Role of antibiotics in the ecology of actinomycetes]

The organisms producing ristomycin, rifamycin, lincomycin, tobramycin, rubomycin carminomycin, olivomycin, bleomycin and actinomycin D were practically not sensitive to their own antibiotics in the concentrations close to those produced during the biosynthetic process. At the same time other actinomycetous species close to the above organisms were suppressed to a significant extent by their antibiotics in the same concentrations. The experimental data indicated that the antibiotics had a protective effect on the organisms producing them and played a significant role in ecology of the actinomycetes.     

Mutagenesis in Streptomycete cultures exposed to bleomycin

Mutagenic properties of bleomycin, an antitumor antibiotic were studied with respect to 2 species of streptomycetes producing practically important antibiotics. A multifold increase in the frequency of prototrophic revertants among the survivors of strains His- and Met- of Actinomadura carminata exposed to bleomycin was observed. Bleomycin was effective in induction of various morphological mutants, and auxotrophs at a high survival rate of the spores of Str. cremeus var. tobramycini, a tobramycin-producing organism. It was shown with the method of subsequent mutagenesis that the efficacy of induction of morphological and auxotrophic mutants in germinating spores of Actinomadura carminata, a carminomycin-producing organism by bleomycin in a concentration of 100 micrograms/ml and an exposure time of 5 minutes was much higher that in the latent spores. The mutagenic effect of bleomycin is comparable with that of ionizing radiation.     

Immunoregulatory cytokine release in rat spleen cell cultures after treatment with bleomycin and its analogues in vivo

Summary We have studied the immunological effects that accompany a change in the chemical structure of a group of antineoplastic antibiotics by comparing the immunoregulatory cytokine release during mitogen-stimulated spleen cell culture after in vivo drug treatment. Whereas bleomycin and peplomycin increased cytokine levels in culture supernatants when compared with supernatants from untreated control rat spleen cell cultures, liblomycin generally reduced cytokine levels under the same culture conditions. We then compared these results with the antitumor effects of equivalent doses of the three drugs against a highly antigenic rat fibrosarcoma, KMT-17, both in vivo and in vitro. The results suggest that the immunoaugmenting effects of these antitumor antibiotics are essential for an optimal antitumor effect in vivo, and that these effects can be drastically altered by modification of the chemical structure of the drugs employed.     

Bleomycin, an Antitumor Antibiotic: Improved Microbiological Assay and Tissue Distribution Studies in Normal Mice

A microbiological assay was developed for bleomycin, an antitumor antibiotic reported to be active in human trials. The assay bacterium was a strain of Escherichia coli which is resistant to ethionine. Studies revealed relatively high concentrations of bleomycin in the blood and urine of mice after a single dose, < 0.33 ld(10), injected intraperitoneally.     

Taxonomic characteristics of soil Mycobacteria and their antibiotic properties]

Morphological, cultural and chemotaxonomic properties of 12 gram-positive soil cultures isolated were studied by using a test system developed for screening the organisms producing broad-spectrum antibiotics among Nocardiaforms (Coryneforms). The cultures were found to belong to Actinomycetales, Nocardioforms, Mycobacteriaceae and Mycobacterium. The saprophytic rapidly growing soil mycobacteria showed antibiotic activity against a large number of gram-positive and gram-negative test microbes including those belonging to Pseudomonas and Proteus resistant to the majority of the antibiotics currently used in medicine.     

Obtaining a productive strain of Streptoverticillium griseocarneum var. bleomycini that yields the new antineoplastic antibiotic, bleomycetin

Selection of the organism producing bleomycin, a multicomponent antitumor antibiotic, was performed. The aim was the selection of a more active strain with preferable synthesis of component A5 (bleomycetin) of the bleomycin complex. Optimal variants of the conditions for mutagensis with UV light and gamma-rays in step-wise selection of the active strain were determined and a possibility of selecting analog-resistant mutants with the use of structural analogs of the metabolites participating in synthesis of the bleomycin molecule was studied. A mutant analog-resistant strain capable of supersynthesis of bleomycin A5 (bleomycetin) was selected, the biosynthetic capacity of Streptoverticillum griseocarneum var. bleomycini being increased at least 19 times.     

