Identification of Variable-Number Tandem-Repeat (VNTR) Sequences in Acinetobacter pittii and Development of an Optimized Multiple-Locus VNTR Analysis Typing Scheme.

OBJECTIVE: To develop a multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) assay for Acinetobacter pittii typing. METHODS: Polymorphic VNTRs were searched by Tandem Repeats Finder. The distribution and polymorphism of each VNTR locus were analyzed in all the A. pittii genomes deposited in the NCBI genome database by BLAST and were evaluated with a collection of 20 well-characterized clinical A. pittii strains and one reference strain. The MLVA assay was compared with pulsed-field gel electrophoresis (PFGE) for discriminating A. pittii isolates. RESULTS: Ten VNTR loci were identified upon bioinformatic screening of A. pittii genomes, but only five of them showed full amplifiability and good polymorphism. Therefore, an MLVA assay composed of five VNTR loci was developed. The typeability, reproducibility, stability, discriminatory power, and epidemiological concordance were excellent. Compared with PFGE, the new optimized MLVA typing scheme provided the same and even greater discrimination. CONCLUSION: Compared with PFGE, MLVA typing is a faster and more standardized alternative for studying the genetic relatedness of A. pittii isolates in disease surveillance and outbreak investigation.

A DNA minor groove binder shows high effectiveness as a quencher for FRET probes.

A non-fluorescent quencher based on thiazole orange was incorporated into oligonucleotides. Fluorimetry and fluorogenic real-time polymerase chain reaction experiments demonstrated that the quencher is effective for fluorescein amidite dyes. The thiazole orange quencher also increased the melting temperature of DNA duplexes, which may facilitate the design of shorter and more discriminatory probes. The effectiveness of the quencher in TaqMan probes was also demonstrated.

Nanoclay-reinforced alginate aerogels: preparation and properties.

Flame-retardant materials that are mechanically robust, low cost and non-toxic from green and renewable resources are highly demanded in many fields. In this work, aerogels of alginate extracted from seaweeds were fabricated and reinforced with nanoclay. The nanoclay particles increase the molecular ordering (crystallinity) of the aerogels through physical interactions with alginate molecules. They also served as cross-linkers and flame-retardant additives to improve the mechanical strength, elasticity, thermal stability and flame-retarding properties of the aerogels. Under exposure to a butane flame (750 °C), the aerogels maintained their structural integrity and did not produce drips. An optimal loading of nanoclay which led to the best flame retardancy (non-flammable) of the aerogel was determined. The results of this work demonstrate that alginate-nanoclay composite aerogels can be promisingly used as flame-retardant thermal insulation materials.

Identification of potential pathogenic targets and survival strategies of Vibrio vulnificus through population genomics.

Vibrio vulnificus, a foodborne pathogen, has a high mortality rate. Despite its relevance to public health, the identification of virulence genes associated with the pathogenicity of currently known clinical isolates of V. vulnificus is incomplete and its synergistic pathogenesis remains unclear. Here, we integrate whole genome sequencing (WGS), genome-wide association studies (GWAS), and genome-wide epistasis studies (GWES), along with phenotype characterization to investigate the pathogenesis and survival strategies of V. vulnificus. GWAS and GWES identified a total of six genes (purH, gmr, yiaV, dsbD, ramA, and wbpA) associated with the pathogenicity of clinical isolates related to nucleotide/amino acid transport and metabolism, cell membrane biogenesis, signal transduction mechanisms, and protein turnover. Of these, five were newly discovered potential specific virulence genes of V. vulnificus in this study. Furthermore, GWES combined with phenotype experiments indicated that V. vulnificus isolates were clustered into two ecological groups (EGs) that shared distinct biotic and abiotic factors, and ecological strategies. Our study reveals pathogenic mechanisms and their evolution in V. vulnificus to provide a solid foundation for designing new vaccines and therapeutic targets.

[Detection of enterohemorrhagic Escherichia coli O157:H7 by loop-mediated isothermal amplification].

OBJECTIVE: To develop a loop-mediated isothermal amplification (LAMP) method for rapidly diagnosing of Escherichia coli (EHEC) O157:H7 in pathogen detection department or small-scale laboratories. METHODS: Primers for LAMP test were designed by targeting the antigen coding rfbE of EHEC O157:H7, the Shiga-like toxin stx2 and the fliC encoding gene of H7 flagella antigen, respectively. The reaction condition and reaction system of LAMP were optimized. 2 EHEC O157:H7 type strains, 17 local strains and 33 other enterobacteria were analyzed to evaluate the LAMP's specificity and sensitivity. The results of the LAMP reaction were also compared with routine PCR method. RESULTS: The amplification products of O157 which had the corresponding target genes turned green by visual inspection and had ladder-like pattern on the gel, but products of other enterobacteria remained orange by visual examination and had no band on the gel. The detection results of LAMP were the same as of routine PCR method. The reaction time of the LAMP method was only 1.5 hours and the detection limit of LAMP assay was 26 CFU/reaction. In addition, the LAMP results could be determined only by visual inspection. CONCLUSION: LAMP assay is rapid, specific, and sensitive for the detection of EHEC O157:H7. This method might not only reduce the dependence of complicated equipments but also be a potential method for wider use in pathogen detection department, small-scale laboratory, emergency motor vehicle or field survey.

