A review: taking the sterile out of sterility

Users of in-dwelling medical devices, prostheses and surgical dressings rely implicitly on their sterility. Rarely do consumers give any thought to what sterility really means. The general assumption is that manufacturers have adopted the most efficient and cost-effective methods of achieving sterility. Currently, terminal sterilization processes appropriate for the manufacture of medical devices are those that are deemed to give less than one chance in a million of a single, finished product item containing a viable organism. Such a definition of sterility is embodied in the European standard EN556 as a Sterility Assurance Level of 10(-6), based on the properties of heat-resistant endospores. However, is this level of sterility assurance appropriate for all categories of medical device? Moreover, do all medical devices which are labelled as sterile require the same level of treatment? This paper will demonstrate that in some instances, the high standards set for sterilization processing are unreasonable, not cost-effective and exclude new sterilization technologies from being accepted by the regulatory authorities.     

微波及其联合杀菌技术在食品中的应用研究进展

微波在食品中的应用已逐渐成为研究热点，但微波作为一种新型食品杀菌技术，特别是和其他杀菌技术联合应用的综述目前还较少。本文通过分析已有的食品微波杀菌技术，包括单微波杀菌技术、微波-巴氏杀菌技术、微波-超声联合杀菌技术、微波-红外杀菌技术、微波-脉冲电场杀菌技术的特点，总结微波及其联合杀菌技术对不同类型食品的杀菌条件和效果，旨在为微波在各类食品杀菌工艺中的应用提供参考。     

Complete design analysis of a continuous sterilizer for fermentation media containing suspended solids

An improved mathematical model was developed to design a continuous sterilizer for liquid fermentation media containing suspended solids. Unsteady-state energy balances were used to determine the temperature distribution in the liquid medium and in the solid particles as a function of time and position within the particle, as the medium flows through the sterilizer. Such temperature profiles were used to determine the level of microbial reduction achieved by each component of the sterilizer and by the entire sterilization process. A considerable difference exists between the temperature in the particle core and in the surrounding liquid. This has a significant impact on the degree of sterility achieved by the process. The level of microbial reduction in the particles was found to be tens and or even hundreds of order of magnitude lower than the corresponding level achieved in the liquid. The role of the particle material on the degree of sterilization was also investigated. Solid materials typically found in fermentation media, such as wood or flour clumps were found to offer considerable resistance to the sterilization of the organisms lodged inside them. (c) 1993 Wiley & Sons, Inc.     

Regret,shame, and denials of women's voluntary sterilization

Women face extraordinary difficulty in seeking sterilization as physicians routinely deny them the procedure. Physicians defend such denials by citing the possibility of future regret, a well‐studied phenomenon in women's sterilization literature. Regret is, however, a problematic emotion upon which to deny reproductive freedom as regret is neither satisfactorily defined and measured, nor is it centered in analogous cases regarding men's decision to undergo sterilization or the decision of women to undergo fertility treatment. Why then is regret such a concern in the voluntary sterilization of women? I argue that regret is centered in women's voluntary sterilization due to pronatalism or expectations that womanhood means motherhood. Women seeking voluntary sterilization are regarded as a deviant identity that rejects what is taken to be their essential role of motherhood and they are thus seen as vulnerable to regret.     

Effects of Maternal Status on the Movement and Mortality of Sterilized Female White-Tailed Deer

Abstract: Surgical sterilization by tubal ligation has been proposed as a technique for controlling white-tailed deer (Odocoileus virginianus) populations in urban or suburban areas where other forms of population control are impractical, but little is known about demographic rates in populations under management with surgical sterilization. We analyzed seasonal movement and mortality data collected during a 4-year study of surgical sterilization in suburban Chicago, Illinois, USA. We calculated 323 home range size estimates for 62 individual females within season and year. Non-gravid females without young exhibited home range sizes 52% larger than gravid females and females with fawns. Mortality rate was positively correlated with home range size. We suggest that the increased mortality rate observed in surgically sterilized females may be due to greater movement by non-maternal females. Population managers will need to account for potential effects of maternal status on movement and mortality when considering the use of sterilization for management of suburban populations of white-tailed deer.     

