Comparative genome analysis identifies few traits unique to the Escherichia coli ST131 H30Rx clade and extensive mosaicism at the capsule locus

Background

E.coli ST131 is a globally disseminated clone of multi-drug resistant E. coli responsible for that vast majority of global extra-intestinal E. coli infections. Recent global genomic epidemiological studies have highlighted the highly clonal nature of this group of bacteria, however there appears to be inconsistency in some phenotypes associated with the clone, in particular capsule types as determined by K-antigen testing both biochemically and by PCR.

Results

We performed improved quality assemblies on ten ST131 genomes previously sequenced by our group and compared them to a new reference genome sequence JJ1886 to identify the capsule loci across the drug-resistant clone H30Rx. Our data shows considerable genetic diversity within the capsule locus of H30Rx clone strains which is mirrored by classical K antigen testing. The varying capsule locus types appear to be randomly distributed across the H30Rx phylogeny suggesting multiple recombination events at this locus, but that this capsule heterogeneity has little to no effect on virulence associated phenotypes in vitro.

Conclusions

Our data provides a framework for determining the capsular genetics of E. coli ST131 and further beyond to ExPEC strains, and highlights how capsular mosaicism may be an important strategy in becoming a successful globally disseminated human pathogen.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-830) contains supplementary material, which is available to authorized users.     

Rapid methods to extract DNA and RNA from Cryptococcus neoformans

Extraction of nucleic acids from the pathogenic yeast Cryptococcus neoformans is normally hampered by a thick and resistant capsule, accounting for at least 70% of the whole cellular volume. This paper presents procedures based on mechanical cell breakage to extract DNA and RNA from C. neoformans and other capsulated species. The proposed system for DNA extraction involves capsule relaxation by means of a short urea treatment and bead beating. These two steps allow a consistent extraction even from strains resistant to other procedures. Yield and quality of DNA obtained with the proposed method were higher than those obtained with two earlier described methods. This protocol can be extended to every yeast species and particularly to those difficult to handle for the presence of a capsule. RNA purification is accomplished using an original lysing matrix and the FastPrep System (Bio101) after a preliminary bead beating treatment. Yields range around 1 mg RNA from 15 ml overnight culture (10(9) cells), RNA appears undegraded, making it suitable for molecular manipulations.     

Nrc of Streptococcus pneumoniae suppresses capsule expression and enhances anti-phagocytosis

Streptococcus pneumoniae is a major pathogen of community-acquired pneumonia and one of its major virulence factors is pneumolysin, which functions as a cholesterol-dependent cytolytic pore-forming toxin. In this study, we identified the ply-like gene spd0729 in a BLAST search. Unexpectedly, hemolytic and cytotoxic assays showed no significant differences between a Δspd0729 mutant strain and the wild-type strain, whereas the mutant strain exhibited weaker anti-phagocytic activity in human peripheral blood. In addition, real-time RT-PCR analysis revealed that four capsular biosynthesis genes in the mutant strain had expressions 7- to 432-fold greater than those of the wild type, while an enzyme-linked immunoassay showed a mean 3-fold greater amount of total capsular polysaccharide in the mutant strain. These results suggest that Spd0729 is not a cytolysin, though it plays crucial roles in anti-phagocytosis and regulation of capsule expression. Thus, we named Spd0729 as a negative regulator of capsular polysaccharide synthesis (Nrc).     

速效止泻胶囊含量测定方法的初步研究

目的：探讨速效止泻胶囊质量标准中含量测定方法的建立。方法：采用中性氧化铝柱层析-紫外分光光度法建立了盐酸小檗碱的含量测定方法。结果：线性关系r=0.99996,平均回收率为106．42％,含量限度为90mg/粒。结论：建立的含量测定方法准确可靠,可以控制产品质量。     

Unexpected link between lipooligosaccharide biosynthesis and surface protein release in Mycobacterium marinum

