A method for determining the antimicrobial susceptibility of a microorganism in a clinical sample said method comprising: a) providing a clinical sample culture of a clinical sample in a culture vessel containing culture medium; b) removing a test aliquot from said clinical sample culture in said culture vessel, wherein said aliquot is removed when the culture in the culture vessel is less than 0.5 McFarland units; c) selectively isolating microbial cells from said test aliquot, such that the microbial cells are separated from the non-microbial cells; d) transferring said isolated microbial cells into a culture medium suitable for microbial cell growth thereby to prepare a microbial culture preparation; e) inoculating a series of test microbial cultures for an antibiotic susceptibility test using the microbial culture preparation of step (d), wherein the series of test microbial cultures comprises at least two different growth conditions, wherein the different growth conditions comprise one or more different antimicrobial agents, and each antimicrobial agent is tested at two or more different concentrations; f) assessing (e.g. monitoring) the degree of microbial growth in each growth condition; wherein the concentration of microbial cells in said microbial culture preparation is determined between steps (d) and (e) and/or the concentration of microbial cells is determined in the test microbial cultures during or after step (e) but prior to step (f), and optionally and if necessary the concentration of microbial cells in said microbial culture preparation and/or said test microbial cultures is adjusted to a desired or pre-determined concentration; and wherein the degree of microbial growth in each growth condition is used to determine at least one MIC value for at least one antimicrobial agent, thereby to determine the antimicrobial susceptibility of said microorganism in said clinical sample. a) providing a clinical sample culture of a clinical sample in a culture vessel containing culture medium; b) removing a test aliquot from said clinical sample culture in said culture vessel, wherein said aliquot is removed when the culture in the culture vessel is less than 0.5 McFarland units; c) selectively isolating microbial cells from said test aliquot, such that the microbial cells are separated from the non-microbial cells; d) transferring said isolated microbial cells into a culture medium suitable for microbial cell growth thereby to prepare a microbial culture preparation; e) inoculating a series of test microbial cultures for an antibiotic susceptibility test using the microbial culture preparation of step (d), wherein the series of test microbial cultures comprises at least two different growth conditions, wherein the different growth conditions comprise one or more different antimicrobial agents, and each antimicrobial agent is tested at two or more different concentrations; f) assessing (e.g. monitoring) the degree of microbial growth in each growth condition; wherein the concentration of microbial cells in said microbial culture preparation is determined between steps (d) and (e) and/or the concentration of microbial cells is determined in the test microbial cultures during or after step (e) but prior to step (f), and optionally and if necessary the concentration of microbial cells in said microbial culture preparation and/or said test microbial cultures is adjusted to a desired or pre-determined concentration; and wherein the degree of microbial growth in each growth condition is used to determine at least one MIC value for at least one antimicrobial agent, thereby to determine the antimicrobial susceptibility of said microorganism in said clinical sample. wherein the concentration of microbial cells in said microbial culture preparation is determined between steps (d) and (e) and/or the concentration of microbial cells is determined in the test microbial cultures during or after step (e) but prior to step (f), and optionally and if necessary the concentration of microbial cells in said microbial culture preparation and/or said test microbial cultures is adjusted to a desired or pre-determined concentration; and wherein the degree of microbial growth in each growth condition is used to determine at least one MIC value for at least one antimicrobial agent, thereby to determine the antimicrobial susceptibility of said microorganism in said clinical sample.