Comparison of the sporicidal activity of a UV disinfection process with three FDA cleared sterilants

BACKGROUND

Endocavitary probes are semi-critical devices and must undergo, at least, high level disinfection (HLD) between uses. Therefore, they should be high level disinfected between uses (i.e., with a product/process that kills all forms of microbial life; bacteria, fungi, mycobacteria, and virus, and in some countries, a demonstrated potential for sporicidal activity). In this study, the sporicidal activity of three common Food and Drug Administration cleared sterilants (CIDEX OPA Solution, SPOROX II Sterilizing and Disinfection Solution and CIDEX Activated Dialdehyde Solution) was compared with the sporicidal activity of an ultraviolet disinfection technology (Hypernova Chronos, Germitec) against Bacillus subtilis ATCC 19659 spores spread on silicone flat carriers in the presence of inorganic and organic soil.

RESULTS

The results indicate that the UV disinfection process presented within a 35 seconds exposure time a sporicidal efficacy substantially higher than the chemical sterilants used according to manufacturer instructions for HLD.

CONCLUSIONS

This study demonstrated that even if it cannot be tested/approved as a sterilant according to AOAC 966.04, the UV unit is much more effective than usual Food and Drug Administration approved chemical HLD products to kill spores in real use conditions. This finding questions the relevancy of evaluating product efficacy within extended conditions giving results that could mislead users to select the most effective HLD product/process for the reprocessing of their medical devices.

Inhibitory activities of propolis, nisin, melittin and essential oil compounds on Paenibacillus alvei and Bacillus subtilis

Background

Natural products represent important sources of antimicrobial compounds. Propolis and compounds from essential oils comprise good examples of such substances because of their inhibitory effects on bacterial spores, including bee pathogens.

Methods

Ethanol extracts of propolis (EEP) from Apis mellifera were prepared using different methods: double ultrasonication, double maceration and maceration associated with ultrasonication. Together with the antimicrobial peptides nisin and melittin, and compounds present in the essential oils of clove (Syzygium aromaticum) and cinnamon (Cinnamomum zeylanicum), assays were carried out on one Bacillus subtilis isolate and Paenibacillus alvei (ATCC 6344) against vegetative and sporulated forms, using the resazurin microtiter assay. Synergism with all the antimicrobials in association with tetracycline was verified by the time-kill curve method. Potassium and phosphate efflux, release of proteins and nucleic acids were investigated.

Results

EEPs showed the same MIC, 156.25 µg/mL against B. subtilis and 78.12 µg/mL against P. alvei. The peptides showed better activities against B. subtilis (MIC of 12 µg/mL for melittin and 37.50 µg/mL for nisin). Antimicrobials showed similar inhibitory effects, but cinnamaldehyde (39.06 µg/mL) showed the best action against P. alvei. Melittin and nisin showed the greatest capacity to reduce spores, regarding B. subtilis there was a 100% reduction at 6.25 and 0.78 µg/mL, respectively. Concerning P. alvei, the reduction was 93 and 98% at concentrations of 80 µg/mL of melittin and 15 µg/mL of nisin. EEPs showed the highest effects on the protein release against B. subtilis and P. alvei. Nucleic acid release, phosphate and potassium efflux assays indicated bacterial cell membrane damage. Synergism between antimicrobials and tetracycline was demonstrated against both bacteria.

Conclusion

All antimicrobials tested showed antibacterial activities against vegetative and sporulated forms of P. alvei and B. subtilis, especially nisin and melittin. Synergism with tetracycline and damage on bacterial cell membrane also occurred.

