The determinant for streptomycin resistance in some strains of Staphylococcus aureus isolated from clinical specimens was found to be lost during storage as stock cultures or by high temperature treatment. This fact has added an additional proof that many genetic determinants for drug-resistance in staphylococci are easily and irreversibly lost.

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Stability to heat and acid of the virus-inhibiting factor (IF) or interferon induced by viruses is generally accepted. Published data suggest, however, a heterogeneity in the virus-induced IFs in their physico-chemical and biological properties. The present work shows that the IF activity of rabbit serum collected 2 hr after intravenous inoculation with Newcastle disease virus is as labile as E. coli endotoxin-induced IF when heated at 56C or dialysed at pH 2, whereas the serum-IF at 6 hr is significantly more stable.

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A genetic analysis of resistance to chloramphenicol (CM) in Staphylococcus aureus S1337 was carried out through transduction. About 3 to 18% of the transductants jointly acquired resistance to both tetracycline (TC) and CM, even when singly selected for either CM- or TC-resistance. When singly selected for either TC- or streptomycin (SM)resistance, about 1 to 4% of the transductants jointly acquired resistance to both TC and SM. Joint transduction of both CM- and SM-resistance was never observed, when singly selected for either TC- or CM-resistance. These findings indicate that the genetic loci govering CM, TC and SM resistance in S1337 are closely linked, and appear to possess the following linkage order, -CM-TC-SM-. The finding that penicillin (PC) resistance is not cotransducible with either CM-, TC-, or SM-resistance, is also accordance with a previous result in MS27, indicating that PC-resistance is governed by a genetic unit different from the one carrying resistance to TC, SM and CM in S1337.

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The T-agglutination complex or pattern of Streptococcus pyogenes which cannot be strain typed by a single definite anti-T monovalent serum but, because of the presence of a common T antigen, requires a set of two or more anti-T sera. Of these complexes, strains belonging to the 3-13-B3264; 8-25-Imp 19; and 5-27-44-complexes from outside Japan were studied, and each could be typed as a definite T-type. These discrepancies were attributed to the different procedures employed by us in adsorbing the original antisera. We observed the same patterns or complexes after complete removal, from our original antisera, of the non-type-specific or group-specific antibodies by absorption. Consequently we postulate that these patterns merely represent cross reactions occurring in minor T antigens. Therefore we attempted in this investigation to improve the absorption procedures using a much larger amount of whole cells, to obtain separate factor sera. These were attained with little difficulty and the results given by these factor sera were clear cut. The present paper reports on the reexamination and characterization of the complex or pattern of the resulting T-agglutination complexes.

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A rapid and simple test method for the detection of acylamidase activity of Pseudomonas aeruginosa was devised. One loopful of a nutrient agar overnight culture of a test organism was inoculated into 1 ml of a test medium consisting of 0.2% KH₂PO₄, 0.01% MgSO₄·7H₂O, 0.5% NaCl and 0.1% acetamide (final pH 6.8). After aerobic incubation at 37C for 6 hr, one drop of Nessler's reagent was dropped into the test medium. A reddish-brown sediment appeared immediately if results were positive. Of 40 test strains of P. aeruginosa 39 gave strongly positive results. A strain showed a weakly positive result after 6 hr incubation, but the reaction became stronger after 18 hr culture. Other species of Pseudomonas, and various species of bacteria such as genera Vibrio and Aeromonas, and family Enterobacteriaceae were negative in this test. From these experimental results, the acylamidase test was considered to be highly specific for strains of P. aeruginosa, and therefore useful as a reliable method for the identification of this species.

