In Vitro Leakage Testing of Tissue Containment Bags When Subjected to Power Morcellation Forces.

STUDY OBJECTIVE: To determine the ability of tissue containment systems to prevent leakage of cancer cell surrogates when subjected to forces encountered during power morcellation procedures. DESIGN: In vitro study. SETTING: Medical device research laboratory. INTERVENTIONS: Samples from 7 different legally marketed tissue containment bags (1 of which is indicated for power morcellation) were subjected to dye and bacteriophage penetration tests at pressures ranging from 0.5 to 50 times the insufflation pressure. The minimum pressure required to cause bag leakage was measured. Subsequently, the morcellation leakage safety factor for each bag was determined as the ratio of the minimum leakage pressure of the bag to the total pressure contributed from insufflation pressure and mechanical forces acting during the power morcellation procedure. MEASUREMENT AND MAIN RESULTS: The leakage performance of the bags varied markedly from brand to brand. No correlation was found between leakage pressure and the bag material or the total bag thickness. The leakage pressures ranged from 26 mmHg to >1293 mmHg for the 7 bags, and safety factors ranged from 1 to 50 when only the insufflation pressure was considered. However, if the morcellation forces were included in the calculation, the safety factor dropped by 6-fold for all brands and dropped below 1, indicating likelihood of leakage, for 2 of the 7 brands. CONCLUSION: This study provides a mechanism for more realistically simulating the conditions experienced by containment bags during morcellation and quantifying the level of safety provided by the bags.

Research: Comparing ASTM F1671 with a Modified Dot-Blot Method to Evaluate Personal Protective Materials.

Effective personal protective equipment (PPE) is critical in preventing the spread of infectious diseases. Appropriate test systems and test soils are needed to adequately evaluate PPE. ASTM test method F903, which specifies the test method setup also used in ASTM F1670 and F1671, has been used for decades to test liquid (ASTM F1670) or viral (ASTM F1671) penetration resistance of PPE fabrics. However, an alteration of the bacteriophage propagation method detailed in the standard was necessary to obtain consistent titers of virus. In this study, modification of the nutrient broth provided consistently higher titers of virus and the use of the top agar in smaller increments prevented premature solidification. This study then compared the standard ASTM F1671 (using bacteriophage ϕχ174) with a modified dot-blot method to assess viral penetration of PPE materials. The results indicated that ASTM F1671 and the dot-blot apparatus methods were equivalent. The dot-blot method described here is less labor intensive and faster than the ASTM F1671 method. However, using the dot-blot system, which uses antibodies to detect the bacteriophage and signal amplification, does not indicate if virus viability or infectivity is retained, whereas the ASTM F1671 method indicates both. Nonetheless, the method presented in this investigation is a substantial improvement of a standard method for viral challenge testing of PPE materials.

Mechanical and leakage integrity testing considerations for evaluating the performance of tissue containment systems.

Tissue containment systems (TCS) are medical devices that may be used during morcellation procedures during minimally invasive laparoscopic surgery. TCS are not new devices but their use as a potential mitigation for the spread of occult malignancy during laparoscopic power morcellation of fibroids and/or the uterus has been the subject of interest following reports of upstaging of previously undetected sarcoma in women who underwent a laparoscopic hysterectomy. Development of standardized test methods and acceptance criteria to evaluate the safety and performance of these devices will speed development, allowing for more devices to benefit patients. As a part of this study, a series of preclinical experimental bench test methods were developed to evaluate the mechanical and leakage performance of TCS that may be used in power morcellation procedures. Experimental tests were developed to evaluate mechanical integrity, e.g., tensile, burst, puncture, and penetration strengths for the TCS, and leakage integrity, e.g., dye and microbiological leakage (both acting as surrogates for blood and cancer cells) through the TCS. In addition, to evaluate both mechanical integrity and leakage integrity as a combined methodology, partial puncture and dye leakage was conducted on the TCS to evaluate the potential for leakage due to partial damage caused by surgical tools. Samples from 7 different TCSs were subjected to preclinical bench testing to evaluate leakage and mechanical performance. The performance of the TCSs varied significantly between different brands. The leakage pressure of the TCS varied between 26 and > 1293 mmHg for the 7 TCS brands. Similarly, the tensile force to failure, burst pressure, and puncture force varied between 14 and 80 MPa, 2 and 78 psi, and 2.5 N and 47 N, respectively. The mechanical failure and leakage performance of the TCS were different for homogeneous and composite TCSs. The test methods reported in this study may facilitate the development and regulatory review of these devices, may help compare TCS performance between devices, and increase provider and patient accessibility to improved tissue containment technologies.

