Three easy and rapid microtiter plate assays for determining phage sensitivity of lactococei and enterococei have been developed. In the microlysis assay, the degree of sensitivity was measured on the basis of the ability of the bacterial cells to grow in the presence of various concentrations of phage and to effect a color change of an acid-base indicator as a result of acid production. Two assays that specifically measure phage adsorption to bacterial cells have been developed on the basis of the enzyme-linked immunosorbent assay (ELISA) technique. In the direct phage pdsorption ELISA, adsorption of phage particles to cells immobilized onto microtiter plate wells was measured using specific anti-phage antibody. In the competitive phage adsorption ELISA, phage adsorption was assayed by allowing phage to compete with specific antibody binding to the bacterial cell surface. All three assays were quantifiable photometrically.
Bibliographical noteFunding Information:
The authors thank Monica Chiao and Karen Booth for excellent technical support and Jean Gallo (formerly Jean Adsit) for highly efficient lab management. This work was supported by Competitive Research Grant 87-CRCR-1-2421 of the U.S. Department of Agriculture and by Cooperative State Research Service (Hatch) Grant NYC-144404.