Citrobacter freundii作用下球状碳酸盐矿物的形态演化过程研究

不少微生物都具有形成球状碳酸盐矿物的能力。对形成过程的动态跟踪研究是了解球状碳酸盐矿物形成机理的关键。利用光学显微镜和电子显微镜对Citrobacter freundii作用下球状碳酸盐矿物的形成过程进行了跟踪研究。结果表明,纳米晶体在有机物质的包裹下逐渐聚集,最终生长为具有辐射状内部结构和菱形表面纹理的球状构造。在球状构造形成之前,矿物集合体经历了花形、哑铃形、花菜形、纺锤形以及类似于十字形的多种过渡形态。对最初、过渡和最终形态进行总结,有助于理解微生物作用下的球状碳酸盐矿物形成机理,为识别微生物活动在沉积环境中遗留的痕迹提供更多有用的信息。以往的研究极少涉及Citrobacter freundii诱导碳酸盐矿物的形成。研究结果将丰富微生物促进球状碳酸盐矿化的研究内容。

微生物燃料电池中一株产电菌Citrobacter freundii的分离及特性研究

通过形态、生理生化特性及系统进化分析表明,从微生物燃料电池中分离出的产电菌株LY-3与弗氏柠檬酸杆菌(Citrobacter freundii)最相近,将其命名为Citrobacter freundii LY-3。循环伏安扫描显示,该菌株具有电化学活性,在微生物燃料电池中,以牛肉膏为燃料产生的最大电压为0.43V,最大功率密度为98.2mW/m2。

Citrobacter farmeri降解间甲酚的特性分析

从某焦化厂废水好氧生物处理的污泥中分离出一株能以间甲酚为唯一碳源、能源生长代谢的菌株Citro-bacter farmeri。考察了间甲酚在不同初始浓度下Citrobacter farmeri细菌生长动力学,4种等浓度酚类物质的降解先后顺序,分别添加共基质葡萄糖和蛋白胨对低浓度和高浓度间甲酚降解的影响,以及在添加共基质葡萄糖时Citrobacter farmeri降解高浓度间甲酚过程中产生的酶活。结果表明,当间甲酚初始质量浓度低于375 mg/L时,Citrobacter farmeri菌株生长符合一级动力学方程;Citrobacter farmeri降解4种酚类物质的降解顺序依次为苯酚>邻甲酚>间甲酚>萘酚;外加葡萄糖或蛋白胨对质量浓度低于375 mg/L的间甲酚的降解没有影响,但对高于375mg/L的间甲酚降解有明显的促进作用,在最佳葡萄糖添加量为800 mg/L或最佳蛋白胨添加量为640 mg/L时,缩短降解时间分别为30 h和29 h;对酶活的测定发现儿茶酚1,2-双加氧酶和儿茶酚2,3-双加氧酶有明显增大,初步判断Citrobacter farmeri以邻位和间位裂解的途径对间甲酚进行降解。

Establishment and Comparison of Pulsed-field Gel Electrophoresis,Multiple-locus Variable Number Tandem Repeat Analysis and Automated Ribotyping Methods for Subtyping of Citrobacter Strains

Objective To establish and compare the pulsed-field gel electrophoresis （PFGE）, multiple-locus variable number tandem repeat analysis （MLVA） and automated ribotyping for subtyping of Citrobacter strains. Methods PFGE protocol was optimized in terms of plug preparation procedure, restriction enzymes and configuration of electrophoretic parameters. MLVA method was evaluated by finding variable number tandem repeats in two genomes of Citrobacter strains. The ribotyping was performed by using the automated RiboPrinter system. Results We optimized the plug preparation procedure, focused on the cell suspension concentration （turbidity of 2.5 to 3.5）, SDS addition （no SDS needed） and lysis time （1 h）, and selected the appropriate restriction enzyme （Xbal） and the electrophoretic parameters （1.0 s-20.0 s for 19 h） of PFGE. There was nearly no discriminatory power of MLVA between Citrobacter strains. For 51 Citrobacter strains, automated ribotyping gave a D-value of 0.9945, while PFGE gave a D-value of 0.9969. Both PFGE and automated ribotyping clustered strains from the same sources （with the same species from the same place at the same time identified as the same source） and divided strains from different sources （from different years, places and hosts） into different subtypes. Conclusion PFGE protocol established in this paper and automated ribotyping are suitable for application in Citrobacter subtyping.

