Synergistic effect of polymixin B with other antibiotics on the transformation of

Preston, Terence M.; O'Dell, D.S.

doi:10.1016/0014-4827(71)90177-7

Cited by 7 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because eukaryotic cells also contain phospholipids in their cell membranes (7), it was reasonable to expect that polymyxin B would disrupt permeability barriers in them as well. Two previous studies have shown this to be true in a protozoan (6) and in the yeast Candida tropicalis (5). The latter study, however, failed to demonstrate a polymyxin B effect in a variety of other yeasts.…”

mentioning

confidence: 84%

Antifungal Properties of Polymyxin B and Its Potentiation of Tetracycline as an Antifungal Agent

Schwartz

Medoff

Kobayashi

et al. 1972

Antimicrob Agents Chemother

View full text Add to dashboard Cite

High concentrations of polymyxin B inhibited the growth of Candida albicans and Saccharomyces cerevisiae. When these yeasts were incubated with concentrations of polymyxin B too low to affect growth, and were then exposed to tetracycline, protein synthesis was inhibited and at least 99% of the organisms were killed. Neither inhibition of protein synthesis nor cell death occurred in cultures treated with high concentrations of tetracycline alone. We conclude that polymyxin B at high concentrations affects the cell membrane of yeasts, which results in inhibition of growth. At low concentrations, it increases the permeability of the yeast cell membrane to tetracycline, which then inhibits protein synthesis and leads to cell death.Polymyxin B is a surface-active bactericidal antibiotic which alters the permeability of the bacterial cell envelope by binding to the negatively charged phospholipid component of the membrane and causing cell lysis (4). Because eukaryotic cells also contain phospholipids in their cell membranes (7), it was reasonable to expect that polymyxin B would disrupt permeability barriers in them as well. Two previous studies have shown this to be true in a protozoan (6) and in the yeast Candida tropicalis (5). The latter study, however, failed to demonstrate a polymyxin B effect in a variety of other yeasts.Several agents have been shown to be ineffective against yeasts because of failure to penetrate the cytoplasmic membrane and gain access to their site of action. For example, tetracycline has been shown to inhibit protein synthesis in extracts of yeasts (1) but was ineffective against whole organisms (C. N. Kwan et al., Bacteriol. Proc., p. 179, 1972). In this report, we have investigated the antifungal properties of polymyxin B against certain yeasts, and have exploited the changes in membrane permeability caused by this antibiotic to potentiate the antifungal effect of tetracycline. Synergism studies. The susceptibility of each organism to polymyxin B and tetracycline was determined by the broth-dilution method, as previously described (2). A wide range of antibiotic concentrations was examined for each organism, and cell viability was determined by colony counts after 1, 2, 3, and 7 days of incubation. The minimal inhibitory concentration (MIC) was defined as the lowest concentration of drug required to inhibit completely the growth of the organism over the designated time interval.Synergism was also determined by colony counts of each organism in the presence of the antibiotics used singly and in combination. Exposure to the two drugs was done either by 24-hr pretreatment of the yeasts with polymyxin B or by simultaneous addition of the polymyxin B and tetracycline. Our definition of antifungal drug synergy was a decrease of 100-fold or more in colony counts caused by the drugs in combination as compared with the counts when the drugs were used singly (3). The level of each antibiotic used in the combined drug studies was well below the respective MIC. In the MIC and synergism studies, a s...

show abstract

mentioning

confidence: 84%

Antifungal Properties of Polymyxin B and Its Potentiation of Tetracycline as an Antifungal Agent

Schwartz

Medoff

Kobayashi

et al. 1972

Antimicrob Agents Chemother

View full text Add to dashboard Cite

show abstract

“…When cells were required in the amoeboid phase cultures were harvested within 20 h of inoculation as previously described (Preston & O'Dell, 1971). Extension of the incubation period beyond 48 h resulted in encystment of most of the amoebae; a pure, viable cyst suspension could be readily secured if residual trophic cells were removed by mild detergent lysis with Triton XIOO, 0-05 % (v/v) in 2 mM-tris (Fulton, 1970) before harvesting.…”

Section: Protozoamentioning

confidence: 99%

“…Preparations of cells were initially contaminated with Klebsiella aerogenes from the culture plates, but the bacteria were readily eliminated by chloramphenicol treatment. Since our strain of N. gruberi is impermeable to this drug unless treated with agents such as polymyxin B (Preston & O'Dell, 1971), it was possible to treat a mixture of amoebae and bacteria selectively with chloramphenicol.…”

Section: Separation Techniquesmentioning

confidence: 99%

“…Flagellates were treated with D,O in the presence of 10 pg/ml cycloheximide, an inhibitor of protein synthesis which penetrates Naegleria gruberi amoebae without difficulty and inhibits the initial transformation into flagellate (Preston & O'Dell, 1971). Reversion proceeded as before, with the onset of streaming, eruption of pseudopodia and loss of flagella.…”

