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PubMed1999

Effect of sterilization on the physical and structural characteristics of polyhydroxyoctanoate (PHO).

The present study examined the potential applicability of poly(beta-hydroxy octanoate) (PHO), a bacterial polyester, as a candidate for biomaterial applications, by investigating the effect of sterilization on the physical and structural characteristics of PHO. PHO-cast films were sterilized by either ethylene oxide (EO) gas at 38 degrees C or gamma radiation (2.5 Mrad) in air at room temperature. The physical characteristics of the EO and gamma-sterilized PHO were determined by scanning electron microscopy (SEM) and tensile strength analyses. In addition, various analytical methods were used to detect modifications in the chemical and morphological structure of PHO, namely, electron spectroscopy for chemical analysis (ESCA), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and size exclusion chromatography (SEC). The results show that EO sterilization did not modify the chemical and physical characteristics of PHO, however, significant modifications in both the structural and tensile properties were observed with gamma-sterilized PHO. These changes accounted for decreases in both the weight average, number average and melting temperature, and increases in the heat of fusion and tensile strength. No residual EO was detected following sterilization as revealed by head-space chromatography. The physical and structural properties of PHO were shown to be well preserved following EO sterilization, whereas gamma radiation caused random chain scission and physical cross-linking, a frequent phenomenon observed with organic polymers.

Bacteria↗
PubMed2001

Fluid absorption study in ultra-high molecular weight polyethylene (UHMWPE) sterilized and unsterilized acetabular cups.

The weight gain due to fluid absorption was measured in gamma-sterilized, ethylene oxide (ETO) gas-sterilized, and unsterilized ultra-high molecular weight (UHMW) polyethylene acetabular cups. After about 2 months the total average fluid absorption gain of the polyethylene cups was: 1.76 +/- 0.45 mg (average +/- standard deviation) for the unsterilized polyethylene cups, 2.81 +/- 0.95 mg for the gamma-sterilized polyethylene cups and 1.51 +/- 0.34 for the ETO gas-sterilized polyethylene cups. There was little difference in fluid absorption between the sterilized and unsterilized specimens. In particular, the gamma-sterilized acetabular cups absorbed more than the ETO gas-sterilized and the unsterilized cups. However, the weight gain was higher in serum compared with that in water.

Absorption↗
PubMedDate not supplied

Child disability and mothers' tubal sterilization.

CONTEXT: The needs of children with disability can be substantial, leading some parents to consider contraceptive sterilization to prevent additional births. METHODS: Matched records from the 1993 National Health Interview Survey and the 1995 National Survey of Family Growth were used to investigate the relationship between child disability and mothers' sterilization. Data included the birth records of 8,711 children, information on older children in the household, and the mothers' background and reproductive characteristics. Logistic and Cox regression models were used to estimate the effect of the birth of a child with a disability on the risk of mothers' sterilization. RESULTS: The birth of a child with disability has no effect on the likelihood that a mother will undergo sterilization within the next month; however, women who have an older child with severe disability are more likely than those whose older children are nondisabled to undergo sterilization within a month after the birth of another child (odds ratio, 2.6). Severe disability in a newborn significantly increases the risk of sterilization 1-36 months after birth (risk ratio, 1.7); severe disability among older children also appears to increase the risk of sterilization 1-36 months after birth (1.5), although this result was only marginally significant. CONCLUSIONS: Women often respond to the birth of children with disabilities by changing their fertility plans, although usually not immediately unless they have older children with severe disability. These findings are consistent with parents'desire to have a nondisabled child and with their need to care for an exceptional child by forgoing additional births.

Adolescent↗
PubMed1991

Effectiveness of dental office instrument sterilization procedures.

To evaluate instrument sterilization procedures in Minnesota, biological indicators were used to monitor 406 sterilizers in 381 dental offices. Findings suggest a general improvement in instrument performance over that of a decade ago, but sterilization failure rates are still too high. Sterilizer operator errors are a major cause of sterilization failures. BIs are useful in monitoring sterilization performance only when sterilization procedures are performed consistently and competently by well-trained staff using adequately maintained equipment.

Bacillus subtilis↗
PubMedDate not supplied

Endotoxin levels in steam and reservoirs of table-top steam sterilizers.

