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SUMMARY : 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. In the course of a study of Gram-negative bacilli these organisms were examined to see whether they possessed coagulases capable of clotting plasma. A survey of literature showed that numerous bacterial species have been examined for plasma-coagulating ability. Conflicting results have been obtained, due possibly to different experimental conditions. In the present communication only intestinal Gram-negative bacilli will be considered. Loeb (1903) used aseptically drawn goose-blood, which was centrifuged and diluted 1/10. He noticed the strong coagulating power of Staphylococcus aureus and that Salmonella typhi had no apparent effect, while Pseudomonas aeru- ginosu and Escherichia coli had some coagulating ability. Much (1908), in experiments with human plasma and citrate, fluoride or hirudin as anti- coagulants, reported negative results with Sal. typhi, E. coli, Friedlander's bacillus and Proteus spp. Kemkes (1928) published negative findings in tests with oxalated plasma and the following organisms: Ps. aeruginosa, Ps. jiuorescens, Sal. typhi, Shigella jlexneri and Sh. dysenteriae. Lusena (1929) noted that some Sal. typhi cultures coagulated decalcified plasma. Gross (1931), found various bacteria, Sal. typhi, Sal. paratyphi, Ps. aeruginosa, shigella and proteus strains, negative in their action on rabbit plasma. Fisher (1936) investigated the coagulating properties of staphylococci on oxalated and citrated plasma and observed that contaminants such as some strains of Bacillus subtitis and Ps. aeruginosa caused clotting of rabbit but not human plasma, while Friedlander's bacillus, Alcaligenes sp., E. coli and Aerobacter aerogenes did not clot either. Reimer (1936) used various kinds of plasma without addition of anticoagulant and compared the clotting time of plasma mixed with bacterial cultures with that of control plasma. He found no

Clotting of Citrated Plasma and Citrate Utilization by Intestinal Gram-negative Bacilli