DE10215179A1 - Process to sterilize medical and veterinary products with modulated pulsed ultra violet light beam - Google Patents

Abstract

In a process to kill germs by exposure to ultraviolet light, the required energy is especially discharged as a light beam pulse forming a plasma gas around the product. The process operates in the temperature range 35 to 80 degreesC. Exposure to the pulsed beam takes place in association with exposure to chemical agents. The product is pre-wrapped in transparent packaging which prevents recontamination. The pulse beam is subject to continual modification of intensity. The pulse energy is reduced as necessary.

Description

The invention relates to a method for killing germs by means of plasma-assisted UV radiation and the application of this method in human and veterinary medicine.

By germ killing we mean the inactivation of biological units with the Ability to reproduce or transfer genetic material.

State of the art

Sterilization, high-level disinfection and disinfection are for one intended product and antimicrobial processes designed for a specific application not detached from a possible influence on the functionality and the The biocompatibility of the respective product may be considered [Spicher, G., Zbl. Hyg. 194, 1993: 223-235; Winckels, H.W., Dorpema, J.W., Med. Dev. Technol. 5 (9), 1994: 38-43].

Sterility of a product or article means the absence of any viable microorganisms, including viruses, that could pose a risk in use [Donawa, ME, Med. Dev. Technol. 7 (1), 1996: 12-15; Spicher G, Zbl. Hyg. 194, 1993: 223-235; Wallhäusers, KH, practice of sterilization-disinfection-preservation-germ identification-industrial hygiene. Georg Thieme Verlag Stuttgart, New York, 1988: 284-305)]. Since this absolute state is practically neither attainable nor verifiable, the Pharmkopöen demands that sterilization must guarantee a theoretical germ load of at most one living germ in 10 ⁶ products treated with the same [European Pharmacopoeia, 3rd edition. German pharmacist publisher, Govi-Verlag-Pharmaceutical publisher Stuttgart, Eschborn, 1997, 379-381; The United States Pharmacopeia, The National Formulary. United States Pharmacopeial Convention, Rockville, 1994: 1976-1981].

New technical teachings must also be measured against this requirement of the pharmacopoeias become. Proof of achievement of sterilization assurance level (sterility assurance level) SAL) is the decisive criterion for the assessment of a sterilization process.

In contrast, a reduction in the concentration of pathogens, which can transmit a disease when the intended use of the object to be disinfected is used, is required for disinfection by at least 5 log ₁₀ steps.

Measures to reduce the number of bacteria are referred to as high-level disinfection, through the resistant pathogens, which are not sufficiently inactivated during disinfection, such as. B. bacterial spores are killed and / or a reduction in the number of bacteria by more than 5 log ₁₀ steps is achieved without a sterilization safety level of 10 ^-6 can be guaranteed.

The germ-reducing effect of UV radiation has been known for a long time and is widely used to reduce the number of bacteria in the air and in aqueous solutions (Wallhäuser KH: practice of sterilization, disinfection, preservation. 4th ed. Stuttgart: Georg Thieme, 1988, 330 -337; Kiefer J, Wienhard I: Biological effects. In: Kiefer J, ed. Ultraviolet rays. Berlin, New York: Walter de Gruyter 1977: 482-533). Combinations of UV radiation with hydrogen peroxide have been used to sanitize contact lenses (Forstrom RJ, Wardle MD (Moore-Perk Corp., US): Cold gas sterilization process using hydrogen peroxide at low concentrations. US 4230663 1980) and paper (Barkowski E , Schippler B (PWA Industriepapier, DE): Method and device for the sterilization of paper with the aid of aqueous H ₂ O ₂ solutions. DE 34 42 399 A1 1984). In combination with UV radiation, hydrogen peroxide shows increased microbicidal properties (Kodera T, Hohino M, Hyakutomene K (Dai Nippon Insatsu KK, JP): Sterilization apparatus and process utilizing synergistc effect of combining hydrogen peroxide and ultra-violet-ray sterilization (US 4366125 A 1982, CA 1147526 A 1983, JP 56075158 A 1981; Peel JL, Waites WM (Nat Res. Dev. Corp., GB): Procede perfectionne de sterilization / Method of sterilization: WO 8001457 A 1980, EP 22801 (B1 983, B2 1993), GB 20603070 A 1981; Wang JJ (FMC Corp., US): Sterilization of containers using hydrogen peroxide, peracids and UV radiation. EP 0411970 B1 1993). However, shadowing effects and the low depth effect limit the wide use of these technologies ( Wallenwein, Zentr Steril 3: 1995: 380).