PURPOSE: To document endotoxin levels in "Statim" cassette sterilizer reservoirs and in steam delivered to the cassette in the unwrapped instrument cycle. To document endotoxin levels in sterilizer reservoir water using different management protocols. METHODS: Endotoxin levels were determined using the Limulus Amebocyte Lysate test. Endotoxin preparations were from Escherichia coli and Ralstonia pickettii. All samples were collected in depyrogenated glassware and stored at -20 degrees C until assayed. RESULTS: The majority of water samples contained < 1.0 Endotoxin Unit (EU)/ml. The highest level found in sterilizers in clinical use was 5.3 EU/ml. Endotoxin was not detected in steam condensate within the limits of the assay. When the endotoxin level in the reservoir water was experimentally enhanced to 200 EU/ml, cassette steam condensate endotoxin levels were from 0.5% to 5% of the reservoir level. Daily and weekly emptying of the cassette reservoir consistently yielded low endotoxin levels as did monthly emptying, but with the latter there was a trend toward higher levels that favors weekly emptying as a precautionary measure. CONCLUSIONS: Endotoxin levels in the reservoirs of 23 sterilizers involving 240 samplings were never high enough to yield detectable endotoxin levels in steam in the sterilizer cassette. Regular weekly emptying of sterilizer reservoirs would eliminate the risk of endotoxin transfer during steam sterilization.

Ambulatory Care↗
PubMedDate not supplied

[Effect of methods of sterilization on thermoplastics with special reference to modified surfaces].

For materials intended for use in the medical setting their sterilizability is an indispensable prerequisite. In the case of most polymers the usual sterilization methods result in changes that even extend to cleavage of the polymer chains. A particular problem in this respect are the surfaces modified for improved biocompatibility investigated in the present study, which are characterised by enlarged contact areas. For this reason, possible changes to three different thermoplastics commonly used for medical applications (polyethylene, thermoplastic polyurethane, polycarbonate) were investigated. Steam, gas and radiation were used for sterilization. Tensile tests were employed to identify changes in mucosal characteristics caused by different sterilization techniques irrespective of the surface modification. Sterilization-related changes to the structure of the modified surfaces were investigated with the scanning electron microscope (SEM). Differential thermo analysis (DTA) was used to determine changes in the thermal characteristics of the plastics. Clear tendencies with regard to the behaviour of the plastics after sterilization with various techniques were found. A general statement about the compatibility of plastic materials with a specific sterilization method is not possible on the basis of this study. For every new polymeric product used for medical purposes, the characteristics required must first be defined and compliance with the permissible variations of these characteristics investigated for each of the various sterilization techniques available.

Equipment Failure Analysis↗
PubMed1999

[Validation of sterilization processes].

Sterilization is a special process, where the results of processes (efficacy of sterilization) cannot be verified by subsquent inspection and testing of the product (the items sterilized). For this reason sterilization process must be validated. Validation of sterilization processes is required by Medical Devices Directive 93/42 EEC and GMP. Also the sterilization processes in the hospitals shall be validated. The validation of sterilization of processes as described in European Standards: EN 550--for ethylene oxide EN 554--for moist heat.

Documentation↗
PubMed2002

Safety of plasma-based sterilization: surface modifications of polymeric medical devices induced by Sterrad and Plazlyte processes.

Plasma-based sterilization is a promising alternative to the use of pure ethylene oxide (EO), for low-temperature clinical sterilization of medical instruments and devices. However, few studies have been published that evaluate its safety in terms of possible damage to materials, particularly polymers. The objective of this work was to evaluate polymer surface modifications induced by commercial plasma-based sterilizers, in comparison with pure EO: Samples from 5 polymer-based devices were subjected to 1, 5, and 10 sterilization cycles by Sterrad-100, Plazlyte, and pure EO. Surface analysis was carried out by X-ray photoelectron spectroscopy (XPS), dynamic contact angle measurements (DCA), and scanning electron microscopy (SEM). Surface oxidation and wettability changes were observed on all samples sterilized by plasma-based techniques, the degree of modifications depending on the sterilizer (Sterrad, Plazlyte) and the type of polymer. Drastic changes of surface appearance were also observed by SEM on PVC samples sterilized by Plazlyte and by pure EO. Possible repercussions on safety are discussed.

Adsorption↗
PubMed1964

Some biological and physical factors in dry heat sterilization: a general review.

