The use of bacteriophage MS2 as a model system to evaluate virucidal hand disinfectants

Evaluating the antimicrobial efficacy of long-lasting hand sanitizers on skin

BACKGROUND

The microbicidal efficacy of hand sanitizer formulations is usually measured through standardized quantitative suspension tests and fingerpad tests; these cannot evaluate long-lasting formulations or are impractical due to biological risks, high cost, or time required for testing. With increased numbers of long-lasting microbicidal activity claims of commercially available hand sanitizers, alternative testing strategies are required.

AIM

To explore the use of a standardized ex-vivo pig skin model to reproducibly measure long-lasting efficacy of an alcohol-free hand sanitizer formulation.

METHODS

The microbicidal efficacy of an alcohol-free hand sanitizer was tested against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae, and the enveloped virus SARS-CoV-2 with quantitative suspension tests (EN13727 and EN14476) with a contact time of 5 min. The product was then tested over a 6 h period using an ex-vivo pig skin model with a modified version of PAS 2424 to simulate the impact of skin abrasion.

FINDINGS

Quantitative suspension tests yielded a >5 log10 reduction for all organisms tested within a 5 min contact time. Pig skin tests showed reduced but consistent efficacy at all time points and indicated no significant impact of abrasion on efficacy.

CONCLUSION

The use of the ex-vivo pig skin model provides a potentially viable and convenient model system to test long-lasting hand sanitizer formulations, providing a path for sustainable hand sanitizer formulation claims of activity on skin.

A simple and effective aerosol pathogen disinfection test for a flowing air disinfector

Aerosol transmission is an important disease transmission route and has been especially pertinent to hospital and biosafety laboratories during the SARS-CoV-2 pandemic. The thermal resistance of airborne SARS-CoV-2 is lower than that of Bacillus subtilis spores, which are often used to test the effectiveness of SARS-CoV-2 and other pathogen disinfection methods. Herein, we propose a new method to test the disinfection ability of a flowing air disinfector (a digital electromagnetic induction air heater) using B. subtilis spores. The study provides an alternative air disinfection test method. The new test system combined an aerosol generator and a respiratory filter designed in-house and could effectively recover spores on the filter membrane at the air outlet after passing through the flowing air disinfector. The total number of bacterial spores used in the test was within the range of 5 × 10⁵-5 × 10⁶ colony-forming units (CFUs) specified in the technical standard for disinfection. The calculation was based on the calculation method in Air Disinfection Effect Appraisal Test in Technical Standard for Disinfection (2002 Edition). At an air speed of 3.5 m/s, we used a digital electromagnetic induction air heater to disinfect flowing air containing 4.100 × 10⁶ CFUs of B. subtilis spores and determined that the minimum disinfection temperature was 350 °C for a killing rate of 99.99%. At 400 °C, additional experiments using higher spore concentrations (4.700 × 10⁶ ± 1.871 × 10⁵ CFU) and a higher airspeed (4 m/s) showed that the killing rate remained>99.99%. B. subtilis spores, as a biological indicator for testing the efficiency of dry-heat sterilization, were killed by the high temperatures used in this system. The proposed method used to test the flowing air disinfector is simple, stable, and effective. This study provides a reference for the development of test systems that can assess the disinfection ability of flowing air disinfectors.

Disinfectants against SARS-CoV-2: A Review

The pandemic due to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has emerged as a serious global public health issue. Besides the high transmission rate from individual to individual, indirect transmission from inanimate objects or surfaces poses a more significant threat. Since the start of the outbreak, the importance of respiratory protection, social distancing, and chemical disinfection to prevent the spread of the virus has been the prime focus for infection control. Health regulatory organizations have produced guidelines for the formulation and application of chemical disinfectants to manufacturing industries and the public. On the other hand, extensive literature on the virucidal efficacy testing of microbicides for SARS-CoV-2 has been published over the past year and a half. This review summarizes the studies on the most common chemical disinfectants and their virucidal efficacy against SARS-CoV-2, including the type and concentration of the chemical disinfectant, the formulation, the presence of excipients, the exposure time, and other critical factors that determine the effectiveness of chemical disinfectants. In this review, we also critically appraise these disinfectants and conduct a discussion on the role they can play in the COVID-19 pandemic.

