摘要:

The activity of carbenicillin (CB) on 20 strains ofPseudomonas pseudomalleiwas determined by the agar-diffusion and tube-dilution methods. Under the conditions of the tube-dilution method oxygen diffusion limited the growth of this obligate aerobe and KNO3(0.1%) was added to the assay medium as an alternate electron acceptor. The range of minimal inhibitory concentrations (MIC) for the strains studied was 50 μg/ml, 100 μg/ml, and 200 μg/ml. Thus, 17 of the 20 strains had MIC's below the blood level of CB achievable in vivo (in excess of 100 μg/ml). Activity of CB declined in the presence of heavy inocula and early logarithmic phase cells were more sensitive to CB than stationary phase cells. Variation in incubation temperature or electron acceptor availability caused changes in the MIC.Survival curves ofP.pseudomalleiin the presence of CB (at the minimal bactericidal concentration (MBC)) indicated a loss of colony-forming units at a rate of 1 log per 1.75 h. The increase in OD ofP.pseudomalleicultures in the presence of CB was found to be due to filament formation.

ISSN:0008-4166    

DOI:10.1139/m74-184

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Culture filtrates ofProteus mirabiliscontain a viral inhibitory substance (VIS) which has a selective action. It inhibits the plaque formation by Sindbis and vesicular stomatitis viruses in chick embryo cell cultures without parallel depression of viral yield or cytopathogenic effect in cultures maintained in fluid medium.The action of VIS is both time- and temperature-dependent. The inhibitor does not affect viral replication or degenerative changes produced by vaccinia, polio 1, echo 11, and coxsackie A9 viruses in tube cultures.The action of VIS is intracellular. It isnotcaused by direct inactivation of viral infectivity, by cytotoxicity, by impairment of viral adsorption properties of cells, or by interference with the process of virus release. Furthermore, the action of VIS is mediated by a mechanism other than the induction of interferon.The inhibitor is a soluble non-dialyzable substance. It is thermostable at 60 °C for 1 h but is labile when stored at either 4 °C or −20 °C for periods more than 3 weeks. Neither ultraviolet irradiation nor treatment with trypsin affects VIS activity. The antiviral action is destroyed by either 0.1 M potassium periodate or dialysis against pH 2 buffer.Other members of theProteusgroup produced substance(s) that inhibited Sindbis virus plaque formation. Such inhibitors have not been characterized.Principles such as VIS may serve as models of inhibitors which are selectively active against in vitro localized viral lesions.

ISSN:0008-4166    

DOI:10.1139/m74-185

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The development of cellular bodies during the conversion of conidial cells to chlamydospores inFusarium sulphureum(F.sambucinumf.6) is described. Development of the bodies from dilated cisternae within the endoplasmic reticulum begins before there are other recognizable changes in cell structure and is completed before new cell wall material is laid down. Each body is bounded by a single membrane derived from the endoplasmic reticulum and contains electron-dense particles, vesicular structures, and usually a microbody. These components remain intact within the body until a late stage in chlamydospore development. At that time the contents become granular, the vesicles and microbodies disappear, and the body becomes vacuole-like. A similar body was found in cells ofFusarium poaeat comparable stages of chlamydospore development.

ISSN:0008-4166    

DOI:10.1139/m74-186

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Suspensions of mycobacteriophages added to cultures of white blood cells (WBC's) reduce the phytohaemagglutinin (PHA) stimulated blast responses. Ultraviolet (UV) inactivation of the phages abolishes the inhibitory effect. Buffy coat cells from guinea pigs inoculated with mycobacteriophages and mice inoculated with these phages or with lysogenic mycobacteria show, without prior in vitro exposure to the antigen, significant reductions in the rate of their migration. This "spontaneous" migration inhibition is removed by prior treatment of the cells with trypsin or puromycin.

ISSN:0008-4166    

DOI:10.1139/m74-187

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The bacterial flora in the alimentary tract of five species of freshwater salmonid fishes was examined both qualitatively and quantitatively. The fish were obtained from 16 different locations in British Columbia. The predominant microflora consisted of Gram-negative rods with species ofEnterobacter,Aeromonas, andAcinetobacterpresent in the largest numbers. As many as 108viable organisms per gram wet weight of alimentary tract plus contents were counted.

ISSN:0008-4166    

DOI:10.1139/m74-188

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Microscopic observation ofP.pseudomalleirevealed that impaired cell division occurred upon the addition of carbenicillin to early exponential phase cultures. Cells were noticeably elongated after 1 h, and continued to increase in length with time. At 6 h filaments were abundant. Spherical bodies, some of which appeared to lyse, were frequently observed along the length of these filaments. Electron microscopy of thin sections confirmed that filament formation proceeded without fission, and constrictions were absent. Replication and segregation of DNA appeared normal; and the density of ribosomes suggested that protein synthesis was not impaired. Two types of inclusion bodies, observed in the nucleoid region of the filaments, were more pronounced compared with untreated cells. It was speculated that one of the inclusions was polyphosphate. The cell walls of the filaments showed decreased electron density. These observations suggest that synthesis of components of the cell wall is impaired by carbenicillin.