The high antimicrobial effectiveness of UV radiation depends on unimpeded exposure on the one hand on the wavelength and on the other hand on the duration and intensity of the radiation from. Death curves after UV radiation always run with a decreasing number of bacteria flacher [Oberdoerster, F., in: Horn, Prívora, Weuffen (ed.). Disinfection manual and Sterilization. Volume II: Basics of Sterilization. People and Health, Berlin 1973: 146-180; Schmidt J, Naumann G, Horsch W: sterilization, disinfection, preservation and Disinfestation in medical and pharmaceutical practice. Leipzig: Georg Thieme, 1990: 15, 36-37, 60-69, 157-161; Zemke V, Podgorsek L, Schoenen D: Ultraviolet Disinfection of Drinking water. 1. Communocation: Inactivation of E. coli and Coliform Bacteria. Zbl Hyg 1990; 190: 51-61].

A can be used to evaluate the maximum number of germs to be expected after irradiation logarithmic dying process not consistent throughout the process be taken as a basis. The death kinetics in the area of low bacterial counts can only through a complex combination of experimental data and statistical Evaluation methods can be described reliably. An extrapolation of values at high initial bacterial counts were observed on the low germ count range due to the course of the inactivation kinetics described under UV influence not allowed. Even with UV radiation acting from all sides, the Evidence of sufficient germ killing was not provided at a low bioburden become.

The state of the art corresponds to the fact that taking the inactivation kinetics into account for a logarithmic bacterial count reduction of 5 log ₁₀ steps requires 40 mWs.cm ^-2 (BERNHARDT ET AL. [1994].). In other experimental arrangements, more than 150 mWs.cm ^{-2 are} required to achieve this effect ([PHILIPS LICHT, SCHENCK 1980, HANDBUCH DER ILLICHTUNG].

An improvement in antimicrobial efficacy that has a use for sterilization would allow with ultraviolet light, according to most experts, is not possible [Schmidt, J., Naumann, G., Horsch, W., sterilization, disinfection, preservation and disinfestation in medical and pharmaceutical practice. Georg Thieme Leipzig, 1990: 157-161; Szycher, M., in: Sharma CP, Szycher M (ed.). Blood Compatible Materials and devices. Technomic Publishing Co., Lancaster, Basel, 1991: 87-122].

Due to the strong UV absorption of most materials and due to so far the suitability of UV radiation for decontamination becomes inevitable shadow formation further restricted [Wallhäußer, K. H. Practice of Sterilization-Disinfection-Conservation- Germ identification industrial hygiene, Georg Thieme Verlag, Stuttgart, New York, 1988: 297-305; Block, S. S., in: Lederberg, J. (ed.), Encyclopedia of Microbiolgy, Vol. 4. Academic Press, San Diego, New York, Boston, London, Sydney, Tokyo, Toronto, 1992: 87-103]. UV radiation is therefore not accepted as a sterilization method [RUSSELL 1999].

Various plasma-assisted sterilization processes are an alternative worldwide developed, but there is still a lot of uncertainty about their possible uses. The lies z. T. that about the antimicrobial effect of plasma technology significant components (UV radiation, radicals, direct ion effects) and their optimal interaction z. Currently there is insufficient knowledge. Even with these Proceedings can provide evidence that what is required in the pharmacopoeias Sterilization security level is reached, have not yet been achieved.

