Plasmids from E. coli strains of 38 donors were transconjugated to common recipient SY663 Escherichia coli K12. The restriction patterns of the isolated plasmids were highly heterogenous. However, the streptomycin (Sm) resistance genes of the plasmids were identical or closely homologous in 29 of the 33 plasmids conferring Sm resistance. These data were based on Southern blot analysis, using the Sm resistance gene (encoding aminoglycoside phosphoryl transferase) as probe cut out from pBP1 plasmid. Our data suggest an extensive spreading of streptomycin resistance gene of this type.

View full abstract

An Escherichia coli mutant, C18, which plates at an efficiency of 5.0×10^-4 under anaerobic condition, was isolated among spontaneous nalidixic-acid-resistant mutants. This strict aerobic mutation was mapped by P1 cotransduction with a gyrA linked transposon Tn10 and found to be at the gyrA gene. A low degree of superhelicity of pBR322 DNA isolated from C18 was demonstrated by agarose gel electrophoresis with various concentrations of ethidium bromide. The superhelical density of pBR322 isolated from C18 was 80% of the value of pBR322 isolated from wild-type bacteria cultured under aerobic condition, and 50% cultured under anaerobic condition. These results lead us to conclude that a certain mutation of the gyrA gene causes a decrease in DNA superhelicity and prevents anaerobic growth.

View full abstract

We determined the number of large ribosomal RNA genes in five strains of Leptospira by hybridization of 15 restriction endonuclease digests of genomic DNA to the [³²P]-labeled fragment of 23s rRNA gene. Almost all the restriction gels gave two radioactive bands. The conclusion from these results is that there are at least two rRNA genes in these leptospiral strains. Furthermore, the hybridization patterns of L. icterohaemorrhagiae strains Ictero No. I and RGA are almost identical. The number of rRNA genes and taxonomic relationships of these leptospires were discussed.

View full abstract

We have studied the protective effect of OK-432, a biological response modifier (BRM) of Streptococcus pyogenes origin, on the lethal infection of mice with herpes simplex virus (HSV)-1. A single intraperitoneal (i.p.) injection of more than 10μg of OK-432, when given at least two days before the infection, gave a marked effect yielding nearly 100% protection against ordinarily lethal infection. The protection was independent of the amount of infected virus inoculated. When given after the infection, the agent even at the maximal dose (100μg), produced only a marginal effect. A single i.p. administration of OK-432 augmented the natural killer (NK) activity of peritoneal exudate cells and spleen mononuclear cells in mice 2 to 3 days after injection of OK-432, coinciding with the times when it induced a survival effect on HSV-infection. Treating OK-432-treated mice with a combination of an anti-macrophage agent, silica, and an anti-NK cell agent, anti-asialo GM₁ serum, before infection diminished the antiviral effect of OK-432. The OK-432 protection against HSV infection was also markedly diminished in athymic nude mice. Thus, the protective effect of OK-432 on lethal HSV infection seems to be based on the activation of NK cells, macrophages, and T lymphocytes.

View full abstract

In order to assess the role of the route of immunization on the immunogenicity of killed Salmonella vaccine, mice were immunized with killed S. enteritidis by intraperitoneal (i.p.) and intradermal (i.d.) routes. Whereas the former was non-immunogenic, the i.d. immunization generated an excellent delayed-type hypersensitivity response; further, i.p. immunization could even suppress the subsequent i.d. immunization. Since the peritoneal macrophages (MO) are known to be particularly low in Ia or MHC-class II antigens, so essential for antigen presentation, the non-immunogenicity by i.p. route was thought to be due to their poor presentation efficiency. Poly I: poly C, an interferon inducer, is known to enhance the MHC-class II expression; hence effect of poly I: poly C treatment on the immunogenicity of the killed vaccine by i.p. route was tested and indeed the non-immunogenicity was corrected. Poor efficiency of presentation of S. enteritidis antigen by peritoneal cells and its improvement by prior poly I: poly C treatment was further confirmed by in vitro lymphocyte transformation test using primed T cells and peritoneal cells from normal and poly I: poly C treated mice. Poly I: poly C treatment also enhanced expression of Ia antigens on peritoneal cells.

View full abstract

The human T cell leukemia virus type I (HTLV-I)-transformed T lymphocyte cell line MT-2 constitutively produces differentiation-inducing factor (DIF) for the human promyelocytic leukemia cell line HL-60. Purification and characterization of DIF derived from MT-2 were performed here to identify T cell-derived DIF. DIF was purified from conditioned medium of the MT-2 cell culture with serum-free medium by utilizing the sequential chromatographies of anion-exchange (mono-Q) column, gel filtration (superose-12) column, and hydrophobic (phenyl 5PW) column and finally the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In the SDS-PAGE, one major band with a molecular weight of 56, 000 and one minor band with 15, 000 were stained with Coomassie Brilliant Blue and both showed DIF activity after extraction from gels. DIF had an isoelectric point of 5.8. In all purification steps, DIF activity for HL-60 and cytotoxic activity to the sublines of mouse L-929 were not able to be separated. Further, DIF was neutralized by antibody against lymphotoxin (LT) but not by antibody against tumor necrosis factor. These results indicate that the major DIF activity derived from MT-2 is LT.

View full abstract

A study of carotenoid pigments of the genus Rhodococcus was carried out. According to carotenes contained, Rhodococcus species were divided into three groups: the first group of Rhodococcus luteus, R. coprophilus, R. lentifragmentus, and R. maris, which formed β-carotene; the second group of R. equi, R. rubropertinctus, R. aichiensis, R. sputi, R. chubuensis, R. obuensis, R. bronchialis, R. roseus, R. rhodochrous, R. rhodnii, and R. terrae, which formed γ-carotene-like substance; and the third group of R. aurantiacus, which formed neither carotene. Other carotenoid pigments were different according to the species.

View full abstract

Mycobacterium avium and M. intracellulare of human and natural sources, identified by the Gen-Probe ®Rapid Diagnostic System for M. avium Complex (MAC) were studied for susceptibility to eight different drugs. In the case of human isolates of MAC, the following was noted. M. avium showed nearly the same susceptibility to streptomycin, kanamycin, ethambutol, and clofazimine as was seen with M. intracellulare. M. avium was much more resistant to rifampicin and rifabutin than was M. intracellulare, and M. avium was more susceptible to quinolones such as ofloxacin and ciprofloxacin. Conversely, in the case of MAC from natural sources, there was no difference between the susceptibility of M. avium and M. intracellulare to these antibacterial agents.

View full abstract

The antibody prevalence to human herpesvirus 6 (HHV-6) was compared between pregnant women and control women of similar ages in Thailand. No significant difference was detected in the antibody positive rate and antibody titers between both groups. The antibody titers in sera collected from pregnant women at 1st and 3rd trimester remained unchanged. Next, the antibody prevalence in infants were examined and the positive rate decreased until 3 months and started to increase from 6 months after birth. The present results suggest that the reactivation of HHV-6 might not occur during pregnancy and this virus infects infants postnatally.

View full abstract