Common Disinfectants Research Articles

Integrative assessment of mixture toxicity of household chemicals using the toxic unit approach and mode of action.

Household chemicals used daily are often combined, leading to inhalation exposure to mixtures. However, methods for assessing their toxic effects are limited. This study proposes an in vitro assay strategy for evaluating household chemical mixtures using benzalkonium chloride (BKC) and didecyldimethylammonium chloride (DDAC), a common disinfectant. Our approach utilizes the mode of action (MOA) of chemicals by applying toxicity units (TU) to assess the key events related to lung disease, such as reactive oxygen species (ROS) production and cell death. The TU (EC50) values for BKC and DDAC were 3.97 µg/mL and 1.89 µg/mL, respectively, from cytotoxicity results. The TU value of the mixture (5:5 ratio of BKC to DDAC) was calculated as 2.56 µg/mL. Using the OpenMRA platform, the TU values were predicted as 2.37 µg/mL with the concentration addition (CA) model and 11.26 µg/mL with the independent action (IA) model, indicating that the mixture effects were additive and closer to that predicted using the CA model. Both BKC and DDAC induced apoptosis and ROS production in human epithelial cells in a dose-dependent manner, suggesting similar modes of action in promoting cell death. Our results suggested that BKC and DDAC exhibited additive toxicity when combined. Our results demonstrate the utility of the TU-based approach, which combines cytotoxicity, ROS induction, and apoptosis measurements to evaluate mixture toxicity. This approach may be beneficial for assessing early key events relevant to lung diseases and offers a practical strategy for evaluating the inhalation toxicity of household chemical mixtures.

Research Note: Evaluation of selected chlorhexidine salts/product and/or cetylpyridinium chloride as potential pre-slaughter crop disinfection agents using an in vitro assay simulating crop contents.

Salmonellae remain a prominent issue for poultry products regarding food safety. A predominant source of broiler carcass contamination at processing is from crop rupturing and subsequent contamination of the carcass during evisceration. Chlorhexidine (CHX) salts are commonly used in dental products for their antimicrobial capabilities. We evaluated CHX gluconate and CHX digluconate alongside cetylpyridinium chloride (CPC), a common disinfectant to test their antimicrobial properties and any possible synergistic effects between the two. These effects were evaluated using an in vitro assay simulating the crop contents of poultry. CHX digluconate, CHX gluconate, commercially available CHX gluconate and CPC were tested at 0.1 %, 0.2 %, 1 %, 1.8 %, and 2 %. Borosilicate tubes containing 2.5 g of chicken mash feed, pasteurized to remove unwanted bacteria, were used for assay. Pasteurized feed within tubes were suspended in CHX, CPC, CHX + CPC, or saline vehicle alone (control). Tubes were then inoculated with Salmonella Typhimurium (ST) (except non-inoculated controls) and allowed to statically incubate for 2 h at 37°C. Tube contents were then serially diluted for CFU enumeration. CHX and CPC, when used individually, demonstrated meaningful and significant (p < 0.05) reduction in ST recovery, especially at higher concentrations (1-2 %). Combinations of CHX + CPC at lower concentrations (0.1-0.2 %) were shown to have major antimicrobial effects and either reduced (p < 0.05) or eliminated ST recovery in this assay. These lower concentrations might be used for antemortem disinfection of crop contents prior to live haul at processing in future studies. In vivo efficacy may be affected by limitations on voluntary ingestion of drinking water during pre-slaughter feed withdrawal and was not evaluated in these studies.

Efficacy of copper-impregnated antimicrobial surfaces against Clostridioides difficile spores.

