Effect of Capsular Polysaccharide of Klebsiella pneumoniae on Host Resistance to Bacterial Infections

In normal mice, the total count of peritoneal leukocytes was markedly decreased after intraperitoneal (i.p.) injection of the capsular polysaccharide of Klebsiella pneumoniae (CPS-K) depending on the dosage injected. This decrease was mainly due to the depletion of macrophages, and a decrease in the number of lymphocytes occurred to a lesser extent. CPS-K in relatively smaller doses mobilized polymorphonuclear neutrophilic leukocytes (PMN) into the peritoneal fluid but it decreased them transiently in larger doses. In mice infected i.p. with a virulent strain of Salmonella enteritidis, there was an abundant emigration of PMN into the peritoneal fluid. When 200 μg of CPS-K was injected i.p. immediately before bacterial challenge, emigration of PMN was markedly delayed for 48 hr after infection. Associated with this suppressed emigration of PMN, the numbers of macrophages and lymphocytes in the peritoneal fluid were significantly less in mice treated with CPS-K than those in untreated control mice for 48 hr after infection. The numbers of both cell-associated and extracellular bacteria in the peritoneal fluid were markedly greater in mice treated with CPS-K than those in untreated control mice. In both in vivo and in vitro experiments, ingestion of bacteria by macrophages and PMN was not blocked by CPS-K or neutral CPS-K, the active substance responsible for the infection-promoting effect of CPS-K. It appeared that CPS-K somehow impaired the intraphagocytic bactericidal activity.     

Prior stimulation of antigen-presenting cells with Lactobacillus regulates excessive antigen-specific cytokine responses in vitro when compared with Bacteroides

The development of allergy is related to differences in the intestinal microbiota. Therefore, it is suggested that the immune responses induced by different genera of bacteria might be regulated through adaptive as well as innate immunity. In this study, we examined whether antigen-specific immune responses were affected by stimulation with the different genera of intestinal bacteria in vitro. Mesenteric lymph node (MLN) cells isolated from germ-free ovalbumin (OVA)-specific T cell receptor transgenic (OVA-Tg) mice were stimulated with OVA and intestinal bacteria. Cecal contents from conventional mice but not germ-free mice could induce OVA-specific cytokine production. Among the murine intestinal bacteria, Bacteroides acidofaciens (BA) enhanced OVA-specific IFN-γ and IL-10 production while Lactobacillus johnsonii (LA) increased OVA-specific IL-10 production only. The expression of cell surface molecules and cytokine production by antigen-presenting cells (APCs) from germ-free Balb/c mice were analyzed. BA increased the expression of MHC II and co-stimulatory molecules on APCs compared with LA. BA increased IL-6 and IL-10 production but induced less IL-12p40 than LA. To examine the effects of prior stimulation of APCs by intestinal bacteria on the induction of antigen-specific immune responses, cytokine production was determined following co-culture with OVA, CD4⁺ T cells from OVA-Tg mice, and APCs which were pre-stimulated with the bacteria or not. APCs pre-stimulated with LA did not enhance OVA-specific cytokine production while BA stimulated OVA-specific IL-10 production. These results suggest that the prior stimulation of intestinal immunocytes by Lactobacillus might regulate excessive antigen-specific cytokine responses via APCs when compared with prior stimulation by Bacteroides.     

A New Hypothalamic Polypeptide Is a Regulator of Myelopoiesis

The effect of hypothalamic proline-rich polypeptide (PRP) against Pseudomonas aeruginosa infection in BALB/c mice with leukopenia was investigated. Mice were treated with cyclophosphamide (CPA) and were then injected with PRP 24 h after CPA treatment. The lethal doses of P. aeruginosa were injected to mice when the number of peripheral blood leukocytes reached a nadir on day 5 after CPA administration. The administration of PRP significantly increased the survival of infected mice, and had a pronounced protective effect during the period of development of the infection. The number of bacteria in internal organs of PRP-treated mice was significantly lower than that in control mice. In PRP-treated mice, the neutrophil levels in peripheral blood started to increase 7 days after CPA administration and were consistently higher, and they were more mature than those in controls. Our results may indicate the ability of PRP to stimulate recovery of myelopoiesis and enhance mature neutrophil function.     

