Antibiotic resistance is a worldwide public health concern. Conjugative transfer between closely related strains or species of bacteria is an important method for the horizontal transfer of multidrug-resistance genes. The extent to which nanomaterials are able to cause an increase in antibiotic resistance by the regulation of the conjugative transfer of antibiotic-resistance genes in bacteria, especially across genera, is still unknown. Here we show that nanomaterials in water can significantly promote the horizontal conjugative transfer of multidrug-resistance genes mediated by the RP4, RK2, and pCF10 plasmids. Nanoalumina can promote the conjugative transfer of the RP4 plasmid from Escherichia coli to Salmonella spp. by up to 200-fold compared with untreated cells. We also explored the mechanisms behind this phenomenon and demonstrate that nanoalumina is able to induce oxidative stress, damage bacterial cell membranes, enhance the expression of mating pair formation genes and DNA transfer and replication genes, and depress the expression of global regulatory genes that regulate the conjugative transfer of RP4. These findings are important in assessing the risk of nanomaterials to the environment, particularly from water and wastewater treatment systems, and in the estimation of the effect of manufacture and use of nanomaterials on the environment.

Chemical disinfection is the most common method used to inactivate viruses from drinking water throughout the world. In this study, cell culture, ELISA, RT-PCR, and spot hybridization were employed to investigate the mechanism underlying chlorine dioxide (ClO(2) )-induced inactivation of Poliovirus type 1 (PV1), which was also confirmed by recombinant viral genome RNA infection models. The results suggested that ClO(2) inactivated PV1 primarily by disrupting the 5'-non-coding region (5'-NCR) of the PV1 genome. Further study revealed that ClO(2) degraded specifically the 40-80 nucleotides (nt) region in the 5'-NCR. Recombinant viral genome RNA infection models confirmed that PV1 RNA lacking this 40-80 nt region was not infectious. This study not only elucidated the mechanism of PV1 inactivation by ClO(2), but also defined the critical genetic target for the disinfectant to inactivate Poliovirus. This study also provides a strategy by which rapid, accurate, and molecular methods based on sensitive genetic targets may be established for evaluating the effects of disinfectants on viruses.

Yunnan Baiyao is a famous Chinese medicine that has long been directly applied to wounds to reduce bleeding, pain, and swelling without causing infection. However, little is known about its ability to prevent infection. The present study aimed to assess in vitro the anti-virulence activity of an aqueous extract of Yunnan Baiyao (YBX) using Pseudomonas aeruginosa as a pathogenic model. We found that a sub-MIC (2.5 mg/ml) of YBX can efficiently interfere with the quorum-sensing (QS) signaling circuit. Real-time polymerase chain reaction analysis showed that a sub-MIC of YBX down-regulated the transcriptions of lasR, lasI, rhlR, and rhlI, which resulted in global attenuation of QS-regulated virulence activities, such as biofilm formation, and secretion of LasA protease, LasB elastase and pyocyanin. Further, YBX reduced the motility of P. aeruginosa related to QS, and impaired the formation of biofilms. These results suggest that YBX may possess global inhibitory activity against the virulence of P. aeruginosa and that YBX may also exhibit antimicrobial activity in vivo. The present study suggests that Yunnan Baiyao represents a potential source for isolating novel, safe, and efficacious antimicrobial agents.

Recently, the potential risks of nanomaterials and the spread of antibiotic resistance have become two important environmental concerns. The conjugative transfer of antibiotic resistance genes between bacteria is the most important pathway for the acquisition of antibiotic resistance by bacteria. Both environmental and genetic factors influence the conjugative transfer of antibiotic resistance genes in bacterial populations. The extent to which nanomaterials are able to bring about an increase in antibiotic resistance by regulating the conjugative transfer of antibiotic resistance genes in bacteria is still unknown. In this paper, an Orthogonal Design L 64 (4 21) was used in duplicate to evaluate the effects of bacterial concentration, nano-alumina concentration, mating time, mating temperature and the interactions of those factors on the conjugation transfer in LB broth. The mechanisms by which nano-alumina promote the horizontal transfer of antibiotic multiresistance features were explored by morphological, biochemical, and molecular biological methods. We have shown that nano-alumina promotes the horizontal conjugative transfer multiresistance genes mediated by RP4 up to 250-fold in LB broth and 100-fold in PBS. And it would appear that the effect of promoting conjugative transfer of nano-alumina exceeds the effects of mating temperature and mating time. We also explored the mechanisms behind this phenomenon and demonstrated that nano-alumina is able to induce oxidative stress, cause the damage of bacterial cell membranes, enhance the transcriptional activity of conjugative genes and depress the global regulatory factor genes expression. The findings in this study support the notion that nano-alumina in the environment could result in ecological hazards. More important, an enhanced rate of plasmid transfer among microorganisms may have an enormous impact on human health and environmental safety. Journal of Nanomedicine & Nanotechnology J o u rna l of N a n o m ed icine & N a n o te chnolo g y