Clotting of citrated plasma and citrate utilization by intestinal gram-negative bacilli.

Abstract

Salmonella, shigella, alkalescens-dispar, proteus, paracolon and coli-form strains were tested for the presence of a coagulase enzyme as manifested by the ability to clot plasma. The shigella and proteus strains examined gave negative results; a high percentage of the remaining strains clotted citrated plasma but this reaction was due to metabolism of citrate and subsequent liberation of calcium ions and not to a coagulase enzyme. Results depended on the bacterial strain and on the kind and dilution of plasma used. Utilization of citrate in citrated plasma was compared with the ability of the tested strains to attack citrate in Koser’s ammonium citrate medium and in sodium citrate peptone medium. The Shigella and Proteus species examined failed to utilize citrate in any of the media under the conditions of the tests, Salmonella species gave fairly uniform results in the three media, while paracolon, coliform and alkalescens-dispar strains differed in their activity, the highest percentage of positive reactions being obtained in plasma-containing media.