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

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

CRISPR spacer content of the 21 <i>S</i>. Choleraesuis isolates.

<p>^#Novel spacer identified in this study.</p><p>CRISPR spacer content of the 21 <i>S</i>. Choleraesuis isolates.</p

Mutations detected in the <i>gyrA</i> and <i>parC</i> gene of H₂S-negative <i>S</i>. Choleraesuis isolates.

<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 H₂S-negative <i>S</i>. Choleraesuis isolates.</p

Antimicrobial Resistance and Molecular Investigation of H₂S-Negative <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Choleraesuis Isolates in China

<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 H₂S-negative <i>S</i>. Choleraesuis isolates and two H₂S-positive isolates. This is the first report of H₂S-negative <i>S</i>. Choleraesuis isolated from humans. The majority of H₂S-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 H₂S-negative and H₂S-positive <i>S</i>. Choleraesuis isolates. PFGE revealed two groups, with all 19 H₂S-negative <i>S</i>. Choleraesuis isolates belonging to Group I and H₂S-positive isolates belonging to Group II. By MLST analysis, the H₂S-negative isolates were all found to belong to ST68 and H₂S-positive isolates belong to ST145. By CRISPR analysis, no significant differences in CRISPR 1 were detected; however, one H₂S-negative isolate was found to contain three new spacers in CRISPR 2. All 19 H₂S-negative isolates also possessed a frame-shift mutation at position 760 of <i>phsA</i> gene compared with H₂S-positive isolates, which may be responsible for the H₂S-negative phenotype. Moreover, the 19 H₂S-negative isolates have similar PFGE patterns and same mutation site in the <i>phs</i>A gene, these results indicated that these H₂S-negative isolates may have been prevalent in China. These findings suggested that surveillance should be increased of H₂S-negative <i>S</i>. Choleraesuis in China.</p></div

Dendrogram analysis of PFGE for the 21 <i>S</i>. Choleraesuis isolates by <i>Xba</i>I-digestion.

<p>The strain number, species, origin and ST are shown for each isolate.</p

Strain information of <i>S</i>. <i>flexneri</i> serotype 1b isolates from diarrheal patients.

<p>Strain information of <i>S</i>. <i>flexneri</i> serotype 1b isolates from diarrheal patients.</p

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

<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

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

<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

Antibiogram and molecular analysis of the antibiotic-resistance determinants and integrons of 15 cephalosporin resistant isolates.

<p>Antibiogram and molecular analysis of the antibiotic-resistance determinants and integrons of 15 cephalosporin resistant isolates.</p