A new approach to toxin neutralization in Staphylococcus aureus therapy

Staphylococcus aureus is a significant human pathogen responsible for a range of diseases including pneumonia, sepsis, skin, and soft tissue infections. An important component of its success as a human pathogen is the production of a large array of virulence factors including several toxins. In this issue of EMBO Reports, Reyes‐Robles and colleagues 1 identify a glycine‐rich motif shared by bicomponent leukocidins. When this motif is deleted, the altered toxin exerts dominant‐negative effects that neutralize leukocidin function and thus represents a potentially novel avenue for S. aureus therapy.     

Production of the Streptomyces scabies coronafacoyl phytotoxins involves a novel biosynthetic pathway with an F420‐dependent oxidoreductase and a short‐chain dehydrogenase/reductase

Coronafacoyl phytotoxins are secondary metabolites that are produced by various phytopathogenic bacteria, including several pathovars of the Gram‐negative bacterium Pseudomonas syringae as well as the Gram‐positive potato scab pathogen Streptomyces scabies. The phytotoxins are composed of the polyketide coronafacic acid (CFA) linked via an amide bond to amino acids or amino acid derivatives, and their biosynthesis involves the cfa and cfa‐like gene clusters that are found in P. syringae and S. scabies, respectively. The S. scabies cfa‐like gene cluster was previously reported to contain several genes that are absent from the P. syringae cfa gene cluster, including one (oxr) encoding a putative F₄₂₀—dependent oxidoreductase, and another (sdr) encoding a predicted short‐chain dehydrogenase/reductase. Using gene deletion analysis, we demonstrated that both oxr and sdr are required for normal production of the S. scabies coronafacoyl phytotoxins, and structural analysis of metabolites that accumulated in the Δsdr mutant cultures revealed that Sdr is directly involved in the biosynthesis of the CFA moiety. Our results suggest that S. scabies and P. syringae use distinct biosynthetic pathways for producing coronafacoyl phytotoxins, which are important mediators of host‐pathogen interactions in various plant pathosystems.     

Recurrent abscesses due to Finegoldia magna, Dermabacter hominis and Staphylococcus aureus in an immunocompetent patient

A case of recurrent abscesses in an immunocompetent patient is reported, involving the opportunistic human pathogen Dermabacter hominis, the virulent anaerobic pathogen Finegoldia magna and Staphylococcus aureus.     

功能作图(functional mapping)分析大肠杆菌和金黄色葡萄球菌之间的竞争互作

【背景】功能作图(functionalmapping)模型是基于统计方法的分析生物体动态复杂性状发育的全基因组作图方法,旨在定位性状发育过程中的数量性状位点(quantitative trait loci, QTL),将功能作图应用于微生物研究有助于解析复杂的互作过程。【目的】利用功能作图定位两种微生物在动态生长发育过程中发挥显著作用的QTL,通过基因功能注释找到影响微生物表型生长的基因。【方法】将大肠杆菌和金黄色葡萄球菌各100个菌株单独培养和一一配对共同培养,将取得的各菌株生长丰度表型数据和单核苷酸多态性(singlenucleotidepolymorphism,SNP)数据进行关联分析,找到同一物种在不同培养条件下对生长起作用的显著QTL。【结果】通过功能作图分析,在大肠杆菌中定位到217个QTL,金黄色葡萄球菌中定位到152个QTL;通过功能聚类和基因注释分析发现,QTL所在候选基因中金黄色葡萄球菌scdA、sdrC、sdrD、ftsA和大肠杆菌phr、nagC、eptA、ppsA、priA、flim基因对微生物的生长发挥了较大作用。【结论】本文借助功能作图定位了大肠杆菌和金黄...     

金黄色葡萄球菌病防治研究进展

金黄色葡萄球菌(Staphylococcus aureus, SA)被认为是最常见的食源性致病菌之一,引起人畜的感染性疾病,导致皮肤、软组织和血液感染,引发脓毒症和中毒性休克综合征。随着抗生素的滥用,金黄色葡萄球菌的耐药性逐渐增强,导致耐甲氧西林金黄色葡萄球菌(methicillin resistant Staphylococcus aureus, MRSA)的出现,并且在全球范围内散播,严重危害公共卫生安全。目前亟需有效控制SA感染的新疗法,因此本文对金黄色葡萄球菌防治技术的研究进展进行综述,并对其防治前景进行了分析,以期对金黄色葡萄球菌尤其是MRSA的控制提供理论指导。     

银白色葡萄球菌的发现、分布与致病性

银白色葡萄球菌(Staphylococcus argenteus)是金黄色葡萄球菌(S.aureus)的近缘新种,于2015年正式被鉴定、命名.在此之前,银白色葡萄球菌一直被认为是金黄色葡萄球菌种内的一个远源支系.该物种绝大多数菌株分离自人体,基因组上含有大量与金黄色葡萄球菌同源的毒力基因,可导致与金黄色葡萄球菌类似的...     