Bifunctional intercalation of antitumor antibiotics BBM-928A and echinomycin with deoxyribonucleic acid. Effects of intercalation on deoxyribonucleic acid degradative activity of bleomycin and phleomycin

The binding of peptide antitumor antibiotics, BBM-928A and echinomycin, to superhelical PM2 DNA and the effects of the resulting conformational changes of DNA on the DNA-degradative activity of two related antitumor antibiotics, bleomycin A2 and phleomycin D1, have been studied. The bifunctional intercalative mode of the DNA binding of BBM-928A concluded previously from viscometric and fluorometric studies has been confirmed by gel electrophoretic analysis. Under the employed electrophoretic conditions, DNA-bound BBM-928A showed little dissociation whereas echinomycin and ethidium bromide showed partial and nearly complete dissociation, respectively. BBM-928A induced neither single-strand nor double-strand breaks in DNA. Competitive binding studies by fluorescence changes suggested that binding sites on DNA molecules for BBM-928A (or echinomycin) may differ from those for ethidium bromide, since binding to DNA by the two drugs was not competitive even at saturating concentrations. The lack of such a competition between the two drugs is not consistent with the neighbor-exclusion principle. The DNA-degradative activity of both bleomycin A2 and phleomycin D1 increased with the removal of the negative superhelicity of DNA by the BBM-928A intercalation and decreased with the formation of positive superhelical turns induced by high concentrations of BBM-928A. Thus the degradative activity of both bleomycin A2 and phleomycin D1 is sensitive in a similar manner to the degree of superhelicity rather than the double helicity of DNA, although there are differences between these two drugs in interaction with DNA.     

C4-alkylthiols with activity against Moraxella catarrhalis and Mycobacterium tuberculosis

Antimicrobial resistance represents a global threat to healthcare. The ability to adequately treat infectious diseases is increasingly under siege due to the emergence of drug-resistant microorganisms. New approaches to drug development are especially needed to target organisms that exhibit broad antibiotic resistance due to expression of β-lactamases which is the most common mechanism by which bacteria become resistant to β-lactam antibiotics. We designed and synthesized 20 novel monocyclic β-lactams with alkyl- and aryl-thio moieties at C4, and subsequently tested these for antibacterial activity. These compounds demonstrated intrinsic activity against serine β-lactamase producing Mycobacterium tuberculosis wild type strain (Mtb) and multiple (n=6) β-lactamase producing Moraxella catarrhalis clinical isolates.     

Potentiation of bleomycin cytotoxicity by membrane-interacting drugs and increased calcium ions

The cytotoxic effect of the antitumor antibiotic peplomycin (PEP), a new member of bleomycin group antibiotics, toward HeLa cells and mouse FM3A cells is enhanced by some membrane-interacting drugs such as verapamil, persantin, prenylamine, chlorpromazine and anafranil. The enhancing action of verapamil is selective to this group antibiotics, since it does not potentiate the cytotoxic effects of vincristine, adriamycin, mitomycin C, cis-diamminedichloroplatinum(II) and macromomycin. An enhanced PEP cytotoxicity has been also demonstrated by the treatment of cells in the presence of increased CaCl₂. This enhancing effect of increased CaCl₂ is prevented by the Ca²⁺ transport inhibitor ruthenium red. Since these membrane-directed drugs have been shown to affect Ca²⁺ metabolism, we conclude that potentiation of PEP cytotoxicity by these drugs is mediated by an increase in intracellular Ca²⁺.     

产β-内酰胺酶金黄色葡萄球菌的耐药分析

目的对产β-内酰胺酶金黄色葡萄球菌的标本分布和药物敏感试验进行分析,为临床使用抗生素提供依据。方法按照《全国临床检验操作规程》的要求接种．对分离出的220株金黄色葡萄球菌（Sta phylococcs aureus,Sau）,用头孢菌素显色法测定其β-内酰胺酶。结果220株金黄色葡萄球菌中产β-内酰胺酶171株,产酶率为77．7％,产酶株除对万古霉素、替考拉宁、利福平及复方新诺明敏感外,对其它的抗生素均呈现不同程度耐药,其中青霉素G、氨苄西林耐药率均为99．4％,红霉素为86．1％。结论产β-内酰胺酶株对青霉素类、大环内酯类抗生素呈现高度耐药,临床治疗不宜使用此类抗生素,提示临床选择药物时,应在药敏试验的指导下合理选择抗生素。     

Action of antibiotics on the growth and metabolic processes of streptomycetes and Nocardia

New experimental data on the effect of novobiocin, ristomycin and nystatin on growth and metabolism of Streptomycetes and Nocardia are presented. The study of the organisms producing other antibiotics showed that they were tens, hundreds and even thousands times more sensitive to the tested biologically active compounds than the organisms producing these compounds. The protein synthesis and antibiotic biosynthesis proved to be most sensitive out of the processes studied. The findings showed that during their evolution the antibiotic-producing organisms have developed definite protective mechanisms which enable them to resist relatively high concentrations of their own metabolites (antibiotics). This ensures them in their struggle for existence.     