Clostridioides difficile (C. difficile) is one of the most common causes of healthcare-associated infections (HAIs). Elimination of C. difficile spores is difficult as they are resistant to common hospital-grade disinfectants. Copper-impregnated surfaces provide continuous reduction of multiple pathogens, potentially lowering the risk of infections. This manuscript aims to evaluate the efficacy of copper-impregnated surfaces on C. difficile spores. Control (no copper) coupons and copper coupons containing 20% copper-oxide were inoculated with C. difficile spore loads ranging from 105 to 107 spores, with or without 5% fetal bovine serum soil load. After 4 hours of contact time, the C. difficile spores were recovered, plated on C. difficile growth media, and colony forming units were counted. The efficacy of copper (log10 kill) was estimated using a Bayesian latent variables model. After 4 hours, unsoiled copper bedrail and copper table coupons at mean spore inoculation resulted in a 97.3% and 96.8% reduction in spore count (1.57 and 1.50 log10 kill, respectively). That of soiled bedrail and table coupons showed a 91.8% and 91.7% reduction (1.10 and 1.10 log10 kill, respectively). Copper coupons can substantially reduce C. difficile spores after 4 hours, but results vary depending on the initial spore concentration and presence or absence of organic material. Higher initial spore loads or excess organic material may prevent spores from contact with copper surfaces, thus decreasing kill efficacy. Continuous sporicidal effect of copper-impregnated surfaces may decrease spore burden and help prevent transmission of spores.

Development of disinfectant tolerance in Klebsiella pneumoniae

Disinfectants are a critical infection control measure that are relied upon globally in a range of settings including healthcare, food production, and domestic environments. However, bacteria have been shown to survive disinfectant treatments when harboured in dry surface biofilms or when disinfectants are used ineffectively. This provides an opportunity for organisms to develop low-level tolerance to various disinfectants. The capability of bacteria to develop adaptations to non-antibiotic antimicrobial agents is often overlooked. This study investigates the ability of Klebsiella pneumoniae NDM-1 strain NCTC 13443 to adapt to a range of common chemical disinfectants (benzalkonium chloride, didecyldimethylammonium chloride, polyhexamethylene biguanide, chlorocresol and bronopol) via serial passage exposure method. After long-term adaptation K. pneumoniae developed tolerance to all tested disinfectants, exhibiting a minimum inhibitory concentration increase of between 30-413% compared to the untreated parent samples. Characterisation of disinfectant cross-tolerance showed that while cross-tolerance can occur, most adapted samples became more susceptible to the second disinfectant treatment, likely because of the fitness cost of adaptation. Observed cross-tolerance/increased susceptibility was not always reciprocated between disinfectant-tolerant samples, indicating that the order of disinfectant exposure is important during tolerance development. This has significant implications for disinfectant cleaning routines, and is likely due to variations in the underpinning tolerance mechanisms, even when the disinfectants display similar mechanisms of action. This study reports the capability and readiness of clinically relevant K. pneumoniae to adapt to common disinfectants that are relied upon every day across the world, delivering much-needed insights into an often-overlooked aspect of antimicrobial resistance.

A New Approach to Evaluate the Bactericidal Activity of Different Antiseptic Ophthalmic Preparations Used as Surgical Prophylaxis.

Background: A survey conducted by the European Observatory on Cataract Surgery showed high heterogeneity in the use of antiseptics both preoperatively and in the operating room, highlighting the absence of a global consensus regarding ocular infection prophylaxis in cataract surgery. Methods: The antibacterial activity of seven antiseptic ophthalmic formulations (AOFs) registered as medical devices and the two most common disinfectants were evaluated in vitro against five bacterial species. The viability of bacterial strains after exposure to the antiseptic was evaluated with different techniques: the in vitro Minimum Inhibitory Concentration and the subsequent Minimum Bactericidal Concentration, performed on liquid and solid culture medium. Furthermore, a real-time assessment of bacterial viability was conducted using double staining for live/dead bacterial cells by fluorimetric assay. This evaluation was performed on both the time-killing curve and the tear dilution effect test. Results: We observed a high variability across the different AOFs in terms of inhibitory/bactericidal concentration and timing on Gram-positive and Gram-negative bacterial classes. The results indicated that among the tested AOFs, Visuprime, Iodim, and Oftasteril were the most rapid and effective for ocular surface disinfection against the tested bacterial species. Conclusions: The obtained results can support the clinician's choice of the most suitable AOF for the prevention and treatment of ophthalmic infections associated with surgery.

