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.

Optimized Protocol for Testing Multipurpose Contact Lens Solution Efficacy Against Acanthamoeba.

OBJECTIVES: To evaluate the interlaboratory and intralaboratory reproducibility of a proposed protocol for multipurpose contact lens solution (MPS) disinfection efficacy against Acanthamoeba. METHODS: Acanthamoeba castellanii and Acanthamoeba polyphaga and four MPS with different biocidal agents were used to evaluate the protocol in two different laboratories. In addition to the negative control, a positive control and neutralization control were used. One experiment was performed in triplicate, and all other experiments were performed in duplicate in each laboratory. Acanthamoeba trophozoites were grown axenically, and cysts were generated using the starvation method. Trophozoites and cysts at a concentration of 2.0 × 10 to 2.0 × 10 organisms per milliliter were exposed to the test MPS for 0, 4 or 6 (manufacturer's recommended soak time [MRST]), 8, and 24 hr. Survivors were determined by a limiting dilution method that used a most probable number evaluation. RESULTS: The positive and negative controls displayed consistent results and trends both within each laboratory and between each laboratory for trophozoites and cysts of both A. castellanii and A. polyphaga. The neutralization control consistently demonstrated the ability of the neutralizing agents to neutralize the MPS and the positive control and demonstrated no inhibition of Acanthamoeba by the negative control. Testing in triplicate and duplicate demonstrated the reproducibility of the protocol both within each laboratory and between the laboratories. Our results demonstrated that the MPS at the MRST and at 8 hr (likely overnight soak time) are generally more effective against trophozoites than they are against cysts. Only the MPS with hydrogen peroxide as the biocidal agent was able to provide a greater than three-log kill of cysts at the MRST and longer. Among the MPS we tested, trophozoites of A. castellanii and A. polyphaga showed similar responses. Some variability was observed when testing cysts of both species. In both laboratories, one nonhydrogen peroxide containing MPS had some effect (>1 log kill) on A. polyphaga cysts. This solution had no effect (<1 log kill) on A. castellanii cysts, A. castellanii trophozoites, and A. polyphaga trophozoites. CONCLUSIONS: The protocol that we have revised and evaluated is a well-controlled and reproducible procedure that can effectively evaluate the efficacy of MPS against Acanthamoeba trophozoites. Some variability was observed when testing the cyst stage.

Bacterial endotoxin detection in hyaluronic acid-based medical devices.

A simple and rapid method has been developed for testing bacterial endotoxin in hyaluronic acid (HA)-based medical devices. High-molecular-weight HA (HMW HA) in solution or HA-based medical devices was digested by the enzyme hyaluronidase to reduce solution viscosity by truncating the long chains of HA and to test for bacterial endotoxin. The bacterial endotoxin level was detected and measured by kinetic chromogenic Limulus Amebocyte Lysate (LAL) assay. The method was applied to two different ophthalmic viscosurgical devices (OVDs) and one dermal filler, and may easily be adapted to use with up to 3% HA solutions and other HA-based medical devices. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. J Biomed Mater Res Part B: Appl Biomater, 2016. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1210-1215, 2017.

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.

Rapid detection of bacterial endotoxins in ophthalmic viscosurgical device materials by direct analysis in real time mass spectrometry.

