Zhenhong Chen

Molecular pathogenesis of Klebsiella pneumoniae

Typical Klebsiella pneumoniae is an opportunistic pathogen, which mostly affects those with weakened immune systems and tends to cause nosocomial infections. A subset of hypervirulent K. pneumoniae serotypes with elevated production of capsule polysaccharide can affect previously healthy persons and cause life-threatening community-acquired infections, such as pyogenic liver abscess, meningitis, necrotizing fasciitis, endophthalmitis and severe pneumonia. K. pneumoniae utilizes a variety of virulence factors, especially capsule polysaccharide, lipopolysaccharide, fimbriae, outer membrane proteins and determinants for iron acquisition and nitrogen source utilization, for survival and immune evasion during infection. This article aims to present the state-of-the-art understanding of the molecular pathogenesis of K. pneumoniae.

NDM-1 encoded by a pNDM-BJ01-like plasmid p3SP-NDM in clinical Enterobacter aerogenes

A carbapenem-nonsusceptible Enterobacter aerogenes strain named 3-SP was isolated from a human case of pneumonia in a Chinese teaching hospital. NDM-1 carbapenemase is produced by a pNDM-BJ01-like conjugative plasmid designated p3SP-NDM to account for carbapenem resistance of 3-SP. p3SP-NDM was fully sequenced and compared with all publically available pNDM-BJ01-like plasmids. The genetic differences between p3SP-NDM and pNDM-BJ01 include only 18 single nucleotide polymorphisms, a 1 bp deletion and a 706 bp deletion. p3SP-NDM and pNDM-BJ01 harbor an identical Tn125 element organized as ISAba125, blaNDM−1, bleMBL, ΔtrpF, dsbC, cutA, ΔgroES, groEL, ISCR27, and ISAba125. The blaNDM−1 surrounding regions in these pNDM-BJ01-like plasmids have a conserved linear organization ISAba14-aphA6-Tn125-unknown IS, with considerable genetic differences identified within or immediately downstream of Tn125. All reported pNDM-BJ01-like plasmids are exclusively found in Acinetobacter, whereas this is the first report of identification of a pNDM-BJ01-like plasmid in Enterobacteriaceae.

Heme oxygenase-1 system, inflammation and ventilator-induced lung injury.

Mechanical ventilation is an indispensable supportive intervention for acute respiratory failure. However, mechanical ventilation can provoke ventilator-induced lung injury, which remains one of the major causes of morbidity and mortality in critically ill patients. Excessive inflammatory response characterized by infiltration of inflammatory cells and overproduction of inflammatory mediators contributes to the pathogenesis of ventilator-induced lung injury. At present, apart from the protective ventilation strategy, no other pharmacological intervention is available to attenuate ventilator-induced lung injury. Heme oxygenase-1 (HO-1) is the inducible isoform of the first and rate-limiting enzyme which degrades heme into carbon monoxide, ferritin and bilirubin. Accumulating evidence suggests that HO-1 system may function as a crucial negative regulator in the modulation of inflammatory process. This anti-inflammatory action of HO-1 is mediated essentially by the regulation of the key cells involved in inflammation and restoration of the balance between pro-inflammatory and anti-inflammatory mediators. Therefore, HO-1 system represents a promising therapeutic target for intervention of ventilator-induced lung injury.

Analysis of Long Non-Coding RNA Expression Profiles in Non-Small Cell Lung Cancer