New technique to evaluate decontamination methods for filtering facepiece respirators

BACKGROUND

A major concern among health care experts is a shortage of N95 filtering facepiece respirators (FFRs) during a pandemic. One option for mitigating an FFR shortage is to decontaminate and reuse the devices. The focus of this study was to develop a new evaluation technique based on 3 major decontamination requirements: (1) inactivating viruses, (2) not altering the respirator properties, and (3) not leaving any toxic byproduct on the FFR.

METHODS

Hydrophilic and hydrophobic FFRs were contaminated with MS2 virus. In the solution-based deposition, the virus-containing liquid droplets were spiked directly onto FFRs, while in the vapor-based and aerosol-based depositions, the viral particles were loaded onto FFRs using a bio-aerosol testing system. Ultraviolet germicidal irradiation (UVGI) and moist heat (MH) decontamination methods were used for inactivation of viruses applied to FFRs.

RESULTS

Both UVGI and MH methods inactivated viruses (>5-log reduction of MS2 virus; in 92% of both method experiments, the virus was reduced to levels below the detection limit), did not alter the respirator properties, and did not leave any toxic byproduct on the FFRs.

CONCLUSIONS

Both UVGI and MH methods could be considered as promising decontamination candidates for inactivation of viruses for respirator reuse during shortages.

Effect of selected sampling media, flow rate, and time on the sampling efficiency of a liquid impinger packed with glass beads for the collection of airborne viruses

The liquid impingers can be used for sampling of viral aerosols, such as COVID-19 virus, influenza, and measles. However, the lowest cutoff diameter of commercially available liquid impingers was about 0.3 μm, and the physical collection efficiency for nano-bioaerosol is only about 10-20%. Here, we enhanced the impinger's collection efficiency and recovery of viable viral aerosols by using packed glass beads and selected sampling media (1% peptone and lysogeny broth, LB). Single-stranded RNA (ssRNA) MS2 bacteriophage with uranine (as a physical tracer) was used as model viral aerosols. The effects of different sampling flow rates (4, 6, and 12.5 L per minute) and different sampling time (10, 20, and 30 min) on the collection efficiency and recovery of MS2 aerosols were also tested. Collection efficiency and recovery of viable viral aerosols were analyzed as a function of sampling media, flow rate, and sampling time and packed glass beads by using a general linear model. Although the packed glass beads considerably enhanced the collection efficiency of the liquid impinger for MS2 aerosols, the recovery of viable MS2 becomes lower due to the higher pressure drop across the impinger. Using peptone or LB as sampling media, reducing sampling flow rate, and decreasing sampling time was proven to improve the recovery of viable MS2. Conclusively, this study provides some practical methods to improve the collection efficiency of liquid impinger for viral aerosols and preserve their viability.

Alcohol-based hand sanitisers as first line of defence against SARS-CoV-2: a review of biology, chemistry and formulations

The pandemic due to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has emerged as a serious global public health issue. Since the start of the outbreak, the importance of hand-hygiene and respiratory protection to prevent the spread of the virus has been the prime focus for infection control. Health regulatory organisations have produced guidelines for the formulation of hand sanitisers to the manufacturing industries. This review summarises the studies on alcohol-based hand sanitisers and their disinfectant activity against SARS-CoV-2 and related viruses. The literature shows that the type and concentration of alcohol, formulation and nature of product, presence of excipients, applied volume, contact time and viral contamination load are critical factors that determine the effectiveness of hand sanitisers.

