Enhancement of bactericidal effects of sodium hypochlorite in chiller water with food additive grade calcium hydroxide

High-performance ratiometric fluorescent probe for rapid, visual and ultrasensitive monitoring/bioimaging of hypochlorite in real-life samples and living systems

Hypochlorite (ClO-) is a highly reactive chemical extensively used in households, public areas, and various industries due to its multiple functions of disinfection, bleaching, and sterilization. However, overuse of ClO- may contaminate the water, soil, air and food, leading to negative impacts on the environments, ecosystems and food safety. Meanwhile, excessive ClO- in human body can also cause severe damage to the immune system. Thus, the development of effective and precise detection tools for ClO- is of great significance to better understand its complicated roles in environments and biosystems. Herein, a new high-performance ratiometric fluorescent probe 2-amino-3-((10-propyl-10H-phenothiazin-3-yl)methylene)-amino)maleonitrile (PD) was developed for effective detection of ClO- in various bio/environmental and food samples. Probe PD exhibits highly-specific "ratiometric" fluorescent response to ClO- with rapid response (< 1 min), excellent sensitivity (detection limit, 47.4 nM), wide applicable pH range (4 -12), and excellent versatility in practical applications. In practical applications, PD enables the sensitive and quantitative detection of ClO- levels in various water samples, bio-fluids, dairy products, fruits and vegetables with high-precision (recoveries, 97.00 -104.40 %), as well as the successful application for visual tracking ClO- in fresh fruits and vegetables. Furthermore, test strips containing PD offer a visual and convenient tool for quick identification of ClO- in aqueous media by the naked eye. Importantly, the good biocompatibility of PD enables its practical applications in real-time bioimaging of endogenous/exogenous ClO- levels in living cells, bacteria, onion cells, Arabidopsis, as well as zebrafish. This study provided an effective method for visual monitoring and bioimaging of ClO- levels in various environments, foods and living biosystems.

Susceptibility of Campylobacter jejuni to Stressors in Agrifood Systems and Induction of a Viable-but-Nonculturable State

Many bacteria can become viable but nonculturable (VBNC) in response to stressors commonly identified in agrifood systems. Campylobacter is able to enter the VBNC state to evade unfavorable environmental conditions, but how food processing can induce Campylobacter jejuni to enter this state and the potential role of foods in inducing the VBNC state in C. jejuni remains largely unknown. In this study, the culturability and viability of C. jejuni cells were investigated under chlorine treatment (25 ppm), aerobic stress (atmospheric condition), and low-temperature (4°C) conditions that mimicked food processing. In addition, the behaviors of C. jejuni cells in ultrahigh-temperature (UHT) and pasteurized milk were also monitored during refrigerated storage. The numbers of viable and culturable C. jejuni cells in both the pure bacterial culture and food matrices were separately determined by propidium monoazide (PMA)-quantitative PCR (qPCR) and plating assay. The C. jejuni cells lost their culturability but partially retained their viability (1% to 10%) once mixed with chlorine. In comparison, ~10% of C. jejuni cells were induced to enter the VBNC state after 24 h and 20 days under aerobic and low-temperature conditions, respectively. The viability of the C. jejuni cells remained stable during the induction process in UHT (>10%) and pasteurized (>10%) milk. The number of culturable C. jejuni cells decreased quickly in pasteurized milk, but culturable cells could still be detected in the end (day 21). In contrast, the number of culturable C. jejuni cells slowly decreased, and they became undetectable after >42 days in UHT milk. The C. jejuni cells responded differently to various stress conditions and survived in high numbers in the VBNC state in agrifood systems. IMPORTANCE The VBNC state of pathogens can pose risks to food safety and public health because the pathogens cannot be detected using conventional microbiological culture-based methods but can resuscitate under favorable conditions to develop virulence. As a leading cause of human gastroenteritis worldwide, C. jejuni can enter the VBNC state to survive in the environment and food-processing chain with high prevalence. In this study, the effect of food-processing conditions and food products on the development of VBNC state in C. jejuni was investigated, providing a better understanding of the interaction between C. jejuni and the agroecosystem. The knowledge elicited from this study can aid in developing novel intervention strategies to reduce the food safety risks associated with this microbe.

