Mutagenicity testing with eukaryotic microorganisms

The different genetic end-points which can be tested to detect genotoxicity of chemicals in fungi and especially in the yeast Saccharomyces cerevisiae are described. They include reversion and forward mutation, mitochondrial deletions and point mutations, mitotic or meiotic intra- and intergenic recombination, chromosomal non-disjunction and aneuploidy. Several factors known to affect the response to genotoxic agents such as the growth parameters, the repair ability, the cells permeability, etc., are discussed. The recent validation studies on the mutagenic and recombinogenic activities of a number of chemicals indicate that within the battery of rapid, low cost and quantitatively reliable tests, the yeast system can be profitably used.     

The organospecific activity of metronidazole and azanidazole in the intrasanguineous host-mediated assay

The genotoxicity of nitroimidazoles and, in particular, their potential carcinogenicity has been demonstrated. In order to investigate the specific target organ(s) for these drugs or their metabolites, a method for measuring mutations in microorganisms, with reference to the metabolism of mammals, was used in mice. Metronidazole and azanidazole were tested for their ability to induce genetic effects in a diploid strain (D7) of Saccharomyces cerevisiae in the Intrasanguineous Host-Mediated Assay. The test compounds showed dose-related increases of point mutation and mitotic gene conversion frequencies in liver, kidney and lung. Azanidazole seemed to favour the kidney and the liver, although increases in genotoxicity were observed also in the lung. Metronidazole was toxic and induced both point mutation and mitotic gene conversion when recovered from the liver. Yeast recovered from the kidney and the lung showed an increase especially in point mutation. This work provides more information about the mechanisms involved in the mutagenicity of nitroimidazoles at the site of action.     

Teichomycins, new antibiotics from Actinoplanes teichomyceticus Nov. Sp. I. Description of the producer strain, fermentation studies and biological properties

A soil isolate of Actinoplanes that produces the chemically unrelated new antibiotics teichomycins A1 and A2 has been proposed as a new species named Actinoplanes teichomyceticus nov. sp. (ATCC 31121). Studies of medium and fermentation conditions indicated that the highest antibiotic titers, ca 900 u/ml, are obtained in a medium containing 1% (w/v) glucose, 1% cotton seed meal, 1% malt extract, and 0.4% yeast extract. Both teichomycin A1 and teichomycin A2 are highly active against gram-positive bacteria. Teichomycin A1 shows some activity against gram-negative bacteria. Both antibiotics cured mice experimentally infected with sensitive bacteria and showed low acute toxicity. Of the two antibiotics teichomycin A2 is the more active.     

Benzanthrins A and B, a new class of quinone antibiotics. I. Discovery, fermentation and antibacterial activity

Nocardia lurida has been shown to produce two novel quinone antibiotics, benzanthrins A and B. The antibiotics were discovered in concentrated butanol extracts of fermentation broths and were separated by TLC and HPLC. Benzanthrins A and B were produced in a fermentation medium consisting of glucose, yeast, selected peptones and CaCO3. The antibiotics were present primarily at 66 hours in shake flask fermentations and from 66 to 162 hours in 14-liter fermentors. Benzanthrins A and B inhibited a number of Gram-positive pathogenic bacteria but were inactive against Gram-negative bacteria.     

44-Homooligomycins A and B, new antitumor antibiotics from Streptomyces bottropensis. Producing organism, fermentation, isolation, structure elucidation and biological properties.

Oligomycin antibiotics, 44-homooligomycin A (NK86-0279 II) and B (NK86-0279 I) are newly discovered antitumor antibiotics with the substitution of ethyl for methyl at carbon 26. They were isolated from the culture broth of Streptomyces bottropensis NK86-0279. The structure of these two compounds was deduced by spectroscopic and X-ray crystallographic analyses. These antibiotics showed potent antitumor activities against various tumor cells in vitro, and were active against Colon 26 carcinoma in vivo. Although they showed no activity at 1,000 micrograms/ml against Gram-positive and Gram-negative bacteria and yeast, they have antifungal activity.     

抗击超级细菌:耐药酶的起源研究和变异预测

随着抗菌药物在临床和农、林、牧、副、鱼业上广泛应用,细菌的耐药性现象越来越严重,新出现的携带新德里金属β-内酰胺酶-1(new delhi metallo-β-lactamase-1,NDM-1)基因的超级细菌,几乎对临床上所有抗菌药物均具有耐药性,而且这一耐药基因位于质粒上,会在细菌中水平转移,对人类健康具有潜在的极大威胁。更严重的是,目前尚无法预知今后将出现何种新的耐药基因,但抗菌药物选择性压力的结果必然导致新的更为棘手的耐药性出现。国内外已有一些探索性工作试图揭示耐药基因的起源,并着力于预测这些基因今后可能的演变方向,以期在新的耐药性出现前作出应对。该文将以β-内酰胺耐药酶为主,概述国内外在耐药酶起源、自然进化、模拟进化等领域的研究进展,希望能为抗击超级细菌提供新的实验思路。     

Potential ecological and human health impacts of antibiotics and antibiotic-resistant bacteria from wastewater treatment plants

