Identification of pneumococcal serotypes from culture-negative clinical specimens by novel real-time PCR

Pneumococcal parapneumonic empyema is an increasingly common complication in children. Conventional microbiological cultures indicate bacterial causes in as few as 8% of cases; therefore, there is a vital need for new molecular methods of detection and diagnosis. The development and clinical evaluation of real-time PCR-based assays to detect the pneumococcal capsular wzg gene of all serotypes tested are reported here, and 24 of them have been identified in clinical specimens. Using real-time PCR assays with highly specific TaqMan MGB probes that target DNA sequences within the capsular polysaccharide gene cluster, it was possible to differentiate serotypes  1, 3, 5, 4, 6A, 6B, 7F/A, 8, 9V/A/N/L, 14, 15B/C, 18C/B, 19A, 19F/B/C, 23F and 23A. These assays showed high sensitivity (five to ten pneumococcal DNA equivalents) and they were validated with 175 clinical isolates of known serotypes. The clinical value of this approach was demonstrated by analysis of 88 culture-negative pleural fluids from children diagnosed with parapneumonic empyema in three Spanish hospitals. Pneumococcal DNA was detected in 87.5% of pleural fluids, and serotypes  1, 7F and 3 were responsible for 34.3%, 16.4% and 11.9%, respectively, of cases of parapneumonic empyema in children. Such molecular methods are critical for the diagnosis of invasive pneumococcal disease and continued epidemiological surveillance in order to monitor serotype vaccine effectiveness.     

Impact of pneumococcal conjugate vaccine in children on the serotypic epidemiology of adult invasive pneumococcal diseases in Taiwan

Background

Invasive pneumococcal disease (IPD) causes significant morbidity and mortality, especially in children and older adults. Pneumococcal 7-valent and 13-valent conjugate vaccines (PCV7 and PCV13) were introduced in Taiwan in 2005 and 2011, respectively, for children. This study was conducted to evaluate the impact of PCV administered in children on adult IPD.

重组核衣壳蛋白用于肾综合征出血热病人IgG抗体检测

目的检测肾综合征出血热病人的IgG抗体及发现在我国可能存在的新的血清型。方法 用五种血清型汉坦病毒核衣壳重组蛋白作抗原建立间接ELISA法,检测HFRS病人血清中特异性IgG。结果检测了91份病人血清,发现我国山东、北京地区的汉坦病毒感染以HTN血清型群为主(56.1％);首次检测到2份疑似DOB型病毒感染血清。结论我国有可能存在DOB病毒血清型。     

Detection and characterization of human rotavirus among children with diarrhoea in Botswana

This study reports the detection, for the first time, of human rotavirus in stools of children and the molecular characterization of isolated circulating strains in Botswana. We collected 249 stool samples between 1999 and 2001 from children with diarrhoea in three health districts of Botswana and examined them for the presence of rotavirus antigens and particles. Group A rotavirus antigen was detected in 43 of 249 (17%) of the samples tested by enzyme-linked immunosorbent assay. Of the 43 children shedding rotaviruses, 37 (86%) were infants < or =2 years of age. The presence of rotavirus particles was also confirmed by direct electron microscopy. The characteristic 11 segments of the double-stranded RNA mobility pattern of rotavirus were demonstrated by polyacrylamide electrophoresis in 20 of 43 (47%) of the rotavirus-positive samples. The predominant electrophoretic pattern detected was the long (L) electrophoretype 14 of 20 (70%) followed by the short (S) electrophoretype five of 20 (25%). One strain had a mixed (L/S) pattern. Of the 26 samples subjected to subgrouping by enzyme immuno assay, eight were typed as subgroup-II specific and seven were subgroup I. The predominant VP7 genotypes detected were G1 (59%). Two mixed strains of G1 + G3 (5%) and G1 + G2 (5%) were also detected. VP4 genotypes in circulation were: P[4] (5%), P[6] (33%) and P[8] (33%). Mixed P-types P[4 + 6] (5%) and P[6 + 8] (18%) were also detected. Rotavirus strains G1 P[8] and GI P[6 + 8] were the most common cause of diarrhoea in our study area.     

研制14型肺炎链球菌培养基和优化其荚膜多糖提纯的工艺

目的研制国产培养14型肺炎链球菌的培养基,然后制备和纯化该菌的荚膜多糖,并对其全过程的工艺进行优化。方法测试添加不同种血清、培养基成分对肺炎链球菌生长的影响,在此基础上对比进口培养基和本实验自制培养基培养细菌的效果。测试不同裂解细菌方案对获得荚膜多糖多少的影响,并比较DNA酶和RNA酶酶解方法和常规乙醇沉淀方法去除残留核酸的效果。结果实验室自配培养基与进口培养基均能使肺炎链球菌较好生长。用1%NP40加胰酶的裂解方法可使多糖从细菌菌体更好的释放,使用DNA酶和RNA酶去除残留核酸,在多糖产量和核酸去除效率方面都取得了较好的结果,再进一步纯化后可以得到较纯的多糖。结论本文在培养基国产化、菌体裂解后多糖释放和核酸去除三大方面为肺炎球菌荚膜多糖提取提供了有效可行的方案。     

Regions of botulinum neurotoxin A light chain recognized by human anti-toxin antibodies from cervical dystonia patients immunoresistant to toxin treatment. The antigenic structure of the active toxin recognized by human antibodies