Infection control for norovirus

Norovirus infections are notoriously difficult to prevent and control, owing to their low infectious dose, high shedding titre, and environmental stability. The virus can spread through multiple transmission routes, of which person-to-person and foodborne are the most important. Recent advances in molecular diagnostics have helped to establish norovirus as the most common cause of sporadic gastroenteritis and the most common cause of outbreaks of acute gastroenteritis across all ages. In this article, we review the epidemiology and virology of noroviruses, and prevention and control guidelines, with a focus on the principles of disinfection and decontamination. Outbreak management relies on sound infection control principles, including hand hygiene, limiting exposure to infectious individuals, and thorough environmental decontamination. Ideally, all infection control recommendations would rely on empirical evidence, but a number of challenges, including the inability to culture noroviruses in the laboratory and the challenges of outbreak management in complex environments, has made it difficult to garner clear evidence of efficacy in certain areas of infection control. New experimental data on cultivable surrogates for human norovirus and on environmental survivability and relative resistance to commonly used disinfectants are providing new insights for further refinining disinfection practices. Finally, clinical trials are underway to evaluate the efficacy of vaccines, which may shift the current infection control principles to more targeted interventions.

Temperature and humidity influences on inactivation kinetics of enteric viruses on surfaces

Norovirus (NoV) and hepatitis A virus (HAV) are pathogenic enteric viruses responsible for public health concerns worldwide. The viral transmission occurs through fecally contaminated food, water, fomites, or direct contact. However, the difficulty in cultivating these viruses makes it a challenge to characterize the resistance to various environmental stresses. In this study, we characterized the inactivation rates of murine norovirus (MNV), MS2, and HAV on either lacquer coating rubber tree wood or stainless steel under different temperature and relative humidity (RH) conditions. The viruses were analyzed at temperatures of 15 °C, 25 °C, 32 °C, and 40 °C and at RHs of 30%, 50%, and 70% for 30 days. Overall, they survived significantly longer on wood than on steel at lower temperature (P < 0.05). The inactivation rate of MS2 and MNV increased at higher RH levels, whereas HAV survived the best at a medium RH level (50%). The effect of RH was significant only for MS2 (P < 0.05). MS2 persisted longest under all of the environmental conditions examined. Both a linear and a nonlinear Weibull model were used to describe the viral inactivation data in this study. The data produced a better fit to the survival curves that were predicted by the Weibull model.

Inactivation of aerosolized Bacillus atrophaeus (BG) endospores and MS2 viruses by combustion of reactive materials

Accidental release of biological agents from a bioweapon facility may contaminate large areas, possibly causing disastrous environmental consequences. To address this issue, novel halogen-containing reactive materials are being designed with the added capability to inactivate viable airborne microorganisms. This study determined the efficiency of combustion products of such materials to inactivate aerosolized bacteria and viruses. Spores of Bacillus atrophaeus and MS2 viruses dispersed in dry air were exposed for subsecond time intervals to hydrocarbon flames seeded with different reactive powders so that bioaerosol particles interacted with the combustion products in a controlled high-temperature environment. The experiments were designed to quantify differences in the biocidal effects of different reactive material powders including Al and Mg, a B•Ti nanocomposite, an 8Al•MoO(3) nanothermite, and a novel Al•I(2) nanocomposite. Compared to pure hydrocarbon flame, powder-seeded flame (with no iodine) produced about an order of magnitude greater inactivation of bacterial spores. The iodine-containing material increased the spore inactivation by additional 2 orders of magnitude. The aerosolized MS2 viruses (generally not as stress-resistant as spores) were fully inactivated when exposed to combustion of either the iodinated or noniodinated powders. Overall, the study suggests a great biocidal potential of combustion products generated by novel iodine-containing nanocomposite materials.

Effect of Biocides on MS2 and K Coliphages

Several biocides commonly used in disinfection processes as antibacterial and antifungal agents were tested for activity against MS2 and K coliphages. MS2 was resistant to most biocides; only glutaraldehyde (0.5%) and peracetic acid (1%) achieved a 4-log(10) titer reduction in 20 min. In contrast, K phage was sensitive to most biocides, being resistant only to phenol (2%) and chlorhexidine (1%).

Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets

The aim of this study was to develop a test system to evaluate the effectiveness of procedures for decontamination of respirators contaminated with viral droplets. MS2 coliphage was used as a surrogate for pathogenic viruses. A viral droplet test system was constructed, and the size distribution of viral droplets loaded directly onto respirators was characterized using an aerodynamic particle sizer. The sizes ranged from 0.5 to 15 mum, and the sizes of the majority of the droplets were the range from 0.74 to 3.5 mum. The results also showed that the droplet test system generated similar droplet concentrations (particle counts) at different respirator locations. The test system was validated by studying the relative efficiencies of decontamination of sodium hypochlorite (bleach) and UV irradiation with droplets containing MS2 virus on filtering facepiece respirators. It was hypothesized that more potent decontamination treatments would result in corresponding larger decreases in the number of viable viruses recovered from the respirators. Sodium hypochlorite doses of 2.75 to 5.50 mg/liter with a 10-min decontamination period resulted in approximately 3- to 4-log reductions in the level of MS2 coliphage. When higher sodium hypochlorite doses (> or =8.25 mg/liter) were used with the same contact time that was used for the dilute solutions containing 2.75 to 5.50 mg/liter, all MS2 was inactivated. For UV decontamination at a wavelength of 254 nm, an approximately 3-log reduction in the level of MS2 virus was achieved with dose of 4.32 J/cm(2) (3 h of contact time with a UV intensity of 0.4 mW/cm(2)), while with higher doses of UV irradiation (> or =7.20 J/cm(2); UV intensity, 0.4 mW/cm(2); contact times, > or =5 h), all MS2 was inactivated. These findings may lead to development of a standard method to test decontamination of respirators challenged by viral droplets.

Polyhexamethylene biguanide exposure leads to viral aggregation

AIMS

This study reports the activity of two biguanides against MS2 bacteriophage used as a surrogate virus for nonenveloped mammalian viruses and provides an explanation as to their apparent limited efficacy.

METHODS AND RESULTS

When tested in a standard suspension test, two polyhexamethylene biguanides (PHMB), VANTOCIL TG and COSMOCIL CQ, reduced the viability of MS2 by only 1-2 log(10) PFU ml(-1). Exposure time up to 30 min did not affect the activity of the biguanides, although both PHMB were shown to strongly interact with MS2 proteins.

CONCLUSIONS

Inactivation kinetics and change in virus hydrophobicity suggested that PHMB induces the formation of viral aggregates. This hypothesis was supported using dynamic light scattering that showed an increase in viral aggregates sizes (up to 500 nm) in a concentration-dependent manner.

SIGNIFICANCE AND IMPACT OF THE STUDY

It has been reported that viral aggregation is responsible for virus survival to the biocide exposure. Here, this might be the case, because the virucidal activity of the biguanides was modest and viral aggregation important. The formation of viral aggregates during virus exposure to PHMB was unlikely to overestimate the virucidal potential of the biguanides.

Development of a test system to apply virus-containing particles to filtering facepiece respirators for the evaluation of decontamination procedures