There is a surprising lack of quantitative data on sterilization by dry heat so that microbiologists have little knowledge of the role played by various biological and physical factors in this sterilizing process. A recent investigation by the author has shown that the aerobic mesophilic bacterial sporeformers, such as Bacillus subtilis and Bacillus coagulans, are the most resistant among several species of sporeforming bacteria to dry heat sterilization. The type of carrier on which the spores are exposed to dry heat markedly affects their thermal resistance. An analysis of four carriers showed that spores on sand or vermiculite are more difficult to destroy than spores on paper or glass. Spores under low vacuums are more susceptible to dry heat sterilization than spores in helium, which are more susceptible than spores in air. Spores trapped in solids have thermal resistance levels two or three times greater than those found for spores exposed to dry heat in air. Preliminary results on the combination of dry heat and ionizing radiation sterilization indicate no synergistic effects, i.e., the destruction obtained with each agent is additive. Another important variable that governs the interpretation of the effectiveness of dry heat sterilization tests is the recovery medium for heat-damaged spores. The kinetics of dry heat sterilization cannot be fully interpreted from the available data. Death follows a logarithmic pattern thereby implying a monomolecular reaction. The mechanism of death is thought to be due to an oxidative process.

Bacillus↗
PubMed1964

Problems in sterilization of unmanned space vehicles.

The probability of achieving and maintaining sterility of an unmanned spacecraft with varied suggested procedures is examined in detail, as are alternative techniques for avoiding biological contamination of the planets. The required degree of assurance against contamination of Mars, Venus and the Moon with Earth organisms is also considered. For Mars landers and orbiters, sterilization of the spacecraft or capsule by dry heat, with no subsequent access, is found to be desirable. For the present, sterilization of Venus landers still seems desirable. For Mars flybys, and for Venus orbiters and flybys, control of the trajectory to minimize the chance of unintentionally entering the planetary atmosphere appears the method of choice. For the Moon, sterilization seems unnecessary, but microbial counts should be kept low. Sterilization lowers spacecraft and system reliability. It reduces the chance of launching within periods fixed by astronomical constraints and increases costs. The gain which should be achieved through spacecraft sterilization, in return of significant biological information about the planets, must be balanced against these losses. In particular, one should keep in mind the loss in return of biological data occasioned by failure of a spacecraft to fulfill its mission; the probability of such failure is increased by sterilization.

Containment of Biohazards↗
PubMed2002

Dependence of population response to fertility control on the survival of sterile animals and their role in regulation.

The species for which fertility control is presently used, or for which it is being developed, range from small mammal pests, such as the house mouse (Mus domesticus), to large mammals, such as the African elephant (Loxodonta africana). However, the possibility of a population response other than a reduction in abundance proportional to the fraction of animals rendered infertile has been shown in field trials. For example, when intermediate levels of sterility were imposed on wild populations of European rabbits (Oryctolagus cuniculus), there was an increase in their abundance, on an annual basis, due to enhanced survival of juveniles and adult females. In this article, we relate intraspecific regulatory processes to the response of populations to fertility control using a set of density-dependent structured-population models. In each of the models, the population is exposed periodically to a fertility control agent that renders a fraction of fertile females sterile. Although our intention is not to predict the population response of any one particular species, the results of the models are illustrated using parameter values that are representative of populations of the European fox (Vulpes vulpes) in south-eastern Australia. When populations were regulated by density-dependent mechanisms in which sterile females did not participate, such as competition for resources among young animals or competition among fertile females for breeding sites or territories, then populations could increase in abundance for low and intermediate levels of imposed sterility. For other intraspecific regulatory mechanisms, such as competition for resources between all individuals, all levels of sterility were observed to reduce abundance. The population response was sensitive to (i) whether the survival of sterile adults was higher than that of fertile adults, (ii) whether animals could be sterilized before sexual maturity, and (iii) whether density dependence was modelled as a threshold process.

Animals↗
PubMed1992

Effects of the Nd:YAG dental laser on plasma-sprayed and hydroxyapatite-coated titanium dental implants: surface alteration and attempted sterilization.

The Nd:YAG dental laser has been recommended for a number of applications, including the decontamination or sterilization of surfaces of dental implants that are diseased or failing. The effects of laser irradiation in vitro (1) on the surface properties of plasma-sprayed titanium and plasma-sprayed hydroxyapatite-coated titanium dental implants, and (2) on the potential to sterilize those surfaces after contamination with spores of Bacillus subtilis have been examined. Surface effects were examined by scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction after laser irradiation at 0.3, 2.0, and 3.0 W using either contact or noncontact handpieces. Controls received no laser irradiation. Melting, loss of porosity, and other surface alterations were observed on both types of implants, even with the lowest power setting. For the sterilization study, both types of implants were first sterilized by exposure to ethylene oxide and then contaminated with spores of B subtilis. After laser irradiation, the implants were transferred to sterile growth medium and incubated. Laser irradiation did not sterilize either type of implant. The spore-contaminated implants in the control group were successfully sterilized with ethylene oxide.