ISSN:0008-4166    

DOI:10.1139/m74-189

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Changes in cell architecture at the electron microscope level have been followed inP.boryanumduring conditions of phosphate starvation and rapid uptake. Cells from 14-day-old cultures were starved of phosphorus for 5 days and then inoculated into a medium containing 10 mg PO4/liter. Polyphosphate bodies developed in five different areas of the cells: (1) in ribosomal areas, (2) on strands of DNA, (3) intrathylakoidally, (4) in polyhedral bodies, and (5) in areas of medium electron density which develop in nucleoplasmic areas. In control cells types 1 and 2 predominate. In phosphate-starved cells types 1, 2, and 5 predominate, and under conditions of rapid uptake types 4 and 5 are predominant. Details of the development process and its significance are discussed. In addition to the described variations in polyphosphate bodies during phosphorus starvation, the number of cyanophycean granules and lipid-like inclusions increase. Cell division is also abnormal in many of the phosphorus-starved cells, with both small cells and abnormally large cells being common. Thylakoid structure is altered under different phosphate concentrations. Expanded thylakoids are found in control algae; the frequency increases during starvation with the greatest number occurring during a rapid uptake. Other aspects of cell architecture are discussed in relation to the "overplus phenomenon."

ISSN:0008-4166    

DOI:10.1139/m74-190

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The relative antifungal properties of haloprogin, a new synthetic antimicrobial agent, and two polyene antibiotics, amphotericin B and nystatin, were determined inCandida albicans. The specific parameters studied included possible effects on (i) cell viability, (ii) oxygen utilization, (iii) uptake and incorporation of labelled leucine and uridine, and (iv) loss of intracellular K+ions. Susceptibility of mammalian erythrocytes to lysis by these antimicrobial agents was also determined. Fungicidal activity of haloprogin appears to be attributable to inhibition of oxygen uptake and disruption of the cell membrane. Haloprogin affects protein and nucleic acid synthesis to a lesser degree as evidenced by uptake and incorporation of labelled precursors. The two polyene antibiotics act in a different manner; nystatin effectively inhibits oxygen utilization and incorporation of leucine and uridine, whereas amphotericin B affects primarily leucine incorporation. Both polyene drugs disturb the cell membrane as shown by intracellular loss of potassium ions fromC.albicanscells and lysis of mammalian erythrocytes.

ISSN:0008-4166    

DOI:10.1139/m74-191

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Groups of CF1 mice were respectively infected intravenously with four decreasing doses of the virulent H37Rv strain ofMycobacterium tuberculosisvar.hominisand the progress of tuberculous disease was followed by three techniques yielding essentially objective results. Survival rates showed that 84% of the mice infected with the largest dose died within 30 days of infection but this technique was unable to differentiate among the other three groups of mice infected with smaller doses. Bacterial culture counts performed after increasing intervals of infection on spleen homogenates of similarly infected groups of mice showed that different degrees of tuberculous involvement had effectively been induced in the four groups. Lung density determinations performed on the same groups of animals gave results establishing that this technique was capable of distinguishing the four groups of mice one from another. The observation that the lung density technique reflects the degree of tuberculous disease accurately was further substantiated by experiments performed on groups of mice respectively injected intravenously with comparable numbers of viable cells of seven mycobacterial strains of different virulence, all harvested at the same "physiological age." Statistically significant differences existed between the experimental groups infected with the virulent strains on the one hand and those injected with the avirulent ones on the other; no differences existed among the groups infected with virulent strains or among those injected with avirulent ones. Of particular interest is the observation that the lung density technique can also differentiate groups of mice injected either with virulent or avirulent strains from those injected with the attenuated bovine BCG strain. The results of both the bacterial culture count and lung density techniques applied to the same groups of mice in the early and late phases of tuberculous disease are discussed.

ISSN:0008-4166    

DOI:10.1139/m74-192

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Nisin in brain heart infusion medium (Difco) and Bacto-Staphylococcus medium 110 completely inhibited the growth ofStaphylococcus aureus196. This restraining action of nisin onS.aureuswas not as effective in the presence of whole milk. This was especially noted when attempts were made to control growth ofS.aureusin cheese made with starter inactivated by phage. Although nisin had some inhibitory action onS.aureusin cheese it was not equal to that exerted by an activeStreptococcus lactisculture. Its presence failed to prevent production of enterotoxin A. A factor influencing the failure of nisin to control growth ofS.aureusin cheese was the presence of butterfat which was shown to interfere with the action of nisin against the growth ofS.aureus.

ISSN:0008-4166    

DOI:10.1139/m74-193

出版商:NRC Research Press    

年代:1974

数据来源: NRC