MEDIUM FOR DIFFERENTIATING THE GRAM-NEGATIVE, NONFERMENTING BACILLI OF MEDICAL INTEREST

Sellers, Walter (U.S. Air Force School of Aerospace Medicine, Brooks Air Force Base, Tex.). Medium for differentiating the gram-negative, nonfermenting bacilli of medical interest. J. Bacteriol. 87:46-48. 1964.-An agar-slant medium is described for differentiating gram-negative, nonfermenting bacilli of medical interest. Differences in the ability of bacilli to grow anaerobically in the presence of nitrate, to produce pH changes, to produce N(2) from nitrite and nitrate (singly and in combination), to fluoresce, and to oxidize a drop of glucose solution to acid in the presence of high peptone concentrations were used in the development of the medium. Organisms differentiated by the medium include Pseudomonas aeruginosa, Bacterium anitratum, Mima polymorpha, and Vibrio alcaligenes or Alcaligenes faecalis.

EFFECT OF PHENOL ON BACILLUS SUBTILIS SPORES AT ELEVATED TEMPERATURES

The nature of the recovery medium is shown to influence the number of Bacillus subtilis spores which, after exposure to 2.5 or 5% phenol at high temperatures, can produce a visible colony. Higher survivor counts were obtained in nutrient agar containing L-alanine and D-glucose than in plain nutrient agar.

EFFECT OF PH ON HUMAN MYCOPLASMA STRAINS

Shepard, Maurice C. (U.S. Naval Medical Field Research Laboratory, Camp Lejeune, N.C.), and Carl D. Lunceford. Effect of pH on human Mycoplasma strains. J. Bacteriol. 89:265-270. 1965.-The optimal reaction of culture media for the cultivation of T-strain Mycoplasma of human origin was investigated. By use of a recently modified tryptic digest medium, the optimal reaction in either agar or fluid medium was found to be pH 6.0. In contrast, human classic (large-colony) Mycoplasma could be cultivated in agar or fluid medium over a rather broad pH range, and the influence of the reaction of the medium appeared to be primarily species-dependent. M. salivarium, for example, grew best in agar from pH 5.5 through 6.5. M. pneumoniae (Easton's agent) yielded largest colony numbers in agar and highest titers in broth at pH 8.0. In the case of T-strain Mycoplasma, both maximal colony numbers in agar and highest titers in fluid media were achieved at a reaction of pH 6.0. In addition, largest colony size of T-strain Mycoplasma was also achieved in agar at pH 6.0, and averaged 50 to 100% larger than that obtained by cultivation at pH 8.0 with the same medium. Although T-strains will develop in agar media over a pH range of from 5.0 through 10.0, the extremely small colony size and poor staining properties resulting from growth in an alkaline medium make their recognition in agar cultures difficult. Aerobic cultivation of T-strains was first achieved in agar adjusted to pH 5.5 to 6.0. In fluid medium, multiplication of T-strains occurred only within the limits of pH 5.0 through 8.0, with highest titers being reached at pH 6.0. Greater attention to the reaction of complete Mycoplasma media is stressed.

SEX-ASSOCIATED DIFFERENCES IN SERUM PROTEINS OF MICE

Agar electrophoresis of serum from mice of C57BL/10-H-2(d), B10.Sn, A.SW, A.CA, R III, and P1 inbred strains shows that the females have a lower concentration of alpha-1 serum globulin than the males and, in some strains, the females also have a lower concentration of alpha-2 and, beta-serum globulin. Females of the A.SW strain have a higher serum albumin concentration than males, and females of the C57BL/10-H-2(d) strain have a higher gamma-globulin concentration than males. Two-dimensional (agar and hydrolyzed-starch) electrophoresis gives a typical sex-associated pattern for alpha-1 and alpha-2 globulins which clearly permits recognition of male and female serums.

INVESTIGATION OF A QUANTITATIVE ANOMALY ENCOUNTERED IN THE ASSAY OF FIBRINOGEN BY IMMUNO-DIFFUSION

When diluted platelet-poor normal plasma is allowed to react with a specific antifibrinogen antiserum by double diffusion in agar the fibrinogen content of the plasma, as estimated immunologically, is less than would be expected from chemical estimation.

This discrepancy is even more marked in plasma exposed to procedures bringing about increased coagulability: such as storage of platelet-rich plasma, glass contact or pre-treatment of the blood with traces of thrombin insufficient to cause coagulation. On the other hand, full development of immune precipitation occurs with purified fibrinogen and is often almost complete in plasmas with severe coagulation defects. Full development of immune precipitation is restored when chelating agents such as sodium citrate or sequestrene are added to both the agar medium and the diluting fluid in re-testing plasmas initially showing the anomaly in saline—agar.

Investigation of this phenomenon suggests that it is not mediated by any one of the plasma factors concerned in thromboplastin generation, but that the anomaly is closely concerned with thrombin evolution. Evidence is presented that the quantitatively anomalous immune behaviour of plasma fibrinogen in saline—agar may be due to fibrin deposition in the agar consequent upon lowered citrate concentration in the plasma and the formation of traces of thrombin during diffusion.

Antifibrinogen—antibody interaction with the products of plasmin lysis of fibrinogen also shows a quantitative anomaly in saline—agar, but this is only demonstrable early in the digestion process. In conformity with other workers it is suggested that the early digestion products (fibrino-peptides) formed as a result of the proteolytic action of thrombin compete with the digestion products of plasmin for interaction with antibody.

The practical implications of this anomaly are discussed in relation to (i) immunological estimation of the fibrinogen content of plasma and (ii) the development of a screening test for plasma coagulation defects.