Inactivation of the phospholipase B gene PLB5 in wild-type Candida albicans reduces cell-associated phospholipase A2 activity and attenuates virulence

Phospholipases are critical for modification and redistribution of lipid substrates, membrane remodeling and microbial virulence. Among the many different classes of phospholipases, fungal phospholipase B (Plb) proteins show the broadest range of substrate specificity and hydrolytic activity, hydrolyzing acyl ester bonds in phospholipids and lysophospholipids and further catalyzing lysophospholipase-transacylase reactions. The genome of the opportunistic fungal pathogen Candida albicans encodes a PLB multigene family with five putative members; we present the first characterization of this group of potential virulence determinants. CaPLB5, the third member of this multigene family characterized herein is a putative secretory protein with a predicted GPI-anchor attachment site. Real-time RT-PCR gene expression analysis of CaPLB5 and the additional CaPLB gene family members revealed that filamentous growth and physiologically relevant environmental conditions are associated with increased PLB gene activity. The phenotypes expressed by null mutant and revertant strains of CaPLB5 indicate that this lipid hydrolase plays an important role for cell-associated phospholipase A(2) activity and in vivo organ colonization.     

The role of Helicobacter pylori infection in gastric carcinogenesis and its prevention by using Chinese medicinal herbs

As the fifth most common cancer and the third most common cause of cancer deaths worldwide, gastric cancer remains a significant public health concern and an economic burden in developed and developing countries. Gastric inflammation induced by Helicobacter pylori may initiate superficial gastritis, which then progresses to atrophic gastritis, gastric epithelial dysplasia, and finally gastric cancer. The pathogenesis of H. pylori infection is related to its virulence factors, including urease, flagella, vacuolating cytotoxin A and cytotoxin-associated gene antigen. The relevant mechanisms of H. pylori-induced inflammation include activation of nuclear factor-κB, mitogen-activated protein kinase pathway, and oxidative stress. To date, therapeutic strategies and results in this infection remain undesirable. Complicated treatment issues include antibiotic resistance, adverse effects of chemical drugs, and recurrence after operation. Therefore, chemoprevention has been regarded as an important measure, and Chinese medicinal herbs have been the research hotspot. This review aimed to summarize the effects of Chinese medicinal herbs on the prevention of gastric cancer, mechanism of action and the treatment prospects, with emphasis H. pylori-induced effects.     

Association of virulence factors,phylogenetic groups and antimicrobial resistance markers in Escherichia coli from Badin city,Pakistan

Background: Escherichia coli, the most frequent cause of UTIs has extensive genetic substructure and can be assigned to eight phylogroups, A, B1, B2, C, D, E, F and Escherichia cryptic clade I. We investigated the distribution of virulence determinants and antimicrobial resistance genes in relation to phylogenetic groups.

Methods: A total of 77 E. coli isolates were collected from Civil Hospital Badin, Pakistan. Isolates were assigned phylogroups using quadruplex PCR method, while virulence and antibiotic resistance genes, bla_CTX-M and bla_NDM-1 were also detected using PCR.

Results: Thirty-four isolates were assigned to group B2, while 23, 2, 1, 7 and 10 isolates were assigned to F, B1, A/C, clade I/II and negative, respectively. Among virulence genes, prevalence of papC (83%) was highest followed by aer (57%), papGII (16%), papGIII (14%), cnf (9%), hly (5%) and sfa (6%). Of these isolates, 23% and 9% were positive for bla_CTX-M and bla_NDM-1, respectively.     

宁波沿海地区贝类产品副溶血性弧菌污染现况分析

目的:了解宁波鄞州区贝类产品中副溶血性弧菌的污染情况,为预防控制副溶血性弧菌引起的食物中毒提供依据。方法:从鄞州区不同农贸市场采集毛蚶、蚶子、牡蛎、蛏子和花蛤5种贝类产品作为检测对象,参照GB/T4789.7-2003方法,用标准血清进行分型,用纸片扩散法进行药敏试验,用PCR测定耐热直接血溶素(thermostabile direct hemoly-sin,tdh)和耐热直接相关血溶素(TDH-related hemolysin,trh)毒力基因。结果:检出阳性标本21份,检出率为50.0%(21/42)。分离到的21株副溶血性弧菌属于7个血清群,分别为O:1群占9.5%(2/21)、O:2群占19.0%(4/21)、O:3群占19.0%(4/21)、O:4群占28.6%(6/21)、O:7群占4.8%(1/21)、O:10群占4.8%(1/21)、O:11群占14.3%(3/21)。药敏试验显示,21株副溶血性弧菌对复方新诺明和氯霉素敏感,对青霉素类、氨基糖苷类、磺胺类、喹诺酮类、头孢类药物都有不同程度的耐药。21株副溶血性弧菌的tdh毒力基因2例阳性,trh毒力基因均为阴性。结论:本次贝类产品分离的副溶...     

宁夏盐池沙鼠疫源地鼠疫菌株毒力因子特性研究

本文对宁夏盐池沙地鼠自然疫源地内９６株鼠疫菌的毒力测定结果进行了分析，有７１株属于强毒鼠疫菌，１７株为中等毒力菌，８株为弱毒菌，从同一地区不同宿主分离的鼠疫菌毒力无明显差异。但流行末期分离的菌株毒力呈下降趋势。质粒分析，发现沙土鼠疫源地区菌株普启蒙具有４条带，分别为６，１３，４５和６５Ｍｄａｌ。９６株菌中仅一株缺失４５Ｍｄａｌ质粒，另外２株菌缺失１３Ｍｄａｌ质粒。菌株的毒力与色素沉着能力和Ｌｃｒ相     

