黏质沙雷菌对碳青霉烯类抗生素的耐药性研究

目的了解黏质沙雷菌的临床感染特点和耐药现状,分析其对碳青霉烯类抗生素的耐药特性。方法回顾性调查2004年—2010年临床分离109株黏质沙雷菌的分布情况,VITEK-60自动化微生物分析仪检测其对临床常用抗菌药物的敏感性,琼脂稀释法测定其对亚胺培南、美罗培南和厄他培南的最低抑菌浓度(MIC)。结果临床分离黏质沙雷菌各年份分离数呈上升趋势。标本来源以痰液标本最多,占73.4%,其次为尿液标本,占12.8%、血液标本,占6.4%;黏质沙雷菌对环丙沙星、复方磺胺甲噁唑、阿米卡星、左氧氟沙星、头孢曲松的敏感率均大于80%,对亚胺培南、美罗培南、厄他培南3种碳青霉烯类抗生素的耐药率分别为8.3%,5.5%和22.0%。结论临床分离的黏质沙雷菌对抗菌药物的总体敏感性较好,但出现较高比例的碳青霉烯类抗生素耐药株,且不同种类碳青霉烯类药物的耐药性存在差异。     

Multicomponent assessment and optimization of the cellulase activity by Serratia marcescens inhabiting decomposed leaf litter soil

In lignocellulosic biomass digestion, the enzymatic hydrolysis of lignocellulosic polymers is regarded as the rate-limiting step for enzyme synthesis. The present study is focused on hydrolytic microbial communities isolation from degraded leaf litter soil, and optimization efforts that aid in the decomposition of biomass in the environment. Based on morphological characteristics and leads from preliminary testing, four of the isolates were determined to be effective cellulose degraders. Molecular identification of robust microbial genera included Galactomyces sp. Cefu3, Aspergillus flavus N11, Serratia marcescens CH1, and Bacillus sp Cp4 species, respectively. Serratia marcescens CH1 was determined to be the most potent of the four isolates for cellulase enzyme activity. Further, Serratia marcescens CH1 exhibited highest multi-enzyme activity for endo-(1,4)-β-D-glucanase, exo-(1,4)-β-D-glucanase, and β-glucosidase. The assay conditions were optimized and determined by the Response Surface Methodology (RSM).     

黏质沙雷菌的产酶现状及抗菌药物耐药性的研究

目的 了解黏质沙雷菌产酶现状和耐药性,为临床治疗黏质沙雷菌提供合理用药的实验依据.方法 常规培养分离细菌,应用VITEK-2全自动细菌分析仪鉴定细菌.常规药敏试验采用K-B纸片法,MIC测定采用微量倍比稀释法,按CLSI规定标准进行.结果 从临床感染的标本中分离出50株黏质沙雷菌,主要是呼吸道标本(占45株).其70%...     

Influence of combined chemicals on prodigiosin Synthesis of Serratia marcescens

The influences of pesticides (Imugan, Diuron, 2,4-D. Simazin, Benodanil, E 600, Parathion, Eserin, Aldrin), heavy metals (ZnCl₂, CdCl₂, CuSO₄, HgCl₂), and mixtures of these two chemical groups on the rate of prodigiosin synthesized by Serratia marcescens in liquid medium have been studied. Prodigiosin synthesis showed a high sensitivity to toxicants. Therefore, a method is suggested using prodigiosin synthesis of S. marcescens for toxicity testing. The amount of prodigiosin and the inhibition zones in cup plate assays were tested in addition. In mixture, various effects depending on the toxin concentrations, used in the test, could be found: The activation of prodigiosin synthesis in submerged cultures by 0.3 mg Benodanil/L was more than 100% in the presence of Imugan or Diuron, and 256% in the presence of 1.5 mg HgCl₂/L.     

Comparative study of phytotoxicity and genotoxicity of soil contaminated with biodiesel,diesel fuel and petroleum