In the current state of the art, the verification of the achievement of the sterilization safety level of 10 ^-6 , as is required in pharmacopoeias [European Pharmacopoeia, 3rd edition. German pharmacist publishing house, Govi publishing house - Pharmaceutical publishing house Stuttgart, Eschborn, 1997, 379-381; The United States Pharmacopeia, The National Formulary. United States Pharmacopeial Convention, Rockville, 1994: 1976-1981], ie the guarantee of a bacterial load after the application of a decontamination process of a maximum of one living bacterium in 10 ⁶ products treated equally, only possible with thermal processes. For decontamination of thermolabile goods, methods are used in which the level of sterilization safety cannot be guaranteed (v. Woedtke and Jülich: Pharmazie 56 (2001) 561-566).

Purpose of the invention

Factors that irreversibly damage microorganisms can be very likely also affect biomaterials. If it doesn't destroy or make big changes the material properties and associated changes in functionality, at least the surface structure and thus the biocompatibility is influenced. Building on the technical teaching of Jülich, Kindel, Klemm and Wilhelm (sterilization of sensitive goods. DP 197 48 098.5 from 10/17/97) should be a technical solution can be found to get a number of hits when disinfecting a contaminated good To achieve plasma radiation per unit of time, on the one hand, the repairability of the contaminating germs is overwhelmed, but photoreactivities largely avoided become. Material damage to the goods should be reduced.

State the nature of the invention

The task was solved by an arrangement in which the decontamination material is exposed to pulsed UV radiation with constantly changing radiation intensity. As was shown experimentally, the antimicrobial activity is surprisingly increased by the radiation source according to the invention. In contrast to the solutions described in the prior art, a germ reduction of more than 9 log ₁₀ steps has been experimentally proven.

According to the invention, the application of the decontamination method is more sensitive Goods that are not sterilized using thermal processes or gas sterilization can.

Short exposure times are a particular advantage. That enables the Decontamination of goods that have to be available again after a short time, such as z. B. the decontamination of straight and contra-angle handpieces in dental practice. The short exposure times when using the invention Decontamination process also enables use in food technology.

The decontamination can be done in recontamination-proof UV-permeable packaging respectively. The goods remain protected until they are used or processed.

According to the invention is also an insert for decontamination of used Instruments through which the protection against infection for the personnel in the preparation of the Instruments is improved since safe cleaning and disassembly is made possible. As a particular advantage of an embodiment of the invention, in which the pulsating Radiation used in combination with hydrogen peroxide results in blood residues do not interfere with decontamination.

Another application according to the invention is the decontamination of in dentistry frequently used impression materials.

Here too, decontamination can be UV-permeable, but more contamination-proof Packaging.

The use of the decontamination method according to the invention is thereby characterized in that the germ killing alone by pulsed UV radiation as well as in Combination of pulsed UV radiation with other germ killing methods used can be. This leads to a significant expansion of the possible uses.

The invention will be explained below using a few examples, without referring to these Restrict examples.

embodiments example 1

In Fig. 1 shows an embodiment for the construction of the particular UV radiation source is shown. The pulsed UV radiation is generated by an Hg low-pressure radiator ( 2 ) shaped into a coil and made of quartz glass in connection with a pulse generator connected to the electrodes ( 4 , 5 ) with a downstream circuit breaker. The radiator ( 2 ) is arranged in a container ( 8 ) filled with a thermostatic liquid ( 3 ). The special, closed thermostat system consists on the one hand of a cooling heat pipe arrangement ( 7 ) in connection with a high-performance air cooler ( 6 ) and on the other hand of a component consisting of heating element ( 10 ), temperature sensor ( 9 ) and temperature control system for temperature control. The decontamination material is arranged in a quartz glass cylinder ( 1 ) for homogeneous radiation on all sides inside the emitter coil ( 2 ).

• - Durch die spezielle Konstruktion wird das Dekontaminationsgut in geringem Abstand allseitig homogen bestrahlt.
• - In Verbindung mit einer für diesen Zweck entwickelten Leistungsschaltstufe kann der Strahler im Pulsmode bei variablen Pulsparametern (Frequenz, Tastverhältnis) betrieben werden.
• - Durch ein spezielles Thermostatisierungssystem kann eine konstante Temperatur des Strahlers und des Sterilgut-Probenraumes im Bereich von 35°C bis 80°C eingestellt werden.

