Inactivation of Foot-and-Mouth Disease Virus by Commercially Available Disinfectants and Cleaners.

Foot-and-mouth disease virus (FMDV) is an animal pathogen of great concern. It is contagious to cloven-hoofed animals and affects animals in extensive areas worldwide. In general, the primary eradication strategies for foot-and-mouth disease (FMD) in Japan are stamping out the disease and restriction of movement. It is also important to completely disinfect the infected area to prevent the spread of FMDV, including vehicles and people as well. However, there is no report on the effect of commercially available disinfectants against FMDV in a short contact time. In this study, we evaluated the virucidal effect of thirteen commercially available products, and got the following results: acidic ethanol disinfectants, alkaline cleaners and sodium hypochlorite had great effect (>3.0 log10 reduction in titer) against FMDV. On the other hand, neutral ethanol disinfectants, hand soaps, and quaternary ammonium compound sanitizers did not show great effect against FMDV. Therefore, it is presumed that acidic ethanol disinfectants are effective for human use and alkaline cleaners are effective for use in the infected environment for the control of a FMD outbreak.

Cytotoxicity assessment of residual high-level disinfectants.

Some studies show the uptake of disinfectants on medical devices but no studies on their cytotoxicity have been reported. This study aimed to assess that cytotoxicity in a 3-dimensional culture system using HeLa cells grown in matrices composed of collagen. Plastic materials were soaked in the use solutions of the widely used high-level disinfectants, glutaraldehyde (GA), ortho-phthalaldehyde (OPA) and peracetic acid (PAA). After being rinsed, they were allowed to dry and were embedded into the cell medium to investigate the cytotoxicity of the residual disinfectants. Cytotoxicity was observed with the polyvinyl chloride, polyurethane and silicon tubes soaked in GA and OPA, indicating that both disinfectants were absorbed in the test pieces, whereas for PAA, none was observed. As for the polytetrafluoroethylene (PTFE) tubes, no disinfectant displayed cytotoxicity. GA and OPA are primary irritants, having a potential to cause anaphylaxis and other forms of allergic reactions. There should be consideration not only about the toxicity of the residual disinfectant from poor rinsing, but also about the toxicity that would result from the disinfectants that were absorbed and consequently released from the medical devices or materials.

Comparison of the cytotoxicity of high-level disinfectants by the MTT assay and direct contact assay.

Most critical instruments are not designed for heat sterilization and autoclaving. These items are usually treated with chemical agents such as peracetic acid(PAA), glutaraldehyde (GA) and ortho-phthalaldehyde (OPA). MTT assay is often used to evaluate the in vitro cytotoxicity of these chemical agents. In this study, disinfectants were allowed to come in direct contact with cells. Their cytotoxicity was evaluated based on cell viability and adhesive properties. The results obtained from the direct contact method were compared with those obtained from the conventional MTT assay wherein the disinfectants were added into a nutrient medium. It was found that the two methods yielded very different results, especially when aldehyde- and halogen-containing disinfectants were tested, and that toxicity may be underestimated in the MTT assay. Hence, it can be assumed that the direct contact assay is more accurate when evaluating the cytotoxicity of residual chemicals. It was also observed that the cytotoxicity of PAA was lower than that of GA and OPA.

Degradation and destabilization of abnormal prion protein using alkaline detergents and proteases.

There is a limited number of reports regarding detergents and proteases inactivating, degrading, or destabilizing abnormal prion protein (PrPSc). In the present study, the effect of alkaline detergents and proteases on the breakdown of PrPSc in the absence of proteinase K (PK) (degradation) and the presence of PK (destabilization) was investigated. PrPSc from brain homogenate of terminally-diseased mice infected with the Chandler strain of scrapie was used as a substrate. A surfactant-free alkaline detergent (pH 11.9, 1% aqueous solution) with potassium hydroxide as the main ingredient and an alkaline detergent (pH 11.9, 1% aqueous solution) containing about 1% surfactant as well as two commercially available alkaline proteases had a destabilizing effect on PrPSc. All these detergents and proteases showed degradative effects on PrPSc under appropriate conditions. These results demonstrate the usefulness of alkaline detergents and proteases for the degradation or destabilization of PrPSc.

Natural synergism of acid and lactone type mixed sophorolipids in interfacial activities and cytotoxicities.