Bacillus subtilis↗
PubMed2002

[Chemical disinfection. An alternative to sterilization in the treatment of cure instruments].

UNLABELLED: Sterilization is the reference method recommended to ensure the asepsia of an instrument used to perform cures. Chemical disinfection has shown itself to be highly effective in this process for endoscope equipment without there being definitive references about its efficiency on instruments used for cures. OBJECTIVE: Evaluate the efficiency of chemical disinfection on instruments used for cures, with the reference method being sterilization. METHODS: Prospective study in which the efficiency of glutaraldehyde-phenolate is compared to sterilization on 9 sets of instruments used for cures, each one having a dissection clamp and a Kocher clamp, used in 122 cures carried out in different wards at the León Hospital. Their efficiency was evaluated by means of microbiological studies after cures were performed and after disinfection or sterilization occurred. RESULTS: There were no positive cultures after either the disinfection or the sterilization. The existence of positive cultures after cures was related to the type of wound treated, clean wounds were always negative while dirty wounds were frequently positive (p < 0.05). CONCLUSION: Chemical disinfection with glutaraldehyde-phenolate is as efficient as sterilization in assuring the asepsia of instruments, while offering some clear advantages compared to sterilization since this chemical disinfection has a low cost, its use avoids the need to have duplicate instrument sets, it provides a longer life for these instruments and does not require moving instruments from their work site, thus preventing their loss.

Disinfectants↗
PubMedDate not supplied

The use of different time/temperature combinations in the optimization of sterilization of Ringers/glucose infusion solution.

The effect of sterilization temperature and sterilization efficacy (F0) on the amount of 5-hydroxymethyl-2-furaldehyde (5-HMF) and glucose, number of particles generated and color of Ringers/glucose infusion solution is described. The infusion solution was a 5% glucose solution containing Ringer-type electrolytes. The solutions were autoclaved in a pilot scale autoclave using different temperature/time combinations to produce the target F0 values of 10, 15, 20 and 25 minutes. The amounts of 5-HMF and glucose were determined by HPLC. The use of the shortest possible sterilization cycle to yield the target F0 resulted in the lowest 5-HMF concentrations in the Ringers/glucose infusion solutions studied. The spectrochromatograms of the sterilized solutions showed that glucose is degraded into various degradation products in the presence of Ringer-type electrolytes. It was also demonstrated by SEM/EDX that a significant part of the particles result from the leaching of the silicon oil used in the manufacture of rubber stoppers for LVP solutions. The number of particles generated in different solutions and the particle size distributions were determined with a Coulter-Counter. The particle size distributions show no clear correlation between sterilization process conditions and the number of particles. The results show that it is possible to minimize the amount of 5-HMF generated even when the same F0 is used, by choosing the highest sterilization temperature possible. This also leads in practice to the shorter sterilization processes, saving both process time and energy.

Furaldehyde↗
PubMedDate not supplied

Effectiveness of steam sterilization on the contents of sharps containers.

The purpose of this study was to evaluate the killing effect that treatment in gravity or high-vacuum steam autoclaves had on endospores present on strips or applied to dental needles within 10 types of small sharps containers. Spore strips containing Bacillus stearothermophilus endospores were used, while needles were soiled with an equal number of spores or with spores mixed with blood. Needles were tested capped and uncapped. Strips and needles were autoclaved in empty and 3/4 filled containers placed in several orientations (vents open or closed, upward or on-side). If sterilization was not accomplished within the initial period, additional exposure time was added up to a one hour maximum. Major findings for gravity autoclaves were: 1) strips and needles present in empty containers could, in most cases, be sterilized within 15 minutes when the vents were left open and the containers were placed on-side; 2) spore- and spore plus blood-soiled needles were more difficult to sterilize then were commercial spore strips; 3) capping of needles and the presence of blood did not decrease sterilization efficiency; 4) sterilization in the presence of fill material required additional exposure times and 5) larger containers (greater than 500 ml volume) were more difficult to sterilize than were the smaller (250 ml) ones. All type of open-vented, filled containers could be sterilized within 10 minutes in a high-vacuum autoclave.