Bacterial endotoxins are lipopolysaccharides bound to the bacterial cell wall and released when bacteria rupture or disintegrate. Possible contamination of endotoxin in ophthalmic devices can cause a painful eye inflammation or result in toxic anterior segment syndrome after cataract surgery. Measurement of bacterial endotoxin in medical device materials is difficult since endotoxin binds with polymer matrix and some of the materials are very viscous and non-water soluble, where traditional enzyme-based Limulus amebocyte lysate (LAL) assay cannot be applied. Here we propose a rapid and high throughput ambient ionization mass spectrometric (MS) method using direct analysis in real time (DART) for the evaluation of endotoxin contamination in medical device materials. Large and structurally complex endotoxin instantaneously breaks down into low-mass characteristic fragment ions using DART and is detected by MS in both positive and negative ion modes. This method enables the identification and separation of endotoxin from medical materials with a detection limit of 0.03 ng mL-1 endotoxins in aqueous solution. Ophthalmic viscosurgical device materials including sodium hyaluronate (NaHA), non-water soluble perfluoro-n-octane (PFO) and silicone oil (SO) were spiked with different known concentrations of endotoxin and analyzed by DART MS, where the presence of endotoxin was successfully detected and featured small mass fragment ions were generated for NaHA, PFO and SO as well. Current findings showed the feasibility of measuring endotoxin contamination in medical device materials using DART-MS, which can lead to a one-step analysis of endotoxins in different matrices, avoiding any potential contamination during sample pre-treatment steps.

Product Sterility Testing . . . To Test or Not to Test? That Is the Question.

The applications for sterility testing in the validation and routine control of sterilization of medical devices have changed dramatically over the years. As the definition of sterility assurance has evolved, so has the state of the science associated with product sterility testing. Historically, product sterility testing has been applied to such things as sterilization validation, sterilization lot release, packaging qualification, aseptic processing qualification, and determination of shelf life for the packaged medical device. In most of these cases, however, the results obtained from performing sterility testing on products do not provide the desired confirmation and assurance. Utilizing sterility testing on fully processed finished product is not appropriate for determination of sterilization process effectiveness, sterility assurance level, package integrity, or shelf life. The industry has developed more robust methods for validation of these applications to assure sterility and package performance. This article outlines the appropriate applications for sterility testing and highlight the applications currently in use that have significant limitations within the results and introduce undesirable risk to the validity of the data.

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.

Evaluating Device Design and Cleanability of Orthopedic Device Models Contaminated with a Clinically Relevant Bone Test Soil.

UNLABELLED: Reusable medical devices need to be cleaned prior to disinfection or sterilization and subsequent use to prevent infections. The cleanability of medical devices depends in part on the design of the device. This study examined how models of orthopedic medical devices of increasing complexity retain calcium phosphate bone cement, a relevant test soil for these devices. METHODS: The dye Alizarin Red S and micro-computed tomography (µCT) were used to assess the amount and location of bone cement debris in a series of model orthopedic devices. Testing was performed after soiling and cleaning once, and soiling and cleaning 10 times. RESULTS: The color change of the dye after reacting with the bone cement was useful for indicating the presence of bone cement in these models. High-resolution µCT analysis provided the volume and location of the bone cement. Models that were more complex retained significantly more bone debris than simpler designs. Model devices repeatedly soiled and cleaned 10 times retained significantly more bone debris than those soiled and cleaned once. CONCLUSION: Significantly more bone cement was retained in the more complex lumen structures. This information may be useful in designing reusable orthopedic devices, and other complex medical devices with lumens.

Lack of correlation between age and/or gender with the force utilized in cleaning an anesthesia machine.

Several human factors influence the cleaning of reusable medical devices and equipment. This study evaluated whether a correlation exists between age and/or gender of a person cleaning, with the force applied to remove artificial blood soil on the surface of an anesthesia machine. The findings from this study may be used to increase our understanding of human factors in the cleaning of reusable medical equipment and suggest improvements in equipment design to address issues of concern.

Cleaning assessment of disinfectant cleaning wipes on an external surface of a medical device contaminated with artificial blood or Streptococcus pneumoniae.

