Destruction of spores on building decontamination residue in a commercial autoclave

Decontamination of Soil Contaminated at the Surface with Bacillus anthracis (Anthrax) Surrogate Spores Using Steam Vapor

In the event of a wide-area release of Bacillus anthracis spores, soils and other outdoor materials will likely become contaminated with the biological agent. Soils may also become contaminated with B. anthracis when livestock or wildlife succumb to anthrax disease. This study was conducted to assess the in situ remediation of soil using steam vapor to inactivate a B. anthracis spore surrogate (Bacillus atrophaeus) inoculated into soil samples. Tests were conducted using small columns (~0.04 m3 of soil) filled with either loam, clay, or a sandy soil. Following steam treatment, the B. atrophaeus spores were recovered from the test and positive control soil samples via liquid extraction and this liquid was subsequently dilution plated to quantify viable spores in terms of colony-forming units. Decontamination efficacy was assessed as a function of soil type, soil depth, soil moisture, soil temperature, and steam exposure time. Results showed that spore inactivation improved with increasing steam exposure time and diminished with depth. The clay soil generally exhibited the highest soil temperatures and correspondingly showed the highest inactivation of spores. Adding moisture to the soil prior to the steam treatment increased heat transfer within the soil column, and sealing the columns to mitigate steam leakage increased spore inactivation. The results showed that a steam mass of 40-50 kg applied per square meter of soil surface was sufficient to inactivate bacterial spores to depths between 7 and 10 cm. With bacterial spores on the soil column surface, a contact time of 15 min with the steam vapor at 99°C was sufficient for complete inactivation. These findings provide a foundation for estimating costs and time requirements for applying steam to the soil surface, and further confirmatory testing at field-scale is suggested.

Sterilization effects of UV laser irradiation on Bacillus atrophaeus spore viability, structure, and proteins

Bacillus spores are highly resistant to toxic chemicals and extreme environments. Because some Bacillus species threaten public health, spore inactivation techniques have been intensively investigated. We exposed Bacillus atrophaeus spores to a 266 nm Nd:YVO₄ laser at a laser power of 1 W and various numbers of scans. As a result, the UV laser reduced the viability of Bacillus atrophaeus spores. Although the outer coat of spores remained intact after UV laser irradiation of 720 scans, damage inside the spores was observed. Spore proteins were identified by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry during the course of UV laser irradiation. Photochemical and photothermal processes are believed to be involved in the UV laser sterilization of Bacillus spores. Our findings suggest that a UV laser is capable of sterilizing Bacillus atrophaeus spores.

Biomedical Waste and Solid Waste Management in the Time of COVID-19: A Comprehensive Review of the National and International Scenario and Guidelines

Biomedical waste generated during the diagnosis, isolation, and treatment of coronavirus disease 2019 (COVID-19) patients can also be the source of new infections; hence, it needs special consideration. Previous guidelines for the management of biomedical waste need to be revisited as the majority of COVID-19 patients remain asymptomatic and reside in community. Personal protective equipment (PPE) like masks, hazmat suits, gloves, and visors are now being used by the public also. Thus, the general household waste and disposables now make an exponential increase in the waste that can be considered an environmental hazard. In this article, the authors have tried to present the problems arising from COVID-19 waste and the recommendations put forth by competent authorities both nationally and internationally on COVID-19 waste management. Furthermore, in all the guidelines, it is crucial that the COVID-19 waste management follows environmentally sound principles and practices of biomedical waste management, with safe work and infection-control practices. Segregation of COVID-19 waste at source, awareness, and precautions at all steps of the waste-cycle are the only way ahead in this crisis.

Decontaminating N95 respirators during the COVID-19 pandemic: simple and practical approaches to increase decontamination capacity, speed, safety and ease of use

BACKGROUND

The COVID-19 pandemic has caused a severe shortage of personal protective equipment (PPE), especially N95 respirators. Efficient, effective and economically feasible methods for large-scale PPE decontamination are urgently needed.