This special UV lamp arrangement has significant advantages for use in decontamination processes compared to commercial Hg low-pressure discharge lamps:

• - Due to the special construction, the decontamination material is irradiated homogeneously on all sides at a short distance.
• - In conjunction with a power switching stage developed for this purpose, the radiator can be operated in pulse mode with variable pulse parameters (frequency, duty cycle).
• - A special thermostatic system allows a constant temperature of the heater and the sterile goods sample room to be set in the range from 35 ° C to 80 ° C.

Example 2 Proof of effectiveness using the example of staphylococci

In each case 1 ml of a S. aureus suspension with an initial bacterial count of 3.2 × 10 ⁸ / ml was irradiated for 15 s with the device according to FIG. 1. The germs were detected by incubation in casein peptone soybean meal peptone solution (CSL, Oxoid, Unipath Ltd., Basingstocke, Hampshire, England) at 37 ° C. A sample was considered to be free of reproductive germs if the nutrient solution was visually clear after incubation and the vaccination was negative. The number of surviving germs per test object m to be expected on a statistical average was calculated from the number of samples without reproducible germs p _o based on the number p according to the formula m = -ln (p _o / p). Results Tab. 1 Inactivation of vegetative germs in suspensions

Only one of the 90 samples examined had germs grown after irradiation. This corresponds to a statistically expected bacterial load of 0.011 germs / ml after the Irradiation. This results in a logarithmic reduction factor of 10.4 (Tab. 1).

Example 3 Inactivation of germs dried on surfaces methodology

Sterile filter paper strips were soaked in 10 µl of a S. aureus suspension and then irradiated to dry.

In a further experiment, autoclaved contra-angles from KaVo Biberach were mixed with 100 μl of a blood-saliva mixture (obtained after a dental operation), which had been mixed 1: 1 with a suspension of S. aureus ATCC 6538. The blood-saliva mixture we used, which was additionally contaminated with S. aureus, adheres very well to the test objects, so that a high and very reproducible recovery rate was achieved. The contaminated instruments were irradiated in the apparatus according to Example 1 for 30 s. The instruments were then rinsed with 20 ml of water of standardized hardness after shaking for one minute on a vortex shaker and the bacterial count with an automated spiral plater, model WASP (from Meintrup Laborgeräte GmbH Lähden). Results Tab. 2

Even with germs that have dried on surfaces, there is a high level of antimicrobial Effectiveness achieved. Decontamination is also with blood contamination possible (Tab. 2).

Example 4 Evidence of dependence on the pulse regime methodology

The parameters frequency, duty cycle and thus also the pulse width were varied and the exposure time.

The materials aluminum (ALU), paper (PA), polyethylene (PE), polystyrene (PS) and BAG bio strips (BAG) were used. These materials were contaminated with 100 μl each of a Bacillus Subtilis spore suspension with an initial bacterial count of 3.0.10 ⁶ .

The number of surviving germs after exposure to the pulsed UV Radiation.

results Annotation

In the diagrams of FIG. 2, the killing was shown in LOG stages with a frequency of 200 Hz and an irradiation time of 30 seconds depending on the duty cycle in the range from 0.5 to 16%. The curves showed an increasing course up to a duty cycle of about 8-12%. Despite an increased energy supply with higher duty cycles, the kill rate could not be increased further.

With an optimal duty cycle, the germ killing varies between 6.02 LOG levels PS and 6.48 LOG levels for BAG, PA and PE.

If the optimum duty cycle is undershot, the kill rate is significantly lower reached. If the optimal duty cycle is exceeded, it is due to the higher Expect energy input with material damage. Varyed at a duty cycle of 0.5% z. B. the reduction factor between with 3.25 LOG levels for PS to 4.58 LOG levels ALU.

At a frequency of 50 Hz and a duty cycle of 0.01%, logarithmic reduction factors between 2.49 LOG levels for PS to 3.36 LOG. Levels observed at BAG ( Fig. 3). As the duty cycle increases, the kill rate is increased up to a duty cycle of 4%. For PS it was the lowest with 4.95 LOG steps and for PE the highest value was achieved with 6.48 LOG steps.

