Vernon Bryson

Reduced toxicity of amphotericin B methyl ester (AME) vs. amphotericin B and fungizone in tissue culture

SummaryThe comparative toxicities of amphotericin B methyl ester (AME), the parent antibiotic amphotericin B (AB), and the deoxycholate solubilized complex of AB, Fungizone2 (FZ), toward five cell lines has been determined as measured by early membrane damage (51Cr release), 24 hr survival, 72 hr viability, and growth rate. Cells used were of turtle (TH-1), marsupial (PT K2), human MA 160), rabbit (RK-13) and hamster (BHK-21) origin. AME: (a) caused less membrane damage at 1 hr than AB or FZ; (b) was less toxic than AB or FZ as indicated by 24 hr cell survival and 72 hr cell viability; and (c) was required in higher levels than AB or FZ to reduce the growth rate of all five cell lines. Spectrophotometric analysis of residual polyene levels indicated that AME had good stability in tissue culture medium. Previous studies have indicated that AME has the same in vitro antifungal activity as the parent antibiotic AB (1, 2). These findings suggest that AME may prove to be superior to AB and FZ for use as an antifungal agent in tissue culture systems.

Toxicity of nystatin and its methyl ester toward parental and hybrid mammalian cells

SummaryNystatin methyl ester (NME), the methyl ester derivative of the polyene macrolide antibiotic nystatin, is known to be effective against fungi and is now found to be relatively less toxic than the parent antibiotic nystatin (NYS) to animal cells in culture as measured by51Cr release, cell survival at different posttreatment periods and cell growth. NYS and NME were tested on TK− mouse (B82) and hamster (B1) cells, HGPRT− mouse (RAG) cells, and on lysolecithin-fused cells selected in HAT medium and confirmed as B82-RAG an B1-RAG hybrids by chromosomal analysis plus polyacrylamide gel electrophoresis of lactate dehydrogenase. NME was less toxic and caused less immediate membrane damage than NYS when tested in all five cell systems. However, differences in innate polyene sensitivity were evident between the three parental cell types. B82 and B1 cells were more resistant than RAG cells to NYS and NME. B82-RAG hybrids reflected the higher level resistance of B82 parental cells, and B1-RAG hybrids reflected the higher level resistance of B1 cells. Where one parental cell type is relatively more polyene sensitive, the use of polyenes in the future may be applicable as selective agents in cell hybridization.

The effect of fetal bovine serum on polyene macrolide antibiotic cytotoxicity and antifungal activity.

SummaryThe relationships between fetal bovine serum (FBS) concentration and polyene macrolide antibiotic cytotoxicity to animal cells and to fungi were evaluated. The toxicity of amphotericin B (AB) and its derivative, amphotericin B methyl ester (AME), toward KB cells was found to be directly related to fetal bovine serum concentration. At higher FBS levels, increased concentrations of AB and AME were required to reduce 72-hr KB viable cell numbers to 50% of control values. Similarly, polyene macrolide antibiotic levels required to inhibit the growth ofSaccharomyces cerevisiae to 50% of controls, and for obtaining minimum fungicidal concentrations (MFC), were greater when higher levels of FBS were used. In addition, AME was less toxic than AB toward KB cells grown in media containing 2, 5, 10, 15 or 20% FBS, whereas the antifungal activities of AB and AME were similar. AME was also capable of eliminatingCandida albicans, Saccharomyces cerevisiae, Aspergillus niger orFusarium moniliforme from KB cultures at antibiotic levels which exhibited less cell toxicity than did the concentrations of AB required for a similar response. These findings indicate that AME may be a potentially useful antifungal antibiotic for tissue culture systems.

Altered Amphibian Cell Morphology Following Treatment with Polyene Antibiotic and a Mammalian RNA Virus

Summary Polyene antibiotics are agents known to damage cell membranes. The hexaene antibiotic, mediocidin, was used in an attempt to introduce a mammalian virus (Mengo) into normally nonpermissive ICR 2A haploid frog cells. Although no infectious virus could be recovered from mediocidin treated cells exposed to Mengo virus, a change in VSV susceptibility, temperature sensitivity and an apparently permanent change in morphology took place—from fibroblastic to epithelial—in the cells cultured at 23°. Neither the polyene antibiotic nor the virus used alone was capable of inducing these alterations in ICR 2A cells.

Chemically Induced Aberrations of Mitosis in Bacteria

Bacillus megaterium was studied cytologically during exposure to a number of toxic agents, including known mitotic inhibitors. Many antibiotics and sodium p-aminosalicylate at inhibitory concentrations induced an increase in the size and optical density of the stained nuclei, and a preponderance of configurations resembling metaphase and anaphase stages. Continued chromosome reduplication results in the establishment of a transient polyploidy. Isoniazid and benzimidazole bring about a decrease in the amount of stainable material in the nucleus. Penicillin and bacitracin produce no obvious changes in the nuclear pattern in this organism. The significance of the aberrations observed is discussed. Further support for the similarity of bacterial nuclei to the nuclei of higher organisms is provided.

Properties of morphologically variant haploid prog cells formed by combined treatment with mengo virus and the polyene antibiotic mediocidin

SummaryComparison have been made of cell surface glycoproteins, concanavalin A agglutinability, and cloning efficiencies in liquid media of ICR 2A (haploid frog cells), ICR 2A M (three cloned populations of haploid frog cells resistant to 5 μg per ml of the polyene antibiotic mediocidin), and ICR 2A M/MV cells (five cloned populations of morphologically variant haploid frog cells produced by exposure of the parental cells to the combined effects of mediocidin and an RNA mammalian virus, Mengo virus). Independently isolated ICR 2A M/MV clones exhibited altered cell surface glycoproteins, increased concanavalin A agglutinability, and enhanced cloning efficiency in liquid media when compared with ICR 2A parental cells. In contrast, ICR 2A M cells had properties similar to ICR 2A cells, with the exception of the formers increased resistance to mediocidin. The differences in properties between ICR 2 M/MV and ICR 2 cells suggest that alterations resembling transformation have occurred in ICR 2A M/MV cells as a consequence of combined treatment with mediocidin and Mengo virus.

Microbial Drug Resistance

Publisher Summary It is unfeasible and unnecessary to coerce the complex biological events contributing to the origin of resistance into a single theory. Experimental evidence suggests that a few models define most examples of resistance development, particularly if the models are so combined as to provide either genotypic or phenotypic alterations of resistance level. If the body of present knowledge is to be kept sufficiently resilient to absorb new information without the impairment of established principles, it must be granted that resistance can arise in a variety of ways to be considered as complementary rather than mutually exclusive. This does not deny that a relatively important place must be assigned to certain methods of resistance development. Geneticists have been concerned with the spontaneous origin of resistance by mutation and the subsequent establishment of mutant clones by selective action of the drug.