AIMS

(1) to develop protocols for effectively decontaminating PPE using vaporized hydrogen peroxide (VHP); (2) to develop novel approaches that decrease set-up and take-down time while also increasing decontamination capacity; (3) to test decontamination efficiency for N95 respirators heavily contaminated by make-up or moisturizers.

METHODS

We converted a decommissioned Biosafety Level 3 laboratory into a facility that could be used to decontaminate N95 respirators. N95 respirators were hung on metal racks, stacked in piles, placed in paper bags or covered with make-up or moisturizer. A VHP® VICTORY™ unit from STERIS was used to inject VHP into the facility. Biological and chemical indicators were used to validate the decontamination process.

FINDINGS

N95 respirators individually hung on metal racks were successfully decontaminated using VHP. N95 respirators were also successfully decontaminated when placed in closed paper bags or if stacked in piles of up to six. Stacking reduced the time needed to arrange N95 respirators for decontamination by approximately two-thirds while almost tripling facility capacity. Make-up and moisturizer creams did not interfere with the decontamination process.

CONCLUSIONS

Respirator stacking can reduce the hands-on time and increase decontamination capacity. When personalization is needed, respirators can be decontaminated in labelled paper bags. Make up or moisturizers do not appear to interfere with VHP decontamination.

Decontamination and reuse of surgical masks and N95 filtering facepiece respirators during the COVID-19 pandemic: A systematic review

OBJECTIVES

Surgical masks and N95 filtering facepiece respirators (FFRs) prevent the spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and protect medical personnel. Increased demands for surgical masks and N95 FFRs during the coronavirus disease 2019 (COVID-19) pandemic has resulted in the shortage crisis. However, there is no standard protocol for safe reuse of the N95 FFRs. In this systematic review, we aimed to evaluate the effectiveness of existing decontamination methods of surgical masks and N95 FFRs and provide evidence-based recommendations for selecting an appropriate decontamination method.

METHODS

We performed systematic searches of Ovid MEDLINE and Ovid EMBASE electronic databases. The last search was performed April 11, 2020. Any trials studying surgical masks and/or N95 FFRs decontamination were included. Outcomes were disinfections of virus and bacteria, restoration of the filtration efficiency, and maintenance of the physical structure of the mask.

RESULTS

Overall, 15 studies and 14 decontamination methods were identified. A low level of evidence supported 4 decontamination methods: ultraviolet (UV) germicidal irradiation (9 studies), moist heat (5 studies), microwave-generated steam (4 studies), and hydrogen peroxide vapor (4 studies). Therefore, we recommended these 4 methods, and we recommended against use were given for the other 10 methods.

CONCLUSIONS

A low level of evidence supported the use of UV germicidal irradiation, moist heat, microwave-generated steam, and hydrogen peroxide vapor for decontamination and reuse of N95 FFRs. These decontamination methods were effective for viral and bacterial disinfection as well as restoration of the filtration efficiency, and the physical structure of the FFRs.

Application of Sterilization Process for Inactivation of Bacillus Stearothermophilus in Biomedical Waste and Associated Greenhouse Gas Emissions

This study investigated the biomedical waste collection, transportation, and treatment activities in the city of Kocaeli, Turkey. As an alternative to incineration technology, a steam autoclave was used to sterilize the biomedical waste. Information regarding the collection, transportation, treatment and associated greenhouse gas emissions (GHG) were also investigated. Prior to sterilization, biological indicator vials containing Bacillus stearothermophilus were placed in the center of the load to ensure that the pathogens were destroyed. GHG emissions were calculated based on the fuel consumed by the biomedical waste collection vehicles and the electricity/natural gas used at the sterilization plant. Results of this work revealed that the total biomedical waste generated per year increased from 1362 tons in 2009 to 2375 tons in 2019. The amount of biomedical waste generated per hospital bed was determined as 1.19 kg.bed−1.day−1. Results show that for efficient sterilization of biomedical wastes, the steam treatment system process should be operated at a contact time of 45 min, a temperature of 150 °C, and at a steam pressure of 5 bar. Biological indicator tests showed that the number of living Bacillus stearothermophilus decreased significantly, with removal rates greater than 6log10. Finally, it was determined that the biomedical waste management activities generated a total of GHG emissions of 5573 ton CO2 equivalency (tCO2-e) from 2009 to 2019. Furthermore, the average global warming factor (GWF) was calculated to be 0.269 tCO2-e per ton of biomedical waste generated. This study showed that the sterilization process is very effective in destroying the pathogens and the management of biomedical waste generates considerable amounts of GHG emissions.

