A method for detecting the presence of beta-hemolytic pathogens in a sample comprising: (a) adding a sample suspected of containing a beta-hemolytic pathogen to a growth medium containing sterically-stabilized liposomes comprising an encapsulated fluorophore to form a test assay mixture; (b) incubating the test assay mixture for a period of time sufficient for the beta-hemolytic pathogen, if present, to form a population of test cells and to cause lysis of sterically-stabilized liposomes to release the fluorophore into the assay mixture for assimilation into the population of test cells; (c) detecting the fluorescence of the population of test cells; and (d) comparing the amount of fluorescence of the population of test cells with the amount of fluorescence of a population of control cells, wherein the sterically-stabilized liposomes are prepared from a mixture of a membrane forming phospholipid selected from the group consisting of (a) a saturated phosphatidylcholine, preferably hydrogenated egg yolk phosphatidylcholine (HEPC), and (b) a synthetic phosphatidylcholine with saturated fatty acid tails selected from the group consisting of dimyristoyl-phosphatidylcholine, dipalmitoyl-phosphatidylcholine, and distearoyl-phosphatidylcholine; cholesterol; and a conjugate of polyethylene glycol, wherein the PEG has a molecular weight from 1,000 to 5,000, preferably 2,000, and wherein the PEG is conjugated to a molecule selected from the group consisting of distearoyl phosphatidylethanolamine (DSPE), dipalmitoyl phosphatidylethanolamine (DPPE), and dimyristoyl phosphatidylethanolamine (DMPE); wherein the molar ratio of: is in the range of 2:1 to 1:1 and is present at 5% (mol/mol). (a) adding a sample suspected of containing a beta-hemolytic pathogen to a growth medium containing sterically-stabilized liposomes comprising an encapsulated fluorophore to form a test assay mixture; (b) incubating the test assay mixture for a period of time sufficient for the beta-hemolytic pathogen, if present, to form a population of test cells and to cause lysis of sterically-stabilized liposomes to release the fluorophore into the assay mixture for assimilation into the population of test cells; (c) detecting the fluorescence of the population of test cells; and (d) comparing the amount of fluorescence of the population of test cells with the amount of fluorescence of a population of control cells, wherein the sterically-stabilized liposomes are prepared from a mixture of a membrane forming phospholipid selected from the group consisting of (a) a saturated phosphatidylcholine, preferably hydrogenated egg yolk phosphatidylcholine (HEPC), and (b) a synthetic phosphatidylcholine with saturated fatty acid tails selected from the group consisting of dimyristoyl-phosphatidylcholine, dipalmitoyl-phosphatidylcholine, and distearoyl-phosphatidylcholine; cholesterol; and a conjugate of polyethylene glycol, wherein the PEG has a molecular weight from 1,000 to 5,000, preferably 2,000, and wherein the PEG is conjugated to a molecule selected from the group consisting of distearoyl phosphatidylethanolamine (DSPE), dipalmitoyl phosphatidylethanolamine (DPPE), and dimyristoyl phosphatidylethanolamine (DMPE); wherein the molar ratio of: is in the range of 2:1 to 1:1 and is present at 5% (mol/mol). a membrane forming phospholipid selected from the group consisting of (a) a saturated phosphatidylcholine, preferably hydrogenated egg yolk phosphatidylcholine (HEPC), and (b) a synthetic phosphatidylcholine with saturated fatty acid tails selected from the group consisting of dimyristoyl-phosphatidylcholine, dipalmitoyl-phosphatidylcholine, and distearoyl-phosphatidylcholine; cholesterol; and a conjugate of polyethylene glycol, wherein the PEG has a molecular weight from 1,000 to 5,000, preferably 2,000, and wherein the PEG is conjugated to a molecule selected from the group consisting of distearoyl phosphatidylethanolamine (DSPE), dipalmitoyl phosphatidylethanolamine (DPPE), and dimyristoyl phosphatidylethanolamine (DMPE); wherein the molar ratio of: is in the range of 2:1 to 1:1 and is present at 5% (mol/mol).