Background/Aims: Long non-coding RNAs (lncRNAs) play an important role in tumorigenesis. However, the role of lncRNA expression in human Non-small cell lung cancer (NSCLC) biology, prognosis and molecular classification remains unknown. Methods: We established the IncRNA profile in NSCLC by re-annotation of microarrays from the Gene expression omnibus database. Quantitative real-time PCR was used to determine expression of LINC00342. Results: 6066 differentially expressed IncRNAs were identified and we found a novel IncRNA, LINC00342 was significantly up-regulated in NSCLC tissues compared with normal tissues. We confirmed the over-expression of LINC00342 in a cohort of NSCLC patients and found LINC00342 expression level was positively correlated with lymph node metastasis and TNM stages. Furthermore, in a large online database of 1942 NSCLC patients, high expression of LINC00342 indicated poor Overall survival (HR = 1.28, 95% CI: 1.13-1.45) and post progression survival (HR = 1.43, 95% CI: 1.09-1.88). Bioinformatics analyses showed that LINC00342 was co-expressed with different protein-coding genes in NSCLC and normal tissues. Additionally, gene set enrichment analyses found that PTEN and P53 pathways genes were enriched in the groups with higher LINC00342 expression level. By small interfering RNAs mediated silence of LINC00342, proliferation ability was significantly inhibited in lung cancer cell line. Conclusion: To summary, our findings indicate that a set of IncRNAs are differentially expressed in NSCLC and we characterized a novel IncRNA, LINC00342 which is significantly up-regulated in NSCLC and could be a prognostic biomarker.

IMP-1 encoded by a novel Tn402-like class 1 integron in clinical Achromobacter xylosoxidans, China

Achromobacter xylosoxidans strain A22732 is isolated from a pneumonia patient in China and produces carbapenemases OXA-114e and IMP-1, which are encoded by chromosome and plasmid, respectively, and confer resistance to multiple ß-lactam antibiotics including carbapenems. The blaIMP-1 gene together with aacA7 and orfE is captured by a novel Tn402-like class 1 integron in a conjugative IncP-1ß plasmid. In addition to the intrinsic integron promoter PcW, there is still a blaIMP-1 gene cassette-specific promoter. This is the first report of carbapenemase-encoding IncP-1ß plasmid in clinical bacterial isolate.

A novel PCR-based genotyping scheme for clinical Klebsiella pneumoniae

AIM To establish a PCR-based genotyping method for clinical Klebsiella pneumoniae. MATERIALS & METHODS The prevalence of six serotype markers, 41 large variably presented gene clusters, and seven additional virulence markers were screened by PCR in 327 clinical K. pneumoniae strains from China. RESULTS Detection of serotype markers enabled the identification of capsular serotypes K1, K2, K5, K20, K54 and K57. K. pneumoniae isolates of different origins gave distinct profiles of virulence loci, allowing us to gain a full overview of virulence gene distribution of the strains tested. A novel genotyping scheme was established to group clinical K. pneumoniae strains into distinct complexes based on the profiles of large variably presented gene clusters and virulence markers. CONCLUSION This PCR-based genotyping method would be useful to not only characterize genetic diversity and virulence gene distribution, but also for genotyping, origin tracing and risk estimation of K. pneumoniae.

WWTR1 promotes cell proliferation and inhibits apoptosis through cyclin A and CTGF regulation in non-small cell lung cancer

The Hippo pathway plays a major role in development and organ size control, and its dysregulation contributes to tumorigenesis. WWTR1 is a transcription coactivator acting downstream of the Hippo pathway. Recently, WWTR1 has been reported to be overexpressed in several human cancers including lung cancer. However, the molecular mechanism of WWTR1 regulating lung cancer aggressiveness remains ambiguous. In the present study, we analyzed the expression of WWTR1 in NSCLC cell lines and found that WWTR1 was overexpressed at both the mRNA and protein levels. Knockdown of WWTR1 by siRNA interference in A549 cells significantly inhibited cell proliferation and increased paclitaxel-induced apoptosis. On the other side, WWTR1 overexpression in HBE cell line promoted cell proliferation and inhibited apoptosis. In addition, we found that the decreased proliferation after siRNA treatment was due to cell cycle arrest. Further analysis showed that WWTR1 could induce cyclin A, connective tissue growth factor (CTGF) expression, and inhibit caspase3 cleavage. In conclusion, WWTR1 promotes malignant cell growth and inhibits apoptosis by cyclin A and CTGF regulation.

