益生菌拮抗阪崎肠杆菌的初步研究

目的研究鼠李糖乳杆菌和植物乳杆菌等8种常见益生菌对阪崎肠杆菌的拮抗作用。方法采用牛津杯法测定益生菌耗尽上清对阪崎肠杆菌的抑菌圈,获得对阪崎肠杆菌具有较强抑菌能力的鼠李糖乳杆菌和植物乳杆菌;采用混合培养法对2株益生菌与阪崎肠杆菌的拮抗竞争能力进行测试。结果 8种益生菌耗尽上清均能抑制阪崎肠杆菌,其抑菌能力具有热稳定性且依赖于酸性pH环境。阪崎肠杆菌(107CFU/mL)与鼠李糖乳杆菌(108CFU/mL或109CFU/mL)共孵育至24 h,其活菌量开始逐渐下降,至120 h孵育结束下降到105CFU/mL;菌量比为1:10的阪崎肠杆菌与植物乳杆菌共孵育至24 h,其活菌量开始逐渐下降,菌量比为1:100时则提前至8 h,至120 h孵育结束活菌量均下降到102CFU/mL。结论鼠李糖乳杆菌和植物乳杆菌均能有效地竞争拮抗阪崎肠杆菌。     

Transformation of Maridomycin III by Maridomycin III-Insensitive Streptomycetes

Transformation of maridomycin III, a macrolide antibiotic, by maridomycin (MDM) III-insensitive streptomycetes was examined. Three main transformation products were obtained. In comparison with authentic samples, these transformation products were identified as 18-dihydro MDM III, 4′′-depropionyl MDM III and 18-dihydro-4′′-depropionyl MDM III. Reduction of the C–18 position of the macro lactone moiety of the antibiotic was thought to be a detoxication mechanism of the antibiotic by these insensitive strains.     

餐饮及相关食品中病原菌活菌多重实时荧光PCR检测方法的研究与开发

为了应对餐饮等食品中病原菌快速检测的需求、研究建立病原菌筛查方法,选取痢疾志贺氏菌（Shigella dysenteriae）、金黄色葡萄球菌（Staphylococcus aureus）、副溶血性弧菌（Vibrio parahaemolyticus）、阴沟肠杆菌（Enterobacter cloacae）、产气肠杆菌（Enterobacter aerogenes）、沙门氏菌（Salmonella）、蜡样芽胞杆菌（Bacillus cereus）、大肠埃希氏菌O157∶H7（Escherichia coli O157∶H7）、单核细胞增生李斯特氏菌（Listeria monocytogenes）等9种病原菌开展多重实时荧光PCR方法研究工作。为了节约预增菌时间与提升检测效率,研发了适用于多种病原菌预增菌的通用型培养基,采取高温裂解法提取菌液核酸,利用PMA染料灭活死亡细菌DNA,筛选出活菌DNA,采用多重实时荧光PCR技术检测目标菌,该方法可在16 h内完成检测,对于目标病原菌的检测低限可达103 CFU·mL-1。     

Bioengineering of the Enterobacter aerogenes strain for biohydrogen production

Enterobacter aerogenes is one of the most widely-studied model strains for fermentative hydrogen production. To improve the hydrogen yield of E. aerogenes, the bioengineering on a biomolecular level and metabolic network level is of importance. In this review, the fermentative technology of E. aerogenes for hydrogen production will be first briefly summarized. And then the bioengineering of E. aerogenes for the improvement of hydrogen yield will be thoroughly reviewed, including the anaerobic metabolic networks for hydrogen evolution in E. aerogenes, metabolic engineering for improving hydrogen production in E. aerogenes and mixed culture of E. aerogenes with other hydrogen-producing bacteria to enhance the overall yield in anaerobic cultivation. Finally, a perspective on E. aerogenes as a hydrogen producer including systems bioengineering approach for improving the hydrogen yield and application of the engineered E. aerogenes in mixed culture will be presented.     

Inoculation of hybrid poplar with the endophytic bacterium Enterobacter sp. 638 increases biomass but does not impact leaf level physiology

Endophytic bacteria have been shown to provide several advantages to their host, including enhanced growth. Inoculating biofuel species with endophytic bacteria is therefore an attractive option to increase the productivity of biofuel feedstocks. Here, we investigated the effect of inoculating hard wood cuttings of Populus deltoides Bartr. × Populus. nigra L. clone OP367 with Enterobacter sp. 638. After 17 weeks, plants inoculated with Enterobacter sp. 638 had 55% greater total biomass than un‐inoculated control plants. Study of gas exchange and fluorescence in developing and mature leaves over a diurnal cycle and over a 5 week measurement campaign revealed no effects of inoculation on photosynthesis, stomatal conductance, photosynthetic water use efficiency or the maximum and operating efficiency of photosystem II. However, plants inoculated with Enterobacter sp. 638 had a canopy that was 39% larger than control plants indicating that the enhanced growth was fueled by increased leaf area, not by improved physiology. Leaf nitrogen content was determined at two stages over the 5 week measurement period. No effect of Enterobacter sp. 638 on leaf nitrogen content was found indicating that the larger plants were acquiring sufficient nitrogen. Enterobacter sp. 638 lacks the genes for N₂ fixation, therefore the increased availability of nitrogen likely resulted from enhanced nitrogen acquisition by the 84% larger root system. These data show that Enterobacter sp. 638 has the potential to dramatically increase productivity in poplar. If fully realized in the production environment, these results indicate that an increase in the environmental and economic viability of poplar as a biofuel feedstock is possible when inoculated with endophytic bacteria like Enterobacter sp. 638.     