Establishment and utilization of an evaluation system for virucidal activity of disinfectants against a coronavirus with apparent applicability to SARS-CoV-2

Decontamination of pathogens on surfaces of substances is very important for controlling infectious diseases. In the present experiments, we tested various disinfectants in aqueous phase as well as on plastic surface carrying a viral inoculum, through dropping and wiping decontamination techniques, comparatively, so as to evaluate virucidal efficacies of those disinfectants toward an avian coronavirus (infectious bronchitis virus: IBV). We regard this evaluation system applicable to SARS-CoV-2. The disinfectants evaluated were 0.17% food additive glade calcium hydroxide (FdCa(OH)2) solution, sodium hypochlorite at 500 or 1,000 ppm of total chlorine (NaClO-500 or NaClO-1,000, respectively), NaClO at 500 ppm of total chlorine in 0.17% FdCa(OH)2 (Mix-500) and quaternary ammonium compound (QAC) diluted 500-fold in water (QAC-500). In the suspension test, all solutions inactivated IBV inoculum that contained 5% fetal bovine serum (FBS) under detectable level within 30 sec. In the carrier test, all solutions, except NaClO-500, could inactivate IBV with 0.5% FBS on a carrier to undetectable level in the wiping-sheets and wiped-carriers. We thus conclude that suspension and carrier tests should be introduced to evaluate disinfectants for the field usage, and that this evaluation system is important and workable for resultful selection of the tested disinfectants against avian coronavirus and SARS-CoV-2 on surfaces, particularly on plastic fomite.

Impact of gas micro-nano-bubbles on the efficacy of commonly used antimicrobials in the food industry

AIM

To study the impact of incorporating micro-nano-bubbles (MNBs) in commonly used food antimicrobials (AMs) against Escherichia coli O157:H7 (EC) and Listeria monocytogenes (LM).

METHODS AND RESULTS

Air, carbon dioxide (CO₂ ) and nitrogen (N₂ ) were used to incorporate MNBs in city water. AM solution (with or without MNBs) of 9 ml was individually taken into sterile test tubes and mixed with 1 ml of inoculum grown in brain heart infusion (BHI) broth to get the net AM concentrations of 28·4 ppm peracetic acid (PAA), 200 ppm chlorine (Cl₂ ), 5·4% citric acid (CA) and 4·5% lactic acid (LA). After treatment time of 1·5 and 3·0 min, 1 ml of sample was neutralized using Dey-Engley neutralizing broth and plated on BHI agar. For EC, Cl₂ -CO₂ solutions resulted in significantly greater log reductions (5·2 logs) compared to that of Cl₂ solutions without MNBs (3·8 logs). For LM, PAA-CO₂ solutions resulted in significantly greater log reductions (4·4 logs) compared to that of PAA solutions without MNBs (1·7 logs).

CONCLUSIONS

This study demonstrated that the efficacy of Cl₂ and PAA AM solutions could be increased by incorporating CO₂ -MNBs against EC and LM in microbiological growth medium.

SIGNIFICANCE AND IMPACT OF THE STUDY

Incorporation of CO₂ -MNBs in AM solutions could increase the efficacy of AMs against pathogens on/in food matrices, which should be tested in future research.

Unravelling the effects of the food components ascorbic acid and capsaicin as a novel anti-biofilm agent against Escherichia coli

This study aimed to evaluate the influence of capsaicin and ascorbic acid on the physiology of biofilm formation and dispersion. The influence of the E. coli ATCC 25922 biofilm and five E. coli isolates were observed in the presence of sodium hypochlorite 2.5 mM and subinhibitory concentrations of capsaicin (7 mM) and ascorbic acid (100 mM). The cells counts were performed through standard plaque count and the architecture visualized by confocal microscopy. The proteins, carbohydrates, and DNA present in the biofilm matrix were also quantified. There was a reduction in adhered cells in the presence of capsaicin (7 mM) and ascorbic acid (100 mM) in the biofilm formation kinetics, however, regarding the dispersion, only capsaicin altered the biofilm, data confirmed by confocal fluorescence microscopy (p < 0.05). It was noted that the matrix composition is dynamic and may be affected by changes in growth conditions such as the presence of antimicrobial substances.