[DNA microarrays and their application in detecting and identifying intestinal pathogens].

DNA microarrays offer many advantages of high throughout, automation, rapid detection, and so on. Therefore, this technology had been used in many fields such as molecular epidemiology of bacteria, microbial gene identification, disease mechanism, gene mutation, gene expression identification, DNA sequencing and medicine screening etc. The assays for identifying pathogens using DNA microarrays reported aboard recently are introduced. The application of DNA microarrays in detecting and identifying intestinal pathogens mainly includes three aspects: the identification of toxin and characteristic genes of pathogens, the identification of bacterial DNA or RNA directly, the simultaneous detection of a large number of intestinal pathogens with the target - gene of ribosomal RNA. Because of its high efficiency, DNA microarrays is superior to other biological method. Obviously DNA microarrays technology may be useful in identifying intestinal pathogens and have a wide prospect.

Characteristic CYP2A6 genetic polymorphisms detected by TA cloning-based sequencing in Chinese digestive system cancer patients with S-1 based chemotherapy.

S-1 is an oral antitumor agent that contains tegafur, which is converted to fluorouracil (5-FU) in the human body. Cytochrome P450 2A6 (CYP2A6) is the principal enzyme responsible for bioconversion of tegafur to 5-FU. A number of CYP2A6 polymorphisms have been associated with variations in enzyme activity in several ethnic populations. The CYP2A6*4C allele leads to deletion of the entire CYP2A6 gene, and is the main finding in patients with reduced CYP2A6 enzymatic activity. Thus, the aim of our study was to evaluate the allele frequencies of CYP2A6 polymorphisms in a population with cancer of the digestive system. We developed a simple screening method, which combined TA cloning and direct-sequencing, to detect CYP2A6 genetic polymorphisms in Chinese patients with cancers of the digestive system. A total of 77 patients with various types of digestive system cancers were screened for CYP2A6 genetic polymorphisms. The allele frequencies of CYP2A6*1A, CYP2A6*1B and CYP2A6*4C in the 77 patients screened were 62, 42 and 13%, respectively. Frequencies of the homozygous genotypes for CYP2A6*1A and CYP2A6*4C were 27 and 12%, respectively. As expected, patients that were determined to be homozygous for CYP2A6*4C exhibited the characteristic chemotherapy efficacy and toxicity profiles. The TA cloning-based direct sequencing method facilitated allele frequency and genotyping determination for CYP2A6*1A, 1B and 4C of cancer patients. The findings indicated that the population carries a high frequency of the CYP2A6*4C homozygous genotype. Thus, the reduced efficacy of standard chemotherapy dosage in Chinese cancer patients may be explained by the lack of CYP2A6-mediated S-1 bioconversion to 5-FU.

[Development of multiplex real time PCR methodology for better identification and discrimination of Vibrio cholerae and O139 serotype].

OBJECTIVE: To develop a rapid, sensitive and specific assay method, based on multiplex real time PCR for identifying Vibrio cholerae and distinguishing Vibrio cholerae O139 serotype from Vibrio cholerae. METHODS: Cholera toxin A subunit gene (ctxA) and glycosyltransferase gene (LPSgt) were chosen as targets according to Vibrio cholerae and Vibrio cholerae O139 serotype, and then the primers and TaqMan-MGB probe were designed. The 5'end of probes was labeled with FAM and VIC fluoresceins respectively while the 3'end of probes was labeled with MGB. The PCR reaction was optimized systematically. Then the specificity, sensitivity and reproducibility of multiplex real time PCR were estimated. Finally, multiplex real time PCR was applied to detect the clinical specimens. RESULTS: Vibrio cholerae was identified by multiplex real time PCR accurately and quickly, which could distinguish Vibrio cholerae O139 serotype from Vibrio cholerae. Vibrio cholerae was identified positive for primer pairs and probes from ctxA gene, and Vibrio cholerae O139 serotype tested was positive for LPSgt gene. Meanwhile, none of other bacteria was identified. Sensitivity of the test was 2 × 10(2) cfu/ml. When this assay was applied directly to identify 45 clinical specimens, results showed that 10 were positive to Vibrio cholerae, in which 4 clinical specimens were positive to Vibrio cholerae O139 serotype. All the results were the same to the one that had been obtained from the conventional assays. CONCLUSION: Our results showed that the multiplex real time PCR was a reliable, accurate and feasible method for identifying Vibrio cholerae that carrying toxin gene and distinguishing Vibrio cholerae O139 serotype from Vibrio cholerae. This method could be applied to the cholera surveillance, prevention and control system for identifying and distinguishing Vibrio cholerae in the labs.

