UV Disinfection Induces a Vbnc State in <i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i>

The occurrence of a viable but nonculturable (VBNC) state in bacteria may dramatically underestimate the health risks associated with drinking water. Therefore, the potential for UV treatment to induce a VBNC state in <i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i> was investigated. UV disinfection effectively reduced the culturability of <i>E. coli</i> and <i>P. aeruginosa</i>, with the destruction of nucleic acids demonstrated using <i>gad</i>A long gene fragment qPCR amplification. Following UV radiation, copy numbers for the high transcriptional levels of the 16S rRNA gene varied insignificantly in both strains, confirming results from plate counting assays indicating that VBNC states were induced in both strains. Furthermore, the virulence genes <i>gadA</i> and <i>oprL</i> remained highly expressed, suggesting that the VBNC bacteria still displayed pathogenicity. Propidium monoazide qPCR indicated that cell membranes remained intact even at a UV dose of 300 mJ/cm². The RT-qPCR results after UV and chlorine treatments in <i>E. coli</i> were significantly different (8.41 and 5.59 log units, respectively), further confirming the induction of VBNC bacteria induced by UV radiation. Finally, resuscitation was achieved, with <i>E. coli</i> showing greater resuscitation ability than <i>P. aeruginosa</i>. These results systematically revealed the potential health risks of UV disinfection and strongly suggest a combined disinfection strategy

Particulate Respirators Functionalized with Silver Nanoparticles Showed Excellent Real-Time Antimicrobial Effects against Pathogens

Particulate respirators designed to filtrate fine particulate matters usually do not possess antimicrobial functions. The current study aimed to functionalize particulate respirators with silver nanoparticles (nanosilver or AgNPs), which have excellent antimicrobial activities, utilizing a straightforward and effective method. We first enhanced the nanosilver-coating ability of nonwoven fabrics from a particulate respirator through surface modification by sodium oleate. The surfactant treatment significantly improved the fabrics’ water wet preference where the static water contact angles reduced from 122° to 56°. Both macroscopic agar-plate tests and microscopic scanning electron microscope (SEM) characterization revealed that nanosilver functionalized fabrics could effectively inhibit the growth of two model bacterial strains (i.e., <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i>). The coating of silver nanoparticles would not affect the main function of particulate respirators (i.e., filtration of fine air-borne particles). Nanosilver coated particulate respirators with excellent antimicrobial activities can provide real-time protection to people in regions with severe air pollution against air-borne pathogens