Antioxidant and hepatoprotective activities of low molecular weight sulfated polysaccharide from Laminaria japonica

A low molecular weight sulfated polysaccharide (LMWF) was prepared from Laminaria japonica by mild acid hydrolysis. The antioxidant activity of LMWF in vitro was studied using three kinds of oxygen free radical systems. LMWF had effective scavenging abilities on superoxide radical, hydroxyl radical and hypochlorous acid directly in vitro. The hepatoprotective effect of LMWF was studied using two acute liver injury mice models induced by carbon tetrachloride (CCl₄) and D-galactosamine (D-GalN). Addition of LMWF significantly lowered the content of serum malonaldehyde and markedly increased the activities of superoxide dismutase and glutathione peroxidase, compared with the model groups in both kinds of liver injury mice. Moreover, administration of LMWF significantly inhibited the elevation of glutamate pyruvate transaminase induced by CCl₄ and D-GalN in mice. The results suggest that the antioxidant activity of LMWF plays an important role in its hepatoprotective effect in the liver injury mice induced by CCl₄ and D-GalN.     

<Emphasis Type="Italic">Nramp1</Emphasis> deletion does not confer susceptibility to<Emphasis Type="Italic"> Rhodococcus equi</Emphasis> infection in mice

Rhodococcus equi is an intracellular bacterium that causes pneumonia in immunocompromised people and foals. The Nramp1 gene influences susceptibility to a variety of intracellular bacteria (including mycobacterial species), but not to Mycobacterium tuberculosis. In this study, we demonstrate that mice functionally deleted of the Nramp1 gene were not more susceptible to infection with virulent R. equi (ATCC 33701) than wild-type mice. Susceptibility of mice to infection with the intracellular bacterium R. equi is more similar to that of M. tuberculosis than to other intracellular bacteria, including other mycobacteria.     

嗜线虫致病杆菌抑制灰葡萄孢的效应

[背景] 灰葡萄孢（Botrytis cinerea）是引起葡萄采后病害的主要病原菌之一,严重影响葡萄的贮期和品质,给葡萄产业带来极大损失。利用拮抗微生物抑制采后病原菌生长已逐渐成为防治葡萄采后灰霉病的重要手段。[目的] 利用昆虫病原线虫共生细菌广谱高效的抑菌特性,从现有共生细菌资源中筛选对灰葡萄孢具有高拮抗作用的菌株,为葡萄采后灰霉病的抑制提供新的材料和研究方向。[方法] 通过平板对峙培养法和菌丝生长速率法分离筛选拮抗共生细菌,并对优选的高效拮抗共生细菌进行16S rRNA基因序列进化分析,采用扫描电镜观察其对灰葡萄孢菌丝生长的影响,利用损伤接种法对红地球葡萄防治效果进行验证。[结果] 初步分离筛选共获得9株拮抗菌,复筛与复测得到一株抑菌效果显著的共生细菌（命名为ALL）,经进化分析其为嗜线虫致病杆菌（Xenorhabdus nematophila）,其16S rRNA基因序列的Genbank登录号为MW488402,与菌株Xenorhabdus nematophi la NC116聚于同一分支,相似性达99.79%。扫描电镜观察该菌株导致灰葡萄孢菌丝扭曲变形、表面皱缩、失水塌陷,该菌株发酵（36 h）上清液浓度为1%时对灰葡萄孢菌丝抑制率达44.5%。在葡萄常温防效实验中,与对照组比较,ALL菌株发酵上清液对灰霉菌防治效果较好,3 d后防效为63.50%。[结论] 本研究应用昆虫病原线虫共生细菌生物防治葡萄贮期灰霉病,筛选出一株高效拮抗灰葡萄孢的昆虫病原线虫共生细菌,而且其上清液对灰葡萄孢具有良好的抑制效果,为生物防治贮期葡萄灰霉病提供了新的生物材料和相关研究基础。     

Mechanism of protective effect of recombinant human granulocyte colony-stimulating factor (rG-CSF) on Pseudomonas infection.