[The emergence of candidate pathogenicity island 89K DNA sequence of Streptococcus suis isolated from sporadic patients in Zhejiang province].

OBJECTIVE: To identify the presence of candidate pathogenicity island 89K DNA sequence of Streptococcus suis serotype 2 (SS2) strains isolated from patient in Zhejiang province. METHODS: Genes and DNA fragments were amplified by PCR, using specific primers, and three amplified fragments of the 89K sequence were directly sequenced. The results were analyzed using software related to bioinformatics and epidemiology. RESULTS: 8 strains of SS2 all contained 89K sequence, cps2J and mrp virulent genes, and species-specific 16S rDNA. 3 amplified fragments of 89K candidate pathogenicity island of SS2 ZJ0501 were above 99% similar to SS2 strain identified from outbreaks in Jiangsu in 1998, and the gene fragment of coding DNA recombinant protein in the 89K sequence was highly homological with that of S. dysgalactiae and S.agalactiae. CONCLUSION: In recent years SS2 strains isolated from patients with clinical symptoms in Zhejiang province had been detected to have contained candidate pathogenic 89K DNA fragment.

Detection and identification of enterohemorrhagic Escherichia coli O157:H7 and Vibrio cholerae O139 using oligonucleotide microarray.

BACKGROUND: The rapid and accurate detection and identification of the new subtype of the pathogens is crucial for diagnosis, treatment and control of the contagious disease outbreak. Here, in this study, an approach to detect and identify Escherichia coli O157:H7 and Vibrio cholerae O139 was established using oligonucleotide microarray. We coupled multiplex PCR with oligonucleotide microarray to construct an assay suitable for simultaneous identification of two subtypes of the pathogens. RESULTS: The stx1, stx2 gene and uidA gene having the specific mutant spot were chosen as the targets for Escherichia coli O157:H7, and meanwhile the ctxA, tcpA, and LPSgt gene for Vibrio cholerae O139. The oligonucleotide microarray was composed of eight probes including negative control and positive control from 16S rDNA gene. The six primers were designed to amplify target fragments in two triplex PCR, and then hybridized with oligonucleotide microarray. An internal control would be to run a PCR reaction in parallel. Multiplex PCR did not produce any non-specific amplicons when 149 related species or genera of standard bacteria were tested (100% specificity). In addition, Escherichia coli O157:H7 and Escherichia coli O157:non-H7, Vibrio cholerae O139 and Vibrio cholerae O1 had been discriminated respectively. Using recombinant plasmid and target pathogens, we were able to detect positive hybridization signals with 102 copies/muL and 103 cfu/mL per reaction. CONCLUSION: The DNA microarray assay reported here could detect and identify Escherichia coli O157:H7 and Vibrio cholerae O139, and furthermore the subtype was distinguished. This assay was a specific and sensitive tool for simultaneous detection and identification of the new subtype of two pathogens causing diarrhea in human.

[Sequence analysis of the complete genome of bocavirus WLL-1].

Human bocavirus, which was firstly discovered in 2005, is a new human parvovirus associated with lower respiratory tract infection in children. In this study, a human bocavirus, named WLL-1 isolate, was identified in Wenlin County, Zhejiang Province. The genome of bocavirus WLL-1 has been sequenced and analyzed. Phylogenetic analyses showed that WLL-1 shares 99% homology with other bocaviruses recently reported, but also has some special variations.

Detection and identification of intestinal pathogens in clinical specimens using DNA microarrays.

The detection and identification of intestinal pathogens is critical for clinical patient diagnosis and antimicrobial therapy. No currently available assays with DNA microarrays can simultaneously detect and identify multiple intestinal pathogens, because there is no appropriate method for choosing target probes. To solve the problem we have experimented for facilitating screening of specific probes and developed a rapid (<3h) and reliable assay for simultaneous detection of intestinal pathogens using two universal PCR primers to amplify two variable regions of bacterial 16S and 23S ribosomal DNA (rDNA) genes, and then applied to DNA microarrays, hybridization between probes and amplicons occurred. Through this idea for screening of probes the assay was successful in discriminating 15 genera or species of intestinal pathogens. The limit of detection was approximately 10(3)CFU/mL for one species of pathogen and 10(5)CFU/mL for six species pathogens existing simultaneously in stool. When this assay was applied directly to identify 99 clinical specimens, 80(80.8%) were correctly analyzed, including four with mixed pathogens; 8(8.08%) received negative results due to no corresponding probes in this array and 11(11.11%) belonging to our targets were misidentified due to low-level pathogens and other factors. This approach is also convenient to obtain specific and proper probes while establishing assays for the applications in other aspects using DNA microarrays. In addition, the more species may be added to this system easily and endlessly by screening of candidate target probes in order to increase the power of simultaneous detection.