Section: The Re Version Process In Deuterium Oxide-t Yea T Ed Flagellmentioning

confidence: 99%

“…The transformation from amoeba to flagellate can readily be controlled in the laboratory and provides a particularly amenable model for the study of morphogenesis in unicellular eukaryotes (Fulton, 1970). The process is temperature dependent and takes about TOO min at 27 "C; it can be prevented by inhibitors of RNA and protein synthesis (Balamuth, 1965 ;Preston & O'Dell, 1971 ; Yuyama, 1971). The reversion of flagellate to amoeba is very much faster and, as will be described here, shows no comparable sensitivity to these inhibitors.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Deuterium Oxide-induced Reversion of Naegleria gruberi Flagellates

Preston

O'Dell

1973

Journal of General Microbiology

View full text Add to dashboard Cite

A bead column technique is described for the separation of Naegleria gruberi flagellates from amoebae and cysts. It is shown that D,O induces a rapid reversion of these flagellates to amoebae, and the behaviour and structure of the reverting cells is described. The amoebae are viable in high concentrations of D,O, and when returned to suspension in H 2 0 readily retransform to the flagellate stage. The reversion of flagellates to amoebae is insensitive to cycloheximide, but the subsequent retransformation to flagellate can be prevented by both actinomycin D and cycloheximide. I N T R O D U C T I O NThe soil protozoon Naegleria gruberi (Schardinger) can exist in three states: as an amoeba which feeds and divides; as a flagellate which swims strongly for a few hours but does not feed or divide; and as a cyst. The transformation from amoeba to flagellate can readily be controlled in the laboratory and provides a particularly amenable model for the study of morphogenesis in unicellular eukaryotes (Fulton, 1970). The process is temperature dependent and takes about TOO min at 27 "C; it can be prevented by inhibitors of RNA and protein synthesis (Balamuth, 1965 ;Preston & O'Dell, 1971 ; Yuyama, 1971). The reversion of flagellate to amoeba is very much faster and, as will be described here, shows no comparable sensitivity to these inhibitors. Spontaneous reversion of individual flagellates, which occurs sporadically and can be increased by, for example, applying mild shearing forces or adding certain fixatives, can create difficulties for the experimentalist. In this paper, methods are described which enable the easy production and fixation of populations consisting entirely of flagellates or amoebae, and it will also be shown that deuterium oxide is an inducer of a general and rapid reversion to the amoeboid stage. These techniques have enabled a number of observations to be made on the reversion process and the transformation back to flagellate. M E T H O D S ProtozoaNaegleria gruberi (stock I 51 8/1 c, Cambridge Culture Collection) was maintained at 25 "C in monoxenic culture with Klebsiella aerogenes on 0 -2 % (w/v) peptone agar plates.When cells were required in the amoeboid phase cultures were harvested within 20 h of inoculation as previously described (Preston & O'Dell, 1971). Extension of the incubation period beyond 48 h resulted in encystment of most of the amoebae; a pure, viable cyst suspension could be readily secured if residual trophic cells were removed by mild detergent lysis with Triton XIOO, 0-05 % (v/v) in 2 mM-tris (Fulton, 1970) before harvesting. Incubation of amoebae suspended in 2 mmtris, pH 7.5, in a shaking water bath at 27 "C resulted

show abstract

Ameboflagellate transformation I. Possible initiation of the ameba-to-flagellate transformation of Naegleria gruberi (NB-1) by divalent cation influx

Perkins

1981

Hydrobiologia

View full text Add to dashboard Cite

The hypothesis that the ameba-to-flagellate transformation (AFT) of Naegleria gruberi (NB-I) requires Ca 2+ and/or Mg 2 ' was tested with divalent cation blockers and competitors. Several compounds were found to decrease the rate and magnitude of the AFT as well as increasing the time of enflagellation onset. The compounds include: the chloride salts of lanthanum, cobalt, and manganese; C-6oo; and EDTA. These results suggest that the AFT requires the influx of Ca 2+ and/ or Mg 2 +.

show abstract

Synergistic effect of polymixin B with other antibiotics on the transformation of

Cited by 7 publications

References 0 publications

Antifungal Properties of Polymyxin B and Its Potentiation of Tetracycline as an Antifungal Agent

Antifungal Properties of Polymyxin B and Its Potentiation of Tetracycline as an Antifungal Agent

Deuterium Oxide-induced Reversion of Naegleria gruberi Flagellates

Ameboflagellate transformation I. Possible initiation of the ameba-to-flagellate transformation of Naegleria gruberi (NB-1) by divalent cation influx

Contact Info

Product

Resources

About