The occurrence of antibiotics and other pharmaceuticals in the environment has become an increasing public concern as recent environmental monitoring activities reveal the presence of a broad range of persistent pharmaceuticals in soil and water. Studies show that municipal wastewater treatment plants (WWTPs) are important point sources of antibiotics and antibiotic-resistant bacteria in the environment. The fate of antibiotics and other pharmaceuticals in WWTPs is greatly influenced by the design and operation of treatment systems. Because knowledge on the fate of antibiotics and resistant bacteria in WWTPs is important in estimating their potential impacts on ecology and human health, investigations on occurrence, treatment, and observed effects are reviewed in this article. In addition, human health risk assessment protocols for antibiotic and resistant bacteria are described. Although data on other pharmaceutical compounds are also presented, discussion is focused on antibiotics in the environment because of the potential link to increased emergence of resistance among pathogenic bacteria. The applications of modern analytical methods that facilitate the identification of novel transformation products of pharmaceuticals in environmental matrices are also included to illustrate that the disappearance of the parent pharmaceuticals in WWTPs does not necessarily equate to their complete removal.     

2005～2009年某院细菌分布及耐药性分析

目的：分析我院近年临床分离细菌分布及耐药状况,指导临床合理使用抗菌药。方法：收集2005～2009年我院临床分离细菌对常用抗菌药的敏感性试验数据,采用SPSS17．0统计软件进行数据统计分析。结果：分离出病原菌3467株,其中革兰阴性杆菌占63．1％,革兰阳性球菌占14．7％,酵母菌占21．7％,其他菌占0．5％。革兰阳性球菌对万古霉素高度敏感,革兰阴性杆菌对头孢哌酮／舒巴坦高度敏感,假单胞菌、大肠埃希菌及肺炎克雷伯菌具多重耐药性。结论：我院临床病原菌分布呈高度集中趋势,耐药率虽有所下降,但多数药物的耐药率仍然偏高,耐药菌株比例及耐药复杂性升高,应引起重视,加强管理。     

聋病患者线粒体DNA突变检测在指导家系成员氨基糖苷类药物个体化使用中的应用

目的：确定母系遗传家系一聋病患者的线粒体DNA（mtDNA）突变位点,指导该家系其他成员氨基糖苷类药物的个体化应用。方法：应用PCR、酶切、电泳和DNA序列测序技术,对一个有明确氨基糖苷类抗生素应用史的母系遗传耳聋患者的mtDNA进行研究。结果：该患者存在mtDNA1555位点A→G的突变。结论：提示线粒体DNA点突变是导致该患者致聋的主要因素之一,该患者的正常听力的兄弟姐妹需慎用氨基糖苷类药物,该患者后代应禁用氨基糖苷类药物。     

Novel antibiotics, furaquinocins A and B. Taxonomy, fermentation, isolation and physico-chemical and biological characteristics

Two novel antibiotics, furaquinocins A and B were isolated from the culture broth of Streptomyces sp. KO-3988. These antibiotics possess cytocidal activities against HeLa S3 cells in vitro at concentrations of 3.1 micrograms/ml for A and 1.6 micrograms/ml for B. Neither substance possessed antimicrobial activities against Gram-positive and Gram-negative bacteria, fungi or yeast at a concentration of 1,000 micrograms/ml.     

亚抑菌浓度抗生素对细菌耐药性和毒力影响的研究进展

细菌的耐药性和毒力是决定抗生素治疗成败的关键。近年来研究表明亚抑菌浓度抗生素可以诱导细菌耐药并影响细菌的毒力。本文介绍了亚抑菌浓度抗生素产生的来源；阐述了亚抑菌浓度抗生素对细菌耐药性和毒力的影响。亚抑菌浓度抗生素对细菌耐药性的影响涉及了细菌的耐药选择性、生物被膜和持留菌的形成、基因突变、水平基因转移和基因表达；对细菌毒力的影响主要包括细菌的黏附性、运动性和其它毒力因子。以期为畜牧生产中减少和避免亚抑菌浓度抗菌药的产生，减缓和克服细菌耐药性，降低致病菌的毒力提供参考。     

Determination of binding parameters of macrolides, lincosamides, and streptogramins to Legionella pneumophila

Parameters of [3H]erythromycin binding to Legionella pneumophila were determined in vitro using both an equilibrium and a kinetic method. Different L. pneumophila serogroups, 1-3, and a virulent strain serogroup, 1, were tested. All strains of bacteria exhibited the same binding pattern, with a dissociation constant of 0.15 microM. Other macrolides, streptogramin B-types, and lincosamides competitively displaced bound erythromycin suggesting that these compounds share common binding sites on the bacteria. Minimum inhibitory concentration (MIC) values for macrolides, streptogramin B-types, and lincosamides were determined with buffered charcoal yeast extract (BCYE) medium. A good correlation (r = 0.994) was found between the corresponding inhibition constants of these antibiotics and their MIC. It was also noted that for lincosamides the microbiological inactivity was associated with a very low bacterium affinity. Thus, it is concluded that binding parameters of these antibiotics reflect their efficacy against L. pneumophila in vitro and may serve as a useful adjunct in developing new compounds.     