Decrease in resistance to systemic Pseudomonas infection in cyclophosphamide (CPA)-induced neutropenic mice was prevented by injections of recombinant human granulocyte colony-stimulating factor (rG-CSF). In order to explore mechanism of the prevention of CPA-induced decrease in the anti-infectious resistance by rG-CSF, CPA-treated and then rG-CSF-injected mice were inoculated i.p. with P. aeruginosa, and growth of the infecting bacteria and infiltration of leukocytes in the peritoneal cavity were determined. In the mice who had received 4 daily s.c. injections of rG-CSF from the day after CPA-injection, a large number of neutrophils were mobilized into the peritoneal cavity in response to the bacterial inoculation and growth of the infecting Pseudomonas in the cavity was markedly inhibited, whereas in CPA-induced neutropenic mice few neutrophils were mobilized and the infecting bacteria proliferated vigorously in the peritoneal cavity. These results suggest that administration of rG-CSF prevents CPA-induced neutropenia and neutrophils circulating at normal level in the number are normally mobilized into the peritoneal cavity in response to Pseudomonas inoculation, and that the mobilized neutrophils inhibit proliferation of the infecting Pseudomonas.     

Mutagenic properties of a nitrofuran, 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), in lacI transgenic mice

The in vivo mutagenic properties of a 5-nitrofuran, the 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), already well known in bacteria, was evaluated in lacI transgenic mice (Big Blue). The mutation frequency was determined in various organs of i.p. — treated mice and the nature of induced mutations was determined for the target organs in which mutation induction was significant. It was found that R7000 is mutagenic in mice, although, on the basis of the number of induced mutants per unit mass in comparison with other known mutagenic chemicals, R7000 appears to be considerably less mutagenic in mice than in bacteria. The most affected organs, small intestine, caecum and colon organs belong to the digestive apparatus. The distribution of R7000-induced mutations in the lacI gene recovered from small intestine of transgenic mice was very similar to that which had been found in E. coli. The difference between mouse and E. coli in the R7000 induced mutational spectra are mainly in the proportion of single base frameshifts versus base substitutions. Since R7000 induced mutations seemed to arise in the population of stem cells and that the stem cells are important for carcinogenesis, our results are compatible with a possible carcinogenic effect of R7000 and other nitrofurans.     

石榴PgUFGT基因克隆及表达分析

利用RT-PCR和RACE方法,从石榴(Punica granatum L.)果皮中克隆到一个类黄酮糖基转移酶(UFGT)基因(PgUFGT)全长cDNA序列(GenBank登录号为KF841620)。PgUFGT基因编码区1 476bp,编码491个氨基酸。PgUFGT蛋白具有保守PSPG基序、UDP-糖基转移酶家族结构域和UDP-葡萄糖醛酸基/葡萄糖基转移酶保守域(UDPGT),与其他植物UFGT蛋白一致性较高;系统进化树分析结果表明,PgUFGT属于类黄酮3-O-糖基转移酶类。荧光定量qRT-PCR结果表明,PgUFGT基因在‘红宝石’和‘水晶甜’2个石榴品种的发育期内具有不同的表达模式,PgUFGT在‘红宝石’石榴中有2个转录表达高峰,而在‘水晶甜’石榴中仅有1个表达高峰,表明PgUFGT可能在2个石榴品种中具有不同的催化作用。该研究结果为进一步研究石榴果实色泽形成的分子机制奠定了基础。     