Isolation,Identification and Antibiotics Susceptibility Test of Citrobacter freundii from Procambarus clarkia

This experiment was conducted to clarify species and drug resistance of pathogen from the diseased Procambarus clarkia. Pathogenic bacteria from hepatopancreas of the diseased P. clarkia were examined using conventional methods,and then were isolated. The further tests and analysis of the isolated strain were developed,including the regression experiment to P. clarkia,the morphology,physiological and biochemical characteristics,sequence analysis of their 16 S rRNA and gyr B genes,and the susceptibility test to antibiotics. Large colonies with similar morphology and color were obtained. Strain X120523 was identified as Citrobacter freundii,proved to have strong pathogenicity,and was susceptible to quinolones and aminoglycosides.

Infective crystalline keratopathy due to Citrobacter koseri

Rationale:Infectious keratopathy is an ocular emergency with the potential to cause irreversible blindness.Patient's concerns:A 63-year-old diabetic man presented with a 3-day history of painful red right eye.He had a history of multiple ocular surgeries in the affected eye without recent ocular trauma.Diagnosis:Infective crystalline keratopathy secondary to Citrobacter koseri.Interventions:Topical corticosteroids were discontinued,and dual topical antibiotic therapy of moxifloxacin 5%and gentamycin 0.3%were applied.Outcomes:Twelve hours after the start of treatment,the crystalline nature of the infiltrate disappeared,with enlargement of the epithelial defect.The antibiotic regime was continued and the lesion healed within a week of presentation with residual scarring.Lessons:Infective crystalline keratopathy classically presents with intrastromal branching fern-like opacities and minimal anterior segment inflammation in an immunosuppressed eye.The mainstay of management is corticosteroid discontinuation and the administration of empirical antibiotics until the results of the culture and sensitivity are available.In Citrobacter-related cases,treatment may result in a suppurative appearance before healing of the lesion.

<i>Citrobacter rodentium</i>, a Gut Pathogen: The Yin and the Yang of Its Pathophysiology, Immunity and Clinical Manifestation in Mice

Pathogenic strains of E. coli including enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC) are principle causes for diarrhoea in many parts of the globe. Citrobacter rodentium (C. rodentium), a gram negative bacterium, is a murine pathogen that also utilizes type III secretion system and similar virulence factors to EPEC and EHEC and forms comparable attaching/effacing lesions in the intestines as EPEC and EHEC. The infection caused by C. rodentium in mice is usually self-limiting and results in only minor systemic effects with higher mortality in some susceptible mouse strains. All these characteristics have made the bacteria a commonly used model to study host immune responses to pathogenic E. coli infection. In this review, we focus on the impact of virulence factors of the pathogen;different immune components involved in the immune response and summarize their role during C. rodentium infection.

Evaluation of the Antimicrobial Activity of Stryphnodendron barbatiman against Citrobacter freundii

Medicinal plants have been presented as a valuable source of preservation of human health. In special, Stryphnodendron barbatiman has been employed due to its antimicrobial activity. This plant is rich in tannins and has been used in popular medicine for the treatment of gastrointestinal disorder, treatment of lesions, and also as anti-inflammatory microbicide. Citrobacter freundii is a member of the family Enterobacteriaceae and is one of the major causes of opportunistic infections. This microorganism is a bacterium (bacillus) aerobic gram-negative with a length in the range of 1 to 5 mm. C. freundii is commonly found in water, soil, food and occasionally in the gastrointestinal tract of animals and humans. In this paper, we have demonstrated the antibacterial activity of S. barbatiman by observing cellular death by using inhibition halo approach. Atomic force microscopy and FT-IR spectroscopy results suggested that interaction between the main active components of S. barbatiman with cellular wall of C. freundii gives rise to cellular wall damage, and then leads this microorganism to death.

