Japanese journal of microbiology最新文献

Using 10(9) or 10(7) colony-forming units of a strain of Staphylococcus epidermidis (strain 1142) in saline or 5% mucin, respectively, 90 to 100% of mice died within 24 to 48 hr after intraperitoneal challenge infection. These organisms gradually multiplied in the peritoneal cavity when injected intraperitoneally into mice, while the mouse avirulent strain (strain 1124) rapidly decreased and no organisms were found there 20 hr after injection. This strain was capable of inducing resistance against challenge with homologous strains. The resistance appeared as early as the first week and disappeared the 4th week after the immunization. However, no resistance was induced with strain 1124 against challenge with strain 1142. Also, hyperimmune rabbit serum prepared with strain 1142 passively protected against challenge with homologous strain in mice. The protective antibody was absorbed out with homologous organisms but not with strain 1124. Subsequently, a surface substance was obtained from strains 1142 or 1124 by the method of Morse. The 1142 surface substance was capable of inducing a resistance against challenge with the homologous strain but not with the 1124 surface substance. Also, this substance absorbed the protective antibody in hyperimmune rabbit serum prepared with the homologous strain but not with the 1124 surface substance nor with the Smith surface antigen extracted from the Smith strain of Staphylococcus aureus. Conversely, the protective antibody in rabbit anti-Smith strain serum against challenge with the homologous strain was absorbed with the Smith surface antigen but not with the 1142 surface substance. In the agar diffusion test, the 1142 surface substance and the Smith surface antigen produced single precipitin lines only against homologous antisera. Biochemical analysis of the 1142 surface substance showed that the substance contained neither nucleic acids nor proteins but is composed of hexosamine, glycerol, phosphorus, alanine, glycine and phenylalanine.

Various factor sinfluencing the plaque formation of mouse hepatitis virus (MHV-2) in DBT cell monolayers were studied and a practical method for plaque assay was developed. Infected DBT cells yielded high-titered virus and were a satisfactory source of complement-fixing viral antigen. The predominant cytopathic effect of MHV-2 in DBT cells was cell rounding and detachment, but no syncytial formation was observed. Fluorescent antibody staining revealed specific fluorescence only in the cytoplasm of infected DBT cells. In one-step growth experiment, newly formed virus was first recognized within 4-hr postinfection and showed subsequently a rapid exponential increase. Release of newly formed virus from the cell was rapid, and a continuous release lasted for a certain period of time. The average per-cell yield of active virus was estimated to be about 6-7 X 10(2) plaque-forming units.

Antibacterial and inducer activities concerning inducible macrolide resistance in Staphylococcus aureus were investigated using 32 erythromycin, oleandomycin and other macrolide antibiotic derivatives and analogues. The macrolides were classified into five groups from very high to none according to their inducer activity.

A serially diluted bacterial suspension of the Kurume-42 strain of Mycobacterium lepraemurium maintained for 1255 days in a mouse foot pad (MFP) cell culture was inoculated in mice subcutaneously. The ID50 value was estimated at more than 10.7 and less than 85 organisms, indicating that pathogenicity of the organism had been maintained well in a long-term cell culture. The cells infected and maintained for a long period in the cell culture showed all the stages of cell mitosis. This suggests that the bacterial increase in cell cultures of M. lepraemurium is not only due to rephagocytosis of the bacilli released from the infected cells but also to a constant intracellular growth cycle of the bacilli accompanied by mitosis of the infected cells. In acid phosphatase activity, no appreciable differences were noted between the infected and uninfected cells as far as the present cell culture system was concerned. Most of the bacilli within the cells were ultrastructurally normal. Solid bacilli in phagosomes were surrounded by less electron-dense clear zones.

A study was performed to clarify the roles of primary and secondary injections of antigen and adjuvant (capsular polysaccharide of Klebsiella pneumoniae, CPS-K) in induction of antibody responses and in the development of immunological memory in mice to bovine serum albumin (BSA). A primary injection of BSA alone neither induced significant primary antibody response nor increased immunological memory for a secondary antibody response but, if primary injections of BSA and CPS-K were performed simultaneously, high antibody responses were induced. Moreover, a prior injection of BSA alone or CPS-K alone decreased the level of primary antibody response and the degree of increase in memory following the subsequent injection of BSA mixed with CPS-K. In contrast, a secondary injection of BSA alone into mice once primed with a mixture of BSA and CPS-K elicited very high secondary type antibody response and increased secondarily the memory for a tertiary antibody response. Injection of CPS-K simultaneously with or shortly before or after the secondary injection of BSA did not increase the level of the secondary antibody response and the degree of the secondary increase in memory. Augmentation of the secondary antibody response was elicited by simultaneous injection of CPS-K only when the secondary response was induced inadequately by a suboptimum or supraoptimum dose of antigen.

The suppression characteristics of Escherichia coli strain KO1 have been investigated. The growth patterns of nonsense mutants of RNA (GA and f2) and DNA (lambda and T4) phages suggested that KO1 carried an amber, but not ochre or opal suppressors. The comparison of KO1 with previously identified amber suppressors indicated that KO1 differed from su1, su3 and su6 in its suppression pattern. KO1 and su2 shared some properties in common, for instance, their ability to suppress GA amber mutants with one exception (amN20) and the restriction of suppression capacity by the strr mutation. However, the suppression efficiency of KO1 (48%) was about three times that of su2 (18%). A possibility that KO1 contained a new amber suppressor is discussed.

In vitro antibacterial activities of ampicillin and amoxycillin were compared against pigmented and non-pigmented strains of Serratia marcescens. Ampicillin appeared more effective than amoxycillin; three-fourths of all strains consistently exhibited an ampicillin minimum inhibitory concentration (MIC) of at least one tube less than that recorded for amoxycillin. Complete cross resistance was not observed as has previously been inferred. Further, greater bactericidal activity was demonstrated with ampicillin; minimum bactericidal concentrations (MBC) were either the same as or one tube greater than the MIC. MBC's for amoxycillin, however, were significantly higher; often four to five times greater than the MIC. Ampicillin exhibited greater bactericidal activity as inferred from differences observed in the biological lesions induced, as recorded through observations by scanning electron microscopy (SEM). Spheroplasts were the predominant morphological alteration induced by ampicillin. In contrast, only filament formation, which demonstrated a degree of reversibility, was induced by amoxycillin.