From one species to another: A review on the interaction between chemistry and microbiology in relation to cleaning in the built environment

Since the advent of soap, personal hygiene practices have revolved around removal, sterilization, and disinfection-both of visible soil and microscopic organisms-for a myriad of cultural, aesthetic, or health-related reasons. Cleaning methods and products vary widely in their recommended use, effectiveness, risk to users or building occupants, environmental sustainability, and ecological impact. Advancements in science and technology have facilitated in-depth analyses of the indoor microbiome, and studies in this field suggest that the traditional "scorched-earth cleaning" mentality-that surfaces must be completely sterilized and prevent microbial establishment-may contribute to long-term human health consequences. Moreover, the materials, products, activities, and microbial communities indoors all contribute to, or remove, chemical species to the indoor environment. This review examines the effects of cleaning with respect to the interaction of chemistry, indoor microbiology, and human health.

Virucidal Efficacy of a Quaternary Ammonium Compound with Food Additive-Grade Calcium Hydroxide Toward Avian Influenza Virus and Newcastle Disease Virus on Abiotic Carriers

The virucidal efficacies of a 0.2% food additive-grade calcium hydroxide [FdCa(OH)₂] solution, a quaternary ammonium compound (QAC) diluted at 1:500 (QACx500), and their mixture [Mix500; FdCa(OH)₂ powder added at a final concentration of 0.2% to QACx500] were investigated as fomites for avian influenza virus (AIV) and Newcastle disease virus (NDV) on abiotic carriers (steel, rubber, and plastic) at two different temperatures (room temperature [RT; 25 ± 2 C] and 2 C). These viruses were seeded on coupons (5 cm×5 cm) of rubber, steel, or plastic with 5% fetal bovine serum. After complete drying, the coupons were covered with the test solutions at RT or 2 C. After fixed incubation periods, viruses were recovered from the coupons and titrated. At RT, Mix500 required a short time (3 min) to inactivate AIV and NDV to effective levels (≥3 log virus reduction) on rubber, steel, and plastic carriers compared with QAC or FdCa(OH)_2. At low temperature, QACx500 inactivated AIV on steel and plastic carriers to effective levels within 60 min, whereas Mix500 did so within 10 min. QACx500 and FdCa(OH)₂ solutions could inactivate NDV on steel and plastic carriers within 20 and 10 min, respectively, and Mix500 could do so within 3 min. Viruses on the carriers required longer incubation periods for inactivation at 2 C than at 25 C. These results demonstrate desirable synergistic virucidal effects of Mix500 for important poultry viruses on abiotic carriers, while indicating high applicability within poultry farming.

Bactericidal Efficacy of Food Additive-Grade Calcium Hydroxide Against Salmonella Infantis on Eggshells

The bactericidal efficacy of food additive-grade calcium hydroxide [FdCa(OH)₂] was evaluated for inactivation of Salmonella Infantis and Salmonella Enteritidis in liquid and Salmonella Infantis on contaminated eggshells. The activity of FdCa(OH)₂ was also compared with that of sodium hypochlorite (NaOCl) containing 150 ppm chlorine (150 ppm NaOCl). FdCa(OH)₂ solutions (0.1% and 0.2%) in the presence or absence of organic materials (5% calf serum [CS]) at pH 12.6 were used to inactivate Salmonella Infantis and Salmonella Enteritidis in a reaction tube or on eggshells artificially contaminated with Salmonella Infantis. Both 0.1% and 0.2% FdCa(OH)₂ were capable of inactivating Salmonella Infantis and Salmonella Enteritidis in liquid at >3 log₁₀ colony-forming units (CFU)/ml within 3 and 1 min of contact time, respectively, even in the presence of 5% CS. Additionally, 0.1% and 0.2% FdCa(OH)₂ reduced bacterial levels on contaminated eggshells to >3 log₁₀ CFU/ml, within 3 and 1 min, respectively, in the presence of 5% CS. Without CS, 0.1% and 0.2% FdCa(OH)₂ could reduce bacteria on eggshells to >3 log₁₀ CFU/ml within 1 min and 30 sec, respectively. In contrast, 150 ppm NaOCl solution could not inactivate bacteria on eggshells down to >3 log₁₀ CFU/ml within 3 min contact time, either with or without CS, and no bacterial reduction was observed in redistilled water. The findings of the present study indicate that FdCa(OH)₂ solution has high efficacy against foodborne bacteria and may be a good candidate for enhancement of biosecurity at farms and egg processing plants.

