Zhaohui Xiong

VFDB 2012 update: toward the genetic diversity and molecular evolution of bacterial virulence factors

The virulence factor database (VFDB, http://www.mgc.ac.cn/VFs/) has served as a comprehensive repository of bacterial virulence factors (VFs) for >7 years. Bacterial virulence is an exciting and dynamic field, due to the availability of complete sequences of bacterial genomes and increasing sophisticated technologies for manipulating bacteria and bacterial genomes. The intricacy of virulence mechanisms offers a challenge, and there exists a clear need to decipher the ‘language’ used by VFs more effectively. In this article, we present the recent major updates of VFDB in an attempt to summarize some of the most important virulence mechanisms by comparing different compositions and organizations of VFs from various bacterial pathogens, identifying core components and phylogenetic clades and shedding new light on the forces that shape the evolutionary history of bacterial pathogenesis. In addition, the 2012 release of VFDB provides an improved user interface.

Enterovirus 71 Outbreak in the People's Republic of China in 2008

Since the discovery of enterovirus 71 (EV71) in 1969, numerous outbreaks have occurred worldwide in countries in Europe, America, and the West Pacific region ([1][1]). Since 1997, the prevalence of EV71 infection in the Asia-Pacific region, especially in southeast Asia, has greatly increased.

Unbiased Parallel Detection of Viral Pathogens in Clinical Samples by Use of a Metagenomic Approach

ABSTRACT Viral infectious diseases represent a major threat to public health and are among the greatest disease burdens worldwide. Rapid and accurate identification of viral agents is crucial for both outbreak control and estimating regional disease burdens. Recently developed metagenomic methods have proven to be powerful tools for simultaneous pathogen detection. Here, we performed a systematic study of the capability of the short-read-based metagenomic approach in the molecular detection of viral pathogens in nasopharyngeal aspirate samples from patients with acute lower respiratory tract infections (n = 16). Using the high-throughput capacity of ultradeep sequencing and a dedicated data interpretation method, we successfully identified seven species of known respiratory viral agents from 15 samples, a result that was consistent with results of conventional PCR assays. We also detected a coinfected case that was missed by regular PCR testing. Using the metagenomic data, 11 draft genomes of the abundantly detected viruses in the samples were reconstructed with 21.84% to 98.53% coverage. Our results show the power of the short-read-based metagenomic approach for accurate and parallel screening of viral pathogens. Although there are some inherent difficulties in applying this approach to clinical samples, including a lack of controls, limited specimen quantity, and high contamination rate, our work will facilitate further application of this unprecedented high-throughput method to clinical samples.

Complete genome sequence of Shigella flexneri 5b and comparison with Shigella flexneri 2a

BackgroundShigella bacteria cause dysentery, which remains a significant threat to public health. Shigella flexneri is the most common species in both developing and developed countries. Five Shigella genomes have been sequenced, revealing dynamic and diverse features. To investigate the intra-species diversity of S. flexneri genomes further, we have sequenced the complete genome of S. flexneri 5b strain 8401 (abbreviated Sf8401) and compared it with S. flexneri 2a (Sf301).ResultsThe Sf8401 chromosome is 4.5-Mb in size, a little smaller than that of Sf301, mainly because the former lacks the SHI-1 pathogenicity island (PAI). Compared with Sf301, there are 6 inversions and one translocation in Sf8401, which are probably mediated by insertion sequences (IS). There are clear differences in the known PAIs between these two genomes. The bacteriophage SfV segment remaining in SHI-O of Sf8401 is clearly larger than the remnants of bacteriophage SfII in Sf301. SHI-1 is absent from Sf8401 but a specific related protein is found next to the pheV locus. SHI-2 is involved in one intra-replichore inversion near the origin of replication, which may change the expression of iut/iuc genes. Moreover, genes related to the glycine-betaine biosynthesis pathway are present only in Sf8401 among the known Shigella genomes.ConclusionOur data show that the two S. flexneri genomes are very similar, which suggests a high level of structural and functional conservation between the two serotypes. The differences reflect different selection pressures during evolution. The ancestor of S. flexneri probably acquired SHI-1 and SHI-2 before SHI-O was integrated and the serotypes diverged. SHI-1 was subsequently deleted from the S. flexneri 5b genome by recombination, but stabilized in the S. flexneri 2a genome. These events may have contributed to the differences in pathogenicity and epidemicity between the two serotypes of S. flexneri.