Sterilization as an alternative strategy to control wildlife diseases: bovine tuberculosis in European badgers as a case study

Sterilization has rarely been considered as an alternative to culling or vaccination to control wildlife diseases. Disease control by sterilization, as by culling, has most promise when the host'ss ability for compensatory growth following the removal of density-dependent inhibitions is limited, and when moderate reductions in population density cause disproportionately large reductions in disease prevalence, or even eliminate the disease. For many host/disease examples this will not be the case and vaccination may have overwhelming advantages or may be the only practical option. The impact of sterilization on host density and disease prevalence will develop relatively slowly because sterilization can prevent the recruitment of only one age-cohort at a time. Moreover, unless there is vertical transmission, this age-cohort will consist only of susceptibles. Culling, on the contrary, removes infected as well as susceptible animals. However, for certain disease/host examples, the r elative effectiveness of the different control strategies may be altered considerably if their variable effects on the probability of disease transmission are taken into account. Social perturbation or stress could render certain culling strategies ineffective or even counter-productive. Depending on how disease dynamics are influenced by the host'ss age-structure and reproductive investment, fertility control could offer epidemiological advantages that have been ignored by most disease/host models. We illustrate some of these principles by investigating the theoretical and practical feasibility of an hypothetical sterilization campaign to control bovine tuberculosis in badgers (and hence cattle) in Britain.     

Synergistic Effects in Sonochemical Sterilization

The synergistic effects observed during the sterilization of Bacillus subtilis var. niger ATCC 9372 by the combined action of ethylene or propylene oxide with high-intensity airborne sound waves (34.8 kc/sec) were investigated. It has been shown that the number of surviving spores deposited on paper strips decreases exponentially with the sound intensity at sample level. Reductions of the order of one-third of the time required for standard propylene oxide sterilization have been observed by using the combined action of sound waves with gaseous sterilization. At the present time, maximal synergistic effects seem to be achieved for the following experimental conditions: propylene oxide concentration, 500 to 1,000 mg/liter; acoustic intensity, 161 to 162 db; contact time, 80 min; temperature, 60 C; and relative humidity, 40%. The basic mechanism involved in sonochemical sterilization seems to be more of a physical (accelerated gas diffusion) than a chemical nature.     

Mental health statistics of the future

Abstract

Sterilized and non‐sterilized males and females are compared with respect to the effects of voluntary sterilization on longitudinally reported changes in desire for sexual intercourse in order to ascertain which of several alternative hypotheses provides the best prediction of postoperation perceptions of changes in sexual desire. The results indicate that sterilized women are less likely than sterilized men to report enhanced desire, a result that supports the idea that a gender‐specific explanation of sterilization effects is required to account for the sexual consequences of sterilization.     

Optimal life stage for radiation sterilization of Anopheles males and their fitness for release

Mating by male Anopheles mosquitoes (Diptera: Culicidae) was evaluated in the laboratory to assess fitness effects of radio-sterilization applied during different life stages of the malaria vectors An. stephensi Liston and An. gambiae Giles sensu stricto. After reproductive sterilization by gamma-irradiation (120 Gy), equal proportions of sterile and fertile (unirradiated) male adults were released into cages with virgin females and allowed to compete for matings. Radio-sterilization was applied when the males were pupae aged 0-7 h or 24-32 h, or adults aged <24 h or 24-55 h. After being radio-sterilized in the adult stage, males of both species competed effectively with unirradiated males, whereas those sterilized in the pupal stage obtained significantly fewer matings than unirradiated males from the same cohort. There was no evidence of females obtaining multiple inseminations. These findings emphasize the need to radio-sterilize males as adults in order to minimize the fitness cost. Such males may be intended for sterile insect technique population suppression or for trial releases of transgenic anophelines.     

Voluntary sterilization in Flanders

From 1966 to 1990 there was a marked rise in the use of voluntary sterilization in Flanders, followed by a fall in women under the age of 40. In the last three decades a remarkable change has occurred in the choice between male and female sterilization. Compared with many other European countries, sterilization of men and women is widely practised in Flanders. In 1996 40% of 40- to 44-year-old women underwent voluntarily sterilization or had voluntarily sterilized partners. Additionally, another 9% of these women were sterilized for medical reasons. Voluntarily sterilized couples are on average older than non-sterilized couples, and, obviously, consider their families to be complete. For couples with a complete family, parity is the most important predictor in the choice between sterilization and non-sterilization. Regularly practising Catholics undergo sterilization least. Also, highly educated couples are less likely to have a sterilization. Couples who ever experienced a contraceptive failure choose sterilization more. Voluntary sterilization has no substantial effect on the fertility of the population since the effect on the prevented numbers of both wanted and unwanted births appears to be small. However, if voluntary sterilization did not occur, differences in fertility within the population would probably increase. It is presumed that the popularity of voluntary sterilization in Flanders has passed its peak and that its use will decline in the near future.     