Role of anaerobiosis in virulence of Salmonella typhimuirium

Intestinal pathogens are exposed to various stress conditions during their infectious cycle. Anaerobiosis, one of such hostile condition, is offered by the host within gut and intestinal lumen, where survival, multiplication and entry into intestinal epithelial cells is priority for the invading pathogen. In the present study, a virulent strain of S. typhimurium (1402/84) was grown under anaerobic conditions and its virulence characteristics such as host cell binding, penetration and intracellular survival were compared with aerobic S. typhimurium. Anaerobically grown S. typhimurium showed significantly higher binding to immobilized mice enterocytes and intestinal mucus as compared to bacteria grown aerobically. Anaerobic bacteria also showed an early penetration of mucus and subsequent binding to underlying immobilized enterocytes, in vitro. Anaerobic S. typhimurium exhibited increased intracellular survival within spleen macrophages of mice and caused significantly higher fluid accumulation in ligated rabbit ileal loops as compared to aerobic bacteria. LD₅₀ of anaerobic S. typhimurium was also observed to be 2 fold lower when compared to aerobic bacteria. Cell surface hydrophobicity of anaerobic S. typhimurium was also found to be significantly higher than aerobic bacteria. Thus, it appears that exposure of S. typhimurium to anaerobiosis results in its enhanced virulence, adhesion and penetration of host cells.     

布鲁氏菌逃逸宿主的抗感染免疫机制

布鲁氏菌病是由布鲁氏菌引发的世界范围的人兽共患传染病。布鲁氏菌为兼性胞内寄生菌,无典型的毒力因子,但却有很强的致病性,常引发人和动物的慢性感染。逃逸宿主的抗感染免疫反应是慢性感染的先决条件,这种能力对于布鲁氏菌的毒力来说似乎也越来越关键。作为成功的致病性病原菌,布鲁氏菌采用"隐秘的"策略以逃避或抑制固有免疫、调节适应性免疫,从而在宿主细胞内建立长期的持续性感染。本文将围绕布鲁氏菌逃逸宿主的抗感染免疫的分子机制进行阐述,旨为阐明布鲁氏菌毒力的新见解,这很可能为布病的预防开辟新的途径。     

Rhizosphere bacteria antagonistic to soybean cyst (Heterodera glycines) and root-knot (Meloidogyne incognita) nematodes: Identification by fatty acid analysis and frequency of biological control activity

Rhizosphere bacteria were isolated from roots of young and mature plants with known antagonism to phytopathogenic nematodes, including velvet bean (Mucuna deeringiana), castor bean (Ricinus communis), sword bean (Cannavalia ensiformis), and Abruzzi rye (Secale cereale). Isolates from antagonistic plants were compared to soybean isolates for the frequency of antagonism to the root-knot (Meloidogyne incognita) and soybean cyst (Heterodera schachtii) nematodes in a disease assay with soybean. Bacterial isolates were identified using fatty acid analysis, and isolates which exhibited a significant reduction in incidence of soybean damage from both nematodes were characterized physiologically. The bacterial taxa associated with antagonistic plants were markedly different from soybean bacteria. Isolates from soybean were predominantly Bacillus spp., while those from antagonistic plants included more coryneform and Gram-negative genera. Pseudomonas cepacia and Pseudomonas gladioli were predominant among Gram-negative bacteria on antagonistic plants but were not isolated from soybean. Four to six times the number of bacteria from antagonistic plants, compared to soybean, significantly reduced disease incidence of both nematodes. No single pattern of physiological reactions was common among all these bacteria, suggesting that multiple mechanisms accounted for the observed biological control. The results suggest that rhizospheres of antagonistic plants may be useful sources of potential biological control agents for phytopathogenic nematodes.     

Microbiological survey for selected bacterial pathogens in European storm petrel (<Emphasis Type="Italic">Hydrobates pelagicus</Emphasis>, Linnaeus 1758) from Grosa Island (Murcia,Southeastern Spain)

The current work shows the first step in the knowledge on the health status of European storm petrel (Hydrobates pelagicus) colony inhabiting Grosa Island (Murcia, SE Spain). We performed a screening about the bacterial pathogens carried by them (among the infectious agents checked, bacteria of the orders Mollicutes and Chlamydiales, and the genera Salmonella are of main interest) and compare these results with similar works performed in Larus species because most of the breeding colonies of storm petrel share habitats with gull colonies, and these could become pathogen reservoirs to petrels. Our results show the European storm petrels sampled have absence of pathogens of main interest and low levels of opportunistic pathogens. No Mycoplasma species were isolated, and no Chlamydophila psittaci were demonstrated by lipopolysaccharide antigen immunodetection. The commensal bacteria were isolated in higher frequencies than the previous [Staphylococcus epidermidis (5/15), Staphylococcus hominis (2/15) and Staphylococcus aureus (1/15)]. The rate of isolation of Gram-negative was lower than in the previous Gram-positive bacteria [Pasteurella sp. (1/15) and Pseudomonas aeruginosa (1/15)], and no Enterobacteriaceae were isolated. The absence of pathogen carriers on European storm petrel is the main conclusion of this survey; it is an evidence that the bacterial infectious pathogens described in gulls may not be an important selective force on their survival.     