Metal oxide nanoparticles for the decontamination of toxic chemical and biological compounds

For several years, the international context is deeply affected by the use of chemical and biological weapons. The use of CBRN (Chemical Biological Radiological Nuclear) threat agents from military stockpiles or biological civilian industry demonstrate the critical need to improve capabilities of decontamination for civilians and military. Physical decontamination systems that operate only by adsorption and displacement such as Fuller's Earth, have the drawback of not neutralizing hazardous agents, giving place to cross contaminations. Consequently, the development of a formulation based on metal oxide nanoparticles attracts considerable interest, since they offer physicochemical properties that allow them to both adsorb and degrade toxic compounds. Thus, the aim of this study is to found metal oxide nanoparticles with a versatile activity on both chemical and biological toxic agents. Therefore, several metal oxides such as MgO, TiO₂, CeO₂, ZnO and ZrO₂ were characterized and their decontamination kinetics of less-toxic surrogate of VX, paraoxon, were studied in vitro. To determine the antimicrobial activity of these nanoparticles, simulants of biological terrorist threat were used by performing a 3-hours decontamination kinetics. This proof-of-concept study showed that MgO is the only one that exhibits both chemical and antibacterial actions but without sporicidal activity.

Effects of the antifungal peptide Skh-AMP1 derived from Satureja khuzistanica on cell membrane permeability, ROS production, and cell morphology of conidia and hyphae of Aspergillus fumigatus

Skh-AMP1 (GRTSKQELCTWERGSVRQADKTIAG) is an antifungal peptide isolated from Satureja khuzistanica which has been shown to have strong antifungal activity against Aspergillus and Candida species, but no obvious hemolytic effects or cell cytotoxicity in vitro. In the present study, Skh-AMP1 was synthesized, and its mode of action on the plasma membrane, mitochondria, and morphological and ultrastructural changes against conidia and hyphae of Aspergillus fumigatus were evaluated. The results indicated that Skh-AMP1 had sporicidal activities against the non-germinated conidia of A. fumigatus at concentrations of 40 and 80 μM. Skh-AMP1 induced the release of K⁺ and the uptake of propidium iodide and enhanced reactive oxygen species (ROS) production in the conidia and hyphae of the fungus. Scanning and transmission electron microscopy showed deformation and shrinkage of the hyphae and conidia, cell membrane disruption and detachment from the cell wall, microvesicle formation, vacuolation and depletion of cytoplasm and organelles of the hyphae of A. fumigatus exposed to 40-80 μM of the peptide. The results further demonstrated that the antifungal activity of Skh-AMP1 may be related to its ability to disrupt fungal cell membrane permeabilization and induce enhanced ROS production. Therefore, Skh-AMP1 can be introduced as a novel antifungal candidate for developing new therapeutic agents.

Construction of Its Evaluation System in Originally Designed Test-Chamber System and Sporicidal Activity of Aerosolized Hypochlorite Solution to Bacillus subtilis Spores

　Effective spatial disinfection systems are required for human health care, public hygiene, and food and medicine manufacturing. Although some aerosolized disinfectants were already applied to its purpose, accurate evaluation systems were under constructed. In this study, the spatial sporicidal activity of aerosolized hypochlorite solution (AHS) to dormant cells, Bacillus subtilis spores, was evaluated by an originally designed chamber system. In the test-chamber, AHS was supplied and existed as micro-droplets, and environmental relative humidity (RH) could be controlled. Available chlorine (AC) exposure was also controlled with appropriate AC loading but was influenced by the acidity of AHS. Our results indicated that inactivation of spore was depend on AC exposure amount and time. On the other hand, unsaturated environmental RH markedly decreased spore inactivation. This study indicated that our test-chamber system can provide reproducible test data under a homogeneous air condition, and, thereby, that the data obtained by the chamber system should contribute to predicting the AC-required dose to disinfect a whole building.

Interlaboratory reproducibility of a test method following 4-field test methodology to evaluate the susceptibility of Clostridium difficile spores

BACKGROUND

Sporicidal surface disinfection is recommended to control transmission of Clostridium difficile in healthcare facilities. EN 17126 provides a method to determine the sporicidal activity in suspension and has been approved as a European standard. In addition, a sporicidal surface test has been proposed.