A multi-omic analysis of an Enterococcus faecium mutant reveals specific genetic mutations and dramatic changes in mRNA and protein expression

BackgroundFor a long time, Enterococcus faecium was considered a harmless commensal of the mammalian gastrointestinal (GI) tract and was used as a probiotic in fermented foods. In recent decades, E. faecium has been recognised as an opportunistic pathogen that causes diseases such as neonatal meningitis, urinary tract infections, bacteremia, bacterial endocarditis and diverticulitis. E. faecium could be taken into space with astronauts and exposed to the space environment. Thus, it is necessary to observe the phenotypic and molecular changes of E. faecium after spaceflight.ResultsAn E. faecium mutant with biochemical features that are different from those of the wild-type strain was obtained from subculture after flight on the SHENZHOU-8 spacecraft. To understand the underlying mechanism causing these changes, the whole genomes of both the mutant and the WT strains were sequenced using Illumina technology. The genomic comparison revealed that dprA, a recombination-mediator gene, and arpU, a gene associated with cell wall growth, were mutated. Comparative transcriptomic and proteomic analyses showed that differentially expressed genes or proteins were involved with replication, recombination, repair, cell wall biogenesis, glycometabolism, lipid metabolism, amino acid metabolism, predicted general function and energy production/conversion.ConclusionThis study analysed the comprehensive genomic, transcriptomic and proteomic changes of an E. faecium mutant from subcultures that were loaded on the SHENZHOU-8 spacecraft. The implications of these gene mutations and expression changes and their underlying mechanisms should be investigated in the future. We hope that the current exploration of multiple “-omics” analyses of this E. faecium mutant will provide clues for future studies on this opportunistic pathogen.

Genome Sequence of Enterococcus faecium Clinical Isolate LCT-EF128

Enterococcus faecium, an opportunistic human pathogen that inhabits the gastrointestinal tracts of most mammals, has emerged as an important opportunistic nosocomial pathogen and is a prominent cause of multiresistant nosocomial infections. Here, we report the draft genome sequence of strain LCT-EF128, isolated from clinical specimens.

Impact of a short-term exposure to spaceflight on the phenotype, genome, transcriptome and proteome of Escherichia coli

Escherichia coli ( E. coli ) is the most widely applied model organism in current biological science. As a widespread opportunistic pathogen, E. coli can survive not only by symbiosis with human, but also outside the host as well, which necessitates the evaluation of its response to the space environment. Therefore, to keep humans safe in space, it is necessary to understand how the bacteria respond to this environment. Despite extensive investigations for a few decades, the response of E. coli to the real space environment is still controversial. To better understand the mechanisms how E. coli overcomes harsh environments such as microgravity in space and to investigate whether these factors may induce pathogenic changes in E. coli that are potentially detrimental to astronauts, we conducted detailed genomics, transcriptomic and proteomic studies on E. coli that experienced 17 days of spaceflight. By comparing two flight strains LCT-EC52 and LCT-EC59 to a control strain LCT-EC106 that was cultured under the same temperature conditions on the ground, we identified metabolism changes, polymorphism changes, differentially expressed genes and proteins in the two flight strains. The flight strains differed from the control in the utilization of more than 30 carbon sources. Two single nucleotide polymorphisms (SNPs) and one deletion were identified in the flight strains. The expression level of more than 1000 genes altered in flight strains. Genes involved in chemotaxis, lipid metabolism and cell motility express differently. Moreover, the two flight strains also differed extensively from each other in terms of metabolism, transcriptome and proteome, indicating the impact of space environment on individual cells is heterogeneous and probably genotype-dependent. This study presents the first systematic profile of E. coli genome, transcriptome and proteome after spaceflight, which helps to elucidate the mechanism that controls the adaptation of microbes to the space environment.