Hydrogen peroxide and sodium hypochlorite disinfectants are more effective against Staphylococcus aureus and Pseudomonas aeruginosa biofilms than quaternary ammonium compounds

Destroying antimicrobial resistant bacteria (AMR) and difficult, opportunistic pathogen using cavitation and natural oils/plant extract

The present study reports, for the first time, a new and techno-economic strategy for effective removal of antimicrobial resistant bacteria (AMR) and difficult, opportunistic pathogen using cavitation and natural oils/plant extract. A hybrid methodology using natural oils of known health benefits has been discussed in combination with conventional physico-chemical method of hydrodynamic cavitation that not only provides efficient and effective water disinfection, but also eliminates harmful effects of conventional methods such as formation of disinfection by-products apart from reducing cost of treatment. A proof-of concept is demonstrated by achieving exceptionally high rates for practically complete removal of antimicrobial resistant (AMR) and relatively less researched, gram-negative opportunistic pathogen, Pseudomonas aeruginosa and gram-positive methicillin resistant, Staphylococcus aureus using a natural oil-Peppermint oil and two different cavitating reactors employing vortex flow (vortex diode) and linear flow (orifice) for hydrodynamic cavitation. >99% disinfection could be obtained, typically in less than 10 min, using vortex diode with operating pressure drop of 1 bar and low dose of 0.1% peppermint oil as an additive, depicting very high rates of disinfection. The rate of disinfection can be further increased by using simple aeration which can result in significant lowering of oil dose. The conventional device, orifice requires relatively higher pressure drop of 2 bar and comparatively more time (~20 min) for disinfection. The cost of the disinfection was also found to be significantly lower compared to most conventional processes indicating techno-economic feasibility in employing the developed hybrid method of disinfection for effectively eliminating bacteria including AMR bacteria from water. The developed approach not only highlights importance of going back to nature for not just conventional water disinfection, but also for eliminating hazardous AMR bacteria and may also find utility in many other applications for the removal of antimicrobial bacteria.

Sodium hypochlorite is more effective than chlorhexidine for eradication of bacterial biofilm of staphylococci and Pseudomonas aeruginosa

PURPOSE

Periprosthetic infection is a common reason for surgical revision. Given the increasing resistance of bacteria to antibiotics (e.g., VRE, 4-MRGN) local antiseptic treatment is gaining in importance. However, no standard guideline-based treatment recommendation is yet available. The aim of this study was to investigate the effectiveness of sodium hypochlorite and chlorhexidine against bacterial biofilms. Furthermore, the toxicity of both antiseptics towards human chondrocytes was examined.

METHODS

Human chondrocytes were isolated, cultivated and treated with sodium hypochlorite and chlorhexidine. The viability of cultures was assessed by determination of cell count, XTT and MTT ELISAs, and fluorescent staining with propidium iodide. Bacterial strains of Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa were added to liquid media and incubated overnight. After determination of bacterial concentrations polyethylene (PE) devices were inoculated with bacteria for 48 h until biofilms formed. The devices were then washed, treated with antiseptics for 2 and 5 min and subsequently spread on agar plates.

RESULTS

Sodium hypochlorite is more effective than chlorhexidine in penetrating biofilms of S. aureus, S. epidermidis and P. aeruginosa. Both antiseptics are chondrotoxic, but sodium hypochlorite damages human chondrocytes less than chlorhexidine in vitro.

CONCLUSIONS

The findings confirm the effectiveness of sodium hypochlorite and chlorhexidine against bacterial biofilms. Both antiseptics can be recommended for the treatment of periprosthetic infections. The toxic effects of sodium hypochlorite and chlorhexidine towards chondrocytes may mean there is a risk of damage to cartilage tissue.

LEVEL OF EVIDENCE

Controlled experimental study.

Disinfectant wipes transfer Clostridioides difficile spores from contaminated surfaces to uncontaminated surfaces during the disinfection process

BACKGROUND

Pre-wetted disinfectant wipes are increasingly being used in healthcare facilities to help address the risk of healthcare associated infections (HAIs). However, HAIs are still a major problem in the US with Clostridioides difficile being the most common cause, leading to approximately 12,800 deaths annually in the US. An underexplored risk when using disinfectant wipes is that they may cross-contaminate uncontaminated surfaces during the wiping process. The objective of this study was to determine the cross-contamination risk that pre-wetted disinfectant towelettes may pose when challenged with C. difficile spores. We hypothesized that although the tested disinfectant wipes had no sporicidal claims, they will reduce spore loads. We also hypothesized that hydrogen peroxide disinfectant towelettes would present a lower cross-contamination risk than quaternary ammonium products.

METHODS

We evaluated the risk of cross-contamination when disinfectant wipes are challenged with C. difficile ATCC 43598 spores on Formica surfaces. A disinfectant wipe was used to wipe a Formica sheet inoculated with C. difficile. After the wiping process, we determined log₁₀ CFU on previously uncontaminated pre-determined distances from the inoculation point and on the used wipes.

