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than 1 log). For each experimental set, one sample was kept untreated (the control sample). The Petrifilmswereincubatedat32.5 ± 2.5 ◦ Cfor24 ± 1 hours. After incubation the results were recorded by counting the colony forming units (CFU) in CFU × ml −1 , following the count plate method from the "Interpretation Guide" of 3M PetriFilms [119]. The calculation of the average number of CFU’s per Petrifilm after the plates were counted was made using the formula: AV × DF = CFU/ml (2.12) where DF is the dilution factor (the absolute value of the reciprocal of the dilution) and AV is the average number of colonies per Petrifilm. Experimental results recorded for a sample treated 1 min by plasma feeded by 100 W injected RF power, are shown in the Fig. 2.5. It can be seen that successive dilutions (I-IV) are plated on two Petrifilms (1 st and 2 nd rows). When colonies are too numerous to count (TNTC) on a plate, typically, the entire growth area will turn pink, as shown in the first two columns (I-II). On the other hand, when the dilution factor (DF) increases, small pink spots of variable dimensions can be distinguished and counted. Usually, the preferable counting range is between 25 and 250 colonies. When the average number is more than 250 CFU,asitcanbeseeninthethirdcolumn from the Fig. 2.5, the average number of colonies in 1 cm 2 is multiplied by 20 (i.e., 35
1 st 2 nd ( I) TNTC (II) TNTC (III) 450 CFU (IV) 46 CFU Figure 2.5: Determination of viable spores using the counting method. For this experimental trial, the results recorded were TNTC (too numerous to count) for the first two dilutions and an average number of 450 and 46 CFU (colony forming units) recorded for the next two dilutions, respectively. approximative area of inoculation is 20 cm 2 )tofind the total count per plate. In this case the viable spores number was recorded as 4.6 × 10 5 CFU/ml. To eliminate other causes which can determine spore inactivation, a series of experiments was carried out only using the contaminated samples, but without producing plasma. This precaution was taken since it was reported that long time desiccation in high vacuum environment can neutralize spores [25]. Therefore 36
Page 1 and 2: PLASMA STERILIZATION USING LOW PRES
Page 3 and 4: my appreciation especially for the
Page 5 and 6: Iis ion saturation current [µA] t
Page 7 and 8: CONTENTS 1 PRINCIPLES OF SURFACE DI
Page 9 and 10: 4 EFFECTS OF LOW TEMPERATURE PULSED
Page 11 and 12: and intuited to bring new important
Page 13 and 14: Figure 1.1: Schematic representatio
Page 15 and 16: Table 1.1: Common disinfection and
Page 17 and 18: the radiation energy is resonantly
Page 19 and 20: ers of heat, optical radiation and
Page 21 and 22: Table 1.2: Main plasma sources used
Page 23 and 24: microorganism population as a respo
Page 25 and 26: UV Photon Before After DNA Figure 1
Page 27 and 28: to sterilize medical tools, but the
Page 29 and 30: sented by both theoretical and expe
Page 31 and 32: Plasma Sterilization Using Low Pres
Page 33 and 34: Figure 2.1: Experimental set-up. MB
Page 35 and 36: Figure 2.3: Electronic circuit of t
Page 37 and 38: such circumstances, the inactivatio
Page 39 and 40: ment time t is N = N0e −αt ≡ N
Page 41 and 42: shows the number of the viable micr
Page 43: has n −1 0 > 281.25 µm 2 availab
Page 47 and 48: U LC blocking filter 19.74 pF 20.24
Page 49 and 50: Figure 2.8: Experimental set-up use
Page 51 and 52: the reactive species from plasma ar
Page 53 and 54: Temperature measurement Relative in
Page 55 and 56: MR MP SH Figure 3.2: Experimental a
Page 57 and 58: a fast temperature increasing rate.
Page 59 and 60: D h (min) 10 3 10 2 10 1 10 0 100 2
Page 61 and 62: MR QP SH Figure 3.6: Experimental a
Page 63 and 64: The contribution of photons and hea
Page 65 and 66: D (min) 10 3 10 2 10 1 10 0 Dν D h
Page 67 and 68: N/N 0 (%) 10 2 10 2 10 2 10 2 10 2
Page 69 and 70: D (min) 10 2 10 1 10 0 D h+ν+p D h
Page 71 and 72: holder is mainly given by particle
Page 73 and 74: 3.5 Power sensitivity of spore inac
Page 75 and 76: If for a reference treatment temper
Page 77 and 78: of the sample was achieved. Moreove
Page 79 and 80: microorganisms were disposed in mon
Page 81 and 82: The pulse period covered a wide int
Page 83 and 84: in chapter 2. The treatment time of
Page 85 and 86: 4.2.2 Injected RF power In order to
Page 87 and 88: ton =500µs, and the duty cycle was
Page 89 and 90: T ( 0 C) 120 100 80 60 40 20 I 0 5
Page 91 and 92: N/N 0 (%) 10 2 10 2 10 2 10 1 10 1
Page 93 and 94: elow 70 ◦ C. 3. Increasing the in
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the second phase of the inactivatio
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k 1, 2 (min -1 ) 1.2 1.0 0.8 0.6 0.
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I (arb. unit) 140 120 100 80 60 40
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I (arb. unit) 5 4 3 2 1 0 0.000 0.0
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I > (arb.unit) 1.0 0.9 0.8 0.7 0.6
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shown in Fig. 4.14. It can be seen
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I is (mA) 0.25 0.20 0.15 0.10 0.05
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value. When ton has been kept const
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survival curve characteristics were
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of the effects produced by differen
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solutely necessary for a profound u
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Conferences 1. Bacillus spores ster
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[9] W. A. Rutala, D. J. Weber, J. H
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[34] J. H. Young: Sterilization wit
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[57] M. K. Boudam, M. Moisan, B. Sa
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[79] J. Schneider, K. M. Baumgartne
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[100] S. Villeger, S. Cousty, A. Ri
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