Citrobacter sp.LW-3对偶氮染料甲基橙的降解脱色特性研究

从长期受染料污染的土壤中分离出一株能对甲基橙高效降解脱色的柠檬酸盐杆菌Citrobacter sp.LW-3.菌株LW-3在添加了0.5%(g/100 mL)葡萄糖的MSM-1培养基中,16 h使100 mg·L-1甲基橙降解掉90.56%.该菌株对甲基橙降解脱色可在完全好氧条件下,脱色与木质素过氧化物酶、NADH-DCIP原酶、核黄素还原酶有关.菌株LW-3降解甲基橙的适宜温度较广,20~40℃24 h均能使超过80%的甲基橙降解脱色,适宜pH范围为6.0~8.0.通气量对菌株LW-3影响较小,24 h各装液量组(25~200 mL)甲基橙均能降解近90%.同时,菌株LW-3具有较广的染料降解谱,3 d内可使20 mg·L-1另3种偶氮染料、两种三苯甲烷类染料和一种蒽醌类染料很好脱色.菌株LW-3在染料废水的生物处理方面有较强的实际应用价值.

Citrobacter sp. CK3对活性红KN-3B的脱色反应动力学研究

采用脱色菌Citrobacter sp. CK3,以活性红KN-3B染料为处理对象,在厌氧批式反应条件下,系统考察了pH值,温度和染料浓度对脱色反应速度的影响;通过动力学模拟及反应过程中染料的UV-Vis扫描图分析,探讨了脱色反应机理。结果表明:Citrobacter sp. CK3对活性红KN-3B的脱色反应的适宜pH为7～9;脱色反应速度在温度为32℃时达到最大。染料初浓度从57 mg/L逐渐增大到458 mg/L时脱色率逐渐降低。脱色过程中染料的偶氮键发生断裂,脱色反应符合二级反应动力学。

Effect of surfactant on phenanthrene metabolic kinetics by Citrobacter sp. SA01

To attain a better understanding of the effects of surfactants on the metabolic kinetics of hydrophobic organic compounds, the biodegradation of phenanthrene by Citrobacter sp. SA01 was investigated in a batch experiment containing Tween 80, sodium dodecyl benzene sulfonate and liquid mineral salt medium. The Monod model was modified to effectively describe the partition, phenanthrene biodegradation and biopolymer production. The results showed that Tween 80 and sodium dodecyl benzene sulfonate （each at 50 rag/L） enhanced phenanthrene metabolism and poly-β-hydroxybutyrate production as indicated by the increasing amounts of intermediates Coy 17.2% to 47.9%）, and percentages of poly-β- hydroxybutyrate （by 107.3% and 33.1%） within the cell dry weight when compared to their absence. The modified Monod model was capable of predicting microbial growth, phenanthrene depletion and biopolymer production. Furthermore, the Monod kinetic coefficients were largely determined by the surfactant-enhanced partition, suggesting that partitioning is a critical process in surfactant-enhanced bioremediation of hydro- phobic organic compounds.

Citrobacter sp.EBS8对施氏矿物和黄钾铁矾的还原溶解及相转化行为的影响

铁硫酸盐次生矿物广泛存在于酸性矿山废水(AMD)污染流域沉积物中,是多种有毒有害重金属的沉淀库.硫酸盐还原菌对矿物的还原作用可破坏矿物的稳定性从而引起共沉淀重金属的释放.在前期研究中发现柠檬酸杆菌Citrobacter sp.存在于AMD流域沉积物中,且在还原条件下具有较强的硫酸盐还原能力.因此,探究其对铁硫次生矿物的还原溶解及矿物晶相转化行为的影响尤为重要.本研究选取矿区沉积物中典型的铁硫次生矿物施氏矿物和黄钾铁矾为研究对象,在实验室条件下考察了从AMD污染沉积物中筛选到的菌株Citrobacter sp. EBS8对矿物的还原溶解及相转化的影响.结果表明,在缺氧、中性pH及电子供体足量时,在EBS8的作用下施氏矿物和黄钾铁矾均出现了明显的还原溶解现象.菌株EBS8可利用乳酸盐作为电子供体还原SO42-和Fe(Ⅲ).SEM结果显示,施氏矿物在反应初期出现表面毛刺不平现象,黄钾铁矾发生由外向内的逐层溶解,矿物转化过程中都出现空壳形貌.XRD检测到施氏矿物组的主要转化产物为菱铁矿和蓝铁矿,黄钾铁矾体系中主要是蓝铁矿和马基诺矿.这些结果有助于了解AMD污染沉积物中铁硫酸盐矿物的转化行为及为AMD污染治理提供理论支撑.