The impact of fertility intentions on behavior: the case of sterilization

In this paper, we take a new approach to the question of whether or not intentions regarding future fertility affect fertility-related behavior. Our approach has three principal features: 1) it takes sterilization as its outcome, rather than pregnancy or birth; 2) it is based on a conceptual model in which fertility-related behavior is seen as determined by a long-range planning process, modified by unanticipated life course contingencies; and 3) it uses data on desired total family size. Using data from the National Survey of Families and Households, we find that achieving one's desired parity has a strong, persistent, and positive effect on the probability of sterilization, supporting our view of the long-term nature of fertility intentions. People do modify their behavior in the face of unanticipated contingencies, but those effects are unexpectedly small.     

Sterilization of Regenerated Collagen Sutures with β-Propiolactone

Data are presented to show that β-propiolactone when properly applied is a very effective agent for sterilization of regenerated collagen sutures. The chemical sterilization is accomplished with little or none of the loss in strength encountered with heat sterilization. The finished sterile suture is obtained without any harmful residue that might be detrimental to the patient.     

Quality assessment for processed and sterilized bone using Raman spectroscopy

To eliminate the potential for infection, many tissue banks routinely process and terminally sterilize allografts prior to transplantation. A number of techniques, including the use of scanning electron microscopy, bone graft models, and mechanical property tests, are used to evaluate the properties of allograft bone. However, as these methods are time consuming and often destroy the bone sample, the quality assessment of allograft bones are not routinely performed after processing and sterilization procedures. Raman spectroscopy is a non-destructive, rapid analysis technique that requires only small sample volumes and has recently been used to evaluate the mineral content, mineral crystallinity, acid phosphate and carbonate contents, and collagen maturity in human and animal bones. Here, to establish a quality assessment method of allograft bones using Raman spectroscopy, the effect of several common sterilization and preservation procedures on rat femoral bones were investigated. We found that freeze-thawing had no detectable effects on the composition of bone minerals or matrix, although heat treatment and gamma irradiation resulted in altered Raman spectra. Our findings suggest Raman spectroscopy may facilitate the quality control of allograft bone after processing and sterilization procedures.     

Radiation and Ethylene Oxide Terminal Sterilization Experiences with Drug Eluting Stent Products

Radiation and ethylene oxide terminal sterilization are the two most frequently used processes in the medical device industry to render product within the final sterile barrier package free from viable microorganisms. They are efficacious, safe, and efficient approaches to the manufacture of sterile product. Terminal sterilization is routinely applied to a wide variety of commodity healthcare products (drapes, gowns, etc.) and implantable medical devices (bare metal stents, heart valves, vessel closure devices, etc.) along with products used during implantation procedures (catheters, guidewires, etc.). Terminal sterilization is also routinely used for processing combination products where devices, drugs, and/or biologics are combined on a single product. High patient safety, robust standards, routine process controls, and low-cost manufacturing are appealing aspects of terminal sterilization. As the field of combination products continues to expand and evolve, opportunity exists to expand the application of terminal sterilization to new combination products. Material compatibility challenges must be overcome to realize these opportunities. This article introduces the reader to terminal sterilization concepts, technologies, and the related standards that span different industries (pharmaceutical, medical device, biopharmaceuticals, etc.) and provides guidance on the application of these technologies. Guidance and examples of the application of terminal sterilization are discussed using experiences with drug eluting stents and bioresorbable vascular restoration devices. The examples provide insight into selecting the sterilization method, developing the process around it, and finally qualifying/validating the product in preparation for regulatory approval and commercialization. Future activities, including new sterilization technologies, are briefly discussed.     