BACKGROUND: Improperly cleaned, disinfected, or sterilized reusable medical devices are a critical cause of health care-associated infections. More effective studies are required to address the improvement of cleaning and disinfection instructions, as well as selection of cleaning and disinfecting agents, for surfaces of reusable devices and equipment. METHODS: Six commercially available disinfectant cleaning wipes were evaluated for their effectiveness to remove a coagulated blood test soil or Streptococcus pneumoniae bacteria from the surface of a reusable medical device. Liquid aliquots of the coagulated blood or bacteria were dried onto the surface of the device and removed with the wipes. Effectiveness of the wipes was assessed by 3 methods: residual protein debris by o-phthaldialdehyde analysis, bacterial survival by adenosine triphosphate measurement, and force required to remove the dried debris by force measurement. RESULTS: A sodium hypochlorite wipe was most effective in removing protein debris from the device surface. All tested wipes were equivalent in disinfecting bacterial contamination from the device surface. CONCLUSION: The active ingredient, wipe design, and wipe wetness are important factors to consider when selecting a disinfectant cleaning wipe. Additionally, achieving conditions that effectively clean, disinfect, and/or inactivate surface bacterial contamination is critical to preventing the spread of health care-associated infections.

The effect of contact lens materials on disinfection activity of polyquaternium-1 and myristamidopropyl dimethylamine multipurpose solution against Staphylococcus aureus.

OBJECTIVES: This study examined the interaction of seven different lens materials with a multipurpose solution (MPS) containing the disinfectants polyquaternium-1 (0.001%) and myristamidopropyl dimethylamine (0.0005%). The objective of this study was to determine whether the different lens materials affect the concentration of a disinfectant in this commercially available MPS and the efficacy of the disinfectant against Staphylococcus aureus. METHODS: Silicone hydrogel lenses (galyfilcon A, senofilcon A, comfilcon A, enfilcon A, balafilcon A, and lotrafilcon B) and a conventional hydrogel lens (etafilcon A) were soaked in polypropylene lens cases filled with commercially available MPS containing 0.001% polyquaternium-1 and 0.0005% myristamidopropyl dimethylamine for 6, 12, 24, 72, and 168 hours. Empty lens cases were also filled with MPS. After each time point, solutions from cases containing the seven types of lenses and controls were assayed for activity against S. aureus according to International Standards Organization 14729 standard with modifications. Test solutions were analyzed for polyquaternium-1 and myristamidopropyl dimethylamine concentration at each time point. RESULTS: The concentration of polyquaternium-1 and myristamidopropyl dimethylamine remaining in the lens cases was reduced only slightly over time. Storage with the lenses did not adversely affect biocidal efficacy of the solution, and in some cases, it was significantly better (P=0.0029). CONCLUSION: The efficacy of this polyquaternium-1 and myristamidopropyl dimethylamine MPS to kill S. aureus was not adversely affected by the presence of lens materials soaking in the cases. Thus, current methods for performing solution antimicrobial testing should be reevaluated.

The effects of contact lens materials on a multipurpose contact lens solution disinfection activity against Staphylococcus aureus.

OBJECTIVES: To determine the effect of 8 different lens materials on polyhexamethylene biguanide (PHMB) concentration in multipurpose solution (MPS) levels over time and to determine the effect of lenses on lens solution microbial efficacy over time. METHODS: Silicone hydrogel lenses and conventional hydrogel lenses were soaked in polypropylene lens cases filled with contact lens MPS containing 1 ppm PHMB for 6, 12, 24, 72, and 168 hours. Cases filled with the same solution without lenses were controls. After each time period, solutions from cases with the 8 types of lenses and controls were assayed for activity against Staphylococcus aureus according to International Organization for Standardization-14729 with modifications. Solutions were analyzed for PHMB concentration at each time point. RESULTS: Some of the different lens materials significantly affected the PHMB concentration (P<0.0001) and the biocidal efficacy. Etafilcon A lenses significantly decreased PHMB levels after only 6 hours of lens soak time. The product lot of MPS used was also significant (P<0.0001). Enfilcon A, senofilcon A, and lotrafilcon B lenses did not significantly decrease PHMB levels. CONCLUSIONS: The efficacy of MPS was affected by some lens materials and PHMB concentration. Lens materials differ in their effect on PHMB concentration and the subsequent efficacy of the MPS. Over time, some lens materials can significantly reduce the PHMB concentration and the MPS's microbial activity against S. aureus.