The mycobacterial cell envelope is characterized by the presence of a highly impermeable second membrane, which is composed of mycolic acids intercalated with different unusual free lipids, such as lipooligosaccharides (LOS). Transport across this cell envelope requires a dedicated secretion system for extracellular proteins, such as PE_PGRS proteins, which are specific mycobacterial proteins with polymorphic GC-rich sequence (PGRS). In this study, we set out to identify novel components involved in the secretion of PE_PGRS proteins by screening Mycobacterium marinum transposon mutants for secretion defects. Interestingly, most mutants were not affected in secretion but in the release of PE_PGRS proteins from the cell surface. These mutants had insertions in a gene cluster associated with LOS biosynthesis. Lipid analysis of these mutants revealed a role at different stages of LOS biosynthesis for 10 novel genes. Furthermore, we show that regulatory protein WhiB4 is involved in LOS biosynthesis. The absence of the most extended LOS molecule, i.e. LOS-IV, and a concomitant accumulation of LOS-III was already sufficient to reduce the release of PE_PGRS proteins from the mycobacterial cell surface. A similar effect was observed for major surface protein EspE. These results show that the attachment of surface proteins is strongly influenced by the glycolipid composition of the mycobacterial cell envelope. Finally, we tested the virulence of a LOS-IV-deficient mutant in our zebrafish embryo infection model. This mutant showed a marked increase in virulence as compared with the wild-type strain, suggesting that LOS-IV plays a role in the modulation of mycobacterial virulence.     

兽疫链球菌荚膜多糖对免疫抑制鼠的抗氧化和免疫调节活性研究

目的测定部分纯化的兽疫链球菌荚膜多糖（PCP）的抗氧化和免疫调节活性。方法以注射用环磷酰胺（CY）造成免疫抑制鼠模型。结果口服PCP诱导了免疫抑制鼠超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）和过氧化氢酶（CAT）的活性,提高了总抗氧化能力（TAOC）的水平。口服PCP后免疫抑制鼠的胸腺和脾脏指数明显增加,血清溶菌酶活性和迟发型超敏反应（DTH）引起的肿胀率也显著提高。结论 PCP对免疫抑制鼠具有免疫调节功能并改变CY诱导的氧化压力,是一种潜在的抗氧化剂和免疫调节剂。     

百令胶囊联合罗氟司特治疗老年支气管哮喘的效果及对免疫功能的影响

目的:研究百令胶囊联合罗氟司特治疗老年支气管哮喘的效果及对免疫功能的影响。方法:选择2018年3月~2019年3月我院第六派驻门诊部收治的110例老年支气管哮喘患者,随机分为两组,每组各55例。对照组患者口服罗氟司特片,每次500 mg,每天1次。观察组患者联合服用百令胶囊,每次5粒,每天3次。比较两组的临床控制率,治疗前后两组诱导痰中炎症因子、中性粒细胞、呼出气一氧化氮(fractional exhaled nitric oxide,FeNO)水平和免疫功能的变化。结果:治疗后,观察组的临床控制率为70.91%(39/55),明显高于对照组[40.00%(22/55)](P<0.05);两组的CD4+、CD4+/CD8+和CD3+均较治疗前明显升高,且观察组的CD4+、CD4+/CD8+和CD3+明显高于对照组(P<0.05);两组患者诱导痰中中性粒细胞绝对值、中性粒细胞百分比、白细胞介素-4(interleukin-4,IL-4)、FeNO、白细胞介素-17(interleukin-17,IL-17)均较治疗前明显降低(P<0.05),诱导痰中的干扰素-γ(Interferon gamma,IFN-γ)均较治疗前明显升高(P<0.05),且观察组诱导痰中的组中性粒细胞绝对值、中性粒细胞百分比、IL-4、FeNO、IL-17明显低于对照组(P<0.05),诱导痰中的IFN-γ均明显高于对照组(P<0.05)。结论:百令胶囊联合罗氟司特对老年支气管哮喘患者具有显著的疗效,其机制可能与抑制中性粒细胞的激活、调节T淋巴细胞亚群的平衡和抑制相关炎症因子的释放相关。     

