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Preliminary studies have shown a very high inhibitory activity in the alpha2 and gamma zone of human serum towards the growth of Cryptococcus neoformans. These findings are now corroborated by single radial immunodiffusion tests, which showed the some loss of IgA and IgM globulins and of the other three globulin fractions (ceruloplasmin, alpha2 macroglobulin and alpha2 HS glycoprotein) which migrate in the alpha2 zone. The data was obtained by single radial immunodiffusion tests. The losses were not statistically significant however. No change in the immunoglobulin content of the sera kept for 6 days in contact with a heat-killed suspension of C. neoformans was noted. These findings suggest, that the inhibitory activity of the normal human serum on the in-vitro growth of C. neoformans is due to the above mentioned globulin fractions and not to a single specific factor.

The reliabilities of five in vitro susceptibility tests (agar dilution, broth microdilution, automated MS-2, Kirby-Bauer disk diffusion, and ability to grow on methicillin-containing agar) to predict the susceptibility of 204 coagulase-negative staphylococcal isolates to penicillinase-resistant semisynthetic penicillins were compared. There was wide variation in susceptibility, with results ranging from 86.3% susceptible by MS-2 to 38.2% by growth on methicillin-containing agar. The results of the broth dilution techniques, including the MS-2, were significantly different (P < 0.02) from the remaining tests. Nafcillin disks were less effective (P < 0.02) than oxacillin disks in predicting resistance. Kirby-Bauer oxacillin disks and the ability to grow on methicillin-containing agar were the most reliable predictors of resistance. The MS-2 did not reliably predict resistance.

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