Variable sensitivity of clinical Candida auris strains to Biocides: implications for infection control in Healthcare Settings

PurposeCandida auris, a multidrug-resistant yeast, poses significant challenges in healthcare settings due to its ability to form biofilms and resistance to common disinfectants. Understanding its susceptibility to biocides used in hospital disinfection practices is crucial for infection control. We investigated the biocide sensitivity of eight clinical C. auris strains from different patients and one reference strain (CDC B11903) using the biocide activity tests.MethodsSpecies identification was confirmed through MALDI-TOF MS, while clade differentiation and phylogenetic classification were determined via whole-genome sequencing. Biofilm formation was assessed using the MTT assay. Antifungal susceptibilities were tested according to CLSI standards. The effectiveness of biocides, including chlorine, chlorhexidine, and benzalkonium chloride, was evaluated through broth microdilution following CLSI standards and quantitative suspension and carrier tests, following EN standards.ResultsAll clinical strains were identified as clade 1, and the reference strain as clade 4, with all exhibiting biofilm formation. Clade 1 strains showed resistance to fluconazole, with MIC values ranging from 8 to 32 µg/ml, while being susceptible to other antifungals. Broth microdilution MIC assays for biocides demonstrated that all strains exhibited resistance to benzalkonium chloride. Chlorine and chlorhexidine showed variable efficacy, dependent on concentration and environmental cleanliness. Alcohol-based hand sanitizers demonstrated effectiveness against C. auris from the first minute of application.ConclusionThe study highlights the variable susceptibility of C.auris to different biocides, underscoring the challenge in eradicating this pathogen from healthcare environments. Our findings advocate for the careful selection of disinfectants in hospital settings, emphasizing the need for high-concentration chlorine and chlorhexidine solutions to combat C. auris, even in especially clean environments.

Inhibition of bacteria adhesion and biofilm formation using a precisely structured nitric oxide-releasing coating with repeatedly renewing antimicrobial and antifouling ability

Bacterial adhesion and colonization usually causes the formation of biofilm that cannot be easily eradicated by common antibiotics and disinfectants. Surface covalent immobilization of nitric oxide (NO)-releasing polymer is an effective surface modification strategy to combat the threat from bacteria. Although surface covalent strategy avoided the leaching of toxic NO donors, the existence of hydrophobic NO donors on topsurface could inevitably accelerate the microorganism adhesion and accumulation, and the NO-releasing period of time was still very limited. In this work, we prepared an antimicrobial and antibiofilm surface via tethering a precision-structured NO-releasing copolymer brush to an organic-inorganic hybrid hard coating (> 5H pencil hardness) on one end. The precision-structured diblock copolymer brush was composed of a surface antifouling block and a subsurface antimicrobial block of NO-releasing units. A typical effect of “kill two birds with one stone” was observed, the NO releasing subsurface segment within a polymeric matrix prolongs NO release while also preventing surface fouling caused by hydrophobic NO donors on top surface. The impacts of polymer architecture on bioactivity was detailed investigated, and the block copolymer brush exhibited the optimal inhibitory effects against bacteria colonization and biofilm formation. The developed bioactive diblock copolymer brush was grafted from a hard hybrid persistent coating that embeds considerable initiation sites for surface modification. Thanks to the presence of initiator throughout the hybrid network, the initiation layer could initiate polymerization repeatedly after the polymer brushes are worn off at high pressure. Thus, the coating exhibited repeatedly renewing antimicrobial and antifouling ability after multiple abrasion cycles. This work not only developed a novel strategy for regulating NO releasing via modulating the polymer architecture, but provided a feasible route for obtaining a robust initiator layer for synthesizing polymer brush for antimicrobial and antifouling applications.

Toxicity of Common Acaricides, Disinfectants, and Natural Compounds against Eggs of Rhipicephalus annulatus.

