43 research outputs found

    Dendrogram displaying the PFGE profiles of the 43 isolates.

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    <p>The strain number, origin, source, sequence type (ST), and H<sub>2</sub>S phenotype are shown for each strain. +, H<sub>2</sub>S-producing isolate; −, non-H<sub>2</sub>S-producing isolate.</p

    Sequence alignment of the <i>phs</i> gene and the protein.

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    <p>A nonsense mutation at position 208 of the <i>phsA</i> gene results in the replacement of a sense codon (CAG) with a termination codon (UAG) leading to the premature termination of <i>phsA</i>. The first sequence, <i>phsA</i>, is based on <i>S</i>. enterica serotype Typhimurium strain LT2 (GenBank AE006468). *, termination codon; +, H<sub>2</sub>S-producing isolate; −, non-H<sub>2</sub>S-producing isolate.</p

    Electrochemical DNA Biosensor Based on a Tetrahedral Nanostructure Probe for the Detection of Avian Influenza A (H7N9) Virus

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    A DNA tetrahedral nanostructure-based electrochemical biosensor was developed to detect avian influenza A (H7N9) virus through recognizing a fragment of the hemagglutinin gene sequence. The DNA tetrahedral probe was immobilized onto a gold electrode surface based on self-assembly between three thiolated nucleotide sequences and a longer nucleotide sequence containing complementary DNA to hybridize with the target single-stranded (ss)­DNA. The captured target sequence was hybridized with a biotinylated-ssDNA oligonucleotide as a detection probe, and then avidin-horseradish peroxidase was introduced to produce an amperometric signal through the interaction with 3,3′,5,5′-tetramethylbenzidine substrate. The target ssDNA was obtained by asymmetric polymerase chain reaction (PCR) of the cDNA template, reversely transcribed from the viral lysate of influenza A (H7N9) virus in throat swabs. The results showed that this electrochemical biosensor could specifically recognize the target DNA fragment of influenza A (H7N9) virus from other types of influenza viruses, such as influenza A (H1N1) and (H3N2) viruses, and even from single-base mismatches of oligonucleotides. Its detection limit could reach a magnitude of 100 fM for target nucleotide sequences. Moreover, the cycle number of the asymmetric PCR could be reduced below three with the electrochemical biosensor still distinguishing the target sequence from the negative control. To the best of our knowledge, this is the first report of the detection of target DNA from clinical samples using a tetrahedral DNA probe functionalized electrochemical biosensor. It displays that the DNA tetrahedra has a great potential application as a probe of the electrochemical biosensor to detect avian influenza A (H7N9) virus and other pathogens at the gene level, which will potentially aid the prevention and control of the disease caused by such pathogens

    Mutations detected in the <i>gyrA</i> and <i>parC</i> gene of H<sub>2</sub>S-negative <i>S</i>. Choleraesuis isolates.

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    <p>Ser, serine. Gly, glycine. Ala, alanine. Tyr, tyrosine. Cys, cysteine. Arg, arginine. Pro, proline.</p><p>Mutations detected in the <i>gyrA</i> and <i>parC</i> gene of H<sub>2</sub>S-negative <i>S</i>. Choleraesuis isolates.</p

    MicroRNA Expression Profile of Mouse Lung Infected with 2009 Pandemic H1N1 Influenza Virus

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    <div><p>MicroRNAs have been implicated in the regulation of gene expression of various biological processes in a post-transcriptional manner under physiological and pathological conditions including host responses to viral infections. The 2009 pandemic H1N1 influenza virus is an emerging reassortant strain of swine, human and bird influenza virus that can cause mild to severe illness and even death. To further understand the molecular pathogenesis of the 2009 pandemic H1N1 influenza virus, we profiled cellular microRNAs of lungs from BALB/c mice infected with wild-type 2009 pandemic influenza virus A/Beijing/501/2009 (H1N1) (hereafter referred to as BJ501) and mouse-adapted influenza virus A/Puerto Rico/8/1934 (H1N1) (hereafter referred to as PR8) for comparison. Microarray analysis showed both the influenza virus BJ501 and PR8 infection induced strain- and temporal-specific microRNA expression patterns and that their infection caused a group of common and distinct differentially expressed microRNAs. Characteristically, more differentially expressed microRNAs were aroused on day 5 post infection than on day 2 and more up-regulated differentially expressed microRNAs were provoked than the down-regulated for both strains of influenza virus. Finally, 47 differentially expressed microRNAs were obtained for the infection of both strains of H1N1 influenza virus with 29 for influenza virus BJ501 and 43 for PR8. Among them, 15 microRNAs had no reported function, while 32 including miR-155 and miR-233 are known to play important roles in cancer, immunity and antiviral activity. Pathway enrichment analyses of the predicted targets revealed that the transforming growth factor-β (TGF-β) signaling pathway was the key cellular pathway associated with the differentially expressed miRNAs during influenza virus PR8 or BJ501 infection. To our knowledge, this is the first report of microRNA expression profiles of the 2009 pandemic H1N1 influenza virus in a mouse model, and our findings might offer novel therapy targets for influenza virus infection. </p> </div