Effects of iron and desferrioxamine on Rhizopus infection

To investigate the association among iron, desferrioxamine, and a Rhizopus infection, the influence of iron and/or desferrioxamine on experimental mucormycosis in mice was examined. All mice pretreated with iron, desferrioxamine, or a combination of iron and desferrioxamine died within 5 days after the inoculation of R. oryzae. In the mice fungal lesions were observed in the brain which resembled human cerebral mucormycosis. By contrast, the mortality in the control mice with R. oryzae was 20% through the 3-week experimental period. Therefore, it was demonstrated that iron as well as desferrioxamine administration markedly promotes the growth of R. oryzae. The increased susceptibility to R. oryzae was considered to be due to increased serum iron in the animals pretreated with iron only; however, pretreatment with desferrioxamine did not affect the amount of serum ion. Thus, the data suggest that desferrioxamine acts as a siderophore to R. oryzae and exerts an adverse effect on mucormycosis. This study has shown that the presence of iron and desferrioxamine enhances the virulence and pathogenicity of R. oryzae by serving as a growth factor.     

The influence of local plant growth conditions on non-fastidious bacterial contamination of meristem-tips ofHydrangea culturedin vitro

A high incidence ofin vitro bacterial contamination (69%) has been detected in meristem-tip explants ofHydrangea from widely differing locations in Ireland and the UK. The bacteria were characterised by API 20E biochemical test kits and by fatty acid profile analysis. The results obtained from the different methods were compatible and anomalies were explicable in terms of the limitations of the respective methods. The majority of the isolates were environmental or animal-associated bacteria with clusters ofEnterobacter isolates in Dublin, and ofEscherichia coli in the main Cork location. A cluster of Pseudomonads was detected in the Derby (UK) plants. The main association was between the location and the contaminant clusters. The main finding was that the nature of organic soil amendments may influence inoculum for the contamination of plants and the conclusion was that fertilisation with organic materials should be avoided in the preparation of plants for micropropagation.     

Secretory expression of K88 (F4) fimbrial adhesin FaeG by recombinant <Emphasis Type="Italic">Lactococcus lactis</Emphasis> for oral vaccination and its protective immune response in mice

K88 (F4) fimbrial adhesin, FaeG, was expressed extracellularly in Lactococcus lactis using a nisin-controlled gene expression system. The antibody response and protective efficacy of the recombinant bacteria (L. lactis [spNZ8048-faeG]) against live enterotoxigenic E. coli (ETEC) C₈₃₅₄₉ challenge were evaluated in ICR mice. Mice vaccinated with L. lactis [spNZ8048-faeG] had a significantly increased antigen-specific IgG level in the serum and decreased mortality rate (P < 0.05) compared with the control. This indicates that oral immunization of L. lactis [spNZ8048-faeG] can induce an immune-response protection upon challenge with live ETEC in ICR mice. An erratum to this article can be found at     

分叉双歧杆菌对小鼠腹水瘤的抑制作用

本文观察了分叉双歧杆菌对小鼠腹腔移植的淋巴细胞腹水瘤(SRS)的抑制作用。结果发现,分叉双歧杆菌在SRS瘤细胞移植前或移植后应用,均能明显抑制瘤细胞的生长,特别在移植后应用,抗瘤效果更显著。主要表现为荷瘤小鼠存活时间延长、存活率提高。将该菌预先进行处理或不处理后加入体外培养的SRS瘤细胞中,发现该菌对离体的瘤细胞生长也有直接抑制作用。     

The association of algicidal bacteria and raphidophyte blooms in South Carolina brackish detention ponds