Immobilization of Lactobacillus plantarum NCIMB 8826 ameliorates Citrobacter rodentium induced lesions and enhances the gut inflammatory response in C57BL/6 weanling mice

Infectious diarrhea is a major cause of infant mortality in most developing countries. In this research, we evaluated the potential of immobilized Lactobacillus plantarum NCIMB 8826 on weanimix infant cereal and its effectiveness in reducing the severity of Citrobacter rodentium-induced diarrhea in weanling mice. Thirty-six C57BL/6 weanling mice were placed into four groups (n = 9 each;negative, positive, prevention and cure). Mice received either L. plantarum (109 CFU/g) immobilized on weanimix infant cereal 3 days before C. rodentium (109 CFU/ ml) infection (Prevention) or 3 days after C. rodentium infection (Cure). A positive control group was infected with C. rodentium only, while a nega-tive control group received neither L. plantarum nor C. rodentium. Positive control mice showed colonic mucosal and submucosal inflammation, erosion, and mucosal epithelia hyperplasia with the C. rodentium infection. Mice in the prevention and cure groups had less severe histologic alterations in the colon. Some beneficial effect of L. plantarum was observed in cecal short-chain fatty acid concentrations, which stimulates water and electrolytes absorption to reduce diarrhea. Our findings demonstrated that L. plantarum NCIMB 8826 could be immobilized on weanimix infant cereal to help reduce diarrhea during weaning.

克氏原螯虾弗氏柠檬酸杆菌的分离鉴定与药敏试验

为确定引起养殖克氏原螯虾(Procambarus clarkii)患病的病原种类及耐药情况,从患病克氏原螯虾肝胰腺取样进行常规细菌学检查,对分离株进行回归感染试验、形态观察、生理生化特性检测、16S rRNA和gyrB基因分析及药敏试验。结果显示:从患病克氏原螯虾肝胰腺分离到大量菌落形态和色泽一致的细菌,代表菌株X120523为弗氏柠檬酸杆菌(Citrobacter freundii),具有较强致病性,对20种抗生素中的喹诺酮类和氨基糖苷类抗生素敏感。

41种中草药对3种鲟源病原菌的体外抑菌效果

采用平板打孔法在观察了弗氏柠檬酸杆菌(Citrobacter freundii)、鲁氏耶尔森氏菌(Yersinia ruckeri)、嗜水气单胞菌(Aeromonas hydrophila)等3种鲟源病原菌对41种中草药敏感性的基础上,进一步采用二倍稀释法测定了具有良好抑菌活性的中草药对3种病原菌的最小抑菌浓度和最小杀菌浓度。实验结果表明,3种病原菌对乌梅、石榴皮、地榆、杞子等均高度敏感,对杜仲、柴胡、丹参、熟地黄等均中度敏感,对麦冬、当归、胖大海、玉竹均不敏感。此外,乌梅、石榴皮、地榆、杞子对3种病原菌的最小抑菌浓度和最小杀菌浓度分别为7.81 mg/mL和15.625 mg/mL、15.625 mg/mL和31.25 mg/mL、15.625 mg/mL和31.25 mg/mL以及15.625 mg/mL和31.25 mg/mL,而杜仲、柴胡、丹参、熟地黄等中度敏感中草药对3种病原菌的最小抑菌浓度和最小杀菌浓度均分别高于31.25 mg/mL和62.5 mg/mL。

Citrobacter Causing Septic Arthritis: A Case Report

The genus Citrobacter commonly found in water and soil as well as the intestinal and urinary tracts of animals and humans.Although Citrobacter infections are infrequently diagnosed in environmental contexts,the rising incidence of nosocomial manifestations underscores the importance of considering this organism in the differential diagnosis of hospital-acquired infections.We present a case of patient with septic arthritis of the shoulder who had been originally admitted for the management of acute-on-chronic congestive heart failure exacerbation and severe sepsis.On hospital day 1,joint aspiration cultures and Gram stain confirmed the presence of Citrobacter koseri,a pathogen not commonly associated with septic arthritis,and ceftriaxone was administered to target it.On hospital day 7,antibiotic was transitioned to levofloxacin,every other day for 4 weeks.The patient was discharged to an acute rehabilitation facility after a 14-day hospital stay.This case stresses the importance of maintaining a broad differential diagnosis for any patients who present with fever and joint inflammation or swelling,especially in a postoperative setting.

