Antimicrobial activity of environmental surface disinfectants in the absence and presence of bioburden

Excessive use of disinfectants against COVID-19 posing a potential threat to living beings

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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan city of China in late December 2019.

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The rapid spread of the COVID-19 across the communities shock the entire population, because of no existing therapies.

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Health professionals recommended frequent washing of hands with soap and alcohol-based sanitizers, but these disinfectants has worst effects on human health.

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Precautionary measures should be ensured to protect ourselves and the community from the possible risk associated with disinfectants.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan city of China in late December 2019 and identified as a novel coronavirus disease 2019 (COVID-19). On January 30, the World Health Organization (WHO) declared the coronavirus outbreak a global public health emergency. The rapid spread of the pathogen across the communities shock the entire population. As no existing therapy were available during the pandemic. Health professionals recommended frequent washing of hands with soap and alcohol-based sanitizers. Disinfectants were extensively sprayed to minimize the possibility of getting COVID-19. Despite the potential benefits of these germicidal agents against COVID-19. Alcohol-based hand sanitizers lead to dry skin, infection, and alcohol poisoning. Children are considered more prone to alcohol poisoning and other major health concern. Precautionary measures should be ensured to protect the community from the possible risk associated with disinfectants.

Correlations between available primary amines, endospore coat thickness, and alkaline glutaraldehyde sensitivity for spores of select Bacillus species

Alkaline glutaraldehyde (GTA) is a high‐level chemical disinfectant/sterilant and has a broad microbial kill spectrum. The precise antimicrobial mechanism of GTA remains debated. GTA kill times are extremely variable across different organisms, illustrating the need for a better understanding of GTA kill mechanisms related to different organisms. A commonly proposed GTA kill mechanism suggests that it works by cross‐linking accessible primary amines on important surface proteins. If true, the antimicrobial activity of GTA may directly correlate to the number of these available functional groups. Bacillus species form highly resistant bacterial endospores that are commonly used as one of the most stringent test organisms for disinfection and sterilization. In this study, we compared the log reduction times of alkaline GTA on spores from 4 Bacillus species to fluorescent profiles generated using Alexa Fluor™ amine‐reactive dyes. GTA kill times were also compared to mean spore coat thicknesses as measured with scanning electron microscopy (SEM). Fluorescence values generated from bound amine‐reactive dye showed a strong, positive correlation to GTA susceptibility, as measured by GTA 6‐log₁₀ reduction times. Spore coat thickness also showed a strong, positive correlation to reduction time values. Results support the hypothesis that GTA kill times are directly related to the number of available primary amines on bacterial endospores. Results also indicated that the killing efficacy of GTA may be influenced by its ability to penetrate the spore coat to reach additional targets, suggesting that damaging important biomolecules beyond surface proteins may be involved in GTA killing mechanisms.

The in Vitro Antibacterial Efficacy of Persian Green Tea Extract as an Intracanal Irrigant on Enterococcus faecalis Biofilm

Introduction:

The aim of this study was to compare the antibacterial effect of Persian green tea extract (GTE) and 2.5% sodium hypochlorite (NaOCl) against Enterococcus faecalis (E. faecalis) as an intracanal irrigant.

Methods and Materials:

Thirty freshly extracted teeth were instrumented and sectioned into mesial and distal segments. The specimens were put into wells containing 2 mL of E. faecalis-containing medium. After 3 weeks, the specimens were removed and divided randomly into three groups (n=20). Each group was exposed to 3 mL of different irrigants for 3 min. Groups 1, 2 and 3 were irrigated with GTE, 2.5% NaOCl and normal saline, respectively. Biofilm formed in the middle third of the root canal was carved by sterile scalpel and cultured in Mueller-Hinton medium. Number of colony forming units (CFU) was counted on each plate. In addition, antimicrobial activity of the irrigants was evaluated by the agar disc diffusion test. The diameter of inhibition zone (IZ) around each irrigant was evaluated. The Kruskal-Wallis and Dunn tests were used to analysis the data.

Results:

While in NaOCl group no bacterial colonies were observed, the mean number of E. faecalis in GTE and control groups were 275±74 CFU/mL (P<0.001) and 119×10⁸±11×10⁸ (P<0.001), respectively. The mean of IZ in NaOCl and GTE groups were 24.35±0.78 and 6.9±0.87 mm, in order of appearance (P<0.001). Zone of inhibition was not observed around the control group (P<0.001).

Conclusion:

This research highlighted the potential role of plant extracts in antimicrobial root canal irrigation protocol.

Effect of Different Disinfectants on Staphylococcus aureus and Candida albicans Transferred to Alginate and Polyvinylsiloxane Impression Materials

BACKGROUND AND AIMS

Several products have been marketed for disinfecting impression materials. The present study evaluated the effect of Deconex, Micro 10, Alprocid and Unisepta Plus sprays on Staphylococcus aureus and Candida albicans transferred to alginate and polyvinylsiloxane impression materials.