Isolation, purification and partial analysis of the lipopolysaccharide antigenic determinant recognized by a monoclonal antibody to legionella pneumophila serogroup 1Isolement, purification et analyse partielle du determinant antigénique lipopolyosidique reconnu par un anticorps monoclonal anti-Legionella pneumophila serogroupe 1

Monoclonal antibody II-6-18 recognizes a serogroup-1-specific Legionella pneumophila antigenic determinant which has been shown to be virulence-associated. We previously reported the physicochemical characterization by means of a quantitative fluorometric assay of monoclonal antibody II-6-18 binding to L. pneumophila, and its implications concerning the nature of the antigen. We describe here the isolation and the purification of the antigen by chemical and immunological methods, followed by its partial chemical analysis. The results demonstrate that the epitope--an immunodominant carbohydrate which includes a fucosamine-like residue--is part of the cell wall lipopolysaccharide (LPS). It is localized in the polysaccharide moiety of the LPS which contains KDO, rhamnose, mannose, glucosamine and an unidentified aminodideoxyhexose X1, but no heptose. The aminodideoxyhexose X1 could be fucosamine and is probably the immunodominant residue in the epitope, localized, at least partially, at the end of the polysaccharide chain.     

利福平—珊瑚羟磷灰石复合物预防骨感染的实验研究

目的：本研究旨在探讨珊瑚羟磷灰石（ｃｏｒａｌｉｎｅｈｙｄｒｏｘｙａｐａｔｉｔｅｐｏｒｉｔｅｓ，ＣＨＡＰ）作为抗生素载体及释放系统的特征以及局部释放抗生素防治骨感染的作用。方法：将ＣＨＡＰ作为抗生素的载体，以利福平（ｒｅ－ｆａｍｐｉｃｉｎ，Ｒ）为模型药物，制备成吸附抗生素的ＣＨＡＰ复合物（Ｒ－ＣＨＡＰ），进行体内、外药物释放试验。采用高效液相色谱法测定标本的ＲＦＰ浓度。将Ｒ－ＣＨＡＰ、空白ＣＨＡＰ分别植入污染不同毒力金葡菌的兔骨缺损区，经放射学检查，细菌培养及组织病理学检查判断骨感染的发生情况。结果：体内、外药物释放试验显示，Ｒ－ＣＨＡＰ在４周内持续释放高浓度的抗生素，血清浓度明显低于局部浓度；组织炎性反应小，生物相容性好。Ｒ－ＣＨＡＰ植入污染不同毒力金葡菌的骨缺损区，其抗菌作用效果无差异（Ｐ＞０．０５），较植入空白ＣＨＡＰ对照组的骨感染发病率低（Ｐ＜０．０５）；两者对金葡菌无特异性的亲和力。结论：ＣＨＡＰ是一种较为理想的抗生素载体及释放系统，局部应用Ｒ－ＣＨＡＰ可有效地预防骨缺损深部感染的发生，应进一步探索其应用前景     

Monitoring gene expression of rcpA from Aggregatibacter actinomycetemcomitans versus antimicrobial photodynamic therapy by relative quantitative real-time PCR

BackgroundAggregatibacter actinomycetemcomitans is an important pathogen that is frequently found in various infections, particularly aggressive periodontitis. In this study, we described the outcome of the expression level of A. actinomycetemcomitans virulence factor following treatment by antimicrobial photodynamic therapy (aPDT) with indocyanine green (ICG) as a photosensitizing agent.Materials and methodsTo determine the aPDT effect on the cell-surviving assay and expression ratio of the rcpA gene in A. actinomycetemcomitans by a colony-forming unit and relative quantitative (q) real-time PCR (qRT-PCR) assays, respectively, the proper dosing of sub-lethal aPDT was specified.ResultsThe results of the current study showed that ICG-mediated aPDT, using 250–1000 μg/mL, showed a significant reduction in A. actinomycetemcomitans growth when compared to the control group (P < 0.05). Also, a sub-lethal dose of aPDT against A. actinomycetemcomitans was 125 μg/mL ICG, with a 30 s diode laser irradiation time at fluency of 15.6 J/cm² that could reduce the expression of rcpA gene approximately 6-fold.DiscussionaPDT with ICG could reduce the cell survival and the virulence agent of A. actinomycetemcomitans. Thus, use of the appropriate aPDT dosage can be used for the successful treatment of periodontitis in vivo.     

Myxoma virus M128L is expressed as a cell surface CD47-like virulence factor that contributes to the downregulation of macrophage activation in vivo

The M128L myxoma virus gene expresses a five-membrane spanning cell surface protein with significant amino acid homology to the cellular CD47 proteins. CD47, also called integrin-associated protein (IAP), is associated with the modulation of leukocyte adhesion, motility, activation, and phagocytosis. Creation of an M128L-deletion mutant myxoma virus strain and subsequent infection of the European rabbit demonstrated that M128L is necessary for the production of a lethal infection in susceptible rabbits, while it is fully dispensable for virus replication in vitro. Secondary sites of infection developed on the majority of rabbits infected with the M128L-deletion mutant (vMyx128KO), demonstrating that the M128L protein is nonessential for the dissemination of virus within the host. Although the size and severity of the primary lesions on vMyx128KO-infected rabbits were comparable to rabbits infected with the wild-type virus at the early stages of disease progression, by day 7 the reduced virulence of the vMyx128KO virus was clearly evident and all of the animals recovered from infection by the M128L-knockout virus. Histological analysis of the tissues of vMyx128KO-infected rabbits revealed greater activation of monocyte/macrophage cells in infected and/or lymphoid tissues when compared to those of wild-type myxoma-infected rabbits. We conclude that the M128L protein is a novel CD47-like immunomodulatory gene of myxoma virus required for full pathogenesis of the virus in the European rabbit and that its loss from the virus results in increased activation of monocyte/macrophage cells during infection.