Multiplex PCR for simultaneous detection of enterococcal genes vanA and vanB and staphylococcal genes mecA, ileS-2 and femB

The experimental transfer of the vanA gene cluster from Enterococcus faecalis to Staphylococcus aureus has raised fears about the occurrence of such genetic transfer in clinical isolates of methicillin-resistant staphylococci. Recently, infections by a S. aureus strain carrying the enterococcal vancomycin resistance vanA gene cluster were reported. The possible emergence and dissemination of these strains is a serious health threat and makes optimization of prevention strategies and fast detection methods absolutely necessary. In the present study, we developed a PCR protocol for simultaneous detection of enterococcal vanA and vanB genes , the staphylococcal methicillin and mupirocin resistance markers mecA and ileS-2, and identification of S. aureus. As no vancomycin-resistant S. aureus isolates were available for our study, we used mixtures of enterococcal and staphylococcal colonies that harbored the different resistance markers to show that these genes could be detected simultaneously. This protocol could be used to facilitate the detection and identification of predictable S. aureus or methicillin-resistant strains carrying vanA or vanB.     

The Staphylococcus aureus ArlRS two-component system regulates virulence factor expression through MgrA

The Gram-positive bacterium, Staphylococcus aureus, is a versatile pathogen that can sense and adapt to a wide variety of environments within the human host, in part through its 16 two-component regulatory systems. The ArlRS two-component system has been shown to affect many cellular processes in S. aureus, including autolysis, biofilm formation, capsule synthesis and virulence. Yet the molecular details of this regulation remained largely unknown. We used RNA sequencing to identify the ArlRS regulon, and found 70% overlap with that of the global regulator MgrA. These genes included cell wall-anchored adhesins (ebh, sdrD), polysaccharide and capsule synthesis genes, cell wall remodeling genes (lytN, ddh), the urease operon, genes involved in metal transport (feoA, mntH, sirA), anaerobic metabolism genes (adhE, pflA, nrdDG) and a large number of virulence factors (lukSF, lukAB, nuc, gehB, norB, chs, scn and esxA). We show that ArlR directly activates expression of mgrA and identify a probable ArlR-binding site (TTTTCTCAT-N₄-TTTTAATAA). A highly similar sequence is also found in the spx P2 promoter, which was recently shown to be regulated by ArlRS. We also demonstrate that ArlS has kinase activity toward ArlR in vitro, although it has slower kinetics than other similar histidine kinases.     

Utilization of glycerophosphodiesters by Staphylococcus aureus

The facultative pathogen Staphylococcus aureus colonizes the human anterior nares and causes infections of various organ systems. Which carbon, energy, and phosphate sources can be utilized by S. aureus in nutrient‐poor habitats has remained largely unknown. We describe that S. aureus secretes a glycerophosphodiesterase (glycerophosphodiester phosphodiesterase, EC 3.1.4.46), GlpQ, degrading the glycerophosphodiester (GPD) head groups of phospholipids such as human phosphatidylcholine (GroPC). Deletion of glpQ completely abolished the GroPC‐degrading activity in S. aureus culture supernatants. GroPC has been detected in human tissues and body fluids probably as a result of phospholipid remodelling and degradation. Notably, GroPC promoted S. aureus growth under carbon‐ and phosphate‐limiting conditions in a GlpQ‐dependent manner indicating that GlpQ permits S. aureus to utilize GPD‐derived glycerol‐3‐phosphate as a carbon and phosphate sources. Thus, S. aureus can use a broader spectrum of nutrients than previously thought which underscores its capacity to adapt to the highly variable and nutrient‐poor surroundings.     

Notch信号途径中的Su(H)和E(spl)基因对果蝇天然免疫的影响

天然免疫系统是多细胞生物抵抗各种入侵微生物的第一道防线.Notch途径介导相邻细胞之间的相互作用,调节细胞、组织、器官的分化和发育.为了进一步探索Notch信号途径在果蝇天然免疫中的功能,利用Notch途径下游基因Su(H)和E(spl)的低表达突变体果蝇,通过体外注射病原体分析了生存率、血细胞的噬菌功能和抗菌肽的表达量以及突变体的血细胞数量.结果表明,革兰氏阴性细菌和真菌感染后果蝇E(spl)突变体的生存率、噬菌能力及抗菌肽的表达量明显降低,而且幼虫期血细胞出现异常增殖;Su(H)突变体只对真菌表现出敏感性,抗菌肽的表达量降低,但是对真菌的噬菌能力正常.此结果表明,Notch途径不仅影响个体的生长发育,而且在果蝇天然免疫中也起重要的调节作用.     