金龙胶囊联合化疗治疗晚期非小细胞肺癌临床疗效观察

目的:观察金龙胶囊联合化疗与单纯化疗对晚期肺小细胞癌患者的疗效、生活质量等因素的影响。方法:将99例患有晚期非小细胞肺癌患者随机分为两组:治疗组,在NP化疗方案基础上加服金龙胶囊治疗;对照组,单纯接受NP方案化疗。对99例患者追踪2个月,观察并比较患者的疗效、体质量、生活质量、毒副反应等方面的差异。结果:在NP化疗方案基础上加服金龙胶囊治疗在患者疗效评价方面与单纯NP方案化疗相比不具有统计学差异(P>0.05);在提高患者体质量、改善患者临床症状和生活质量等方面均优于单纯NP方案化疗(P<0.05);在化疗所引发的白细胞、血红蛋白和血小板降低等部分毒副反应发生率方面低于单纯NP方案化疗组(P<0.05)。结论:金龙胶囊联合NP化疗治疗晚期非小细胞肺癌不仅可以起到化疗增效的作用,而且能够明显提高患者生活质量,有效的改善临床症候,降低化疗引发的毒副反应,这一联合治疗方案可以在临床治疗中广泛推广。     

行胶囊内镜检查67 例患者临床结果分析

目的:评价胶囊内镜在小肠疾病中的诊断价值,总结胶囊内镜临床应用策略。方法:回顾性分析上海市第一人民医院胃肠镜室2009年7月-2011年4月67例行胶囊内镜检查患者的检查结果,结合其中32名患者双气囊小肠镜检查结果及手术病理,分析胶囊内镜在小肠疾病的检出率,诊断率和不良事件发生率,总结胶囊内镜检查时的注意事项。结果:1例胶囊内镜操作失败,66例受检者检出率80.3%,诊断率为66.7%,发现病变中血管病变为主要诊断,占62.1%,其次为肠道占位(息肉、肿瘤)为14.6%,克罗恩病占10.9%,所有患者均未出现严重不良事件。结论:胶囊内镜在小肠疾病检查中安全,无创,诊断率较高,临床胶囊内镜检查时建议充分肠道准备,实时监控及结合双气囊小肠镜检查。     

The role of encapsulated anaerobic bacteria in synergistic infections

Abstract: The effect of encapsulation on the virulence, survival, and protection of anaerobic bacteria from phagocytosis is reviewed. Support for the importance of encapsulated Gram-negative anaerobic rods ( Bacteroides sp., Prevotella sp. and Porphyromonas sp.), anaerobic and facultative Gram-positive cocci (AFGPC) was provided by their higher recovery rate in oropharyngeal infections, abscesses and blood, compared to their number in the normal flora. The pathogenicity of Bacteroides, Fusobacterium, Clostridium , and AFGPC was studied by inoculating them into mice and observing their ability to induce subcutaneous abscesses. Encapsulated Bacteroides, Fusobacteria , and AFGPC generally induced abscesses, whereas non-encapsulated organisms did not. However, many of the strains that had only a minimal number of encapsulated organisms (< 1%) survived in the abscesses, and they became heavily encapsulated when inoculated with other viable or non-viable encapsulated bacteria. Thereafter, these strains were able to induce abscesses when injected alone. Encapsulated Gram-negative anaerobic rods and AFGPC-induced bacteraemia and translocation, and increased the mortality of the infected animals more often than did the non-encapsulated form of the same strains. As determined by using selective antimicrobial therapy and quantitative cultures of abscesses induced in mice, possession of a capsule generally made Gram-negative anaerobic rods more important than their aerobic counterparts. Synergistic potentials were seen between encapsulated Gram-negative anaerobic rods and all tested aerobic bacteria and most AFGPC, and also between most AFGPC and Pseudomonas aeruginosa or Staphylococcus aureus . These studies demonstrated the importance of encapsulated anaerobes in mixed infections.