Influence of type, concentration, exposure time, temperature, and presence of organic load on the antifungal efficacy of industrial sanitizers against Aspergillus brasiliensis (ATCC 16404)

Biocides in the Hospital Environment: Application and Tolerance Development

Hospital-acquired infections are a rising problem with consequences for patients, hospitals, and health care workers. Biocides can be employed to prevent these infections, contributing to eliminate or reduce microorganisms' concentrations at the hospital environment. These antimicrobials belong to several groups, each with distinct characteristics that need to be taken into account in their selection for specific applications. Moreover, their activity is influenced by many factors, such as compound concentration and the presence of organic matter. This article aims to review some of the chemical biocides available for hospital infection control, as well as the main factors that influence their efficacy and promote susceptibility decreases, with the purpose to contribute for reducing misusage and consequently for preventing the development of resistance to these antimicrobials.

Enhanced inactivation of Escherichia coli by ultrasound combined with peracetic acid during water disinfection

Peracetic acid (PAA) is a desirable disinfectant for municipal wastewater because of its potent disinfection performance and limited toxic by-products. This study explored the efficiency and mechanism of Escherichia coli inactivation by PAA combined with ultrasound simultaneously (ultrasound + PAA) or (ultrasound → PAA) sequentially. The result showed that 60 kHz ultrasound combined with PAA sequentially (60 kHz → PAA) had excellent inactivation performance on E. coli, up to 4.69-log₁₀. The result also showed that the increase of pH and humic acid concentration in solution significantly reduced the inactivation efficiency of 60 kHz → PAA treatment. We also observed that the increase of temperature was beneficial to the disinfection, while anions (Cl^-; HCO₃^-) had little effect. With 60 kHz → PAA, the PAA and the synergism between PAA and ultrasound played major contribution to the inactivation, which we assumed might be due to both the diffusion of PAA into the cells and the damage to the cytomembrane by ultrasound, as evidenced through the laser confocal microscopy (LSCM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The inactivation mechanism involved the destruction of cell membrane and loss of intracellular material. Empirically, 60 kHz → PAA was found to be effective for the inactivation of E. coli in actual wastewater, and the regrowth potential of E. coli treated by 60 kHz → PAA was significantly lower than that treated only by PAA.

Evaluation of the ability of commercial disinfectants to degrade free nucleic acid commonly targeted using molecular diagnostics

BACKGROUND

Polymerase chain reaction (PCR) is an essential tool for rapid detection of pathogens, but is susceptible to cross-contamination by residual nucleic acid, leading to false-positive results. Adequate surface decontamination would help prevent this, but most protocols target infectious microbes rather than free nucleic acid. The aim of this study was to evaluate the ability of commercial surface disinfectants to degrade different representative classes of nucleic acid.

METHODS

Commercial surface disinfectants with various active ingredients, as well as 10% chlorine bleach, were tested. Nucleic acid was dried on to stainless steel coupons and treated with disinfectant for 0-4 min prior to neutralization and quantification by quantitative reverse transcription PCR. The effective disinfectants were also evaluated in the presence of organic load.

RESULTS

Only dilute chlorine bleach and the hypochlorite-based commercial disinfectant significantly degraded any type of free nucleic acid. Hydrogen-peroxide- and quaternary-ammonium-based disinfectants gave <1 log reduction after 4 min for all targets. Results were time-dependent for each target, which underscores the importance of adequate contact time. Organic load appeared to have little impact on the efficacy of hypochlorite-based disinfectants for nucleic acid degradation.

CONCLUSIONS

This study demonstrates the importance of proper selection and application of disinfectant to remove residual nucleic acid when processing samples for molecular diagnostic testing.

Factors That Interfere in the Action of Sanitizers against Ochratoxigenic Fungi Deteriorating Dry-Cured Meat Products

This study verified the factors affecting the antifungal efficacy of sanitizers against ochratoxin A-producing fungi. The fungi Penicillium nordicum, Penicillium verrucosum, and Aspergillus westerdijkiae were exposed to three sanitizers at three concentrations: peracetic acid (0.3, 0.6, 1%), benzalkonium chloride (0.3, 1.2, 2%), and sodium hypochlorite (0.5, 0.75, 1%) at three exposure times (10, 15, and 20 min), three temperatures (10, 25, and 40 °C), and with the presence of organic matter simulating clean (0.3%) and dirty (3%) environments. All the tested conditions influenced the antifungal action of the tested sanitizers. Peracetic acid and benzalkonium chloride were the most effective sanitizers, and sodium hypochlorite was ineffective according to the parameters evaluated. The amount of organic matter reduced the antifungal ability of all sanitizers. The longer exposure time was more effective for inactivating fungi. The temperature acted differently for benzalkonium chloride, which tended to be favored at low temperatures, than for sodium hypochlorite and peracetic acid, which were more effective at higher temperatures. The knowledge of the parameters that influence the action of sanitizers on spoilage fungi is vital in decision-making related to sanitizing processes in the food industry.

A preliminary evaluation of chemical interaction between sanitizing products and silk

The ongoing Coronavirus crisis involved almost all sectors as well as museums, collections, and historical sites all over the world. Even though artworks do not have the ability to spread the virus, the pandemic officially introduced in cultural sites alcohol-based products (even by visitors for personal use) as these products were indicated to be able to inactivate the virus and were imposed by many local authorities. In this context, the need to conciliate the safety of the visitors and the protection of artworks represents a challenging task. The possibility that accumulation of vapour coming from the sanitizing solutions or from accidental spills, potentially caused also by visitors, should be considered. The study focuses specifically on the possible interactions between sanitizing alcohol-based products and silk, since this material is present in many cultural sites all over the world on upholsteries and tapestries. The recommended sanitising solution (75% ethanol, 20% water, 5% benzalkonium chloride) selected by the Italian Ministry for Cultural Heritage (MIBACT) was considered. Pure distilled water, absolute ethanol and water/ethanol blends in different concentrations were also tested. Chemical and morphological variations on the silk have been evaluated with Scanning Electron Microscopy - SEM, Atomic Force Microscopy - AFM and portable instruments (contact microscope, colorimeter, Infrared and Raman spectroscopy). IR and Raman analyses did not detect significant chemical changes in silk. However, Raman spectra showed, after immersion treatments, minor variations in the intensity of peaks attributed to dyes. Residues of benzalkonium chloride after immersion tests in sanitising solution are present, confirmed also by SEM and AFM analyses. Even if chemical spectroscopic changes were not relevant, the colour of few samples seemed to consistently fade after immersion treatments, thus affecting the visual appearance of textiles.