Bactericidal and virucidal efficacies of food additive grade calcium hydroxide under various concentrations, organic material conditions, exposure duration, and its stability

Aim:

This study aimed to evaluate the bactericidal and virucidal activity of food additive grade calcium hydroxide (FdCa(OH)₂) under various concentrations, organic material conditions, and exposure duration including its stability.

Materials and Methods:

The FdCa(OH)₂ powder as well as the 0.17% and 3% solutions were evaluated for bacteria and virus inactivating efficacies against Salmonella infantis (SI), Escherichia coli, Newcastle disease virus (NDV), and avian influenza virus (AIV), in the absence or presence of organic materials. In addition, the stability of FdCa(OH)₂, was also examined using wet-dry conditions and under sunlight.

Results:

The FdCa(OH)₂ powder could inactivate both NDV and AIV in the absence and presence of organic materials within a 3 min exposure period. The bactericidal efficacy using solution form revealed that 0.17% and 3% of FdCa(OH)₂ could inactivate SI in the absence and presence of organic materials within 3 min of exposure. However, 3% of FdCa(OH)₂ inactivated E. coli both with and without organic materials within 3min, while 0.17% required 5 min to be efficacious. The virucidal efficacy also showed that 0.17% FdCa(OH)₂ could inactivate NDV in the absence and presence of organic materials within 10 min and 30 min, respectively. However, AIV inactivation was achieved within 30 sec under all conditions. In addition, under wet and dry conditions, FdCa(OH)₂ powder demonstrated high efficacy when re-suspended at least 16 times for NDV and 7 times for AIV. Simultaneously, the FdCa(OH)₂ powder retained its efficacy under the sunlight during up to 4 months for NDV and at least 6 months for AIV.

Conclusion:

The present study indicates that FdCa(OH)₂ powder and solutions could inactivate SI, E. coli, NDV, and AIV while retaining good stability under challenging environmental conditions. Finally, the FdCa(OH)₂ is safe for consumers because it is of food additive grade and can be useful as an alternative disinfectant, especially for biosecurity enhancement on and around poultry farms.

Current Status of Campylobacter Food Poisoning in Japan

According to the annual food poisoning statistics compiled by the Ministry of Health, Labour and Welfare (MHLW) in Japan, Campylobacter replaced Salmonella and Vibrio parahaemolyticus as the leading bacterium responsible for food poisoning in 2003. Although in 2006 the number of cases of Campylobacter food poisoning was 3,439 on the basis of the MHLW statistics, it was estimated to be 1,545,363 on the basis of active surveillance, suggesting that passive surveillance yields an incidence about 450 times lower than that revealed by active surveillance. Epidemiological investigations of Campylobacter food poisoning in Japan have shown that chicken meat and its products are the most important sources of infection, as is the case in other industrialized nations. Over the last two decades, the consumption of fresh raw chicken meat and liver has been increasing in Japan. Although the MHLW recommends that chicken meat should only be eaten after thorough cooking, it is likely to account for much of the increased incidence of human campylobacteriosis. In response to this situation, the Expert Committee on Microorganisms/Viruses, Food Safety Commission of Japan, Cabinet Office, Government of Japan (FSCJ) has revised the previous risk profile of C. jejuni/coli in chicken meat by adding new findings for 2018. Moreover, the MHLW revised the Poultry Slaughtering Business Control and Poultry Meat Inspection Act in 2014 aiming at stepwise introduction of the Hazard Analysis Critical Control Point (HACCP) system into poultry processing plants. Subsequently, the Japanese government amended the Food Sanitation Act in 2018, requiring all food business operators to implement hygiene control based on HACCP principles as a general rule. This paper reviews the current status of Campylobacter food poisoning due to consumption of chicken meat in Japan and extracts the issues underlying each step of the food supply chain in order to examine the implementation of effective measures for risk management.