The effect of cryopreservation or heating on the mechanical properties and histomorphology of rat bone-patellar tendon-bone

The effects of cryopreservation on tendon allograft have been reported, but remain unclear, particularly the potential effects on mechanical properties and histological changes by ice crystal formation. There are also few studies about effects of heating for sterilization of tendon. We evaluated the effect of cryopreservation or heating on the mechanical properties and histomorphology of rat bone-patellar tendon-bones (BTBs). BTBs were processed by cryopreservation at −80°C for 3 weeks, or heating at 80°C for 10 min. Tensile testing and histomorphological examination were performed. The cryopreservation of tendons showed less influences on their mechanical properties. When cryopreserved BTBs in frozen state were fixed by freeze-substitution method, many spaces were observed in interfibrillar substances. These results suggest that the collagen fibers of cryopreserved tendons were histomorphologically affected by ice crystals. The heating of tendons completely destroyed the collagen fibers of the tendons and is therefore thought to be inappropriate for the sterilization of BTBs.     

Effects of sterilization treatments on some properties of alginate solutions and gels.

Aqueous sodium alginate solutions were subjected to various heat sterilization treatments. Sodium alginate powder was also treated by both gamma-irradiation and ethylene oxide sterilization. The effects of these treatments on the viscosities of sodium alginate solutions and both the diameter and strength of the beads formed in 0.1 M CaCl2 solutions were determined quantitatively. The viscosity of sodium alginate solutions and the gel strength of the calcium alginate beads decreased with increasing sterilization temperature while the bead diameters were found to increase. All these effects can be attributable to a reduction in the degree of polymerization of the alginate molecules as a result of the heat treatments. Ethylene oxide and gamma-irradiation treatments caused similar effects. Standard conditions for sterilization are necessary for comparative studies with alginate beads.     

Prospects for a novel ultrashort pulsed laser technology for pathogen inactivation

ABSTRACT: The threat of emerging pathogens and microbial drug resistance has spurred tremendous efforts to develop new and more effective antimicrobial strategies. Recently, a novel ultrashort pulsed (USP) laser technology has been developed that enables efficient and chemical-free inactivation of a wide spectrum of viral and bacterial pathogens. Such a technology circumvents the need to introduce potentially toxic chemicals and could permit safe and environmentally friendly pathogen reduction, with a multitude of possible applications including the sterilization of pharmaceuticals, blood products, and the generation of attenuated or inactivated vaccines.     

Mechanical strength of bone allografts subjected to chemical sterilization and other terminal processing methods

Infectious disease transmission through the use of human donor allografts can be a catastrophic complication in an otherwise straightforward surgical procedure. The use of bone allograft in reconstructive orthopedic surgeries is increasing, yet severe complications, including death, can result if the transplanted tissues transmit a communicable disease to the tissue recipient. The BioCleanse((R)) tissue sterilization process is a fully automated, low-temperature chemical sterilization process that renders allograft tissue sterile. The purpose of this study was to evaluate the effect of a chemical tissue sterilization process on the mechanical strength of cortical bone allografts prior to implantation. Cylindrical cortical bone specimens were harvested from seven human cadaver donors and treated either by: chemical sterilization alone; chemical sterilization and terminal sterilization by gamma irradiation; chemical sterilization, lyophilization, terminal sterilization by STERRAD and rehydration; or untreated. The specimens were tested to failure in axial compression, diametral compression, shear, or bending. There were no significant differences in ultimate stress, strain, or fracture energy between the chemically sterilized and control groups in any of the testing modes.     

Non-surgical methods of contraception and sterilization

The Humane Society of the United States estimates that each year between 8 and 10 million dogs and cats enter shelters and 4-5 million of these animals are euthanized due to lack of homes. Many veterinarians within the United States recommend surgical sterilization for population control in dogs and cats. However, there are non-surgical methods to control reproduction. Pharmacologic methods of contraception and sterilization can be safe, reliable and reversible. Hormonal treatments using progestins, androgens, or gonadotropin releasing hormone (GnRH) analogs act to either directly block reproductive hormone receptor-mediated events, or indirectly block conception via negative feedback mechanisms. Immunocontraception, via vaccination against GnRH, the luteinizing hormone receptor or zona pellucida proteins, is also possible. Intratesticular or intraepididymal injections provide a method for non-surgical sterilization of the male dog and cat. Additional methods have been employed for mechanical disruption of fertility including intravaginal and intrauterine devices and ultrasound testicular ablation. Alternative approaches to surgical sterilization will be reviewed.