Sophorolipids (SLs) naturally produced from Candida bombicola are a mixture of lactonic (SL-lactone) and acidic (SL-acid) sophorosides of 17-L-hydroxydecanoic acid with an SL-lactone:SL-acid ratio of 72:28. SLs are biodegradable low-foaming surfactants with high detergency and hardness-tolerance properties. To analyze the effect of the SL-lactone:SL-acid ratio on these properties, SL-LXs containing X% SL-lactone, in which X varied from 0 to 100, were prepared and their interfacial activities and cytotoxicities examined. The minimum surface tension values for all SLs examined were comparable. The critical micelle concentration (CMC) was 680 mg/L for SL-L0 and 62-110 mg/L for the other SLs. Interestingly, natural SL (SL-L72) had the lowest surface tension and CMC among all of the SLs examined. The foaming ability and stability of the SLs were dependent on the SL-L content. SL-L0 and L17 had higher foaming values than the other SLs examined in 0-ppm hardness water. These values greatly reduced and became constant when the SL-L content increased over 55%. The detergencies of all of the SLs examined were comparable, except for those of SL-L0 and SL-L100, which were slightly lower than those of the other SLs. These results suggest that natural synergism between SLs creates a better balance for many interfacial activities. The cytotoxicity of SL-L72 was higher than that of SL-L0, but was comparable to that of surfactin, which is commercially available for cosmetic use. The low cytotoxicities and high interfacial properties of SLs increase their usefulness as biocompatible surface active agents for many applications.

Novel characteristics of sophorolipids, yeast glycolipid biosurfactants, as biodegradable low-foaming surfactants.

Sophorolipids (SLs) are a family of glycolipid type biosurfactants, which are largely produced by the non-pathogenic yeast, Candida bombicola. In order to investigate the possibility of SLs for industrial use, here we examined the interfacial activities, cytotoxicity and biodegradability of SLs, and compared these properties with those of two lipopeptide type biosurfactants (surfactin and arthrofactin), sodium laurate (soap, SP) and four kinds of chemically synthesized surfactants including two block-copolymer nonionic surfactants (BPs), polyoxyethylene lauryl ether (AE) and sodium dodecyl sulfate (SDS). It was indicated that SLs had extremely low-foaming properties and high detergency comparable with commercially available low-foaming BPs. These interfacial activities of SLs were maintained under 100 ppm water hardness. Cytotoxicity of SLs on human keratinocytes was the same as surfactin, which has already been commercialized as cosmetic material, but higher than BPs. Moreover, biodegradability of SLs using the OECD Guidelines for Testing of Chemicals (301C, Modified MITI Test) displayed that SLs can be classified as "readily" biodegradable chemicals, which are defined as chemicals that are degraded 60% within 28 days under specified test methods. We observed 61% degradation of SLs on the eighth day of cultivation. Our results indicate that SLs are low-foaming surfactants with high detergency, which also exhibit both low cytotoxicity and readily biodegradable properties.

Structures of 17,19-hexatriacontadiyne monolayers on Au(111) studied by infrared reflection absorption spectroscopy and scanning tunneling microscopy.

The aggregation and reaction of 17,19-hexatriacontadiyne molecules are studied on a Au(111) surface. The molecular orientation and arrangement are elucidated by infrared reflection absorption spectroscopy (IRAS) and scanning tunneling microscopy (STM). A vapor-deposited monolayer and a multilayered film formed by adsorption from the solution provide IRA spectra with bands due to the antisymmetric and symmetric stretching of methylenes in the gauche conformation. After the adsorbed film is rinsed with the solvent, however, the spectrum loses the gauche bands and is characterized by the enhanced C-H(distal) and C-H(proximal) stretching bands, which means that all-trans molecules are laid flat. Only STM images for the rinsed film display columnar structures on the herringbones of the reconstructed Au(111) surface; the alkyl chain direction is found to be parallel to the Au atom row. The results indicate that an ordered monolayer is formed first at the liquid-solid interface, and then, disordered overlayers with the gauche conformation are grown but removed by a rinse. Upon exposure to UV light, thus obtained monomer columns are converted into oligomers with flexible backbones and an increased gauche population in the alkyl chains, which resemble red phase polydiacetylenes in LB films.