Disinfection and Sterilization of Microorganisms

Environmental decontamination and water disinfection practices are hallmarks of disease prevention and control in agricultural and public health settings. Informed fit-to-purpose biocontainment is thus dependent on methodologies accurately assessing microbial burden and viability. Also, rigorous evaluation of the efficacy of biocontrol measures implies monitoring microbial inactivation after decontamination/disinfection procedures. In this study, we used flow cytometry coupled with a resuscitation protocol to monitor the metabolic inactivation of bacteria capable of entering non-cultivable states, after the application of a chlorine-based water disinfectant. For this purpose, we used Mycobacterium bovis BCG as a model of slow-growing bacteria able to enter dormancy and representing a multi-host pathogen in a zoonotic disease system—animal tuberculosis—thriving both across temperate and semi-arid regions and involving environmental contamination. The biocide activity of a commercial sodium dichloroisocyanurate (NaDCC) disinfectant against M. bovis BCG was evaluated through mock environmental matrix tests. Using the manufacturer-recommended dosage of NaDCC, BCG cells were apparently inactivated after 24 h upon exposure. However, we show via flow cytometry that, upon exposure to optimal growth conditions, mycobacterial cells were able to regain metabolic activity shortly after, highlighting a sublethal effect of NaDCC at the recommended commercial dosage due to reversible BCG cell damage. In contrast, increasing twice the disinfectant dosage completely inactivated BCG cells after 24 h of exposure, with full irreversible loss of metabolic activity. Methodological workflows based on conventional culture or PCR would have missed the detection of these dormant subpopulations that were in fact able to resume growth when following the recommendations of a commercial disinfectant. This study highlights the superior, high-resolution value of single-cell approaches, such as flow cytometry, to accurately assess the activity of biocides against metabolically heterogeneous and dormant pathogenic bacteria with environmental cycles, supporting data-driven prioritization of environmental management and disinfection options in contaminated vulnerable settings. Full article

The aim of this study was to test the inactivation of viruses on germ carriers of different types of wood using a disinfectant in order to assess the biosafety of wood as a building material in animal husbandry. The laboratory disinfectant efficacy tests were based on German testing guidelines and current European standards. Five different types of wood germ carriers, i.e., spruce (Picea abies), pine (Pinus sylvestris), poplar (Populus sp.), beech (Fagus sylvatica) and Douglas fir (Pseudotsuga menziesii), were inoculated with enveloped or non-enveloped viruses and then treated with one of three different disinfectants. The results revealed that intact, fine-sawn timber with a low roughness depth can be effectively inactivated. Peracetic acid proved to be the most effective disinfectant across all tests. Regardless of the pathogen and the type of wood, a concentration of 0.1% of the pure substance at a temperature of 10 °C and an exposure time of one hour can be recommended. At a temperature of −10 °C, a concentration of 0.75% is recommended. The basic chemicals formic acid and glutaraldehyde demonstrated only limited effectiveness overall. The synergistic effects of various wood components on the inactivation of viruses offer potential for further investigation. Disinfectant tests should also be conclusively verified in field trials to ensure that the results from standardised laboratory tests can be transferred to real stable conditions. Full article

Three lipid-enveloped viruses (bovine viral diarrhea virus [BVDV], vaccinia virus, and severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) were evaluated in side-by-side liquid inactivation efficacy studies of low pH (3.0 to 3.1) treatment and of the non-formulated microbicidal actives sodium hypochlorite (100 ppm), ethanol (70%), quaternary ammonium compound BTC^® 835 (100 ppm), and peracetic acid (100 ppm). Low pH was evaluated at 10 and 60 min contact times, and the microbicides were evaluated at 1 min contact time at room temperature per the ASTM E1052 standard. In each case, 5% animal serum was included in the viral inoculum as a challenge soil load. The three viruses displayed similar susceptibility to sodium hypochlorite and ethanol, with complete inactivation resulting. Significant differences in susceptibility to BTC^® 835 and peracetic acid were identified, with the ordering of the three viruses for susceptibility to BTC^® 835 being SARS-CoV-2 > vaccinia virus = BVDV, and the ordering for peracetic acid being vaccinia virus > SARS-CoV-2 > BVDV. The ordering for susceptibility to low pH treatment (60 min contact time) was vaccinia virus > SARS-CoV-2 > BVDV. Not all enveloped viruses display equivalent susceptibilities to inactivation approaches. For the chemistries evaluated here, BVDV appears to represent a worst-case enveloped virus. Full article