The worldwide spillage of fossil fuels causes an ever-increasing environmental concern due to their resistance to biodegradation and toxicity. The diesel fuel is one of the derivative forms of petroleum that is widely used in the world. Its composition has many aromatic compounds and long hydrocarbons chains, both persistent and hazardous, thus requiring complex microbial dynamics to achieve full biodegradation. At this point, biodiesel has advantages because it is produced from renewable sources. It also has a relatively fast biodegradation. Biodiesel formulation chemically varies according to the raw material used for its production. While vegetable oils tend to have homogeneous proportions of linoleic and oleic fatty acids, animal fats have an heterogeneous distribution of stearic, palmitic and oleic fatty acids. As some studies have already detected the toxic potential of biodiesel from vegetable oil, this study sought information on the phytotoxic and genotoxic potential of animal fat-based biodiesel and compare it with fossil fuel as diesel fuel and crude petroleum. The impacts on the microbial activity of soils contaminated with biodiesel, diesel fuel and crude petroleum were performed by the dehydrogenase activity. Phytotoxicity tests were performed with Eruca sativa seeds and genotoxicity bioassays with Allium cepa seeds. The results showed a rapid assimilation of biodiesel by the autochthonous soil microorganisms. Soil contaminated with either diesel or crude petroleum inhibited the root and hypocotyl elongation of E. sativa. Overall, petroleum contaminated soils showed higher genotoxic potential. Biodiesel from animal fat was rapidly assimilated by soil microorganisms and did not present significant phytotoxic or genotoxic potential, but significantly reduced the mitotic index of A. cepa roots. Our results showed that biodiesel from animal fat have rapid biodegradability. Biodiesel also led to less impacts during seed development and lower genotoxic potential when compared to crude petroleum and diesel fuel. In addition, biodiesel from animal fat does not present the same toxicity demonstrated by biodiesel from soybean-based biodiesel described in current literature.

     

The inactivation of gentamicin and netilmicin by carbenicillin: its effect on Serratia marcescens.

Ten clinical isolates of Serratia marcescens were tested on Mueller-Hinton agar containing gentamicin or netilmicin with carbenicillin. The isolates grew on plates where inactivation occurred, at higher antibiotic concentrations, but failed at lower concentrations. This growth response was individualistic and not closely related to the minimum inhibitory concentrations.     

Multidrug resistance in Serratia marcescens and cloning of genes responsible for the resistance

Six clinically isolated strains of Serratia marcescens were tested for their drug resistance. All showed fairly high resistance to many antimicrobial agents tested including norfloxacin, streptomycin, ampicillin, erythromycin, tetracycline, chloramphenicol, and antimicrobial dyes. Using the drug-hypersensitive strain of Escherichia coli KAM32 as the host, we cloned the genes responsible for multidrug resistance from chromosomal DNA of one of the strains of S. marcescens, NUSM8906. We obtained 28 hybrid plasmids that made host cells resistant to several antimicrobial agents. Many of the transformants harboring each of the plasmids showed multidrug resistance, and some showed resistance to specific drugs. The hybrid plasmids were classified into several groups based on their drug specificity. It appears that each class of plasmid carries different types of drug resistance genes. Analysis of such genes will reveal the multiple mechanisms involved in multidrug resistance in S. marcescens.     

Chemical and electrophoretic changes induced by polymyxin B on outer membrane components from Serratia marcescens.

The effects of polymyxin B (PB) on outer membrane (OM) components from resistant (strain 08) and sensitive (strain Bizio) cells of Serratia marcescens were characterized by chemical analysis and polyacrylamide gel electrophoresis (PGE) in sodium dodecylsulfate. Chemical analysis revealed no major differences in the OM fractions after PB treatment of both strains, except for the loss of protein in PB treated OM of the sensitive strain. The yield and composition between the lipopolysaccharides (LPS) of the two strains were different both before and after treatment. PGE revealed that there was a complex formation between the LPS of resistant strain and PB but both dissociation and degradation occurred in the LPS components in the sensitive strain. In addition, it was found that the protein components were destabilized by PB with subsequent loss of some of the components from OM of the sensitive strain. The difference in the amount of LPS and their ability to complex with PB may reflect different degrees of antibiotic susceptibility of these two strains of S. marcescens. A sequential multistep mechanism is proposed for the action of PB on outer membranes of this species.     

Molecular cloning and characterization of a multidrug efflux pump, SmfY, from Serratia marcescens

We cloned a gene smfY for multidrug efflux pump from chromosomal DNA of Serratia marcescens using drug-hypersensitive Escherichia coli KAM32 as the host, and characterized the pump. E. coli KAM32/pESM42 carrying the smfY showed significantly increased MICs of various drugs including DAPI, norfloxacin, benzalkonium chloride, acriflavine and ethidium bromide, compared with the control. We also detected energy-dependent ethidium and acriflavine efflux due to the SmfY. Sequence analysis revealed that the SmfY was a multidrug efflux pump of the MF (Major Facilitator) superfamily transporters. This is the first report of a multidrug efflux pump belonging to the MF superfamily in S. marcescens.     