RESULTS

We found that the disinfectant wipes transferred C. difficile spores from inoculated surfaces to previously uncontaminated surfaces. We also found that wipes physically removed C. difficile spores and that hydrogen peroxide disinfectants were more sporicidal than the quaternary ammonium disinfectants.

CONCLUSION

Regardless of the product type, all disinfectant wipes had some sporicidal effect but transferred C. difficile spores from contaminated to otherwise previously uncontaminated surfaces. Disinfectant wipes retain C. difficile spores during and after the wiping process.

Solid Oxygen-Purifying (SOP) Filters: A Self-Disinfecting Filters to Inactivate Aerosolized Viruses

Normal heating, ventilation, and air conditioning (HVAC) systems typically use high-efficiency particulate air (HEPA) filters, which can filter dust, various pollutants, and even bacteria and viruses from indoor air. However, since HEPA filters cannot not clean themselves and due to the nature of these microbes which can survive for long periods of time, changing these filters improperly could transmit pathogenic bacteria or viruses, and could even lead to new infections. This study indicated that these manufactured Solid Oxygen-purifying (SOP) filters have the potential to self-disinfect, filter, and inactivate aerosolized viruses. MS2 bacteriophage was used as a model virus in two different experiments. The first experiment involved aerosolization of the virus, while the second were a higher viral load using a soaking method. The SOP filters inactivated up to 99.8% of the virus particles in both experiments, provided that the density of the SOP filter was high. Thus, SOP filters could self-clean, which led to protection against airborne and aerosolized viruses by inactivating them on contact. Furthermore, SOP filters could be potentially use or addition in HVAC systems and face masks to prevent the transmission of airborne and aerosolized viruses.

Cross-contamination by disinfectant towelettes varies by product chemistry and strain

Background

Disinfectant products are used frequently on environmental surfaces (e.g. medical equipment, countertops, patient beds) and patient care equipment within healthcare facilities. The purpose of this study was to assess the risk of cross-contamination of Staphylococcus aureus and Pseudomonas aeruginosa during and after disinfection of predetermined surface areas with ready-to-use (RTU) pre-wetted disinfectant towelettes.

Methods

This study tested six disinfectant towelette products against S. aureus ATCC CRM-6538 and P. aeruginosa strain ATCC-15442 on Formica surfaces. Each disinfectant was evaluated on a hard nonporous surface and efficacy was measured every 0.5 m² using a modified version of EPA MLB SOP-MB-33 to study the risk of cross-contamination.

Results

We found that all of the wipes used in this study transferred S. aureus and P. aeruginosa from an inoculated surface to previously uncontaminated surfaces. Disinfectant towelettes with certain chemistries also retained a high level of viable bacteria after disinfection of the surface area. The cross-contamination risk also varied by product chemistry and bacterial strain.

Conclusion

Disinfectant wipes can cross-contaminate hard nonporous surfaces and retain viable bacterial cells post-disinfection, especially over larger surface areas. This highlights a need to further investigate the risk disinfectant wipes pose during and post-disinfection and guidance on maximum surface areas treated with a single towelette.

Increased Sensitivity of Amoeba-Grown Francisella Species to Disinfectants

Francisella tularensis is a highly infectious, intracellular bacterium and it is the causative agent of tularemia. The bacterium has been isolated from more than 250 species, including protozoa. Previous studies have shown that the growth of Legionella pneumophila within the amoeba results in a dramatic increase in the resistance to disinfectants. Since Francisella persists in the environment for years, this study investigates whether Acanthamoeba castellanii-grown F. novicida exhibits an alteration in the resistance to disinfectants. The disinfectants used are didecyldimethylammonium chloride (DDAC) combined with isopropyl alcohol (D1), benzalkonium chloride combined with DDAC and formic acid (D2), and polyhexamethylene biguanide (PHMB, D3). The effect of disinfectants on the bacterial viability is determined by a colony-forming unit (CFU), by transmission electron microscopy (TEM), by fluorescence microscopy, and the damage of the bacterial membrane. Our data has shown that only a one-log₁₀ loss in bacterial viability is exhibited upon treatment of agar-grown Francisella, while in amoeba-grown Francisella there was a three-log₁₀ difference with D3. The D1 disinfectant sterilized the bacteria within 10 s. The treatment of agar-grown F. novicida with D2 reduces bacterial viability by seven-log₁₀ within 10 s and 15 min, respectively. Surprisingly, the treatment of amoeba-grown F. novicida with D2 results in a total loss of bacterial viability. In conclusion, A. castellanii-grown F. novicida is more susceptible to many disinfectants.