Material properties that predict preservative uptake for silicone hydrogel contact lenses.

OBJECTIVES: To assess material properties that affect preservative uptake by silicone hydrogel lenses. METHODS: We evaluated the water content (using differential scanning calorimetry), effective pore size (using probe penetration), and preservative uptake (using high-performance liquid chromatography with spectrophotometric detection) of silicone and conventional hydrogel soft contact lenses. RESULTS: Lenses grouped similarly based on freezable water content as they did based on total water content. Evaluation of the effective pore size highlighted potential differences between the surface-treated and non-surface-treated materials. The water content of the lens materials and ionic charge are associated with the degree of preservative uptake. CONCLUSIONS: The current grouping system for testing contact lens-solution interactions separates all silicone hydrogels from conventional hydrogel contact lenses. However, not all silicone hydrogel lenses interact similarly with the same contact lens solution. Based upon the results of our research, we propose that the same material characteristics used to group conventional hydrogel lenses, water content and ionic charge, can also be used to predict uptake of hydrophilic preservatives for silicone hydrogel lenses. In addition, the hydrophobicity of silicone hydrogel contact lenses, although not investigated here, is a unique contact lens material property that should be evaluated for the uptake of relatively hydrophobic preservatives and tear components.

Impact of contact lens materials on multipurpose contact lens solution disinfection activity against Fusarium solani.

OBJECTIVE: To investigate the effects of eight different soft contact lenses on disinfection efficacy of a multipurpose solution (MPS) containing polyhexamethylene biguanide (PHMB) against Fusarium solani. METHODS: Six silicone hydrogel lenses (galyfilcon A, senofilcon A, comfilcon A, enfilcon A, balafilcon A, and lotrifilcon B) and two conventional hydrogel lenses (polymacon and etafilcon A) were placed in polypropylene lens cases filled with MPS containing 0.0001% PHMB and soaked for 6, 12, 24, 72, and 168 hours. After each interval, depleted MPS from lens cases were removed and assayed for activity against F. solani according to International Organization for Standardization (ISO) 14729 stand-alone procedure. A portion was aliquoted for chemical analysis. RESULTS: Soaking etafilcon A, balafilcon A, and polymacon lenses for 6 hours reduced the concentration of PHMB in MPS by more than half the stated labeled concentration, with concentrations below the limit of detection for etafilcon A-depleted and balafilcon A-depleted solutions after 12 and 72 hours of soaking, respectively. Except for comfilcon A-depleted solutions, all others failed to consistently obtain one log reduction of F. solani. The solutions soaked with etafilcon A, balafilcon A, and polymacon lenses for 24 hours or more lost all or almost all fungicidal activity against F. solani. CONCLUSIONS: Over time, the disinfectant uptake by some lenses can significantly reduce the PHMB concentration and the fungicidal activity of the MPS against F. solani. Current ISO methodology does not address the reduction in microbiocidal efficacy when lenses are soaked in MPS. The ISO committee should consider adding "soaking experiments" to quantify the effect that contact lens materials have on the performance of MPSs.

Effects of ultrasound and ultrasound contrast agent on vascular tissue.

BACKGROUND: Ultrasound (US) imaging can be enhanced using gas-filled microbubble contrast agents. Strong echo signals are induced at the tissue-gas interface following microbubble collapse. Applications include assessment of ventricular function and virtual histology. AIM: While ultrasound and US contrast agents are widely used, their impact on the physiological response of vascular tissue to vasoactive agents has not been investigated in detail. METHODS AND RESULTS: In the present study, rat dorsal aortas were treated with US via a clinical imaging transducer in the presence or absence of the US contrast agent, Optison. Aortas treated with both US and Optison were unable to contract in response to phenylephrine or to relax in the presence of acetylcholine. Histology of the arteries was unremarkable. When the treated aortas were stained for endothelial markers, a distinct loss of endothelium was observed. Importantly, terminal deoxynucleotidyl transferase mediated dUTP nick-end-labeling (TUNEL) staining of treated aortas demonstrated incipient apoptosis in the endothelium. CONCLUSIONS: Taken together, these ex vivo results suggest that the combination of US and Optison may alter arterial integrity and promote vascular injury; however, the in vivo interaction of Optison and ultrasound remains an open question.