MATERIALS AND METHODS

A total of 180 impressions of a maxillary model (90 alginate and 90 polyvinylsiloxane im-pressions) were taken for the purpose of this in vitro study. Half of the impressions were infected with Staphylococcus au-reus and the other half were infected with Candida albicans. Then the microorganisms were cultured and their counts were determined. Subsequently, the impressions were divided into groups of 15 impressions each. Each group was disinfected with Deconex, Micro10, Alprocid and Unisepta Plus according to manufacturers' instructions except for the control group. The culturing procedure was repeated after disinfection and microbial counts were determined again. Data was analyzed by ANOVA and paired-sample t-test.

RESULTS

There were statistically significant differences in the means of S. aureus and C. albicans counts before and after the use of disinfectants (P < 0.05). The use of the four disinfectants reduced S. aureus counts to zero in 80% of the cases. There were no statistically significant differences in S. aureus count reductions between the four disinfectants evaluated (P = 0.31). Micro 10 was more effective on alginate; Deconex was more efficient for polyvinylsiloxane and Alprocid had a better efficacy in both impression materials in eliminating C. albicans (P < 0.05).

CONCLUSION

All the disinfectants evaluated have high disinfecting postentials.

Quantitative method to determine sporicidal decontamination of building surfaces by gaseous fumigants, and issues related to laboratory-scale studies

Chlorine dioxide gas and vaporous hydrogen peroxide sterilant have been used in the cleanup of building interiors contaminated with spores of Bacillus anthracis. A systematic study, in collaboration with the U.S. Environmental Protection Agency, was jointly undertaken by the U.S. Army-Edgewood Chemical Biological Center to determine the sporicidal efficacies of these two fumigants on six building structural materials: carpet, ceiling tile, unpainted cinder block, painted I-beam steel, painted wallboard, and unpainted pinewood. Critical issues related to high-throughput sample processing and spore recovery from porous and nonporous surfaces included (i) the extraction of spores from complex building materials, (ii) the effects of titer challenge levels on fumigant efficacy, and (iii) the impact of bioburden inclusion on spore recovery from surfaces and spore inactivation. Small pieces (1.3 by 1.3 cm of carpet, ceiling tile, wallboard, I-beam steel, and pinewood and 2.5 by 1.3 cm for cinder block) of the materials were inoculated with an aliquot of 50 microl containing the target number (1 x 10(6), 1 x 10(7), or 1 x 10(8)) of avirulent spores of B. anthracis NNR1Delta1. The aliquot was dried overnight in a biosafety cabinet, and the spores were extracted by a combination of a 10-min sonication and a 2-min vortexing using 0.5% buffered peptone water as the recovery medium. No statistically significant drop in the kill efficacies of the fumigants was observed when the spore challenge level was increased from 6 log units to 8 log units, even though a general trend toward inhibition of fumigant efficacy was evident. The organic burden (0 to 5%) in the spore inoculum resulted in a statistically significant drop in spore recovery (at the 2 or 5% level). The effect on spore killing was a function of the organic bioburden amount and the material type. In summary, a high-throughput quantitative method was developed for determining the efficacies of fumigants, and the spore recoveries from five porous materials and one nonporous material ranged between 20 and 80%.

Inactivation of Bacillus anthracis spores by liquid biocides in the presence of food residue

Biocide inactivation of Bacillus anthracis spores in the presence of food residues after a 10-min treatment time was investigated. Spores of nonvirulent Bacillus anthracis strains 7702, ANR-1, and 9131 were mixed with water, flour paste, whole milk, or egg yolk emulsion and dried onto stainless-steel carriers. The carriers were exposed to various concentrations of peroxyacetic acid, sodium hypochlorite (NaOCl), or hydrogen peroxide (H(2)O(2)) for 10 min at 10, 20, or 30 degrees C, after which time the survivors were quantified. The relationship between peroxyacetic acid concentration, H(2)O(2) concentration, and spore inactivation followed a sigmoid curve that was accurately described using a four-parameter logistic model. At 20 degrees C, the minimum concentrations of peroxyacetic acid, H(2)O(2), and NaOCl (as total available chlorine) predicted to inactivate 6 log(10) CFU of B. anthracis spores with no food residue present were 1.05, 23.0, and 0.78%, respectively. At 10 degrees C, sodium hypochlorite at 5% total available chlorine did not inactivate more than 4 log(10) CFU. The presence of the food residues had only a minimal effect on peroxyacetic acid and H(2)O(2) sporicidal efficacy, but the efficacy of sodium hypochlorite was markedly inhibited by whole-milk and egg yolk residues. Sodium hypochlorite at 5% total available chlorine provided no greater than a 2-log(10) CFU reduction when spores were in the presence of egg yolk residue. This research provides new information regarding the usefulness of peroxygen biocides for B. anthracis spore inactivation when food residue is present. This work also provides guidance for adjusting decontamination procedures for food-soiled and cold surfaces.

