21 research outputs found

    Highly Stable Graphene-Based Nanocomposite (GO–PEI–Ag) with Broad-Spectrum, Long-Term Antimicrobial Activity and Antibiofilm Effects

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    Various silver nanoparticle (AgNP)-decorated graphene oxide (GO) nanocomposites (GO–Ag) have received increasing attention owing to their antimicrobial activity and biocompatibility; however, their aggregation in physiological solutions and the generally complex synthesis methods warrant improvement. This study aimed to synthesize a polyethyleneimine (PEI)-modified and AgNP-decorated GO nanocomposite (GO–PEI–Ag) through a facile approach through microwave irradiation without any extra reductants and surfactants; its antimicrobial activity was investigated on Gram-negative/-positive bacteria (including drug-resistant bacteria) and fungi. Compared with GO–Ag, GO–PEI–Ag acquired excellent stability in physiological solutions and electropositivity, showing substantially higher antimicrobial efficacy. Moreover, GO–PEI–Ag exhibited particularly excellent long-term effects, presenting no obvious decline in antimicrobial activity after 1 week storage in physiological saline and repeated use for three times and the lasting inhibition of bacterial growth in nutrient-rich culture medium. In contrast, GO–Ag exhibited a >60% decline in antimicrobial activity after storage. Importantly, GO–PEI–Ag effectively eliminated adhered bacteria, thereby preventing biofilm formation. The primary antimicrobial mechanisms of GO–PEI–Ag were evidenced as physical damage to the pathogen structure, causing cytoplasmic leakage. Hence, stable GO–PEI–Ag with robust, long-term antimicrobial activity holds promise in combating public-health threats posed by drug-resistant bacteria and biofilms

    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

    Antimicrobial Resistance and Molecular Investigation of H<sub>2</sub>S-Negative <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Choleraesuis Isolates in China

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    <div><p><i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Choleraesuis is a highly invasive pathogen of swine that frequently causes serious outbreaks, in particular in Asia, and can also cause severe invasive disease in humans. In this study, 21 <i>S</i>. Choleraesuis isolates, detected from 21 patients with diarrhea in China between 2010 and 2011, were found to include 19 H<sub>2</sub>S-negative <i>S</i>. Choleraesuis isolates and two H<sub>2</sub>S-positive isolates. This is the first report of H<sub>2</sub>S-negative <i>S</i>. Choleraesuis isolated from humans. The majority of H<sub>2</sub>S-negative isolates exhibited high resistance to ampicillin, chloramphenicol, gentamicin, tetracycline, ticarcillin, and trimethoprim-sulfamethoxazole, but only six isolates were resistant to norfloxacin. In contrast, all of the isolates were sensitive to cephalosporins. Fifteen isolates were found to be multidrug resistant. In norfloxacin-resistant isolates, we detected mutations in the <i>gyrA</i> and <i>parC</i> genes and identified two new mutations in the <i>parC</i> gene. Pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and clustered regularly interspaced short palindromic repeat (CRISPR) analysis were employed to investigate the genetic relatedness of H<sub>2</sub>S-negative and H<sub>2</sub>S-positive <i>S</i>. Choleraesuis isolates. PFGE revealed two groups, with all 19 H<sub>2</sub>S-negative <i>S</i>. Choleraesuis isolates belonging to Group I and H<sub>2</sub>S-positive isolates belonging to Group II. By MLST analysis, the H<sub>2</sub>S-negative isolates were all found to belong to ST68 and H<sub>2</sub>S-positive isolates belong to ST145. By CRISPR analysis, no significant differences in CRISPR 1 were detected; however, one H<sub>2</sub>S-negative isolate was found to contain three new spacers in CRISPR 2. All 19 H<sub>2</sub>S-negative isolates also possessed a frame-shift mutation at position 760 of <i>phsA</i> gene compared with H<sub>2</sub>S-positive isolates, which may be responsible for the H<sub>2</sub>S-negative phenotype. Moreover, the 19 H<sub>2</sub>S-negative isolates have similar PFGE patterns and same mutation site in the <i>phs</i>A gene, these results indicated that these H<sub>2</sub>S-negative isolates may have been prevalent in China. These findings suggested that surveillance should be increased of H<sub>2</sub>S-negative <i>S</i>. Choleraesuis in China.</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

    The number of differentially expressed microRNAs during influenza virus BJ501 and PR8 infections.

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    <p>The y axis indicates the number of differentially expressed microRNAs. Significance was determined using a fold-change threshold of at least 2 and a nominal <i>P</i> value cutoff of 0.05.</p