Review of Decontamination Techniques for the Inactivation of Bacillus anthracis and Other Spore-Forming Bacteria Associated with Building or Outdoor Materials

Since the intentional release of Bacillus anthracis spores through the U.S. Postal Service in the fall of 2001, research and development related to decontamination for this biological agent have increased substantially. This review synthesizes the advances made relative to B. anthracis spore decontamination science and technology since approximately 2002, referencing the open scientific literature and publicly available, well-documented scientific reports. In the process of conducting this review, scientific knowledge gaps have also been identified. This review focuses primarily on techniques that are commercially available and that could potentially be used in the large-scale decontamination of buildings and other structures, as well as outdoor environments. Since 2002, the body of scientific data related to decontamination and microbial sterilization has grown substantially, especially in terms of quantifying decontamination efficacy as a function of several factors. Specifically, progress has been made in understanding how decontaminant chemistry, the materials the microorganisms are associated with, environmental factors, and microbiological methods quantitatively impact spore inactivation. While advancement has been made in the past 15 years to further the state of the science in the inactivation of bacterial spores in a decontamination scenario, further research is warranted to close the scientific gaps that remain.

Terahertz vibrational signature of bacterial spores arising from nanostructure decorated endospore surface

This theoretical effort is the first to explore the possible hypothesis that terahertz optical activity of Bacillus spores arises from normal vibrational modes of spore coat subcomponents in the terahertz frequency range. Bacterial strains like Bacillus and Clostridium form spores with a hardened coating made of peptidoglycan to protect its genetic material in harsh conditions. In recent years, electron microscopy and atomic force microscopy has revealed that bacterial spore surfaces are decorated with nanocylinders and honeycomb nanostructures. In this article, a simple elastic continuum model is used to describe the vibration of these nanocylinders mainly in Bacillus subtilis, which also leads to the conclusion that the terahertz signature of these spores arises from the vibration of these nanostructures. Three vibrating modes: radial/longitudinal, torsional and flexural, have been identified and discussed for the nanocylinders. The effect of bound water, which shifts the vibration frequency, is also discussed. The peptidoglycan molecule consists of polar and charged amino acids; hence, the sporal surface local vibrations interact strongly with the terahertz radiation.

Biosafety Level 3 setup for multiphoton microscopy in vivo

Multiphoton microscopy has revealed important insights into cellular behavior in vivo. However, its application in infectious settings often encounters technical, safety and regulatory limitations that prevent its wider use with highly virulent human pathogens. Herein, we present a method that renders multiphoton microscopy in vivo compatible with biosafety level 3 regulations and present an example of its application and potential to visualize a Mycobacterium tuberculosis infection of the mouse lung.

Effects of minimal exposures to atmospheric pressure plasma on the activity of Salmonella Typhimurium: Deactivation of bacterial motility and suppression of host-cell invasion

Atmospheric pressure plasma (APP) has been shown effective in sterilization by reducing the number of viable microbes during surface cleaning, food processing, or human tissue treatment. For safe conduct, the majority of previous research focused on complete abolition of microbes, which may require severe treatments. Our aim is to investigate the minimal treatment conditions necessary for effective inactivation of bacteria in such a manner that the APP treated bacteria would not be able to harm the host cells. For this, we ought to identify the objective criteria to make the bacteria dysfunctional. We choose the motile properties and the host-cell invasion capability as two measures to quantify the pathogenic state of bacteria. In this paper, we investigated how the APP treatment in a minimal dosage affects the activity of Salmonella Typhimurium. At 100 W and 15 kHz for 20 s, the APP treatment effectively suppressed active "run and tumble" type motility and induced formation of abnormally long structures. With 20 s exposure, the bacterial cells failed to cause pyroptosis in the host cells with >90% survival after 12 h of co-incubation. Our results suggest novel measures to evaluate the functional pathogenic state for identifying safe APP treatment conditions.