Effect of pH of Medium and Size of Inoculum on Activity of Antibiotics Against Group D Streptococcus (Enterococcus)

Seventy-one clinical isolates of 5 species of group D Streptococcus (Enterococcus) were tested for susceptibility to 15 antibiotics at pH 5.0, 7.4, and 8.5. Penicillin G, ampicillin, cephalothin, cephaloridine, and novobiocin were considerably more active against all strains at pH 5.0 than in the more alkaline media. On the other hand, lincomycin, clindimycin, erythromycin, and gentamicin were moderately to markedly more active at pH 8.5. No important differences were noted in the susceptibility of the strains to kanamycin and streptomycin, at the pH levels tested, but the organisms were quite resistant to them in these tests. The various species differed quantitatively in their susceptibility to the individual drugs and in the effects of pH. The size of the inoculum also had a variable effect on susceptibility, depending on the species of Enterococcus, the antibiotics, and the pH of the test medium. The data suggest that, in the antibiotic treatment of urinary tract infections caused by Enterococcus, attempts should be made to achieve the optimum pH in the urine, particularly in view of the fact that organisms of this group are often resistant to several antibiotics in the usual tests.     

Intracellular degradation of bleomycin hydrolase in two Chinese hamster cell lines in relation to their peplomycin susceptibility

The Chinese hamster lung (V79) cell was intrinsically 10-times more resistant to peplomycin, a bleomycin-related antitumor antibiotic, than the Chinese hamster ovary (CHO) cell. This may be associated with the 3-times higher levels of recovery of bleomycin hydrolase activity of the V79 cell. The degradation of bleomycin hydrolase molecules in both V79 and CHO cells was examined using a monoclonal antibody specific for the enzyme. Labelling experiments showed that the bleomycin hydrolase in CHO cells was less stable than the comparable enzyme in V79 cells, and that 48 kDa subunits comprising bleomycin hydrolase (a homohexameric enzyme) molecules were degraded into 31 kDa forms in both cell lines. The 105,000 X g pellet (microsomes) fraction obtained after subcellular fractionation of CHO cells contained both 48 kDa subunit and 31 kDa forms of bleomycin hydrolase, while the 105,000 X g supernatant cytosol fraction yielded only 48 kDa subunit forms of the enzyme. Moreover, bleomycin hydrolase activity of both V79 and CHO cells was almost entirely recovered from the cytosol fraction. These results suggest that degradation of the 48 kDa subunit form of bleomycin hydrolase in these two lines of cultured cells into the 31 kDa form occurs on the plasma membrane or the endoplasmic reticulum, with which the resulting large number of bleomycin hydrolase molecules or degraded forms of the enzyme that have lost enzymatic activity are associated.     

Selective enhancement of bleomycin cytotoxicity by local anesthetics

The cytotoxic effect of the antitumor antibiotic bleomycin toward cultured mouse FM3A cells was greatly enhanced by exposure of the cells to local anesthetics either before or together with treatment with bleomycin. Such local anesthetics include dibucaine, tetracaine, butacaine, lidocaine and procaine. Dibucaine-induced cell sensitization to bleomycin cytotoxicity produced a decrease in cell survival that became dependent on dose and time of bleomycin treatment. This effect of local anesthetics seems to be selective to bleomycin, since dibucaine and lidocaine do not enhance the cytotoxic effect of other antitumor agents including adriamycin, mitomycin C and $\text{cis}$-diamminedichloroplatinum(II).     

The iron chelating cardioprotective prodrug dexrazoxane does not affect the cell growth inhibitory effects of bleomycin

The clinical use of bleomycin is limited by a dose-dependent pulmonary toxicity. Bleomycin is thought to be growth inhibitory by virtue of its ability to oxidatively damage DNA through its complex with iron. Our previous preclinical studies showed that bleomycin-induced pulmonary toxicity can be reduced by pretreatment with the doxorubicin cardioprotective agent dexrazoxane. Dexrazoxane is thought to protect against iron-based oxygen radical damage through the iron chelating ability of its hydrolyzed metabolite ADR-925, an analog of ethylenediaminetetraacetic acid (EDTA). ADR-925 quickly and effectively displaced either ferrous or ferric iron from its complex with bleomycin. This result suggests that dexrazoxane may have the potential to antagonize the iron-dependent growth inhibitory effects of bleomycin. A study was undertaken to determine if dexrazoxane could antagonize bleomycin-mediated cytotoxicity using a CHO-derived cell line (DZR) that was highly resistant to dexrazoxane through a threonine-48 to isoleucine mutation in topoisomerase IIalpha. Dexrazoxane is also a cell growth inhibitor that acts through its ability to inhibit the catalytic activity of topoisomerase II. Thus, the DZR cell line allowed us to examine the cell growth inhibitory effects of bleomycin in the presence of dexrazoxane without the confounding effect of dexrazoxane inhibiting cell growth. The cell growth inhibitory effects of bleomycin were unaffected by pretreating DZR cells with dexrazoxane. These results suggest that dexrazoxane may be clinically used in combination with bleomycin as a pulmonary protective agent without adversely affecting the antitumor activity of bleomycin.     