A chamber to apply aerosolized virus-containing particles to air-permeable substrates (coupons) was constructed and validated as part of a method to assess the virucidal efficacy of decontamination procedures for filtering facepiece respirators. Coliphage MS2 was used as a surrogate for pathogenic viruses for confirmation of the efficacy of the bioaerosol respirator test system. The distribution of virus applied onto and within the coupons was characterized, and the repeatability of applying a targeted virus load was examined. The average viable virus loaded onto 90 coupons over the course of 5 days was found to be 5.09 +/- 0.19 log(10) PFU/coupon (relative standard deviation, 4%). To determine the ability to differentiate the effectiveness of disinfecting procedures with different levels of performance, sodium hypochlorite and steam treatments were tested in experiments by varying the dose and time, respectively. The role of protective factors was assessed by aerosolizing the virus with various concentrations of the aerosol-generating medium. A sodium hypochlorite (bleach) concentration of 0.6% and steam treatments of 45 s and longer resulted in log reductions (>4 logs) which reached the detection limits for both levels of protective factors. Organic matter (ATCC medium 271) as a protective factor afforded some protection to the virus in the sodium hypochlorite experiments but was not a factor in the steam experiments. The evaluation of the bioaerosol respirator test system demonstrated a repeatable method for applying a targeted viral load onto respirator coupons and provided insight into the properties of aerosols that are of importance to the development of disinfection assays for air-permeable materials.

Improved inactivation of nonenveloped enteric viruses and their surrogates by a novel alcohol-based hand sanitizer

Norovirus is the leading cause of food-related illness in the United States, and contamination of ready-to-eat items by food handlers poses a high risk for disease. This study reports the in vitro (suspension test) and in vivo (fingerpad protocol) assessments of a new ethanol-based hand sanitizer containing a synergistic blend of polyquaternium polymer and organic acid, which is active against viruses of public health importance, including norovirus. When tested in suspension, the test product reduced the infectivity of the nonenveloped viruses human rotavirus (HRV), poliovirus type 1 (PV-1), and the human norovirus (HNV) surrogates feline calicivirus (FCV) F-9 and murine norovirus type 1 (MNV-1) by greater than 3 log(10) after a 30-s exposure. In contrast, a benchmark alcohol-based hand sanitizer reduced only HRV by greater than 3 log(10) and none of the additional viruses by greater than 1.2 log(10) after the same exposure. In fingerpad experiments, the test product produced a 2.48 log(10) reduction of MNV-1 after a 30-s exposure, whereas a 75% ethanol control produced a 0.91 log(10) reduction. Additionally, the test product reduced the infectivity titers of adenovirus type 5 (ADV-5) and HRV by > or =3.16 log(10) and > or =4.32 log(10), respectively, by the fingerpad assay within 15 s; and PV-1 was reduced by 2.98 log(10) in 30 s by the same method. Based on these results, we conclude that this new ethanol-based hand sanitizer is a promising option for reducing the transmission of enteric viruses, including norovirus, by food handlers and care providers.

Control of aerosol contaminants in indoor air: combining the particle concentration reduction with microbial inactivation

An indoor air purification technique, which combines unipolar ion emission and photocatalytic oxidation (promoted by a specially designed RCI cell), was investigated in two test chambers, 2.75 m3 and 24.3 m3, using nonbiological and biological challenge aerosols. The reduction in particle concentration was measured size selectively in real-time, and the Air Cleaning Factor and the Clean Air Delivery Rate (CADR) were determined. While testing with virions and bacteria, bioaerosol samples were collected and analyzed, and the microorganism survival rate was determined as a function of exposure time. We observed that the aerosol concentration decreased approximately 10 to approximately 100 times more rapidly when the purifier operated as compared to the natural decay. The data suggest that the tested portable unit operating in approximately 25 m3 non-ventilated room is capable to provide CADR-values more than twice as great than the conventional closed-loop HVAC system with a rating 8 filter. The particle removal occurred due to unipolar ion emission, while the inactivation of viable airborne microorganisms was associated with photocatalytic oxidation. Approximately 90% of initially viable MS2 viruses were inactivated resulting from 10 to 60 min exposure to the photocatalytic oxidation. Approximately 75% of viable B. subtilis spores were inactivated in 10 min, and about 90% or greater after 30 min. The biological and chemical mechanisms that led to the inactivation of stress-resistant airborne viruses and bacterial spores were reviewed.