AIM

To determine the interlaboratory reproducibility of a test method for evaluating the susceptibility of a C. difficile spore preparation to a biocidal formulation following the 4-field test (EN 16615 methodology).

METHODS

Nine laboratories participated. C. difficile NCTC 13366 spores were used. Glutaraldehyde (1% and 6%; 15 min) and peracetic acid (PAA; 0.01% and 0.04%; 15 min) were used to determine the spores' susceptibility in suspension in triplicate.

FINDINGS

One-percent glutaraldehyde revealed a mean decimal log₁₀ reduction of 1.03 with variable results in the nine laboratories (0.37-1.49) and a reproducibility of 0.38. The effect of 6% glutaraldehyde was stronger (mean: 2.05; range: 0.96-4.29; reproducibility: 0.86). PAA revealed similar results. An exemplary biocidal formulation based on 5% PAA was used at 0.5% (non-effective concentration) and 4% (effective concentration) to determine the sporicidal efficacy (4-field test) under clean conditions in triplicate with a contact time of 15 min. When used at 0.5% it demonstrated an overall log₁₀ reduction of 2.68 (range: 2.35-3.57) and at 4% of 4.61 (range: 3.82-5.71). The residual contamination on the three primarily uncontaminated test fields was <50 cfu/25 cm² in one out of nine laboratories (0.5%) and in seven out of nine laboratories (4%).

CONCLUSION

The interlaboratory reproducibility seems to be robust.

Antimicrobial effect of a combination of herb extract and organic acid against Bacillus subtilis spores

The sporicidal activities of the herbs were investigated to screen for novel antimicrobial substances against Bacillus subtilis spores. The bacterial inactivation effects of ethanol extracts of coriander, caraway, mace at concentrations of 0.5% (w/v) and 1.0-2.5% were about 10- and 100-fold respectively against spores. At pH 5, the antimicrobial activity was about 92%, but at pH 4 the sporicidal activity was particularly high, reducing the spore count by 99.99%. The 0.1-2.5% ethanol extract of herbs adjusted to pH 4-5 exhibited significantly marked deactivation effects, with 3-4 log CFU/mL reductions. The herb-acid combination exerted a further increase in sporicidal activity, with an additional 1-3 log CFU/mL reduction. The sporicidal mechanism was assumed to involve a two-step: (1) the hydrophobic binding of surfactants in the herbs onto the spore coat destroys its protein, and (2) the acid then penetrates into the interior, generating unstable growth conditions.

A novel enzyme-based antimicrobial system comprising iodide and a multicopper oxidase isolated from Alphaproteobacterium strain Q-1

Alphaproteobacterium strain Q-1 produces an extracellular multicopper oxidase (IOX), which catalyzes iodide (I-) oxidation to form molecular iodine (I2). In this study, the antimicrobial activity of the IOX/iodide system was determined. Both Gram-positive and Gram-negative bacteria tested were killed completely within 5 min by 50 mU mL(-1) of IOX and 10 mM iodide. The sporicidal activity of the system was also tested and compared with a common iodophor, povidone-iodine (PVP-I). IOX (300 mU mL(-1)) killed Bacillus cereus, B. subtilis, and Geobacillus stearothermophilus spores with decimal reduction times of 2.58, 7.62, and 40.9 min, respectively. However, 0.1% PVP-I killed these spores with much longer decimal reduction times of 5.46, 38.0, and 260 min, respectively. To evaluate the more superior sporicidal activity of the IOX system over PVP-I, the amount of free iodine (non-complexed I2) was determined by an equilibrium dialysis technique. The IOX system included more than 40 mg L(-1) of free iodine, while PVP-I included at most 25 mg L(-1) free iodine. Our results suggest that the new enzyme-based antimicrobial system is effective against a wide variety of microorganisms and bacterial spores, and that its strong biocidal activity is due to its high free iodine content, which is probably maintained by re-oxidation of iodide released after oxidation of cell components by I2.