    Dominant serotype distribution and antimicrobial resistance profile of <i>Shigella</i> spp. in Xinjiang, China

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    <div><p><i>Shigella</i> represents one of the major diarrhea-inducing pathogens threatening public health, but its prevalence and antimicrobial resistance profile in Xinjiang Uygur Autonomous region, China, remains unclear. We conducted comprehensive investigation of <i>Shigella</i> serotype distribution and antimicrobial resistance pattern in Xinjiang, identifying 458 <i>Shigella</i> isolates between 2008 to 2014. <i>Shigella flexneri</i> was identified as predominant species, and several <i>S</i>. <i>flexneri</i> serotypes were isolated, including atypical serotypes 1c, 2c, and 4s. Dominant <i>S</i>. <i>flexneri</i> serotypes were 2a, 1b, 2b, and Xv, different from those generally dominant in China. A hybrid serotype pattern was observed, which included the major Chinese serotypes (2a, Xv) and those predominant in Pakistan (1b, 2b). <i>Shigella sonnei</i> was shown to have a lower frequency compared with that generally observed in China, but an increasing trend of infections associated with this pathogen was observed. Furthermore, a high frequency of drug resistance and different <i>Shigella</i> antimicrobial resistance patterns were demonstrated as well, including very severe resistance phenotypes, such as multidrug resistance and resistance to frontline antibiotics. Seventy-five cephalosporin-resistant <i>Shigella</i> isolates were frequently identified with the resistance determinants that can undergo horizontal transfer, such as <i>bla</i><sub>OXA</sub>, <i>bla</i><sub>TEM</sub>, <i>bla</i><sub>CTX-M</sub>, and integrons, facilitating the development of cephalosporin resistance among <i>Shigella</i> subtypes. Additionally, genetic analyses demonstrated that all 86 quinolone-resistant <i>S</i>. <i>flexneri</i> isolates possess 3–4 mutation sites in quinolone resistance-determining regions, primarily contributing to their resistance to quinolone. However, <i>S</i>. <i>sonnei</i> isolates were not shown to be quinolone resistant. Co-resistance to cephalosporins and quinolones was detected in 17 <i>S</i>. <i>flexneri</i> isolates, and these isolates were additionally multidrug resistant and carried β-lactamase genes and quinolone-resistance determinants. As is demonstrated in this study, dominant serotypes of <i>Shigella</i> were distributed in unique trend with dangerous drug resistance patterns. Novel strategies are urgently required to prevent the development of drug resistance among diarrhea-inducing pathogens.</p></div

    Stable Nanocomposite Based on PEGylated and Silver Nanoparticles Loaded Graphene Oxide for Long-Term Antibacterial Activity

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    The increasing occurrence of antibiotic-resistant pathogens, especially superbugs, is compromising the efficacy of traditional antibiotics. Silver nanoparticles (AgNPs) loaded graphene oxide (GO) nanocomposite (GO-Ag) has drawn great interest as a promising alternative antibacterial material. However, GO-Ag nanocomposite often irreversibly aggregates in physiological solutions, severely influencing its antibacterial capacity and practical application. Herein, a PEGylated and AgNPs loaded GO nanocomposite (GO-PEG-Ag) is synthesized through a facile approach utilizing microwave irradiation, while avoiding extra reducing agents. Through PEGylation, the synthesized GO-PEG-Ag nanocomposite dispersed stably over one month in a series of media and resisted centrifugation at 10 000×<i>g</i> for 5 min, which would benefit effective contact between the nanocomposite and the bacteria. In contrast, GO-Ag aggregated within 1 h of dispersion in physiological solutions. In comparison with GO-Ag, GO-PEG-Ag showed stronger bactericidal capability toward not only normal Gram-negative/positive bacteria such as <i>E. coli</i> and <i>S. aureus</i> (∼100% of <i>E. coli</i> and ∼95.3% of <i>S. aureus</i> reduction by 10 μg/mL nanocomposite for 2.5 h), but also superbugs. Moreover, GO-PEG-Ag showed lower cytotoxicity toward HeLa cells. Importantly, GO-PEG-Ag presented long-term antibacterial effectiveness, remaining ∼95% antibacterial activity after one-week storage in saline solution versus <35% for GO-Ag. The antibacterial mechanisms of GO-PEG-Ag were evidenced as damage to the bacterial structure and production of reactive oxygen species, causing cytoplasm leakage and metabolism decrease. The stable GO-PEG-Ag nanocomposite with powerful and long-term antibacterial capability provides a more practical and effective strategy for fighting superbugs-including pathogen threats in biomedicine and public health