Current Status of Campylobacter Food Poisoning in Japan

According to the annual food poisoning statistics compiled by the Ministry of Health, Labour and Welfare (MHLW) in Japan, Campylobacter replaced Salmonella and Vibrio parahaemolyticus as the leading bacterium responsible for food poisoning in 2003. Although in 2006 the number of cases of Campylobacter food poisoning was 3,439 on the basis of the MHLW statistics, it was estimated to be 1,545,363 on the basis of active surveillance, suggesting that passive surveillance yields an incidence about 450 times lower than that revealed by active surveillance. Epidemiological investigations of Campylobacter food poisoning in Japan have shown that chicken meat and its products are the most important sources of infection, as is the case in other industrialized nations. Over the last two decades, the consumption of fresh raw chicken meat and liver has been increasing in Japan. Although the MHLW recommends that chicken meat should only be eaten after thorough cooking, it is likely to account for much of the increased incidence of human campylobacteriosis. In response to this situation, the Expert Committee on Microorganisms/Viruses, Food Safety Commission of Japan, Cabinet Office, Government of Japan (FSCJ) has revised the previous risk profile of C. jejuni/coli in chicken meat by adding new findings for 2018. Moreover, the MHLW revised the Poultry Slaughtering Business Control and Poultry Meat Inspection Act in 2014 aiming at stepwise introduction of the Hazard Analysis Critical Control Point (HACCP) system into poultry processing plants. Subsequently, the Japanese government amended the Food Sanitation Act in 2018, requiring all food business operators to implement hygiene control based on HACCP principles as a general rule. This paper reviews the current status of Campylobacter food poisoning due to consumption of chicken meat in Japan and extracts the issues underlying each step of the food supply chain in order to examine the implementation of effective measures for risk management.

Bactericidal efficacies of food additive grade calcium hydroxide toward Legionella pneumophila

Food additive grade calcium hydroxide (FdCa(OH)₂) in the solution of 0.17% was evaluated for its bactericidal efficacies toward Legionella pneumophila with or without sodium hypochlorite (NaOCl) at a concentration of 200 ppm total residual chlorine, at room temperature (RT) (25°C ± 2°C) and 42°C, either with or without 5% fetal bovine serum (FBS). Besides, FdCa(OH)₂ in different concentration solutions were prepared in field water samples (hot spring and bath tab water) and evaluated for their bactericidal efficacies at 42°C. FdCa(OH)₂ (0.17%) inactivated the L. pneumophila to the undetectable level (<2.6 log CFU/ml) within 5 min and 3 min, respectively, at RT and 42°C, with 5% FBS. At RT and 42°C, NaOCl inactivated L. pneumophila to the undetectable level within 5 min, without 5% FBS, but with 5% FBS, it could only inactivate this bacterium effectively (≥3 log reductions). Conversely, at RT and 42°C, the mixture of 0.17% FdCa(OH)₂ and 200 ppm NaOCl could inactivate L. pneumophila to the undetectable level, respectively, within 3 min and 1 min, even with 5% FBS, and it was elucidated that FdCa(OH)₂ has a synergistic bactericidal effect together with NaOCl. FdCa(OH)₂ 0.05% solution prepared in hot spring water could inactivate L. pneumophila to the undetectable within 3 min at 42°C. So, FdCa(OH)₂ alone could show nice bactericidal efficacy at 42°C, even with 5% FBS, as well as in field water samples.

Inhibitory effect of grapefruit seed extract (GSE) on avian pathogens

The inhibitory activities of grapefruit seed extract (GSE) on avian influenza virus (AIV), Newcastle disease virus (NDV), infectious bursal disease virus (IBDV), Salmonella Infantis (SI) and Escherichia coli (EC) were evaluated. Original GSE contained 0.24% benzalkonium chloride (BZC), however, 0.0025% BZC solution could not inactivate bacteria. The activity of diluted GSE (×100, ×500 and ×1,000 with redistilled water) against selected viruses and bacteria was evaluated in this study. The GSE solutions were incubated with the pathogens over a period of time after which the remaining viruses were titrated and the bacterial colonies were counted. In the presence of organic material-5% fetal bovine serum (FBS), the test solutions were sprayed at 1 cm and 30 cm distances to test the efficacy of GSE in a spray form. Furthermore, the efficacy of GSE against bacteria on clothes was tested using non-woven cloth. GSE×100 reduced the viral titer of both AIV and NDV even in 5% FBS condition. IBDV showed high resistance to GSE. GSE×1,000 inactivated both SI and EC within 5 sec, even in the presence of 5% FBS. The disinfectant was able to maintain its efficacy in the spray form at 30 cm distance. GSE was also effective against SI and EC inoculated on fabric. GSE is a potential novel disinfectant against viruses and bacteria, effective even within a short contact time.