COVSACK: an innovative portable isolated and safe COVID-19 sample collection kiosk with automatic disinfection

The Corona VIrus Disease 2019 (COVID-19) is one of the significant medical disaster that changed the life of humankind in the 21st century. The deadly virus is transmittable from infected person, through his nasal droplets, to surrounding people among whom, the healthcare personnel are the utmost affected. The present article brings out an innovative chamber, which is used for collection of throat, or nasal swabs/samples for diagnosis of COVID-19 suspected persons. The chamber, called COVid SAmple Collection Kiosk (COVSACK), eliminates the transmission of the deadly virus to the health care personnel while collecting the sample. The kiosk is designed based on CFD simulations for effective spread of disinfectant in fine droplet form, built with a lightweight composite that is sustainable in extreme weather conditions and the kiosk can be easily sanitized within 3 min after sample collection. The chamber is first positioned in ESI Hospital, Hyderabad, and other hospitals and diagnostics centres across India, extensively being used for testing the COVID-19 patients at a faster rate, with a drastic reduction in use of personal protection equipment (PPE). This technological innovation, to certain extent, has changed the way the testing of COVID-19 patients carried out in the country.

Controlling biofilms using synthetic biology approaches

Bacterial biofilms are formed by the complex but ordered regulation of intra- or inter-cellular communication, environmentally responsive gene expression, and secretion of extracellular polymeric substances. Given the robust nature of biofilms due to the non-growing nature of biofilm bacteria and the physical barrier provided by the extracellular matrix, eradicating biofilms is a very difficult task to accomplish with conventional antibiotic or disinfectant treatments. Synthetic biology holds substantial promise for controlling biofilms by improving and expanding existing biological tools, introducing novel functions to the system, and re-conceptualizing gene regulation. This review summarizes synthetic biology approaches used to eradicate biofilms via protein engineering of biofilm-related enzymes, utilization of synthetic genetic circuits, and the development of functional living agents. Synthetic biology also enables beneficial applications of biofilms through the production of biomaterials and patterning biofilms with specific temporal and spatial structures. Advances in synthetic biology will add novel biofilm functionalities for future therapeutic, biomanufacturing, and environmental applications.

Activity of Hospital Disinfectants against Vegetative Cells and Spores of Clostridioides difficile Embedded in Biofilms

Clostridioides difficile spores can survive in the environment in either mono- or mixed-species biofilms. However, no previous studies have investigated chemical disinfection of C. difficile spores embedded in biofilms. Thus, the purpose of this study was to assess the in vitro effectiveness of hospital disinfectants against C. difficile spores embedded within biofilms. Five unique C. difficile strains embedded in three different biofilm types grown for 72 or 120 h were exposed to seven different hospital disinfectants. C. difficile abundance [as log(number of CFU/milliliter)] was calculated after manufacturer-determined contact times along with biofilm biomass and microscopy. The primary analysis compared differences between C. difficile vegetative cell and spore counts as well as amounts of biomass after exposure to disinfectants. C. difficile vegetative cells and spores were recovered from biofilms regardless of the type of biofilm growth or biofilm growth time. No disinfectant was able to completely eliminate C. difficile from the biofilms. Overall, Clorox, ortho-phthalaldehyde (OPA), and Virex were most effective at killing C. difficile spores regardless of biofilm age, ribotype, or wash conditions (whether biofilms are washed or unwashed) (P = 0.001, each). Clorox and OPA were also effective at killing total vegetative cell growth (P = 0.001, each), but Virex was found to be ineffective against vegetative cell growth in biofilms (P = 0.77). Clorox and Virex were most effective in reducing biomass, followed by Nixall, OPA, and Vital Oxide. No disinfectant was able to completely eliminate C. difficile embedded within biofilms although differences among disinfectants were noted. Future research will be required to determine methods to eradicate this persister reservoir.

Study on the In Vitro Activity of Five Disinfectants against Nosocomial Bacteria

Nosocomial infections cause significant morbidity and mortality worldwide, and the pathogenic organisms responsible for such infections can develop resistance to antimicrobial agents. Understanding the activity of disinfectants against clinical and environmental bacterial isolates is therefore crucial. We analysed the in vitro activity of five antimicrobial products (phenolic compounds, didecyldimethylammonium chloride (DDAC), sodium hypochlorite, isopropanol + ammonium compounds (IACs), hydrogen peroxide) against 187 bacterial strains comprising clinical isolates, as well as 30 environmental isolates of Pseudomonas aeruginosa from hospital water samples. Disk diffusion assays were employed to assess antimicrobial activity. Hydrogen peroxide was significantly more active (p < 0.0001) than the other disinfectants against all P. aeruginosa, Klebsiella pneumoniae, Enterococcus faecalis and Staphylococcus aureus strains. It was also the only disinfectant with activity against both clinical and environmental strains of P. aeruginosa. DDAC and IAC-based disinfectants were ineffective against Gram-negative strains, but showed significant activity (particularly IACs, p < 0.0001) against the Gram-positive strains. Compared with IACs, DDAC was significantly more active on E. faecalis and less active on S. aureus (p < 0.0001). Sodium hypochlorite and phenol compounds, by contrast, were inactive against all bacterial strains. The development of disinfection procedures that are effective against all microorganisms is essential for limiting the spread of nosocomial infections.