The effects of bee (Apis mellifera) venom phospholipase A2 on Trypanosoma brucei brucei and enterobacteria

The potential role of phospholipases in trypanosomiasis was investigated using bee venom phospholipase A2 (bvPLA2) as a model. The effects of bvPLA2 on the survival of Trypanosoma brucei brucei, 2 h and 12 h cultures of Enterobacter cloacae, Escherichia coli, Citrobacter freundii were studied. About 1 mg ml⁻¹ bvPLA2 was trypanocidal after 30 min. Some growth occurred at lower concentrations up to 2 h after treatment but viability decreased up to 8 h. Even very low concentrations of bvPLA2 (10⁻¹² mg ml⁻¹) had some trypanocidal activity. Bee venom PLA2 was bactericidal to 2 h bacterial cultures but bacteriostatic to 12 h ones. Minimum bactericidal concentrations were 10⁻⁵-10⁻⁶ mg ml⁻¹. The results showed that bvPLA2 had significant trypanocidal and antibacterial effects on Gram-negative bacteria. The relationship to events occurring during infection is discussed. Phospholipases may play a role in increased endotoxin levels in trypanosomiasis.     

Involvement of Enterobacter cloacae in the mortality of the fish, Mugil cephalus

Aims:  To identify the causative agent of the mortality in the fish, Mugil cephalus , in Muttukadu lagoon.
Methods and Results:  An enteric bacterium from the kidneys of moribund fish M. cephalus , was isolated and identified as Enterobacter cloacae (MK). Mugil cephalus was experimentally infected by this isolate and was re-isolated from the kidneys of the moribund fish. Enterobacter cloacae isolates from the lagoon water (MW1, MW2 and reference strain ATCC 13047) and the reference strain were not able to induce similar pathogenesis. The putative factor imparting pathogenicity to the MK isolate was identified as a cationic molecule, which migrated towards the cathode on agarose gel electrophoresis.
Conclusions:  The Ent. cloacae (MK) isolate harbouring a cationic factor was the causative agent for the mortality of M. cephalus , found in Muttukadu lagoon.
Significance and Impact of the Study:  This study reveals that human enteric bacteria MK which is considered as nonpathogenic to fish, may become pathogenic to fish when it harbours this cationic factor. This cationic factor is found to be pathogenic to the fish M. cephalus leading to mortality. It was also found to be pathogenic to mice. Therefore, the shuttling of Ent. cloacae , harbouring cationic factor, between human and fish may be of human health importance.     

Specific probiotic strains and their combinations counteract adhesion of Enterobacter sakazakii to intestinal mucus

Enterobacter sakazakii is an opportunistic pathogen and an occasional contaminant in powdered infant formula. Interaction between specific probiotics and E. sakazakii may reduce the risk of infection. The aim of this study was to characterize in vitro the ability of probiotics (alone and in combinations) to inhibit, compete with and displace the adhesion of E. sakazakii to immobilized human mucus and to assess their capacity to aggregate with pathogen. Specific probiotic strains have proved to aggregate E. sakazakii cells and, through competitive exclusion, inhibition and displacement of the adhered pathogen, were able to inhibit E. sakazakii action on intestinal mucus. The ability to inhibit and to displace adhered pathogen depended on both the probiotic and the pathogen, suggesting that several complementary mechanisms are involved in the processes. We suggest that the selection of specific probiotic strains and their combinations may be a useful means of counteracting E. sakazakii contamination in infant formula and thus to reduce the risk of emerging infection. This approach may also allow the development of new probiotic combinations to counteract the risks associated with other pathogens by improving the intestinal barrier against pathogens.     

2008—2016年临床分离阴沟肠杆菌的 分布及耐药性变迁

摘要：目的 了解贵州医科大学附属医院2008—2016年阴沟肠杆菌的临床感染分布及耐药性变迁。方法 采用WHONET 5.6软件回顾性分析各年阴沟肠杆菌的检出率、标本类型分布及耐药情况。结果 2008—2016年共分离出2 009株阴沟肠杆菌,主要来源于痰液标本,占52.41％。药敏结果显示,阴沟肠杆菌对氨苄西林/舒巴坦的耐药率最高,对亚胺培南的耐药率最低。与2009年相比,2016年阴沟肠杆菌对氨苄西林/舒巴坦和亚胺培南之外的10种抗生素的耐药率均显著下降（P＜0.05）。结论 阴沟肠杆菌对临床常用抗生素的耐药率基本呈下降趋势,对碳青霉烯类抗生素耐药的阴沟肠杆菌应引起重视。     

Optimization of L-asparaginase production from novel Enterobacter sp., by submerged fermentation using response surface methodology

The culture conditions and nutritional rations influencing the production of extra cellular antileukemic enzyme by novel Enterobacter aerogenes KCTC2190/MTCC111 were optimized in shake-flask culture. Process variables like pH, temperature, incubation time, carbon and nitrogen sources, inducer concentration, and inoculum size were taken into account. In the present study, finest enzyme activity achieved by traditional one variable at a time method was 7.6 IU/mL which was a 2.6-fold increase compared to the initial value. Further, the L-asparaginase production was optimized using response surface methodology, and validated experimental result at optimized process variables gave 18.35 IU/mL of L-asparaginase activity, which is 2.4-times higher than the traditional optimization approach. The study explored the E. aerogenes MTCC111 as a potent and potential bacterial source for high yield of antileukemic drug.