Perspectives on phytoremediation of zinc pollution in air,water and soil

In this article, we discuss the phytoremediation of Zn pollution in the environment and the mechanism of plant resistance focusing on the mycorrhiza and subcellular mechanisms affecting metal binding and efflux in plants. Phytoremediation is a green low-cost technology that use plants to remove heavy metals (HMs) from soil. As part of this, it is necessary to consider the plant's tolerance to for example zinc (Zn) together with the plant's ability to accumulate and adapt to the specific local environment. During the process of restoring ecosystem contaminations, pH, organic matter, root exudates and microbial biomass affect the efficiency of phytoremediation while considering chemical modification, biosynthesis, microbial assistance and gene technology. However, obstacles remain in terms of for example chemical modifications that may cause either new pollution or disrupt the plant-microorganism symbiosis while other applications such as genetic engineering to change plant traits and function thereby improving heavy metal tolerance and absorption. The selection of gene fragments is complicated and requiring careful considerations due to environmental and human health side effects. Furthermore, using biochar may help to reduce the costs and increase the efficiency of plant phytoremediation. At the same time, there is an urgent need to combine nanotechnology and use of artificial chelating agents and plant hormones to screen the microbiome conducive to plant Zn absorption in order to improve the efficiency of phytoremediation.     

Studies on the combination action of sisomicin, gentamicin and piperacillin, cefmetazole against Pseudomonas aeruginosa and Serratia marcescens

The combined actions of sisomicin (SISO), gentamicin (GM) and piperacillin (PIPC), cefmetazole (CMZ) against Pseudomonas aeruginosa E-2 and Serratia marcescens T-55 were studied. The following results were obtained. 1. The combinations of SISO-PIPC, SISO-CMZ, GM-PIPC and GM-CMZ using the checker board dilution method on P. aeruginosa E-2 and S. marcescens T-55 were found to have a synergistic effect and the minimum FIC index values were 0.38 in all combinations. 2. With the killing kinetic method, all combinations tested showed a synergistic effect. 3. A synergistic effect of the combinations of SISO-PIPC, SISO-CMZ, GM-PIPC and GM-CMZ was observed in the protective effect on experimental P. aeruginosa E-2 and S. marcescens T-55 infections in mice.     

Prostaglandins and thromboxane in the delayed phase of shock induced by Serratia marcescens endotoxin.

The cardiovascular and metabolic effects of an endotoxin derived from Serratia marcescens were examined in anaesthetized, spontaneously-breathing cats. There was a marked initial elevation of right atrial pressure (the result of pulmonary vasoconstriction) and decreases in systemic arterial pressure and in arterial PO2. The 'delayed' effects of endotoxin shock in this species (1-8 h) consisted of a reduced cardiac output and decreased urinary excretion. Blood pressure and myocardial contractility (assessed from measurement of left ventricular (LV) dP/dt and LV end-diastolic pressure) were maintained throughout this phase. There was evidence of a metabolic (lactic) acidosis largely compensated by hyperventilation. Plasma levels (both arterial and mixed venous blood samples) of prostaglandin (PG)E2, PGF2 alpha, 6-keto PGF1 alpha and thromboxane (TX)B2 were measured by radioimmunoassay techniques. Endotoxin administration caused substantial increases in the plasma levels of all four derivatives of arachidonic acid, especially between 1 and 6 h. Separation of the endotoxin-treated cats into survivors and non-survivors showed that the non-survivors had significantly higher circulating levels of PGE2, TXB2 and PGF2 alpha. It is suggested that TXB2 and PGF2 alpha might contribute to some of the detrimental effects of endotoxin (e.g. pulmonary, mesenteric, renal vasoconstriction; platelet aggregation with resulting organ failure) and that prostacyclin may be beneficial in endotoxin shock in this species.     

In vitro investigations on the action fosfomycin alone and in combination with other antibiotics on Pseudomonas aeruginosa and Serratia marcescens

86.4% of the Pseudomonas aeruginosa and 91% of the Serratia marcescens strains were sensitive to fosfomycin. In combination with mezlocillin, cefoxitin, gentamicin and nalidixic acid a synergistic action was detected against these bacterial strains. It was most marked in the combination fosfomycin/nalidixic acid against Serratia marcescens. An acceleration of the fosfomycin action on the bacterial cells and the speed of bacteriolysis was observed in weakly acid medium (pH 6.0), in the presence of 10% active human serum and with increasing glucose-6-phosphate concentrations in the test medium. There is no parallel resistance between gentamicin and fosfomycin against Pseudomonas aeruginosa.