The presence of fecal test soil protects bacteria during cleaning/disinfection.

Reusable medical devices (RMDs) must be reprocessed between uses to render them safe for each use and each patient. Cleaning used devices removes organic and inorganic soil making them either safe for reuse or ready for disinfection/sterilization depending on the device. Although cleaning is an important step in a RMD's life cycle, it is not always a priority during device design. In addition, when performing cleaning validation, it is recommended that the manufacturer takes into consideration, what the most appropriate or worst case conditions are in terms of type of soil or the presence of bacteria. This study compared the ability of three different cleaning/disinfecting agents (water, alcohol, and bleach) to remove bacteria and fecal test soil from two different polymers: polypropylene and ultrahigh molecular weight polyethylene (UHMWPE) with two different roughness. There were some differences in the effects of the cleaning/disinfecting agents, the materials, and the roughness depending on the particular circumstances. However, the most consistent effect on the removal of bacteria was the presence of soil, which protected the bacteria from being removed. Conversely, the presence of bacteria played little role in the removal of soil. Although the interactions between material type and roughness, soil type, and bacteria are complicated, they should be taken into account during device design and reprocessing validation to create a device that is easy and safe to use. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1706-1710, 2019.

Designing for cleanability: The effects of material, surface roughness, and the presence of blood test soil and bacteria on devices.

Cleaning reusable medical devices removes organic and inorganic soil, which allows for effective disinfection and sterilization. However, it is not always clear what variables to consider when validating cleaning. This study compared the ability of 3 different cleaning agents (ie, water, alcohol, and bleach) to remove bacteria (ie, vegetative and spores) and artificial blood test soil from 2 common device materials: polypropylene and ultra-high-molecular-weight polyethylene. There was a complex interaction between bacteria, soil, and surface roughness.

Evaluation of one-way valves used in medical devices for prevention of cross-contamination.

BACKGROUND: One-way valves used in day use devices (used on multiple patients throughout a day without reprocessing between patients) are intended to reduce the potential for cross-contamination between patients resulting from the backflow of patient fluids. One-way valves are typically designed to withstand high levels of back pressure before failure; however, they may not be explicitly designed as a means of infection control as used in medical device applications. METHODS: Five different medical grade one-way valves were placed in low pressure configurations. After flushing in the intended direction of flow, bacteriophage, bacteria, or dye was placed patient side for 24 hours. The upstream device side of the valve was then evaluated for microbial growth or presence of visible dye. RESULTS: Leakage (ie, backflow) of the microorganisms occurred with a variety of one-way valve designs across a range of fluid properties tested. CONCLUSIONS: This study describes testing of the one-way valves (component-level testing) for the potential of cross-contamination. Although day use medical device systems may use numerous other factors to prevent patient cross-contamination, this work demonstrates that one-way valves themselves may not prevent leakage of contaminated fluid if the fluid is able to reach the upstream side of the one-way valve.

Efficacy of commercially available wipes for disinfection of pulse oximeter sensors.

