Parental migration and cyberbullying victimization among Chinese left-behind children: understanding the association and mediating factors

IntroductionParental absence is greatly associated with school bullying victimization of left-behind children (LBC) in migrant families. With the increasing popularity of the Internet, little is known about the association between parental migration and cyberbullying victimization, and potential mediators.MethodsWe conducted a cross-sectional study in Anhui and Zhejiang Province, China, in 2020. With a sample of 792 currently left-behind children (CLBC), 541 previously left-behind children (PLBC), and 628 never left-behind children (NLBC), path analysis was used to explore the association between parental migration and cyberbullying victimization among children, while considering the independent and sequential mediating roles of parent-child communication, and time spent online.ResultsThe prevalence of cyberbullying victimization was 29.3% among CLBC, 29.2% among PLBC, and 23.4% among NLBC. Path analysis showed that current left-behind status was positively associated with cyberbullying victimization among children (p = 0.024). Furthermore, current left-behind status was associated with worse parent-child communication, which, in turn, predicted a higher prevalence of cyberbullying victimization [95% CI = (0.007, 0.036)]. Similarly, the previous left-behind experience was associated with worse parent-child communication, which, in turn, predicted a higher prevalence of cyberbullying victimization [95% CI = (0.013, 0.043)]. Current left-behind status was associated with increased time spent online, which, in turn, predicted a higher prevalence of cyberbullying victimization [95% CI = (0.013, 0.038)]. Additionally, the current left-behind status positively predicted cyberbullying victimization among children through the serial mediating roles of parent-child communication and time spent online [95% CI = (0.001, 0.006)]. Similarly, previous left-behind experience positively predicted cyberbullying victimization among children through the serial mediating roles of parent-child communication and time spent online [95% CI = (0.002, 0.007)].DiscussionWe propose that to protect CLBC and PLBC from cyberbullying victimization, it is of great importance for migrant parents to regulate children's time spent online and promote daily parent-child communication

Nicotine Enhances Staphylococcus epidermidis Biofilm Formation by Altering the Bacterial Autolysis, Extracellular DNA Releasing, and Polysaccharide Intercellular Adhesin Production

Staphylococcus epidermidis is a common bacterial colonizer of human skin and mucous membranes, yet it has emerged as an important nosocomial pathogen largely due to its ability to form biofilms. Tobacco smoke has been demonstrated as a contributor to various infection diseases by improving the biofilm formation of multiple bacterial species; however, the association between tobacco smoke and S. epidermidis biofilm is still unclear. In this study, we tested the effect of nicotine, one of the most active components of tobacco, on S. epidermidis biofilm formation, and we studied the underlying mechanisms. Our results showed that nicotine promoted the biofilm formation of S. epidermidis 1457 strain (SE1457) and enhanced its initial attachment to a polyethylene surface as well as polysaccharide intercellular adhesin (PIA) production. In addition, an increased extracellular DNA release and a higher autolysis rate of SE1457 was detected after nicotine treatment, which was consistent with the increased ratio of dead cells in nicotine-treated SE1457 biofilm observed with confocal laser-scanning microscopy. Furthermore, the effect of nicotine on several autolysis-related and biofilm-related gene knockout mutants of SE1457 was tested. It showed that in ΔsaeRS, ΔlytSR, and ΔsceD, nicotine induced increase in biofilm formation was similar to that in SE1457; but in ΔarlRS, ΔatlE, and ΔicaC, the effect was obviously impaired. Consistently, the increase of the bacterial autolysis rate in ΔarlRS and ΔatlE induced by nicotine was not as significant as that in SE1457. Meanwhile, the growth inhibition of nicotine on SE1457 was observed, and it was much less on ΔarlRS and restored by the arlRS complementation. The arlRS transcription in SE1457 was inhibited by nicotine during cultivation as indicated by a promoter reporter assay using green fluoresent protein. Taken together, our study indicates that nicotine improves S. epidermidis biofilm formation by promoting its initial attachment and intercellular accumulation; the arlRS, atlE, and ica genes mediating bacterial autolysis and PIA production play an important role in this process

The Two-Component Signal Transduction System ArlRS Regulates <em>Staphylococcus epidermidis</em> Biofilm Formation in an <em>ica</em>-Dependent Manner