An investigation of enzymatic detergents as a potential cause of toxic anterior segment syndrome.

OBJECTIVE: To investigate whether enzymatic detergents used in cleaning ophthalmic surgical instruments can cause toxic anterior segment syndrome (TASS)-like responses in a rabbit model. DESIGN: Randomized, investigator-masked, controlled experimental animal study. PARTICIPANTS: Thirty-five New Zealand white rabbits. METHODS: The rabbit eyes were randomized into 7 treatment groups to receive intracameral injection of 1 of 3 different doses of Medline Dual Detergent or Enzol Detergent, or sterile limulus amoebocyte lysate reagent water as a control. The eyes were evaluated for anterior segment inflammation at baseline and at 1, 3, 6, 24, 48, and 72 hours after treatment by slit-lamp biomicroscopy. MAIN OUTCOME MEASURES: Anterior chamber (AC) inflammation, including cells, flare, fibrin, and iris injection; time course of inflammation; and residual detergent levels in luminated instruments. RESULTS: Moderate to marked injection of the iris vessels was seen as early as 1 hour after treatment with the enzymatic detergents in 41 of 60 eyes, with the response being more severe in the Enzol Detergent-exposed eyes. Severe iris hemorrhages were accompanied by blood in the AC in 13 eyes, which usually persisted through 72 hours, with an associated increase in AC cell and flare. Corneal haze was present in 52 of 56 eyes 1 hour after treatment, but was mild and resolved within 24 hours in all but the Enzol 4.5%-exposed eyes. Median AC cell and flare peaked at 6 hours and resolved by 48 hours. CONCLUSIONS: Enzymatic detergents caused a severe but unusual response from the iris when injected intracamerally into rabbit eyes. This response has not been reported in humans with TASS. The time course of inflammation was faster (peak at 6 hours) and resolved more quickly (within 48 hours) than TASS. Simulated cleaning and extraction studies indicate that the level of residual detergent to which a patient could be exposed is significantly less than the lowest dose used in this study. Because that low dose caused no significant observations other than injection of the iris vessels, these results do not support residual enzymatic detergents on surgical instruments as a cause for TASS.

Centrifugation assay for measuring adhesion of serially passaged bovine chondrocytes to polystyrene surfaces.

A major obstacle in chondrocyte-based therapy for cartilage repair is the limited availability of cells that maintain their original phenotype. Propagation of chondrocytes as monolayer cultures on polystyrene surfaces is used extensively for amplifying cell numbers. However, chondrocytes undergo a phenotypic shift when propagated in this manner and display characteristics of more adherent fibroblastic cells. Little information is available about the effect of this phenotypic shift on cellular adhesion properties. We evaluated changes in adhesion property as bovine chondrocytes were serially propagated up to five passages in monolayer culture using a centrifugation cell adhesion assay, which was based on counting of cells before and after being exposed to centrifugal dislodgement forces of 120 and 350 g. Chondrocytes proliferated well in a monolayer culture with doubling times of 2-3 days, but they appeared more fibroblastic and exhibited elongated cell morphology with continued passage. The centrifugation cell adhesion assay showed that chondrocytes became more adhesive with passage as the percentage of adherent cells after centrifugation increased and was not statistically different from the adhesion of the fibroblast cell line, L929, starting at passage 3. This increased adhesiveness correlated with a shift to a fibroblastic morphology and increased collagen I mRNA expression starting at passage 2. Our findings indicate that the centrifugation cell adhesion assay may serve as a reproducible tool to track alterations in chondrocyte phenotype during their extended propagation in culture.