Culture variability associated with the U.S. Environmental Protection Agency Tuberculocidal Activity Test Method

Tuberculosis continues to be a major world health threat. The etiologic agent is among the vegetative organisms most resistant to chemical disinfection. Tuberculocidal efficacy testing for regulatory approval of chemical germicides has evolved considerably over the past decade. A method currently in use is the Environmental Protection Agency Tuberculocidal Activity Test Method, a suspension test using a Mycobacterium bovis culture grown under specific conditions and stored frozen until used. Differing tuberculocidal label claims on products with similar formulations have raised questions concerning the equivalence of test suspensions prepared by different laboratories. Five M. bovis suspensions from laboratories currently performing this test were compared against a battery of three disinfectants at a single test site. A significant difference between test cultures was found, with two of the five exhibiting a significant difference from the other three and also from each other. There was a significant culture-by-disinfectant interaction, indicating that the five cultures did not respond in a consistent manner across the different disinfectants used. However, these differences were due to cultures that were not prepared in accordance with the standard procedure or otherwise did not meet the test suspension criteria. In addition, a 0.55% sodium hypochlorite solution was found to be a sensitive indicator of culture variability. These data reinforce the need to adhere to published procedures and guidelines when growing and preparing a tuberculocidal test suspension and shed light on the variables associated with this type of testing.

Effectiveness of a professional formula disinfectant for irreversible hydrocolloid

In this study, the effectiveness of Professional Lysol (PL) disinfectant in both its spray and solution forms was evaluated as a surface disinfectant for irreversible hydrocolloid (IH) impressions. Sixteen impressions of a typodont were made with IH, immersed in a microbial broth, and then rinsed in running tap water. The impressions were then treated as follows: four were immersed in PL for 2.5 minutes; four were sprayed by PL and stored for 10 minutes; four were immersed in 2% glutaraldehyde for 10 minutes; four were untreated. Pretest plates showed an average of 421 colonies per plate (c/p). The glutaraldehyde group showed 0.00 c/p. The PL spray group showed 1.75 c/p. The PL immersion group showed 19.00 c/p and showed evidence of surface deterioration in the IH. The untreated group showed 426.25 c/p.

Chemical disinfection to interrupt transfer of rhinovirus type 14 from environmental surfaces to hands

Rhinoviruses can survive on environmental surfaces for several hours under ambient conditions. Hands can readily become contaminated after contact with such surfaces, and self-inoculation may lead to infection. Whereas hand washing is crucial in preventing the spread of rhinovirus colds, proper disinfection of environmental surfaces may further reduce rhinovirus transmission. In this study, the capacities of Lysol Disinfectant Spray (0.1% o-phenylphenol and 79% ethanol), a domestic bleach (6% sodium hypochlorite diluted to give 800 ppm of free chlorine), a quaternary ammonium-based product (7.05% quaternary ammonium diluted 1:128 in tap water), and a phenol-based product (14.7% phenol diluted 1:256 in tap water) were compared in interrupting the transfer of rhinovirus type 14 from stainless steel disks to fingerpads of human volunteers upon a 10-s contact at a pressure of 1 kg/cm2. Ten microliters of the virus, suspended in bovine mucin (5 mg/ml), was placed on each disk, and the inoculum was dried under ambient conditions; the input number on each disk ranged from 0.5 x 10(5) to 2.1 x 10(6) PFU. The dried virus was exposed to 20 microliters of the test disinfectant. The Lysol spray was able to reduce virus infectivity by > 99.99% after a contact of either 1 or 10 min, and no detectable virus was transferred to fingerpads from Lysol-treated disks. The bleach (800 ppm of free chlorine) reduced the virus titer by 99.7% after a contact time of 10 min, and again no virus was transferred from the disks treated with it.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of various surface disinfectants on an irregular surface

Representative samples of hard surface disinfectants were tested against Pseudomonas aeruginosa (ATCC 27853) on frosted glass rods. The same protocol was followed by two investigators on 100 rods for each product tested. Results showed Sporicidin surface disinfectant (Ash Dentsply, York, Pa.) and household bleach 1:10 to be most effective against P. aeruginosa. Lysol disinfectant spray (Lehn & Fink Products, Montvale, N.J.), performed similarly whereas Biocide (Biotrol International, Woods Cross, Utah) failed to inhibit growth on more than half of the rods treated. Failure of the iodophor may be attributed to the use of cotton-filled gauze, because cellulose is believed to react with nascent iodine.