Comparison of steam sterilization conditions efficiency in the treatment of Infectious Health Care Waste

Many studies show that the treatment of Infectious Health Care Waste (IHCW) in steam sterilization devices at usual operating standards does not allow for proper treatment of Infectious Health Care Waste (IHCW). Including a grinding component before sterilization allows better waste sterilization, but any hard metal object in the waste can damage the shredder. The first objective of the study is to verify that efficient IHCW treatment can occur at standard operating parameters defined by the contact time-temperature couple in steam treatment systems without a pre-mixing/fragmenting or pre-shredding step. The second objective is to establish scientifically whether the standard operation conditions for a steam treatment system including a step of pre-mixing/fragmenting were sufficient to destroy the bacterial spores in IHCW known to be the most difficult to treat. Results show that for efficient sterilization of dialysis cartridges in a pilot 60L steam treatment system, the process would require more than 20 min at 144°C without a pre-mixing/fragmenting step. In a 720L steam treatment system including pre-mixing/fragmenting paddles, only 10 min at 144°C are required to sterilize IHCW proved to be sterilization challenges such as dialysis cartridges and diapers in normal conditions of rolling.

Test methods and response surface models for hot, humid air decontamination of materials contaminated with dirty spores of Bacillus anthracis ∆Sterne and Bacillus thuringiensis Al Hakam

AIMS

To develop test methods and evaluate survival of Bacillus anthracis ∆Sterne or Bacillus thuringiensis Al Hakam on materials contaminated with dirty spore preparations after exposure to hot, humid air using response surface modelling.

METHODS AND RESULTS

Spores (>7 log10 ) were mixed with humic acid + spent sporulation medium (organic debris) or kaolin (dirt debris). Spore samples were then dried on five different test materials (wiring insulation, aircraft performance coating, anti-skid, polypropylene, and nylon). Inoculated materials were tested with 19 test combinations of temperature (55, 65, 75°C), relative humidity (70, 80, 90%) and time (1, 2, 3 days). The slowest spore inactivation kinetics was on nylon webbing and/or after addition of organic debris.

CONCLUSIONS

Hot, humid air effectively decontaminates materials contaminated with dirty Bacillus spore preparations; debris and material interactions create complex decontamination kinetic patterns; and B. thuringiensis Al Hakam is a realistic surrogate for B. anthracis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Response surface models of hot, humid air decontamination were developed which may be used to select decontamination parameters for contamination scenarios including aircraft.

Sterilization of rotary NiTi instruments within endodontic sponges

AIM

To determine whether the following can be sterilized by autoclaving - endodontic sponges, rotary nickel-titanium (NiTi) instruments within endodontic sponges, and rotary NiTi instruments with rubber stoppers.

METHODOLOGY

Sixty-four samples of eight different endodontic sponges (n = 512) were placed into brain heart infusion broth (BHI) for 72 h. An aliquot of this was then spread onto horse blood agar and cultured aerobically and anaerobically to test sterility at purchase. Bacterial suspensions of Enterococcus faecalis, Porphyromonas gingivalis and Geobacillus stearothermophilus in BHI were used to contaminate sterile sponges and rotary NiTi instruments (with and without rubber stoppers) inserted into sponges. The various samples were autoclaved and then cultured aerobically and anaerobically. Success of sterilization was measured qualitatively as no growth. The experiment was repeated with clinically used rotary NiTi instruments (n = 512). All experiments were conducted in quadruplicate.