The potential spread of infection caused by aerosol contamination of surfaces after flushing a domestic toilet

AIMS

To determine the level of aerosol formation and fallout within a toilet cubicle after flushing a toilet contaminated with indicator organisms at levels required to mimic pathogen shedding during infectious diarrhoea.

METHODS AND RESULTS

A semisolid agar carrier containing either Serratia marcesens or MS2 bacteriophage was used to contaminate the sidewalls and bowl water of a domestic toilet to mimic the effects of soiling after an episode of acute diarrhoea. Viable counts were used to compare the numbers of Serratia adhering to the porcelain surfaces and those present in the bowl water before and after flushing the toilet. Air sampling and settle plates were used to determine the presence of bacteria or virus-laden aerosols within the toilet cubicle. After seeding there was a high level of contamination on the porcelain surfaces both under the rim and on the sides of the bowl. After a single flush there was a reduction of 2.0-3.0 log cycles cm(-2) for surface attached organisms. The number of micro-organisms in the bowl water was reduced by 2.0-3.0 log cycles ml(-1) after the first flush and following a second flush, a further reduction of c. 2.0 log cycles ml(-1) was achieved. Micro-organisms in the air were at the highest level immediately after the first flush (mean values, 1370 CFU m(-3) for Serratia and 2420 PFU m(-3) for MS2 page). Sequential flushing resulted in further distribution of micro-organisms into the air although the numbers declined after each flush. Serratia adhering to the sidewalls, as well as free-floating organisms in the toilet water, were responsible for the formation of bacterial aerosols.

CONCLUSIONS

Although a single flush reduced the level of micro-organisms in the toilet bowl water when contaminated at concentrations reflecting pathogen shedding, large numbers of micro-organisms persisted on the toilet bowl surface and in the bowl water which were disseminated into the air by further flushes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Many individuals may be unaware of the risk of air-borne dissemination of microbes when flushing the toilet and the consequent surface contamination that may spread infection within the household, via direct surface-to-hand-to mouth contact. Some enteric viruses could persist in the air after toilet flushing and infection may be acquired after inhalation and swallowing.

Comparative efficacy of hand hygiene agents in the reduction of bacteria and viruses

Background

Health care-associated infections most commonly result from person-to-person transmission via the hands of health care workers.

Methods

We studied the efficacy of hand hygiene agents (n = 14) following 10-second applications to reduce the level of challenge organisms (Serratia marcescens and MS2 bacteriophage) from the hands of healthy volunteers using the ASTM-E-1174-94 test method.

Results

The highest log₁₀ reductions of S marcescens were achieved with agents containing chlorhexidine gluconate (CHG), triclosan, benzethonium chloride, and the controls, tap water alone and nonantimicrobial soap and water (episode 1 of hand hygiene, 1.60-2.01; episode 10, 1.60-3.63). Handwipes but not alcohol-based handrubs were significantly inferior from these agents after a single episode of hand hygiene, but both groups were significantly inferior after 10 episodes. After a single episode of hand hygiene, alcohol/silver iodide, CHG, triclosan, and benzethonium chloride were similar to the controls in reduction of MS2, but, in general, handwipes and alcohol-based handrubs showed significantly lower efficacy. After 10 episodes, only benzethonium chloride (1.33) performed as well as the controls (1.59-1.89) in the reduction of MS2.

Conclusions

Antimicrobial handwashing agents were the most efficacious in bacterial removal, whereas waterless agents showed variable efficacy. Alcohol-based handrubs compared with other products demonstrated better efficacy after a single episode of hand hygiene than after 10 episodes. Effective hand hygiene for high levels of viral contamination with a nonenveloped virus was best achieved by physical removal with a nonantimicrobial soap or tap water alone.

The effects of test variables on the efficacy of hand hygiene agents

BACKGROUND

Hand hygiene is essential to interrupting disease transmission in health care facilities. Multiple hand hygiene agents are currently available for use in the health care setting. To evaluate the utility of these agents, both the user acceptability and the efficacy need to be evaluated. Different hand hygiene test methodologies have been used to measure the efficacy of these agents, but efficacy results vary depending on variations to key parameters in these methodologies. The purpose of this study was to evaluate the effect of test variables on the efficacy of hand hygiene agents.

