Portable plasma torch treatment on E. coli, S. aureus, N. meningitidis and other clinical isolates

摘要

The uses of non-thermal plasmas in medical, environmental and consumer industries especially in food processing, air filtration, decontamination and sterilization of bacteria in liquids and solids surfaces, are continued to grow. In this paper we present the research efforts on the effects of a portable non-thermal plasma source treatment on bacteria in liquid phases. We predict that the plasma species can penetrate/diffuse in to the liquid culture media and plasma treatment will efficiently kill the bacteria at unique time and distance parameters. It is also hypothesized that less stringent plasma treatment will negatively affect the growth rate of some species of bacteria and possibly their pathogenicity. Cultures used were at optical densities (O.D.600nm) ranging from 0.2 to 1.0 or McFarland standards of 0.5 and higher. The bacteria were exposed to plasmas at various time lengths and distance parameters and gas temperatures. Our results indicates that less than 120 seconds of plasma treatment with the plasma gun ∼5 cm away from the liquid culture is effective in killing/sterilizing cultures of S. aureus, S. pyogenes, Salmonella spp, N. meningitidis, and E. coli. Less than five minutes of cold plasma with the probe immersed 1–2 cm inside the liquid culture were needed to kill the bacteria. Furthermore, growth curve analysis showed that N. meningitidis, S. aureus and E. coli exposed to less than 2 minutes of treatment experienced decreased growth. N. meningitidis exposed to 1 minute of hot plasma treatment displayed a heavier mucoid appearance on agar plates and subsequent capsule staining will be employed to verify microscopically if a larger capsule is present in comparison to untreated samples. Furthermore, q-real time-RT-PCR will be employed with N. meningitidis to determine quantitative amount of capsule gene expression using primers for synC and synD genes (needed for capsular polysaccharide synthesis) and the ctrA gene (needed for --capsular polysaccharide transport). Additionally, q-real time-RT-PCR work will be used to investigate whether N. meningitidis has decreased synthesis of the PilC gene after 1 minute treatment with hotter plasma. The PilC gene codes for the bacteria''s pili, which are used for adhesion and pathogenicity in its host. Subsequent studies should be done to explore the effects of plasma treatment on the pathogenicity of different species of bacteria.