• said mammalian blood sample has a volume between 1 ml and 20 ml,
• said micro-organisms are selected from the group consisting of bacteria and fungi, and
• there are less than 10,000 micro-organisms per milliliter of the mammalian blood sample,
• adding a selective lysis buffer at a selected concentration to the mammalian blood sample to obtain a final solution having a pH level of around 9.5 or higher, said selective lysis buffer including (i) a non-ionic detergent and (ii) an alkaline buffer, said non-ionic detergent present in a concentration of between 0.1% and 5% (w/v % or v/v %),
• wherein the selected concentration of the selective lysis buffer in the final solution is a concentration that achieves said pH level of around 9.5 or higher for the final solution, with a volume of the selective lysis buffer that is between 200% and 10% of a volume of the mammalian blood sample;
• incubating the final solution in the presence of the selective lysis buffer for a time period sufficiently long to selectively lyse the blood cells in the mammalian blood sample while keeping the micro-organisms intact, thereby forming a lysed sample, wherein the percentage of micro-organism cells that remain intact in the lysed sample is at least two times higher than the percentage of blood cells that remain intact in the lysed sample;
• and
• detecting the presence of the micro-organisms without cultivation of the micro-organisms within said mammalian blood sample.