METHODS

Both a comprehensive literature review and original hand hygiene efficacy studies were undertaken. The literature review was conducted using a Medline search, and hand hygiene efficacy studies were conducted under the American Society for Testing and Materials (ASTM). E 1174 Standard Test Method for Evaluation of the Effectiveness of Health Care Personnel Handwash Formulation.

RESULTS

The literature review and our original data showed that the following variables affected the hand hygiene efficacy measurements: hand jewelry, experimental contamination versus normal flora, method of application of test organism, hand hygiene agent, concentration of active ingredient, volume of hand hygiene agent, duration of application of hand hygiene agent, method of application of hand hygiene agent, and study method (human challenge trial versus in vitro suspension test).

CONCLUSIONS

Although many methodological variables affect efficacy results, infection control professionals in their analysis of product information should always assess the results in light of the following key variables: concentration and type of active ingredient, duration of exposure to hand hygiene agent, volume of hand hygiene agent applied, test organism, and study method (ie, human challenge vs. in vitro suspension test).

Reduction of poliovirus 1, bacteriophages, Salmonella montevideo, and Escherichia coli O157:H7 on strawberries by physical and disinfectant washes

The efficacy levels of different physical and chemical washing treatments in the reduction of viral and bacterial pathogens from inoculated strawberries were evaluated. Escherichia coli O157:H7, Salmonella Montevideo, poliovirus 1, and the bacteriophages PRD1, phiX174, and MS2 were used as model and surrogate organisms. Chemicals readily available to producers and/or consumers were evaluated as antimicrobial additives for the production of washes. The gentle agitation of contaminated strawberries in water for 2 min led to reductions in microbial populations ranging from 41 to 79% and from 62 to 90% at water temperatures of 22 and 43 degrees C, respectively. Significant reductions (> 98%) in numbers of bacteria and viruses were obtained with sodium hypochlorite (50 to 300 ppm of free chlorine), Oxine or Carnebon (200 ppm of product generating "stabilized chlorine dioxide"), Tsunami (100 ppm of peroxyacetic acid), and Alcide (100 or 200 ppm of acidified sodium chlorite) washes. Overall, 200 ppm of acidified sodium chlorite produced the greatest reductions of microorganisms. Hydrogen peroxide (0.5%) was slightly less effective than free chlorine in a strawberry wash and caused slight fruit discoloration. Cetylpyridinium chloride (0.1%) was effective in the reduction of bacterial species, while trisodium phosphate (1%) was effective against viruses. The consumer-oriented produce wash Fit was very effective (> 99%) in reducing the numbers of bacteria but not in reducing the numbers of viruses. Another wash, Healthy Harvest, was significantly less effective than Fit in reducing bacterial pathogens but more effective for viruses. The performance of automatic dishwashing detergent was similar to that of Healthy Harvest and significantly better than that of liquid dishwashing detergent. Solutions containing table salt (2% NaCl) or vinegar (10%) reduced the numbers of bacteria by about 90%, whereas only the vinegar wash reduced the numbers of viruses significantly (ca. 95%).

Hygienic hand antiseptics: should they not have activity and label claims against viruses?