Dental Instruments↗
PubMedDate not supplied

Effect of terminal sterilization by irradiation on amber Type I and Type III glass containers containing veterinary oxytetracycline suspension.

The purpose of this study is to determine the effect of terminal sterilization by gamma irradiation on 500-mL amber Type I and Type III glass containers (bottles) containing oxytetracycline (OTC) (25% W/V) suspension formulated using 20% (W/V) phospholipids syrup. The formulation was developed for veterinary parenteral administration. The results of terminal sterilization were used to assess the acceptability for this suspension product. OTC is light-sensitive and needs to be stored in amber glass containers. Amber Type I and Type III glass containers were considered for this formulation during development. Type I is a highly resistant, borosilicate glass (oxidized glass). Type III, which is soda-lime glass (reduced glass, see Materials and Methods), may also be used for parenteral products. The amber Type I and Type III glass containers, containing the suspension, were irradiated at 20-40 kGy for 150 min. In order to determine the sterility of the suspension, ampoules of the biological indicator, Bacillus pumilus, were placed in a number of bottles of the suspension. The bottles with the biological indicators were then positioned among the rest of the production bottles as per a radiation dose-mapping study conducted at the sterilization facility. Potency determination and stability evaluations for OTC were performed using high pressure liquid chromatography (HPLC). The results indicate that the gamma irradiation dose of 20-40 kGy for 150 min was able to inactivate 10(6) Bacillus pumilus spores in ampoules. After gamma sterilization, OTC concentration, pH, particle size, endotoxins, and sterility were evaluated. The assay results were comparable for the suspension in amber Type I and Type III glass containers. Sterility and pyrogenicity were measured by the USP Membrane Filtration Method and USP Bacterial Endotoxins Test, respectively. The suspension in the amber Type III glass container was also chemically (HPLC) and physically (suspension mean particle size, viscosity, density, and syringeability) stable for at least 12 months at room temperature. However, amber Type I glass darkened following irradiation, leading to a substantial reduction in glass transparency. The appearance of amber Type III glass was acceptable. Thus, the "reduced" glass, such as soda-lime, was found to be much less susceptible to darkening than the highly oxidized borosilicate amber. Due to the potential aesthetic concerns with Type I glass, the amber Type III glass container was selected for this suspension formulation.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Development of a sterilizing in-place application for a production machine using Vaporized Hydrogen Peroxide.

The use of steam in sterilization processes is limited by the implementation of heat-sensitive components inside the machines to be sterilized. Alternative low-temperature sterilization methods need to be found and their suitability evaluated. Vaporized Hydrogen Peroxide (VHP) technology was adapted for a production machine consisting of highly sensitive pressure sensors and thermo-labile air tube systems. This new kind of "cold" surface sterilization, known from the Barrier Isolator Technology, is based on the controlled release of hydrogen peroxide vapour into sealed enclosures. A mobile VHP generator was used to generate the hydrogen peroxide vapour. The unit was combined with the air conduction system of the production machine. Terminal vacuum pumps were installed to distribute the gas within the production machine and for its elimination. In order to control the sterilization process, different physical process monitors were incorporated. The validation of the process was based on biological indicators (Geobacillus stearothermophilus). The Limited Spearman Karber Method (LSKM) was used to statistically evaluate the sterilization process. The results show that it is possible to sterilize surfaces in a complex tube system with the use of gaseous hydrogen peroxide. A total microbial reduction of 6 log units was reached.

Disinfectants↗
PubMedDate not supplied

Sterilization: past, present, future.

Globally, sterilization protects more couples from pregnancy than any other contraceptive method. However, use of sterilization has grown only gradually and annual rates of adoption remain low. The high prevalence of sterilization can be explained by its excellent continuation rate, its appeal to a broad age range at the time of adoption, and its long history of availability. International patterns show that sterilization users are concentrated in the two large countries of China and India, but numerous smaller countries also have high proportions of couples using the method. Four personal characteristics differentiate its use within each country: age, parity, residence, and sex. A new projection method indicates that approximately 159 million sterilization adoptions are expected between 1990 and 2000, half of them in China. Most future sterilization users will be found where they have been in the past, due to their concentration in China and India and to the large carry-over of current users in all countries. Projections for sterilization are more dependable than are those for other contraceptive methods, because most current users are young enough to remain in the pool of active users for 10 years. They constitute a large component of the expected total in the year 2000--about 269 million users, or 29 percent of all couples.

Adult↗