RESULTS

No sponges on purchase had microbial growth when anaerobically cultured but some did when aerobically cultured. All autoclaved sponges and instruments (within or without sponges, and with or without rubber stoppers) were associated with no microbial growth. All nonautoclaved positive control samples showed microbial growth.

CONCLUSIONS

Autoclaving was effective in the sterilization of sponges and endodontic instruments. Endodontic sponges should be autoclaved before clinical use. For clinical efficiency and cost-effectiveness, rotary NiTi instruments can be sterilized in endodontic sponges without removal of rubber stoppers.

Isolation and characterization of aerobic thermophilic bacteria from the savusavu hot springs in fiji

The relative isolation and unique physical properties of the Savusavu Hot Springs in Fiji may yield unique thermophiles. This study was conducted to determine the presence of aerobic thermophilic bacteria in these hot springs. A total of 104 thermophilic bacterial isolates were characterized and using Thermus and Bacillus strains as controls, 58% of the isolates were identified as Anoxybacillus flavithermus, 19% as Geobacillus stearothermophilus/Bacillus licheniformis, 10% as Thermus sp. TG153 and 10% as Thermus sp. TG206. Four isolates were unique in their molecular patterns suggesting there may be novel bacteria in the Savusavu hot springs.

Transport behavior of surrogate biological warfare agents in a simulated landfill: effect of leachate recirculation and water infiltration

An understanding of the transport behavior of biological warfare (BW) agents in landfills is required to evaluate the suitability of landfills for the disposal of building decontamination residue (BDR) following a bioterrorist attack on a building. Surrogate BW agents, Bacillus atrophaeus spores and Serratia marcescens, were spiked into simulated landfill reactors that were filled with synthetic building debris (SBD) and operated for 4 months with leachate recirculation or water infiltration. Quantitative polymerase chain reaction (Q-PCR) was used to monitor surrogate transport. In the leachate recirculation reactors, <10% of spiked surrogates were eluted in leachate over 4 months. In contrast, 45% and 31% of spiked S. marcescens and B. atrophaeus spores were eluted in leachate in the water infiltration reactors. At the termination of the experiment, the number of retained cells and spores in SBD was measured over the depth of the reactor. Less than 3% of the total spiked S. marcescens cells and no B. atrophaeus spores were detected in SBD. These results suggest that significant fractions of the spiked surrogates were strongly attached to SBD.

Destruction of spores on building decontamination residue in a commercial autoclave

The U.S. Environmental Protection Agency conducted an experiment to evaluate the effectiveness of a commercial autoclave for treating simulated building decontamination residue (BDR). The BDR was intended to simulate porous materials removed from a building deliberately contaminated with biological agents such as Bacillus anthracis (anthrax) in a terrorist attack. The purpose of the tests was to assess whether the standard operating procedure for a commercial autoclave provided sufficiently robust conditions to adequately destroy bacterial spores bound to the BDR. In this study we investigated the effects of several variables related to autoclaving BDR, including time, temperature, pressure, item type, moisture content, packing density, packing orientation, autoclave bag integrity, and autoclave process sequence. The test team created simulated BDR from wallboard, ceiling tiles, carpet, and upholstered furniture, and embedded in the BDR were Geobacillus stearothermophilus biological indicator (BI) strips containing 10(6) spores and thermocouples to obtain time and temperature profile data associated with each BI strip. The results indicated that a single standard autoclave cycle did not effectively decontaminate the BDR. Autoclave cycles consisting of 120 min at 31.5 lb/in2 and 275 degrees F and 75 min at 45 lb/in2 and 292 degrees F effectively decontaminated the BDR material. Two sequential standard autoclave cycles consisting of 40 min at 31.5 lb/in2 and 275 degrees F proved to be particularly effective, probably because the second cycle's evacuation step pulled the condensed water out of the pores of the materials, allowing better steam penetration. The results also indicated that the packing density and material type of the BDR in the autoclave could have a significant impact on the effectiveness of the decontamination process.