Appropriate doses of 405-nm blue light inhibit the growth of S. aureus in vitro. This research does suggest that S. aureus may be capable of developing resistance to blue light irradiation.

A total of 5 Staphylococcus aureus strains from patients with postinfluenzal staphylococcal pneumonia, 7 from burn patients with staphylococcal pneumonia, and 21 from the nasopharynx of carriers were phenotypically characterized. Ali or most strains produced coagulase, clumping factor, DNase, thermostable DNase, protease, gelatinase, lipase, and pigment; the strains were low to moderate producers of extracellular protein A, fibrinolysin, and a-hemolysin. All strains were sensitive to mercury, half were sensitive to arsenate and cadmium, and 67 to 92% were resistant to penicillin. Differences between strains were not statistically significant. Cell surface hydrophobicity was determined by measuring percent adsorption to hexadecane. Hydrophobicity of postinfluenzal staphylococcal pneumonia strains was significantly lower than that of pneumonia strains from burn patients and carriers (P < 0.005). Immunoblot experiments with sera immune to one clinical test strain allowed the separation of ail strains into three groups based on probe-positive reactions with primarily four staphylococcal polypeptides (154,200, 130,000, 77,100, and 64,400 molecular weight). The difference in distribution of clinical and carrier strains was highly significant (P = 0.007).

From the heats of formation, an enthalpy change of 10 kcal. is predicted for the reaction Crl,(c) = Crl,(c) + 7,1,(c)(3) 3 kcal. less than previously estimated by extrapolation of thermal dissociation equilibrium data at 570°.6 The heat of reaction (3) at 25°has been determined by comparison of the heats of solution of Cris and Crl2 with excess solid iodine in 750 ml. of 0.02 N HC1 solution. Known mixtures of Crl3 and Crl2 were dissolved and iodine was subsequently introduced. The heat of solution of pure Crl2 was determined under similar conditions and the contribution of each component in the mixtures calculated. Inasmuch as iodine readily oxidizes chromium(II) to chromium(III), the final state of chromium after dissolving Crl2 is the same as that with Crl3. The results for the mixtures are somewhat less consistent than those for the pure substances; however, the difference between the mean values, 11 kcal. (Table I), agrees with the predicted result within experimental uncertainty.Experimental Procedure A description of the simple adiabatic calorimeter and its operation6 and the preparation of Crla7 have been given previously. Heats of solution were measured at 25 ± 1°.Crli was prepared by thermal decomposition of Crla in vacuum (400-500°), followed by sublimation in vacuum at 700°. The chromium chlorides were also purified by sublimation. The composition of these substances was checked by analysis; deviation from theoretical values did not exceed 0.5%. Samples were introduced into the calorimeter in sealed thin glass capsules, previously filled in a dry-box.It is a pleasure to acknowledge support of this work by the

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