Over the past 5 years, raphidophyte blooms have been frequently observed along the South Carolina coastal zone. During the 2002, 2003, and 2004 sampling seasons, we investigated temporal fluctuations of algicidal bacteria abundance against raphidophycean flagellates (Heterosigma akashiwo, Chattonella subsalsa, and Fibrocapsa japonica) using the microplate most probable number (MPN) method in three Kiawah Island brackish stormwater detention ponds (K1, K2, and K75). Local axenic isolates of H. akashiwo, C. subsalsa, and F. japonica were obtained and their susceptibility to algicidal bacteria tested. A total of 195 algicidal bacterial strains were isolated from raphidophyte blooms in the study ponds, and 6 of them were identified at the genus level, and the taxonomic specificity of their algicidal activity was tested against local (pond) and nonlocal isolates of raphidophytes (3 species, 10 total strains). In the ponds, a consistent association was found between raphidophyte bloom development and an increase in bacteria algicidal to the bloom species. In 12 of 15 cases, bloom decline followed the increase in algicidal bacteria to maximum abundances. Although variability was found in the taxonomic specificity of the algicidal bacteria effect (i.e. the number of raphidophyte species affected by a particular bacteria strain) and raphidophyte susceptibility (i.e. the number bacteria strains affecting a particular raphidophyte species), a toxic effect was always found when strains of a raphidophyte species were exposed to algicidal bacteria isolated from a bloom caused by that same species. The results suggest that algicidal bacteria may be an important limiting factor in raphidophyte bloom sustenance and can promote bloom decline in brackish lagoonal eutrophic estuaries.     

沙门菌噬菌体抗性菌的筛选鉴定及致病力研究

【目的】筛选鉴定沙门菌噬菌体侵染裂解过程中的抗性菌株,研究抗性菌株的生物学特性及致病力的差异,为解决噬菌体治疗应用中的抗性菌问题提供理论依据。【方法】本研究通过次级感染法和双层平板法筛选沙门菌噬菌体抗性菌,通过生物学特性和毒力基因检测比较宿主菌ATCC 13076及其噬菌体抗性菌株R3之间的差异,并通过小鼠攻毒实验和细胞粘附实验比较致病力强弱。【结果】噬菌体抗性菌株R3的生长速度较宿主菌略慢;生化及毒力基因检测均表明抗性菌株与宿主菌无差异;与宿主菌相比,抗性菌R3的LD50增加了74.8%(P>0.05);对MODE-K细胞粘附能力稍弱,但是差异不显著。【结论】该研究表明,与噬菌体宿主菌相比,噬菌体抗性菌株的生物学特性和毒力基因并没有改变,对小鼠致病力减弱,但是对MODE-K细胞粘附能力差异不显著。     

对硝基苯酚对细菌产生持留菌的影响及其相关机制

【目的】研究对硝基苯酚(PNP)对大肠杆菌和铜绿假单胞菌产生持留菌的影响,并对转录组进行分析,阐明对硝基苯酚影响持留菌形成的相关机制。【方法】采用氧氟沙星抗生素探究对硝基苯酚对细菌产生持留菌的影响,并通过检测细菌自溶情况和呼吸抑制剂羰酰氰氯苯腙(CCCP)对持留菌比例的影响,然后通过转录组分析其相关基因的表达,最后通过实时荧光定量PCR和反义核酸进行相关功能基因的验证。【结果】PNP可以通过抑制大肠杆菌和铜绿假单胞菌的呼吸作用使其产生持留菌的比例增加,PNP不同浓度、作用不同时间和作用不同生长时期的菌体都会影响细菌产生持留菌的比例。PNP和呼吸抑制剂CCCP均能够抑制2个菌体的自溶情况,包括溶解氧含量的变化、蛋白质降解情况、细胞尺寸的变化和RNA完整性。转录组分析和实时荧光定量PCR实验结果表明加入PNP后,cyo A、app C两个基因在大肠杆菌和铜绿假单胞菌中的表达量均显著下降,再通过反义核酸抑制cyo A、app C的表达发现持留菌的比例和原始菌株相比均有所增加。【结论】PNP可以通过抑制细胞呼吸作用来增加细菌产生持留菌的比例。