Group B streptococci: extracellular neuraminidase production and virulence in mouse.

Neuraminidase production by reference strains of various group B streptococci serotypes was investigated before and after serial passages in mouse. The enzyme production was tested in culture filtrates using bovine submaxillary mucin as substrate. Although passages in mouse markedly increased the virulence of all the strains it was not possible to demonstrate a relationship between the increased virulence and the enzyme production.

Resistance of genus Proteus to ovotransferrin.

A total of 100 strains of Proteus, clinically isolated, were tested for sensitivity to ovotransferrin and CrCl3. Only a minority of the tested strains were not capable of growing in the presence of these iron chelating substances. Significant differences in the resistance among the four species of Proteus were noticeable only by addition to the culture medium of CrCl3 5 mM. The fact that sensitive strains were capable of growing after addition of citrate to culture medium containing ovotransferrin or CrCl3 suggests the presence in the genus Proteus of a citrate-dependent iron transport system.

Separation by affinity chromatography of human very low and low density lipoproteins inhibiting Sindbis virus haemagglutination.

The haemagglutination-inhibiting activity of human serum towards Sindbis virus is linked to very low and low density lipoprotein classes, in particular to their lipid component. To investigate the specific role played in this inhibition by carbohydrates contained in the molecule, inhibitor separation was carried out by Concanavalin A-Sepharose affinity chromatography. A different behaviour among the inhibiting molecules in relation to the carbohydrate content was observed. The importance of mannose for the biological activity of the inhibitor is discussed.

Capacity of staphylococci to grow in the presence of ovotransferrin or CrCl3 as a character of potential pathogenicity.

A total of 150 strains of staphylococci, clinically isolated, were tested for sensitivity to ovotransferrin (conalbumin). Among these, all the 50 coagulase-positive, mannitol-positive, and deoxyribonuclease-positive staphylococci appeared to be resistant to conalbumin, i.e., capable of growing in the presence of this transferrin. Among the other 100 strains, which were not classified as S. aureus, some appeared to be resistant and some were sensitive. The different behavior toward conalbumin is related to varying degrees of efficiency of the bacterial iron transport systems and, to test this, a simple method can be used, based on the addition of CrCl3 to the culture medium. The precipitation of iron produced by chromium salts has an effect on the growth of staphylococci similar to that produced by conalbumin and reveals the differences in the iron transport systems which occur in the genus Staphylococcus.

Different sensitivity of hemagglutinating and hemolytic activities of Sendai virus to non-antibody inhibitors.

Research was carried out in order to verify if some components of human serum, which are capable of inhibiting the hemagglutination by Sendai virus, are active even towards the hemolysis by the same virus. It was ascertained that both orosomucoid and low-density lipoproteins obtained by floatation had no action on the hemolysis by Sendai virus while lipoproteins precipitated with dextrane sulphate showed a certain inhibiting effect. This action however is not due to lipoproteins but is probably related to some substances used in the method of precipitation.

Identification of a glycoprotein inhibitor of human serum, active towards the hemagglutinating activity of Sendai virus.

Non-antibody hemagglutination-inhibiting activity of human serum is due, at least partially, to a glycoprotein inhibitor. This inhibitor was obtained from the whole serum or the fraction VI (Cohn) by means of methods of purification generally used for the preparation of the orosomucoid and was identified more precisely with an acid alpha 1-glycoprotein.

[Studies of the possible importance of complement in increasing the hemagglutination-inhibiting activity of rabbit IgM against Sendai virus]. / Indagine sull'eventuale importanza del complemento nell'esaltare l'attività emagglutino-inibente di IgM di coniglio verso il virus Sendai.

An investigation has been carried out in order to ascertain the effect of the presence of complement on the HI antibodies of the IgM class obtained in rabbit against Sendai virus. Contrary to the results obtained by some AA. with other viruses, in this case the presence of complement in the form of fresh guinea-pig serum has not modified the HI titre. It has however been demonstrated that in the guinea-pig serum an inhibitor is present, which is active towards Sendai virus and can be identified as a 19S alpha-globulin.