Efficacy of chlorhexidine, polihexanide and tissue-tolerable plasma against Pseudomonas aeruginosa biofilms grown on polystyrene and silicone materials.

BACKGROUND: The formation of biofilms is crucial in the pathogenesis of many acute and subacute microbial infections, including chronic wounds and foreign-body-related infections. Topical antimicrobial therapy with chemical antiseptics or physical treatment with tissue-tolerable plasma (TTP) may be promising to control bacterial infection. METHODS: We assessed the efficacy of 0.1% chlorhexidine digluconate (CHX), 0.02 and 0.04% polihexanide (polyhexamethylene biguanide, PHMB) and of TTP against Pseudomonas aeruginosa SG81 biofilm grown in microtitre plates (polystyrene) and on silicone materials in an artificial wound fluid. RESULTS: Overall, PHMB was as effective as CHX in reducing the total amount of biofilm (gentian violet assay) and in reducing the bacterial metabolism in biofilms (XTT assay). TTP also led to a significant reduction in colony-forming units. CONCLUSION: The antimicrobial activity of PHMB in biofilms is comparable to that of CHX. TTP could become an interesting physical alternative to chemical antisepsis in the future.

Antiseptic efficacy and tolerance of tissue-tolerable plasma compared with two wound antiseptics on artificially bacterially contaminated eyes from commercially slaughtered pigs.

AIM: To compare the tissue tolerance and efficacy of two wound antiseptics with tissue-tolerable plasma (TTP) on enucleated contaminated eyes from slaughtered pigs in order to draw consequences for the use of TTP on wounds. METHOD: The corneas of extracted eyes were contaminated with Staphylococcus aureus or Pseudomonas aeruginosa. One and 10 min after application of 10% povidone (PVP)-iodine and 0.04% polyhexanide, respectively, the eyes were rinsed with inactivating solution. To test TTP, the plasma pen meandered over the eyes at a speed of 30 mm/s and a distance of 5 mm; the eyes were then rinsed with balanced salt solution. The reduction factor was calculated by the difference between the logarithm of colony-forming units in the rinse before and after antisepsis or TTP application. RESULTS: The efficacy of TTP (reduction factor 2.4-2.9) was significantly higher (p < 0.001) than that of PVP-iodine and polyhexanide (reduction factor 1.7-2.1). CONCLUSION: TTP is more effective than the tested wound antiseptics. The lack of histological damage to the eyes of slaughtered pigs would seem to make its use as a wound antiseptic a viable alternative. In contrast to antiseptics, it supplies additional energy in the form of heat, electric fields and radicals by TTP.

Antimicrobial efficacy and potential application of a newly developed plasma-based ultraviolet irradiation facility.

A low-pressure mercury vapour discharge tube generating high-intensity ultraviolet (UV) resonance radiation at 254 nm was designed to achieve a nearly simultaneous all-round UV irradiation of products. Testing this 'universal homogeneous ultraviolet (UHUV) irradiation facility' with suspended Bacillus subtilis spores, resulted in a 10(6)-fold reduction in viable count within 30 s applying irradiation energy of 0.3 mW/cm(2). Moreover, this irradiation dose reduced the number of immobilized B. subtilis spores on several material surfaces (wood-free paper, aluminium foil, polystyrol, polypropylene, and polyethylene foil) 10(2)-10(4)-fold. To evaluate potential applications of this UHUV irradiation technique under more realistic conditions, dental hand pieces and orthodontic forceps were contaminated by a blood-saliva mix containing Staphylococcus aureus. Under these conditions, a reduction in viable count of 10(5)-10(6)-fold was achieved within 5-15 min, but higher irradiation energy levels up to 13 mW/cm(2) were necessary. Because of its construction, the shape of the newly developed UHUV irradiation device can be adapted to various shapes to achieve a fast and effective antimicrobial treatment.

Skin decontamination by low-temperature atmospheric pressure plasma jet and dielectric barrier discharge plasma.

BACKGROUND: Over the past few years, plasma medicine has become an important field in medical science. Cold plasma has proven anti-inflammatory, antimicrobial and antineoplastic effects. AIM: To test the decontamination power of two cold plasma sources [low-temperature atmospheric pressure plasma jet (APPJ) and dielectric barrier discharge plasma (DBD)] in vivo on human fingertips. METHODS: After 3, 15, 30, 60, 90, 120, 150, 180, 210 and 240 s of spot treatment with the APPJ and DBD, the log reduction factors (RFs) of physiological (PF) and artificially (AF) contaminated flora (Staphylococcus epidermidis and Micrococcus luteus) were calculated. The bacterial load was determined after counting. Tolerance (paresthesia, pain and heat) was measured using a numerical rating scale. FINDINGS: Both plasma devices led to a significant reduction in PF and AF. The maximum log reduction factors for PF were 1.3 for the DBD at 210 s and 0.8 for the APPJ at 60 s. For AF, the maximum log reduction factors were 1.7 for the DBD at 90 s and 1.4 for the APPJ at 120 s. Treatment with both devices was well tolerated. CONCLUSION: Both the APPJ and DBD were highly effective in eradicating PF and AF from the fingertips of healthy volunteers. No plasma-resistant isolates were observed. Cold plasma appears to have potential for skin disinfection. For hand hygiene purposes, plasma exposure times would need to be reduced significantly by technical means.

Self-consistent model of a positive column in a glow discharge under free-flight and collisional regimes of charged-particle motion.

We consider the nonlocal theory of a positive column in a glow discharge in two cases, where the mean free path of charged particles is either greater than the discharge tube radius (the free-flight regime) or much less than the radius (the collisional regime). The great bulk of electrons, which determines the density and the discharge current in the axial direction, appears to be trapped by the radial field of a positive column. The electron flux to the wall, which compensates for the ionization in a volume, is determined by fast electrons with energies of the order of wall potential, which are able to leave in a loss cone. The electron kinetic equation, which is solved by averaging it over the radial transits for the two regimes considered, permits us to obtain the electron density and the ionization rate. Thus, we develop the theory of a positive column for the non-Boltzmann electron distribution in the radial field. Under the free-flight regime, this theory is developed by analogy with the Langmuir-Tonks one. Under the collisional regime, the spatial distribution of the potential is obtained from the ion motion equation with the ambipolar diffusion coefficient, which depends on the radial coordinate. The concrete calculations are carried out for the xenon discharge under the free-flight and collisional regimes. The theoretical calculations are compared with the results of experiments on the measurements of the electric field and the densities of metastable and resonance xenon atoms.