Enteric and respiratory viruses are among the most frequent causes of human infections, and hands play an important role in the spread of these and many other viral diseases. Regular and proper hand hygiene by caregivers and food handlers in particular is essential to decontaminate hands and potentially interrupt such spread. What would be considered a proper decontamination of hands? Handwashing with regular soap and water is often considered sufficient, but what of hygienic handwash and handrub antiseptic products? Are they more effective? The evidence suggests that some clearly are. Activity against bacteria may not reflect the ability of hygienic hand antiseptics to deal with viruses, especially those that are nonenveloped. In spite of the acknowledged importance of hands as vehicles for viruses, there is a lack of suitable regulatory mechanism for handwash or handrub products to make claims of efficacy against viruses. This is in contrast with the ability of general-purpose disinfectants to make antiviral claims, although transmission of viruses from surfaces other than those of reusable medical devices may play only a minor role in virus transmission. This review discusses the (1). recent information on the relative importance of viruses as human pathogens, particularly those causing enteric and respiratory infections; (2). the survival of relevant viruses on human hands in comparison with common gram-negative and gram-positive bacteria; (3). the potential of hands to transfer or receive such contamination on casual contact; (4). role of hands in the spread of viruses; (5). the potential of hygienic measures to eliminate viruses from contaminated hands; (6). relative merits of available protocols to assess the activity of hygienic hand antiseptics against viruses; and (7). factors considered crucial in any tests to assess the activity of hygienic hand antiseptics against viruses. In addition, this review proposes surrogate viruses in such testing and discusses issues for additional consideration by researchers, manufacturers, end-users, and regulators.

Elution, detection, and quantification of polio I, bacteriophages, Salmonella montevideo, and Escherichia coli O157:H7 from seeded strawberries and tomatoes

This study compared the effect of different physical and chemical treatments of strawberries and tomatoes to determine their ability to recover seeded viral and bacterial pathogens from produce surfaces. Solutions of salts, amino acids, complex media, and detergents were compared as eluants. Phosphate-buffered saline (PBS) containing 0.1% Tween 80 eluted the highest number of seeded microorganisms. Elution with this defined solution was then compared under different conditions of physical agitation. Rotary shaking for 20 min at 36 degrees C eluted higher numbers of viruses and bacteria than did low- or high-speed stomaching. Commercially available and laboratory prepared bacteriological differential media were compared for their ability to recover and distinguish eluted Salmonella Montevideo and Escherichia coli O157:H7 strains from seeded produce. The recovery of seeded bacterial pathogens was low when differential media containing selective ingredients were used (MacConkey sorbitol agar, XLD agar, MacConkey agar). Highest recoveries were obtained on a medium consisting of tryptic soy agar supplemented with sodium thiosulfate and ferric ammonium citrate compared with selective media that inhibited up to 50% of the growth of the eluted microorganisms.

The use of an automated assay to assess phage survival after a biocidal treatment

The coliphage K1-5 has been used in an automated assay to monitor the viricidal activity of various disinfectants. This indirect assay based on the spectrophotometric reading of the lysis of the host cell (Escherichia coli D837) produced encouraging results and was faster than the overlay counting method (previously studied) which relies on plaque formation. However, differences in sensitivity towards some disinfectants were observed between the two methods.

Effect of testing method on apparent activities of antiviral disinfectants and antiseptics

This study was designed to evaluate the independent effects of various test methods on the activities of antiviral chemical germicides. The activities of germicides against MS2 and phi 6 bacteriophages in a new porcine tissue carrier model were compared to those obtained by four other methods (suspension, glass carrier, tile carrier, and fingerpad tissue carrier tests). After a 1-min contact followed by neutralization (and elution off the carriers), the residual virus in the treated samples was quantified and the amount was compared with that in the saline controls. Antiviral activity was highly dependent on the test method for both viruses and was always greatest in suspension tests and lowest in tissue carrier tests. Results obtained for hydrophilic MS2 with the porcine tissue carrier were comparable to those from fingerpads, but lipophilic phi 6 was subject to spontaneous inactivation on human skin and proved unsuitable for fingerpad testing. These data indicate that the activities of germicides in tests with nonbiological substrates may overestimate antiviral antiseptic activity on skin surfaces. Products intended for use as antiviral antiseptics or hand-washing agents should be evaluated in a tissue carrier system. The porcine tissue carrier model provides a safe, inexpensive, accurate, and reproducible method for testing the activities of antiseptics.