Human parainfluenza virus type 4 infection in Chinese children with lower respiratory tract infections: a comparison study.

n Abstractn n Backgroundn Human parainfluenza viruses (HPIVs) are a leading cause of acute respiratory tract infections (ARTIs). Although HPIV-4 has been associated with mild ARTIs for years, recent investigations have also associated HPIV-4 infection with severe respiratory syndromes and with outbreaks of ARTIs in children.n n n Objectivesn To characterize the role of HPIV-4 and its clinical features in children with acute lower respiratory tract infections (ALRTIs) in Beijing, China.n n n Study designn Nasopharyngeal aspirates were collected from 2009 hospitalized children with ALRTIs between March 2007 and April 2010. RT-PCR and PCR analyses were used to identify HPIV types and other known respiratory viruses.n n n Resultsn HPIVs were detected in 246 (12.2%) patients, of whom 25 (10.2%) were positive for HPIV-4, 11 (4.5%) for HPIV-2, 51 (20.7%) for HPIV-1, 151 (61.4%) for HPIV-3, and 8 (3.3%) were co-detected with different types of HPIVs. Like HPIV-3, HPIV-4 was detected in spring, summer, and late fall over the study period. Seasonal incidence varied for HPIV-1 and -2. The median patient age was 20 months for HPIV-4 infections and 7–11 months for HPIV-1, -2, and -3 infections, but the clinical manifestations did not differ significantly between HPIV-1, -2, -3, and -4 infections. Moreover, co-detection of HPIV-4 (44%) with other respiratory viruses was lower than that of HPIV-1 (62.7%), HPIV-2 (63.6%), and HPIV-3 (72.7%).n n n Conclusionsn HPIV-4 plays an important role in Chinese paediatric ALRTIs. The epidemiological and clinical characteristics reported here improve our understanding of the pathogenesis associated with HPIV-4.n n

Complete Genome Sequence of the Extremophilic Bacillus cereus Strain Q1 with Industrial Applications

Bacillus cereus strain Q1 was isolated from a deep-subsurface oil reservoir in the Daqing oil field in northeastern China. This strain is able to produce biosurfactants and to survive in extreme environments. Here we report the finished and annotated genome sequence of this organism.

Sensitive and rapid detection of viruses associated with hand foot and mouth disease using multiplexed MALDI-TOF analysis

BACKGROUNDnHuman enterovirus (HEV) is the major cause of hand foot and mouth disease (HFMD). A powerful method for detecting HEVs associated with HFMD can provide results in a clinically relevant time frame. However, the limitations of the current enterovirus test make it difficult to identify multiple genotypes on the first pass.nnnOBJECTIVEnTo develop a more sensitive and easy applicable assay for detecting 18 HFMD-associated HEV serotypes in multiplex PCR products.nnnSTUDY DESIGNn: A total of 241 clinical specimens were collected from HFMD patients during the 2010 outbreak in China. These samples were tested by DNA sequencing and MassARRAY analysis, respectively.nnnRESULTSnAnalysis of a dilution series of plasmids revealed the detection limit per PCR reaction for the MassARRAY method was one copy for the tested HEVs. We compared results from 241 samples to those of the sequence analysis of the VP1 gene. The MassARRAY method detected all samples found positive by consensus PCR and sequencing method. Comparison of the results of MassARRAY and the DNA sequencing method found concordant results for 225 (93.4%) of the 241 samples. In 14 (5.8%) samples, the MassARRAY method detected multiple types, whereas the DNA sequencing method detected a single type. In another 2 (0.8%) samples, the MassARRAY method detected single types, whereas the DNA sequencing method detected no HEV.nnnCONCLUSIONSnThe MassARRAY assay is a highly sensitive and accurate method for the type-specific detection of 18 HEVs in HFMD and is a powerful complement to current detection methods.

Subproteomic tools to increase genome annotation complexity

Comprehensive and precise annotations of short protein‐coding genes are always a challenging task. Here we propose a new design to facilitate the characterization of previously overlooked short protein‐coding genes by integrating a shotgun proteomics method and oligonucleotide array analysis. Using Shigella flexneri as a model, we validate 163 annotated ORFs and 51 hypothetical or putative transcripts at the protein level, and discover four novel short ORFs. This strategy will contribute significantly to comprehensive and accurate genome‐wide annotation, and to our understanding of prokaryotic genome structure.

Comparison of the virulence plasmid genomes of two strains of Shigella which lost the ability to bind Congo red

We determined and analyzed the Shigella flexneri serotype 5 (pSF5) and S. dysenteriae serotype 1 (pSD1) virulence plasmid genomes. The total length of pSF5 is 136513 bp, including 165 open reading frames (ORFs). Of these ORFs, 133 were identified and 32 of those had no significant homology to proteins with known functions. The length of pSD1 is 182545 bp, including 224 ORFs, of which we identified 181. The remaining 43 ORFs were not significantly homologous to proteins with known functions. The insertion sequence (IS) elements are 53787 bp in pSF5, and 49616 bp in pSD1, which represents 39.4% and 27.1% of the genome, respectively. There are 22 IS element types in pSF5 and pSD1, among which we report ISEc8 and ISSbo6 for the first time in the Shigella virulence plasmid. Compared to pCP301, there are a large number of deleted genes and gene inversions in both pSF5 and pSD1. The ipa-mxi-spa locus in pSF5 is completely absent, and the genes related to the O-antigen biosynthesis are partially missing. In contrast, the above genes in pSD1 are integral, with the exception of virF. The whole genome analysis of the two plasmids shows that the loss of genes related to gene invasion or regulation also obliterates the ability of pPF5 and pSD1 to bind Congo red (Crb). Whether these genes determine the Crb function requires continued investigation.