<div><p>Due to its ability to form biofilms on medical devices, <em>Staphylococcus epidermidis</em> has emerged as a major pathogen of nosocomial infections. In this study, we investigated the role of the two-component signal transduction system ArlRS in regulating <em>S. epidermidis</em> biofilm formation. An ArlRS-deficient mutant, WW06, was constructed using <em>S. epidermidis</em> strain 1457 as a parental strain. Although the growth curve of WW06 was similar to that of SE1457, the mutant strain was unable to form biofilms <em>in vitro</em>. In a rabbit subcutaneous infection model, sterile disks made of polymeric materials were implanted subcutaneously followed with inoculation of WW06 or SE1457. The viable bacteria cells of WW06 recovered from biofilms on the embedded disks were much lower than that of SE1457. Complementation of arlRS genes expression from plasmid in WW06 restored biofilm-forming phenotype both <em>in vivo</em> and <em>in vitro</em>. WW06 maintained the ability to undergo initial attachment. Transcription levels of several genes involved in biofilm formation, including <em>icaADBC</em>, <em>sigB</em>, and <em>sarA</em>, were decreased in WW06, compared to SE1457; and <em>icaR</em> expression was increased in WW06, detected by real-time reverse-transcription PCR. The biofilm-forming phenotype was restored by overexpressing <em>icaADBC</em> in WW06 but not by overexpressing <em>sigB</em>, indicating that ArlRS regulates biofilm formation through the regulation of <em>icaADBC</em>. Gel shift assay showed that ArlR can bind to the promoter region of the <em>ica</em> operon. In conclusion, ArlRS regulates <em>S. epidermidis</em> biofilm formation in an <em>ica</em>-dependent manner, distinct from its role in <em>S. aureus</em>.</p> </div

Biofilms formed on catheter fragments surfaces observed by scanning electron microscope (SEM).

<p><i>S. epidermidis</i> strains WW06, ParlS, ParlRS and SE1457 were incubated with central vein catheter fragments in 96-well plates. After incubation at 37°C for 24 h, biofilm formed on the surface of the catheter fragments were observed under a transmission electron microscope (XL-30, Philips). Images were obtained at different magnifications (x3000, x10000) for biofilms formed by SE1457 (a, b), WW06 (c, d), ParlS (e, f) and ParlRS(g, h).</p

Binding of ArlR to the <i>icaADBC</i> promoter.

<p>Lanes were loaded as follows: lane 1, 0.8 ng Dig-ICAP alone; lane 2, 0.8 ng Dig-ICAP and 2 µg rArlR; lanes 3–5, Dig-ICAP, rArlR and increasing amounts of unlabeled ICAP (12.5, 62.5,125 fold increase in Dig-ICAP, respectively); and lane 6, Dig-ICAP, rArlR and 100 ng of a 405 bp <i>icaA</i> fragment. The DIG-labeled DNA fragments were transferred to positively charged nylon membranes and visualized by an enzyme immunoassay using anti-Digoxigenin-AP, Fab-fragments and the chemiluminescent substrate CSPD. Chemiluminescent signals were recorded on X-ray film. DIG-ICAP, digoxin-labeled <i>icaADBC</i> promoter region; ICAP, unlabeled <i>icaADBC</i> promoter region; icaA’, icaA gene fragment.</p

Biofilm formation in complementation strains PicaADBC, icaCpRS and PsigB in 96-well microtiter plates.

<p>(A) SE1457, WW06, Δ<i>icaC</i> and icaCpRS were cultivated in TSB; PicaADBC and PsigB were cultivated in TSB with or without 0.5% (g/ml) xylose. Biofilms formed over 24 h in 96-well microtiter plates were stained with 2% crystal violet. (B) The crystal violet was dissolved in ethanol and the absorbance was determined at 570 nm. The mean value ± standard deviation for each strain is shown.</p

Regulation of expression of biofilm-related genes by ArlRS.

<p>(A) Effect of ArlRS deficiency on transcription levels of the biofilm-related genes. Gene expression profiles of the <i>arlRS</i>-deficient strain WW06 and the wild-type parent strain SE1457 in the mid-log growth phase were analyzed using RT-qPCR. The experiment was performed in triplicate and the expression ratios of the biofilm-related genes in WW06 and SE1457 are represented as mean ± standard deviation. (B) Effect of <i>arlRS</i> mutation on PIA synthesis. PIA was extracted from cells grown for 24 h under biofilm conditions in 6-well cell culture plates. PIA was detected by dot blot analysis using wheat germ agglutinin coupled to horseradish peroxidase. The PIA-deficient <i>S. epidermidis</i> mutant Δ<i>icaC</i> was used as a negative control, and RP62A was used as a positive control.</p

Primers used in this study.

<p>Primers used in this study.</p

Influence of ArlRS deficiency on viable <i>S. epidermidis</i> cells recovery from the implanted disks in the rabbit model.

<p>Biofilms of SE1457, WW06 and ParlRS were formed <i>in vivo</i> on sterile polyethylene disks that were implanted subcutaneously in three New Zealand White female rabbits. Three days after infection, the implants were removed. Biofilms were scraped from the disks and CFUs of the viable bacteria recovered from the biofilms were determined and expressed as mean ± standard deviation. Asterisks denote statistically significant difference, P<0.001.</p

Plasmids and bacterial strains.

<p>Plasmids and bacterial strains.</p