金黄色葡萄球菌噬菌体vB_Sau_P68的基因组分析和裂解酶

【背景】金黄色葡萄球菌是常见的人畜共患条件致病菌,随着多耐药菌株分离率的增长,研发与抗生素作用模式不同的抗菌剂迫在眉睫。【目的】分离高效且特异性强的金黄色葡萄球菌噬菌体,对其进行功能注释,并对其编码的裂解酶进行功能验证。【方法】通过对噬菌体全基因组序列进行分析找到裂解酶基因,利用原核表达系统对其编码的2个裂解酶蛋白进行克隆,用SDS-PAGE与蛋白免疫印迹法(Western blotting)鉴定目的蛋白是否表达,并采用单斑法验证其裂解活性。【结果】本研究的噬菌体为一株新的金黄色葡萄球菌噬菌体,命名为vB＿Sau＿P68,该基因组全长为139 409 bp,GC含量为31.0%,编码220个开放阅读框(open reading frame,ORF),透射电镜观察具有正二十面体头部和收缩性尾部,形态学分类属于肌尾噬菌体。该噬菌体编码2个裂解酶基因,分别具有CHAP催化结构域与SH3＿5结合结构域,SDS-PAGE与Western blotting表明Lys161能够表达且有裂解活性,Lys163则无法外源表达。对Lys161序列进行分析,该裂解酶无信号肽,无跨膜区域,以无规则卷曲为主。【...     

Enhanced Monocyte Response and Decreased Central Memory T Cells in Children with Invasive Staphylococcus aureus Infections

Staphylococcus aureus has emerged as a significant pathogen causing severe invasive disease in otherwise healthy people. Despite considerable advances in understanding the epidemiology, resistance mechanisms, and virulence factors produced by the bacteria, there is limited knowledge of the in vivo host immune response to acute, invasive S. aureus infections. Herein, we report that peripheral blood mononuclear cells from patients with severe S. aureus infections demonstrate a distinctive and robust gene expression profile which is validated in a distinct group of patients and on a different microarray platform. Application of a systems-wide modular analysis framework reveals significant over-expression of innate immunity genes and under-expression of genes related to adaptive immunity. Simultaneous flow cytometry analyses demonstrated marked alterations in immune cell numbers, with decreased central memory CD4 and CD8 T cells and increased numbers of monocytes. CD14+ monocyte numbers significantly correlated with the gene expression levels of genes related to the innate immune response. These results demonstrate the value of applying a systems biology approach that reveals the significant alterations in the components of circulating blood lymphocytes and monocytes in invasive S. aureus infections.     

In Silico Sub-unit Hexavalent Peptide Vaccine Against an <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> Biofilm-Related Infection

Staphylococcus aureus is responsible for significant and increasing number of hospital-and community-acquired infections worldwide. A pool of pathogenesis factors helps the bacterium to cause the range of mild to severe infections leading the high mortality and morbidity. Staphylococcus aureus and Candida albicans can be co-isolated from all human mucosal sites and are responsible for diverse infections. Vaccine design for related polymicrobial infections should consider the consortia of microorganisms responsible for the disease. In this study we considered biofilm mode of growth and polymicrobial nature of the infections caused by S. aureus. In the first phase of study the prediction of putative antigenic targets of S. aureus and C. albicans was conducted based on data mining and bioinformatic characterization of their proteins. Various properties of proteins were evaluated such as subcellular localization, hydrophilicity, repeat containing modules, beta turns, surface accessibility and number of antigenic determinants. The second phase includes various immunoinformatics analyses on six proteins include ALS, ClfA, FtmB, SdrE, Spa and Bap leading to design a novel sub-unit hexavalent vaccine. Several potential T cell and B-cell epitopes are present in our vaccine. Also the vaccine is expected to strongly induce IFN-gamma production. The amino acid sequence introduced here is expected to enhance cell-mediated and humoral responses against S. aureus biofilm-related infections to clear biofilm communities of S. aureus and intracellular colonies of pathogen as well as planktonic cells and thus reduces colonization and persistence.