大鲵源致病性弗氏柠檬酸杆菌的分离、鉴定和药物敏感性

为鉴定患病大鲵(Andrias davidianus)病原菌,从大鲵肠、胃、脾脏中分离得到菌株int1705,分离菌株经形态特征观察、生理生化特性测定、16S rRNA和aspC管家基因序列测定及系统发育学分析,鉴定为弗氏柠檬酸杆菌(Citrobacter freundii)。经人工感染,结果显示:菌株int1705能使健康大鲵发病并致死,半致死浓度(LD50)为3.16×10 6 CFU/mL,且发病症状与自然发病相似。药敏试验结果显示,菌株int1705对多粘菌素B、头孢他啶、诺氟沙星、氧氟沙星、复方新诺明等10种药物敏感。

一株多重耐药中华鳖源弗氏柠檬酸杆菌的分离鉴定

从患典型鳃腺炎病中华鳖(Pelodiscus sinensis)肝脏和腹水处进行细菌接种,分离获得一株细菌。综合菌落形态,16 S rRNA序列进化分析和API细菌生化鉴定系统判定,所得菌株为弗氏柠檬酸杆菌(Citrobacter freundii)(SX43)。动物回归实验显示,分离株对小鼠的半数致死量(LD50)为106.5CFU,显示该菌株具有较强的致病性,可从实验幼鳖体内再次分离到相同的病原菌。常用药物的抗菌敏感性测定显示,菌株SX43对头孢哌酮、头孢曲松、头孢呋辛、复方新诺明、氯霉素高度敏感。

基于MALDI-TOF MS技术对加州鲈病原弗氏柠檬酸杆菌的快速鉴定

为快速确定广州某养殖水体加州鲈(Micropterus salmoides)暴发性死亡的病原体,本研究利用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)和基于生化法的微生物自动鉴定系统对患病鱼体上分离出的病原菌进行了鉴定,并对该病原菌进行了药物敏感测试。两种方法的检测结果均表明加州鲈患病致死的病原菌为弗氏柠檬酸杆菌(Citrobacter freundii)。药物敏感检测发现该病原菌对氟苯尼考、新霉素、链霉素、诺氟沙星等药物较敏感,对强力霉素红霉素等有耐药性。利用氟苯尼考对水体进行治疗,用药后加州鲈的病情得到有效控制。结果表明,MALDI-TOF MS鉴定结果与生化法完全一致,且具有操作简单、经济快速的特点。

Detection of <i>Escherichia coli</i>and Harmful Enteric Bacterial Pathogens in Domestic Hand-Dug Wells in the Cuvelai Etosha Basin of Namibia

The Cuvelai Etosha Basin of Namibia is characterised by complex aquifer systems with multi-layered aquifers and various water qualities. Some parts of the basin have been covered with a pipeline system that supplies purified surface water from the Kunene River. Locations that lack a pipeline system utilise hand-dug wells as a source of drinking water. These wells draw water from shallow perched aquifers and are not protected from surface contamination nor is the water quality monitored. Sanitised water supply is relevant for the growth and development of societies and is a priority of the United Nations Millennium Development Goals. A bacteriological water quality study aimed at investigating the presence and seasonal variation of;Citrobacter, Escherichia, Klebsiella, Enterobacter, Proteus, Salmonella, Shigella, and Pseudomonas species was conducted on 44 hand-dug wells in the Ohangwena and Omusati regions of the Cuvelai Etosha Basin. Samples were collected from both the wet and dry seasons. Results disclosed the presence of Salmonella, Shigella, Citrobacter, Escherichia, Klebsiella, Enterobacter, Proteus, and Pseudomonas species. Chi-square confirmed a significant seasonal variation in Salmonella (P Shigella (P Citrobacter (P > 0.05), Escherichia (P > 0.05), Klebsiella (P > 0.05), Entero-bacter (P > 0.05), Proteus (P > 0.05) and Pseudomonas (P > 0.05) species. Water from these hand-dug wells is not safe for drinking unless it is subjected to appropriate treatment. It is recommended that hand-dug wells should be properly constructed at safe distances from contaminating structures such as pit latrines and routinely assessed for pathogens, and the water should be sanitized prior to consumption.