Antibiotics and antibiotic resistance in water environments

Antibiotic-resistant organisms enter into water environments from human and animal sources. These bacteria are able to spread their genes into water-indigenous microbes, which also contain resistance genes. On the contrary, many antibiotics from industrial origin circulate in water environments, potentially altering microbial ecosystems. Risk assessment protocols for antibiotics and resistant bacteria in water, based on better systems for antibiotics detection and antibiotic-resistance microbial source tracking, are starting to be discussed. Methods to reduce resistant bacterial load in wastewaters, and the amount of antimicrobial agents, in most cases originated in hospitals and farms, include optimization of disinfection procedures and management of wastewater and manure. A policy for preventing mixing human-originated and animal-originated bacteria with environmental organisms seems advisable.     

Various approaches to the search for the producers of bacteriocin-like substances among bacteria of the genus Pseudomonas

Some methods providing rapid and methodically simple study of large microbial collections and detection of cultures producing bacteriocin-like substances perspective for further investigation are described. The use of cellophane disks and study of the proteolytic enzyme effects allowed the authors to detect organisms producing high molecular antibiotics of protein nature.     

Comparison of virulence factors and R plasmids of Salmonella spp. isolated from healthy and ill swine

The antibiotic resistance and virulence profiles of Salmonella spp. isolated from healthy (group 1) and ill (group 2) swine were compared. Parameters studied included colicin and siderophore production; mannose-sensitive hemagglutination of erythrocytes; resistance to the lethal effect of serum complement; resistance to antibiotics; and the transmissibility of these characteristics to recipient organisms. Group 1 (19 isolates) had 14 serotypes, and group 2 (20 isolates) had 2 serotypes. Isolates from group 2 were resistant to more antibiotics and had a greater ability to hemagglutinate erythrocytes and transfer R plasmids to recipient organisms, but a lesser ability to produce siderophore than group 1. All 39 isolates resisted the lethal effects of serum complement. Colicin was produced by 1 of 19 from group 1 and 0 of 20 from group 2. A donor Escherichia coli isolated from a pig with enteritis transferred R plasmids to 62% of group 1 and 0% of group 2 Salmonella spp. when they were used as recipient organisms. A transconjugant from the mating of donor E. coli to a group 1 Salmonella spp. was further able to pass an R plasmid to recipient E. coli and salmonellae. Plasmid isolation from group 1 yielded 1 of 19 strains with a 56-megadalton plasmid, while 20 of 20 strains from group 2 contained three to five plasmids from 2.4 to 60 megadaltons in size.     

Biosynthesis and control of beta-lactam antibiotics: the early steps in the "classical" tripeptide pathway

The interaction between growth and secondary metabolism develops from physiological responses of the producer organism to its environment. Nutrients are channelled into primary growth processes or into secondary processes such as antibiotic biosynthesis by a variety of metabolic controls, the nature of which has been extensively studied in organisms producing beta-lactam antibiotics via the tripeptide, delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine. In the following article we review the early stages of beta-lactam biosynthesis in fungi and actinomycetes, keeping in mind the regulation of primary pathways that provide the amino acid precursors of this group of antibiotics, as well as the regulation of the secondary pathway itself. Of special importance to organisms engaging in secondary metabolism are the control mechanisms that suppress the nonessential process during rapid growth but allow secondary metabolic genes to be expressed and resources to be diverted when environmental factors generate the appropriate biochemical signals.     

Comparison of virulence factors and R plasmids of Salmonella spp. isolated from healthy and ill swine.

The antibiotic resistance and virulence profiles of Salmonella spp. isolated from healthy (group 1) and ill (group 2) swine were compared. Parameters studied included colicin and siderophore production; mannose-sensitive hemagglutination of erythrocytes; resistance to the lethal effect of serum complement; resistance to antibiotics; and the transmissibility of these characteristics to recipient organisms. Group 1 (19 isolates) had 14 serotypes, and group 2 (20 isolates) had 2 serotypes. Isolates from group 2 were resistant to more antibiotics and had a greater ability to hemagglutinate erythrocytes and transfer R plasmids to recipient organisms, but a lesser ability to produce siderophore than group 1. All 39 isolates resisted the lethal effects of serum complement. Colicin was produced by 1 of 19 from group 1 and 0 of 20 from group 2. A donor Escherichia coli isolated from a pig with enteritis transferred R plasmids to 62% of group 1 and 0% of group 2 Salmonella spp. when they were used as recipient organisms. A transconjugant from the mating of donor E. coli to a group 1 Salmonella spp. was further able to pass an R plasmid to recipient E. coli and salmonellae. Plasmid isolation from group 1 yielded 1 of 19 strains with a 56-megadalton plasmid, while 20 of 20 strains from group 2 contained three to five plasmids from 2.4 to 60 megadaltons in size.