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A new synthetic medium consisting of 0.2% KH₂PO₄, 0.01% MgSO₄·7H₂O, 0.5% NaCl, 0.05% (NH₄)₂SO₄ and 1.0% Tween 80 was devised by the authors as a means of differentiating between Pseudomonas aeruginosa and related species of gram-negative rods. One loopful of an overnight nutrient agar culture of a test strain was inoculated into 1 ml of this media, and incubated at 37 C for 24 hr. All of the 38 test strains of P, aeruginosa showed visible growth in this media, being capable of utilizing Tween 80 as a sole carbon source, whereas strains of Aeromonas, Vibrio parahaemolyticus, Achromobacter sp., Proleus sp., Escherichia coli and Citrobacter sp. could not grow within a 24 hr incubation period, although longer incubation yielded a visible growth with some strains. A strain of P. fluorescens did not show any visible growth at 37 C, but did show a moderate growth after a 48 hr incubation at 18 C. Strains of Klebsiella and Enterobacter showed only slight growth after incubation at 37 C for 24 hr.

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This study concerns the interaction between parental virus RNA and host cell components in tobacco leaves infected with tobacco mosaic virus (TMV). By using a gentle method for disruption, extracts were obtained from tobacco leaves infected with ³²Plabelled TMV and the fate of infecting parental ³²P-TMV-RNA was studied. Sucrose gradient centrifugation analysis showed that the parental ³²P-RNA distributed into four regions: free RNA, partially uncoated TMV, TMV and a structure heavier than TMV. The heavier structure was considered to be polysomes carrying the parental TMV-RNA as messenger RNA based on its size, sensitivity to RNase, dependence of its formation on protein synthesis and the kinetics of its appearance after infection. Control experiments were done to exclude the possibility that the structure is not an artifact aggregate produced by an interaction between partially uncoated virus or its RNA and host cell components. Polysomes containing TMV-RNA were found as membrane hound forms. Based on these data, it is suggested that uncoating of TMV and formation of polysomes are closely related and evidence has been obtained which suggests that uncovering of the viral genome and its translation takes place hand-in-hand on a single virion.

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Some RNAs, including both single- and double-stranded RNAs, when incubated with chick embryo cell culture induce cellular resistance against viruses. Evidence was now obtained indicating that the induction of cellular resistance by RNA depends on the cellular metabolic activity, especially on the synthesis of cellular RNA and protein. Thus, inhibitors of RNA and protein synthesis, actinomycin D and cycloheximide, were found to inhibit the development of an antiviral state when added before, or during the relatively early period of, incubation of the cells with RNA. In the course of induction of cellular resistance, three stages may be distinguished, the priming stage, the developing stage, and the established resistant stage.

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In vitro interferon (IF) production in peritoneal macrophages of normal and Newcastle disease virus (NDV)-immunized mice was studied. Of ascites cells used, 80% were macrophages, 14% lymphocytes, and 6% polymorphonuclear leukocytes. It was indicated that IF was produced mainly in the macrophages after NDV inoculation. IF production in the macrophages derived from immunized mice was more enhanced than that in those from normal mice. It is not clear at present, however, whether this enhancement is based on immunological specificity. The IF production in the culture of macrophages reached its maximum value in 6 to 9 hr after inoculation of the inducer, After 12 hr, the IF titer in the culture fluid decreased gradually. A possible explanation of this fact is that there may be partial inactivation of IF by some cellular components.

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When Newcastle disease virus (NDV) was inoculated into macrophage cultures, interferon (IF) of various molecular weights appeared in the culture fluid. The molecular weight of IF produced in the macrophages derived from normal mice in at least 6 hr post-inoculation of inducer was different from that produced in the macrophages from immunized mice. The IF with a molecular weight as high as 100000 was unstable against pH 2 treatment and heat treatment, while that of 70000 or less was stable.

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The effect of antiserum on the interferon (IF) production in macrophages by Newcastle disease virus (NDV) has been studied. Completely neutralized NDV lost its IF-inducing ability, but under-neutralized NDV revealed an enhanced IF-inducing capability. This enhancement of IF production by unneutralized NDV was also observed in antiserum-treated cells. Enhancement phenomena appeared to be based on immunological specificity. Under- neutralized NDV was also adsorbed more rapidly and at a higher rate to normal cells than unneutralized NDV. Unneutralized NDV also adsorbed more efficiently to antiserum-treated cells and to cells derived from immunized mice than to normal cells. The significance of these phenomena is discussed in relation to the induction mechanism of IF in macrophages

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