Targeting non-multiplying organisms as a way to develop novel antimicrobials

Increasing resistance and decreasing numbers of antibiotics reaching the market point to a growing need for novel antibacterial drugs. Most antibiotics are very inefficient at killing non-multiplying bacteria, which live side by side with multiplying ones of the same strain in a clinical infection. Although non-multiplying bacteria do not usually cause disease, they can revert to the multiplying state that leads to overt disease, at which time resistance can emerge. Here we discuss the concept of developing antibacterial drugs by targeting non-multiplying organisms. We define non-multiplying bacteria, discuss the efficacy of existing antibiotics, and assess whether targeting these bacteria might lead to new antibiotics that will decrease the rate of emergence of resistance. Lastly, we review the potential of new molecular targets and live non-multiplying bacteria as possible routes for the development of novel antimicrobial drugs.     

Antimicrobial activity of millingtonia hortensis leaf extract

Polar extracts of the leaves of Millingtonia hortensis showed good antimicrobial activity. Twenty different bacterial strains and two yeast cultures were used. The aqueous alcohol extract showed good activity against all microbes tested, particularly Escherichia coli and Salmonella typhimurium , both Gram-negative bacteria, with MIC values of 6.25 μg/ml. The activity is compared with known antibiotics such as gentamycin and nystatin.     

Watasemycins A and B,new antibiotics produced by Streptomyces sp. TP-A0597

Two novel antibiotics, watasemycins A and B, were isolated from the fermentation broth of an actinomycete strain. The producing strain TP-A0597 was isolated from the seawater sample collected in Toyama Bay, Japan and identified as Streptomyces sp. based on the taxonomic study. The new antibiotics were obtained by solvent extraction and chromatographic purification and spectroscopic analyses identified that they were new analogs of thiazostatins. Watasemycin possesses a methyl group at 5'-position of thiazostatin instead of a hydrogen atom. Watasemycins showed antibiotic activity against Gram-positive and negative bacteria and yeast.     

The cost of antibiotic resistance from a bacterial perspective

The emergence, spread and stability of antibiotic resistance in a bacterial population will be determined by several factors including (a) the volume of drug use, (b) the rate of formation of resistant mutants, (c) the biological cost of resistance and (d) the rate and extent of the genetic compensation of the costs. Generally, resistance is associated with a cost, suggesting that the frequency of resistant bacteria might decline when the use of antibiotics is decreased. However, evolution to reduce these costs, without a concomitant loss of resistance, can occur and result in a stabilization of the resistant bacteria in the population. The rate and trajectory of this compensatory evolution is dependent on the bacterial species, the specific resistance mutation and the environmental conditions under which evolution occurs.     

Induced DNA Damage by Dental Resin Monomers in Somatic Cells

Abstract: The present in vivo study investigated the genotoxicity of four dental resin monomers: triethyleneglycoldimethacrylate (TEGDMA), hydroxyethylmethacrylate (HEMA), urethanedimethacrylate (UDMA) and bisphenol A‐glycidylmethacrylate (BisGMA). The Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster was applied to analyse their genotoxicity expressed as homologous mitotic recombination, point and chromosomal mutation. SMART detects the loss of heterozygosity of marker genes expressed phenotypically on the fly’s wings. This fruit fly has an extensive genetic homology to mammalians, which makes it a suitable model organism for genotoxic investigations. The present findings provide evidence that the mechanistic basis underlying the genotoxicity of UDMA and TEGDMA is related to homologous recombination and gene/chromosomal mutation. A genotoxic pattern can correspondingly be discerned for both UDMA and TEGDMA: their genotoxicity is attributed respectively to 49% and 44% of mitotic recombination, as well as 51% and 56% of mutational events, including point and chromosomal alterations. The monomer UDMA is 1.6 times more active than TEGDMA to induce mutant clones per treatment unit. BisGMA and HEMA had no statistically significant effect on total spot frequencies – suggesting no genotoxic action in the SMART assay. The clinical significance of these observations has to be interpreted for data obtained in other bioassays.     

Antimicrobial Activity of Millingtonia Hortensis Leaf Extract

Polar extracts of the leaves of Millingtonia hortensis showed good antimicrobial activity. Twenty different bacterial strains and two yeast cultures were used. The aqueous alcohol extract showed good activity against all microbes tested, particularly Escherichia coli and Salmonella typhimurium , both Gram-negative bacteria, with MIC values of 6.25 µg/ml. The activity is compared with known antibiotics such as gentamycin and nystatin.     

A novel antibiotic, sohbumycin. Taxonomy, fermentation, isolation and physico-chemical and biological characteristics

A new antibiotic sohbumycin, was isolated from the culture broth of Streptomyces sp. No. 82-85. It appeared to belong to the peptide lactone type of antibiotics from physico-chemical studies and has an empirical formula of C31H47N8O10Cl. In in vitro studies, the antibiotic was found to possess potent cytocidal activity against HeLa S3 cells and antimicrobial activities against Gram-positive bacteria with MIC values about 0.3-0.6 microgram/ml, but showed no activity on the Gram-negative bacteria, yeast and fungi tested.