This work was aimed at determining the BoNT/A L-chain antigenic regions recognized by blocking antibodies in human antisera from cervical dystonia patients who had become immunoresistant to BoNT/A treatment. Antisera from 28 immunoresistant patients were analyzed for binding to each of 32 overlapping synthetic peptides that spanned the entire L-chain. A mixture of the antisera showed that antibodies bound to three peptides, L11 (residues 141-159), L14 (183-201) and L18 (239-257). When mapped separately, the antibodies were bound only by a limited set of peptides. No peptide bound antibodies from all the patients and amounts of antibodies bound to a given peptide varied with the patient. Peptides L11, L14 and L18 were recognized predominantly. A small but significant number of patients had antibodies to peptides L27 (365-383) and L29 (379-397). Other peptides were recognized at very low and perhaps insignificant antibody levels by a minority (15% or less) of patients or had no detectable antibody with any of the sera. In the 3-dimensional structure, antibody-binding regions L11, L14 and L18 of the L-chain occupy surface areas and did not correlate with electrostatic potential, hydrophilicity/hydrophobicity, or temperature factor. These three antigenic regions reside in close proximity to the belt of the heavy chain. The regions L11 and L18 are accessible in both the free light chain and the holotoxin forms, while L14 appears to be less accessible in the holotoxin. Antibodies against these regions could prevent delivery of the L-chain into the neurons by inhibition of the translocation.     

Fungal bis-Naphthopyrones as Inhibitors of Botulinum Neurotoxin Serotype A

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N-linked glycosylation of dengue virus NS1 protein modulates secretion, cell-surface expression, hexamer stability, and interactions with human complement

Dengue virus (DENV) NS1 is a versatile non-structural glycoprotein that is secreted as a hexamer, binds to the cell surface of infected and uninfected cells, and has immune evasive functions. DENV NS1 displays two conserved N-linked glycans at N130 and N207. In this study, we examined the role of these two N-linked glycans on NS1 secretion, stability, and function. Because some groups have reported reduced yields of infectious DENV when N130 and N207 are changed, we analyzed glycosylation-deficient NS1 phenotypes using a transgenic expression system. We show that the N-linked glycan at position 130 is required for stabilization of the secreted hexamer whereas the N-linked glycan at residue 207 facilitates secretion and extracellular protein stability. Moreover, NS1 mutants lacking an N-linked glycan at N130 did not interact efficiently with complement components C1s and C4. In summary, our results elucidate the contribution of N-linked glycosylation to the function of DENV NS1.     

High prevalence of multidrug-resistant Pneumococcal molecular epidemiology network clones among Streptococcus pneumoniae isolates from adult patients with community-acquired pneumonia in Japan

A total of 141 Streptococcus pneumoniae isolates from patients with community-acquired pneumonia were collected from May 2003 through October 2004. The strains were tested for antimicrobial agent susceptibility, serotype and genotype by multilocus sequence typing (MLST) and the presence of the pilus rlrA islet. MLST analysis identified 49 sequence types (STs), of which 19 were novel. eBURST analysis using the MLST database (3773 STs) grouped the isolates into 27 clonal complexes and three singletons. A total of 92 (65.2%) isolates were related to ten of the 43 international Pneumococcal Molecular Epidemiology Network (PMEN) clones; major clones found were multidrug-resistant Netherlands³-31 [clonal complex (CC) 180], Taiwan^19F-14 (CC271), Taiwan^23F-15 (CC242), and Colombia^23F-26 (CC138) (the latter new to Asia). We adopted univariate and multiple logistic regression models to identify factors associated with PMEN CCs. Multivariate analysis showed that multidrug resistance (OR 6.3; 95% CI 2.0–22.9), carriage serogroups (OR 7.2; 95% CI 2.5–23.7), prevalence of rlrA (OR 12.6; 95% CI 3.6–59.7) and central nervous system-related disorders (OR 7.7; 95% CI 1.8–48.4) were independently associated with PMEN CCs. Our data indicate that multidrug-resistant PMEN clones are highly prevalent, contributing to the high frequency of resistance to antimicrobial agents in Japan, and suggest that certain predisposing factors in patients contribute to the high frequency of these clones.     

Characterization of a new serotype g isolate of Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans is usually isolated from the oral cavity where it is associated with active periodontitis. The species can be divided into six serotypes (a–f) according to their surface carbohydrate antigens. However, some clinical isolates cannot be grouped within these six serotypes. Gram‐negative, facultative anaerobic, catalase‐positive coccobacilli were isolated from a patient with periodontitis and identified by employing genetic, biochemical and serological analyses. Phenotypic data identified the isolate as A. actinomycetemcomitans. Serotype‐specific polysaccharide antigen from the isolate was untypeable by immunodiffusion testing in comparison with reference A. actinomycetemcomitans serotype a to f strains. Biofilm formation by the isolate was strong but cytotoxic activity was low. Gas chromatography/mass spectroscopy analysis of partially methylated alditol acetates from surface polysaccharide showed the presence of 2,4‐di‐O‐methyl‐rhamnose and 2,3,6‐tri‐O‐methyl‐glucose, with a 1 : 1 m ratio. The ¹H‐ and ¹³C‐nuclear magnetic resonance spectra of the antigen showed that both constituent glycoses had α‐anomeric configuration. It is proposed that the untyped strain is a new A. actinomycetemcomitans serotype, designated serotype g.