The inactivation of airborne pathogenic microorganisms is crucial to attenuate the dissemination of infectious diseases induced by airborne pathogens. Conventional air disinfection methodologies, such as ultraviolet (UV) irradiation and ozone treatment, have demonstrated limited efficacy. Consequently, we investigated the potential of employing pulsed voltages to effectively eradicate bacteria within aerosols. Our inquiry revealed that the bacterial disinfection rate increased proportionally with elevated applied voltage and frequency. For instance, when a pulsed voltage of 20 kV and a frequency of 500 Hz were applied, a substantial disinfection rate exceeding 6.0 logarithmic units was attained. Furthermore, with the utilization of the stranded wire anodes, the disinfection intensity could be augmented by up to 2.0 logarithmic units compared with the solid wire configuration. Through the utilization of a stranded wire electrode model, we scrutinized the electric field encompassing the electrode, revealing a non-uniform electric field with the stranded wire electrode. This observation indicated an amplified bacterial disinfection effect, aligning with our experimental outcomes. These findings significantly enhance our comprehension of efficacious approaches to electrically disinfecting airborne bacteria. Full article

Radiation methods are widely used for disinfection and sterilization applications. Microorganisms demonstrate known, variable tolerance levels to inactivation with lower doses of ionizing and non-ionizing radiation based on multiple mechanisms of resistance in their structures and nucleic acid repair mechanisms. The radiation dose required to ensure microbial inactivation during sterilization is typically based on the understanding and routine monitoring of the natural population and resistance of microorganisms on products exposed to radiation sterilization processes. This report describes the isolation of Roseomonas mucosa in a device manufacturing environment that was detected during routine device bioburden and dose verification monitoring. Sources of Gram-negative bacteria in the environment were investigated. Non-sterile examination gloves used during manufacturing were found to be a persistent source of R. mucosa and other microbial contaminants. The source of contamination was determined to be from the glove manufacturing process. Maintenance and routine microbiological controls during glove manufacturing, including water systems, are required to reduce the risks of gloves being a source of unexpected microbiological contamination. Full article

The increased prevalence of multidrug-resistant organisms (MDROs), healthcare associated infections (HAIs), and the recent COVID-19 pandemic has caused the photoinactivation industry to explore alternative wavelengths. Blue light (BL₄₀₅) has gained significant interest as it is much less harmful to the skin and eyes than traditional germicidal wavelengths; therefore, in theory, it can be used continuously with human exposure. At present, the viricidal effects of BL₄₀₅ are largely unknown as the literature predominately addresses bacterial disinfection performed with this wavelength. This work provides novel findings to the industry, reporting on the virucidal effects of BL₄₀₅ on surfaces. This research utilizes three surfaces: ceramic, PTFE, and stainless steel. The efficacy of BL₄₀₅ inactivation varied by surface type, which was due to surface characteristics, such as the contact angle, porosity, zeta potential, and reflectivity. Additionally, the effect of the dew point on BL₄₀₅ inactivation efficacy was determined. This research is the first to study the effects of the dew point on the virucidal effectiveness of BL₄₀₅ surface inactivation. The effects of the dew point were significant for all surfaces and the control experiments. The high-dew-point conditions (18 °C) yielded higher levels of BL₄₀₅ inactivation and viral degradation for the experiments and controls, respectively. Full article

The COVID-19 pandemic highlighted the limitations in scientific and engineering understanding of applying germicidal UV to surfaces. This study combines surface characterization, viral retention, and the related UV dose response to evaluate the effectiveness of UV₂₅₄ as a viral inactivation technology on five surfaces: aluminum, ceramic, Formica laminate, PTFE and stainless steel. Images of each surface were determined using SEM (Scanning Electron Microscopy), which produced a detailed characterization of the surfaces at a nanometer scale. From the SEM images, the surface porosity of each material was calculated. Through further analysis, it was determined that surface porosity, surface roughness, contact angle, and zeta potential correlate to viral retention on the material. The imaging revealed that the aluminum surface, after repeated treatment, is highly oxidized, increasing surface area and surface porosity. These interactions are important as they prevent the recovery of MS-2 without exposure to UV₂₅₄. The dose response curve for PTFE was steeper than ceramic, Formica laminate and stainless steel, as inactivation to the detection limit was achieved at 25 mJ/cm². These findings are consistent with well-established literature indicating UV reflectivity of PTFE is maximized. Statistical testing reinforced that the efficacy of UV₂₅₄ for surface inactivation varies by surface type. Full article

Vaporized hydrogen peroxide (VHP) terminal sterilization is one of the most promising techniques for sterilizing temperature-sensitive medical instruments like endoscopes. This technique requires only electricity and sterilant containers to perform the sterilization process in less than 1 h without any substantial safety concerns for patients, personnel, and the environment. This review studies recent advances and future trends in VHP sterilization cycle development using U.S. patent applications and 510(k) premarket notifications. In this regard, the patents focused on increasing VHP concentration or handling residual moisture are discussed in depth. The expired patents are analyzed to introduce existing unencumbered technologies, and active patents are presented to show the most current novelties and technology trends. In addition, 510(k) premarket notifications are explored to evaluate implemented technologies in US market-leading commercial products. Full article