The test series mentioned were carried out with a constant irradiation time of 30 s each. In the following experiments, the duty cycles of 14% at 200 Hz ( FIG. 4) and 4% at 50 Hz ( FIG. 5), which had proven to be favorable, were chosen and the irradiation time varied between 15 s and 2.5 s ,

At 200 Hz, a spore inactivation of 4.60 LOG steps at BAG is already 15 to 30 s up to 6.16 LOG levels achieved with PE. Optimal germ killing is after 1 to 1.5 min achieved, which can no longer be increased even if the exposure is prolonged. at the maximum kill of 6.48 LOG levels was achieved for all materials.

At the frequency of 50 Hz, an exposure time of 15 seconds Mortality achieved on PS with 3.11 LOG levels up to PE with 5.71 LOG levels. Here too spore activation increased to 1.5 minutes when the exposure time was extended a further extension of the irradiation time has only little influence. at BAG was the highest value at 6.04 LOG levels, all materials were killed up to 6.48 LOG levels reached. Overall, one reached slightly with 200 Hz better results.

Example 5 material compatibility methodology

The studies on the influence of materials were carried out on dental impression materials carried out. A condensation-curing silicone (xantoprene blue, light body / Fa. H. Kulzer) and an addition-curing silicone (Panasil light body, fast setting / Fa. Kettenbach). Only pre-made material was used Cartridges used in accordance with the respective instructions for use.

The manufacturer's instructions on processing, setting and reset times have been observed.

specimen

Test specimens were manufactured in accordance with the standard EN 24823 (Beuth Verlag, 3/94). The test specimens were used to record the linear dimensional change examined according to EN 24823 before and after disinfection using a measuring microscope. 3 defined sections A, B, C were exposed on 36 test specimens without the influence of Disinfection measures measured twice. At Xantoprene, route A was proposed disinfection a reference value 4.99334 + 0.0355, for the route B 2.5211 + 0.0156 and for the distance C from 2.486 + 0.016. The maximum deviation from this reference value was for route A + 1.43%, the minimum deviation -1.55%.

At Panasil, A was 5.0177 + 0.0015, B 2.52088 + 0.0074 and C 2.5064 + 0.0090 determined.

For each disinfection procedure, 12 replicates / test specimens were compared to untreated controls carried out, each route was averaged from 2 measurements. In the controls without disinfection, the second measurement was made after 10 min. to create conditions comparable to immersion disinfection.

The significance test was carried out using the t-test. The test specimens were irradiated in a test arrangement according to Example 1 at a frequency of 204 Hz and a period of 4,990 ms at 920 mV for a period of 30 seconds at 28 ° C. The results were compared with a customary method of immersion disinfection ("Impresept", Espe) (exposure time 10 min). Results of the investigations on the dimensional stability of the impression materials Tab. 3 Average difference between the measurement sections before / after disinfection

The expected change in volume was derived from the mean values of the measuring sections (Tab. 3) calculated and used for statistical analysis.

With both impression materials, the dimensional stability after exposure to pulsating radiation is very good, although the level of high-level disinfection and thus an improvement in virus safety is achieved. ( Fig. 6 and Fig. 7). This means that the application of pulsating radiation is clearly superior to standard immersion disinfection. The difference in mean values before and after disinfection is very small, especially with xantoprene. The maximum deviations for route A are + 1.24% and -1.16% below the corresponding values of the control. Due to the short exposure time, the expected change in volume is less than for controls without disinfection. The dimensional stability of the Panasil is also significantly better than that of conventional immersion disinfection and fully corresponds to the values for the control.

Claims (4)

1. A method for decontamination, characterized in that the energy input required for killing germs by UV radiation is reduced by using pulsed radiation, which is generated in a gas discharge plasma surrounding the material to be decontaminated by an arrangement according to FIG. 1, and the material compatibility sensitive goods is improved. 2. The method according to claim 1, characterized in that the method at Temperatures in the range of 35 ° C to 80 ° C can be carried out. 3. The method according to claim 1 and 2, characterized in that the action pulsating radiation in combination with chemical agents. 4. The method according to at least one of claims 1 to 3, characterized in that decontamination in UV / VUV-permeable packaging is carried out Protection against recontamination guaranteed.