Bactericidal efficacy of a quaternary ammonium compound with food additive grade calcium hydroxide toward Salmonella Infantis and Escherichia coli on abiotic carriers

The bactericidal efficacies of 0.2% food additive grade calcium hydroxide (FdCa(OH)2) solution, a quaternary ammonium compound (QAC) diluted at 1:500 (QACx500) and their mixture-Mix500 (FdCa(OH)2 powder added at final concentration 0.2% to QACx500)-were investigated at two different temperatures (room temperature (RT) (25 ± 2°C) and 2°C), using varying contact time, with or without presence of organic materials (5% fetal bovine serum: FBS), either in suspension or on abiotic carrier (steel, rubber and plastic). In the suspension test, QACx500 could inactivate Salmonella Infantis at effective level (≥3 log reductions), within 30 sec and 5 sec, respectively, with or without 5% FBS at RT; however, at 2°C it required 30 min and 1 min, respectively. Mix500 revealed the same efficacy as QACx500 at RT, but, at 2°C it required 1 min and 30 sec, respectively with or without FBS. Whereas, 0.2% FdCa(OH)2 solution alone could inactivate S. Infantis within 1 min and 3 min, respectively at RT and 2°C, even with 5% FBS. In the carrier test, single disinfectant required bit more (3 or 5 min) contact time to reduce bacterial load (S. Infantis or Escherichia coli) down to the effective level on rubber surface than that on steel and plastic surface. However, Mix500 could inactivate both bacteria on carrier surfaces within 1 min, even at 2°C. Thus, synergistic effects were observed in the suspension test and the carrier test at both temperatures toward both bacteria.

Virucidal activity of a quaternary ammonium compound associated with calcium hydroxide on avian influenza virus, Newcastle disease virus and infectious bursal disease virus

A quaternary ammonium compound (QAC) was evaluated for its virucidal efficacies with food additive grade calcium hydroxide (FdCa(OH)₂). When the QAC was diluted 1:500 (QACx500) with redistilled water (dW₂), it inactivated avian influenza virus (AIV) within 30 sec at 25°C, while at 2°C, it required 1 hr for inactivation. When FdCa(OH)₂ powder was added to QACx500 at a final concentration of 0.17%, the mixture, namely Mix500, inactivated AIV within 3 min at 2°C. After contamination with 1% fetal bovine serum (FBS), Mix500 inactivated AIV within 2 hr at 2°C, but QACx500 did not. These results indicate synergistic effects of the QAC and FdCa(OH)₂ solutions on virucidal activity.

Virucidal efficacy of food additive grade calcium hydroxide against surrogate of human norovirus

An alkaline agent, namely, food additive grade calcium hydroxide (FdCa(OH)₂) in the solution, powder and suspension forms was evaluated as a virucidal agent, using a murine norovirus (MNV) as the surrogate for human norovirus. The main constituent of FdCa(OH)₂ is Ca(OH)₂, which has pH 13 in 0.17% solution. The results showed that 0.17% FdCa(OH)₂ solution could inactivate MNV within 30s even in the presence of organic materials (5% fetal bovine serum (FBS)). In a contaminated surface experiment, MNV with 5% FBS was inoculated on rayon sheets, and the result showed FdCa(OH)₂ solution could markedly reduce virus titer within 1min. When mouse feces were spiked with MNV and FdCa(OH)₂ powder as 10% and 20% w/w was added to the feces, these concentrations could inactivate the virus within 30min and 15min, respectively. Whereas, FdCa(OH)₂ suspension at 2.5% and 5% could inactivate the virus within 30min and at 1% within 45min. These and additional results obtained here indicate that FdCa(OH)₂ is an effective virucidal agent against MNV, and can serve as a useful alternative disinfectant for inactivation and prevention of human norovirus in house and hospital.