BACKGROUND: This study examined the effectiveness of commercially available disinfecting wipes and cosmetic wipes in disinfecting pulse oximeter sensors contaminated with pathogenic bacterial surrogates. METHODS: Surrogates of potential biological warfare agents and bacterial pathogens associated with hospital-acquired infections (HAIs) were spotted on test surfaces, with and without an artificial test soil (sebum), allowed to dry, and then cleaned with different commercially available cleaning and disinfecting wipes or sterile gauze soaked in water, bleach (diluted 1:10), or 70% isopropanol. The percentage of microbial survival and an analytical estimation of remaining test soil on devices were determined. RESULTS: Wipes containing sodium hypochlorite as the active ingredient and gauze soaked in bleach (1:10) were the most effective in removing both vegetative bacteria and spores. In the presence of selective disinfectants, sebum had a protective effect on vegetative bacteria, but not on spores. CONCLUSIONS: The presence of sebum reduces the cleaning efficiency of some commercially available wipes for some select microbes. Various commercial wipes performed significantly better than the designated cleaning agent (70% isopropanol) in disinfecting the oximetry sensor. Cosmetic wipes were not more effective than the disinfecting wipes in removing sebum.

Ability of cleaning-disinfecting wipes to remove bacteria from medical device surfaces.

BACKGROUND: Nosocomial infections are a serious problem in health care facilities. Bacteria can be transferred from patient to patient via contaminated reusable medical devices and equipment. METHODS: An anesthesia machine and objects representative of smooth and ridged machine knobs were contaminated with Staphylococcus aureus, Bacillus atrophaeus spores, and Clostridium sporogenes spores. The ability of 5 commercially available cleaning-disinfecting wipes to remove bacteria was compared with gauze soaked with water or bleach. Gauze soaked with water was used to determine the optimal wetness for bacteria removal, which was then used to evaluate the efficacy of the wipe ingredients. RESULTS: All of the wipes cleaned the device surfaces significantly better than the no wipe control. Some wipes performed equally well as gauze with water, whereas others performed worse. Overall, the wipe containing sodium hypochlorite was the most effective at removing bacteria. When the wipe ingredients were re-evaluated using the determined optimal wipe wetness on gauze, their effectiveness at cleaning S aureus, but not spores, significantly improved. CONCLUSION: Physically removing bacteria from device surfaces with water was often as effective as the cleaning-disinfecting wipes. Of the wipe active ingredients evaluated, sodium hypochlorite was the most effective overall. The wetness of the wipes may also play a role in their effectiveness.

The Bacillus cereus Hbl and Nhe tripartite enterotoxin components assemble sequentially on the surface of target cells and are not interchangeable.

Bacillus cereus is a spore-forming, Gram-positive bacterium commonly associated with outbreaks of food poisoning. It is also known as an opportunistic pathogen causing clinical infections such as bacteremia, meningitis, pneumonia, and gas gangrene-like cutaneous infections, mostly in immunocompromised patients. B. cereus secretes a plethora of toxins of which four are associated with the symptoms of food poisoning. Two of these, the non-hemolytic enterotoxin Nhe and the hemolysin BL (Hbl) toxin, are predicted to be structurally similar and are unique in that they require the combined action of three toxin proteins to induce cell lysis. Despite their dominant role in disease, the molecular mechanism of their toxic function is still poorly understood. We report here that B. cereus strain ATCC 10876 harbors not only genes encoding Nhe, but also two copies of the hbl genes. We identified Hbl as the major secreted toxin responsible for inducing rapid cell lysis both in cultured cells and in an intraperitoneal mouse toxicity model. Antibody neutralization and deletion of Hbl-encoding genes resulted in significant reductions of cytotoxic activity. Microscopy studies with Chinese Hamster Ovary cells furthermore showed that pore formation by both Hbl and Nhe occurs through a stepwise, sequential binding of toxin components to the cell surface and to each other. This begins with binding of Hbl-B or NheC to the eukaryotic membrane, and is followed by the recruitment of Hbl-L1 or NheB, respectively, followed by the corresponding third protein. Lastly, toxin component complementation studies indicate that although Hbl and Nhe can be expressed simultaneously and are predicted to be structurally similar, they are incompatible and cannot complement each other.