Ticks pose a significant threat due to their ability to lay thousands of eggs, which can persist in the environment for extended periods. While the impact of various compounds on adult and larval ticks has been studied, research on their efficacy against tick eggs is limited. This study evaluated the ovicidal activity of commercial acaricides, disinfectants, and natural products against Rhipicephalus annulatus eggs using the egg hatch assay (EHA). Deltamethrin and cypermethrin caused a non-significant inhibition of hatching (IH%), even at concentrations higher than the recommended levels. By contrast, the acaricides chlorpyrifos, phoxim, and amitraz significantly inhibited hatching at all tested concentrations. Ivermectin also demonstrated significant IH% at various concentrations but did not fully inhibit the hatching process. Among the disinfectants tested, Virkon-S®, TH4, and Chlorox showed insignificant effects, whereas formalin achieved an IH% of only 34.1% at a high concentration of 200 mg/mL. Natural products, carvacrol and thymol, exhibited significant ovicidal activity, with a significant IH%. In a semi-field application, phoxim (0.5 mg/mL) and deltamethrin (0.05 mg/mL) were sprayed on tick eggs on pasture soil from a farm. The results indicated that phoxim-treated eggs had a 40% IH%, while deltamethrin-treated eggs showed only an 8.79% IH%. In conclusion, the acaricides amitraz, phoxim, and chlorpyrifos, as well as the natural products carvacrol and thymol, caused significant toxicity to R. annulatus eggs.

Hypervirulent Klebsiella pneumoniae with a hypermucoviscosity phenotype challenges strategies of water disinfection for its capsular polysaccharides

Due to the strong pathogenicity of hypervirulent Klebsiella pneumoniae (hvKP), its performance against disinfectants in water should be understood to protect public health and ecological environment. Unfortunately, the disinfectant tolerance of hvKP with a hypermucoviscosity (HMV) phenotype is a critical underexplored area. Here, the tolerance of K. pneumoniae isolates to common disinfectants was evaluated, and its underlying mechanisms were clarified. Results showed that hvKP strains with HMV exhibited remarkable tolerance to triclosan (TCS), sodium hypochlorite (NaClO), and benzalkonium bromide (BB), surpassing that of low-virulent K. pneumoniae (lvKP) and Escherichia coli, which is the microbial indicator of drinking water quality. Ct value of NaClO reached 4.41 mg/L·min to kill 4-log hvKP, while the values were 2.52 and 2.28 mg/L·min to achieve 4-log killing of lvKP and E. coli, respectively. The curing of the virulence plasmid from hvKP strain K2044 revealed that capsular polysaccharide (CPS) synthesis, driven by the virulence plasmids, helped mitigate cell membrane injury and bacterial inactivation under NaClO stress; consequently, it provided a protective advantage to hvKP. Enhancing the antioxidative stress system to reduce ROS production and mitigate oxidative stress caused by NaClO further improved the disinfectant resistance of hvKP strains with HMV. This study emphasized that hvKP strains with HMV posed a considerable challenge to disinfection procedure of water treatment. It also revealed that an improved dosage of NaClO ensures bacteria killing, indicating the optimization of the design of water treatment processes involving disinfection strategies and technical parameters should be considered.

Phenotypic and genotypic determination of resistance to common disinfectants among strains of Acinetobacter baumannii producing and non-producing biofilm isolated from Iran

BackgroundNosocomial infections are a global problem in hospitals all around the world. It is considered a major health problem, especially in developing countries. The increase in the patient’s stay in hospitals has increased the mortality rate, and consequently, the costs drastically increase. The main purpose of using disinfectants in the hospital environment is to reduce the risk of nosocomial infections. Ethylene diamine tetra acetic acid (EDTA) causes lysis and increases susceptibility to antimicrobial agents in the planktonic form of bacteria. This substance affects the permeability of the outer membrane of bacteria. It also prevents the formation of biofilms by bacteria.Materials and methodsIn the current study, 120 isolates of Acinetobacter baumannii (A. baumannii) were confirmed by phenotypic and genotypic methods. Antibiogram was performed and then the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of isolates against 5% sodium hypochlorite, ethanol %70, sayasept-HP 2%, chlorhexidine 2%, dettol 4/8% were evaluated. In addition, the disinfectant effect was re-evaluated with the mixture of EDTA solution. All isolates were examined for biofilm presence by crystal violet staining method in triplicates and repeated three times for each strain. Also for all isolates detection of efflux pump genes (Qac-E, qacE-Δ1, SUG-E) by PCR technique was done.ResultsAntibiogram results of A. baumannii showed that 6.7% were Multi-drug-resistant (MDR), and 89.2% were Extensively drug-resistant (XDR) isolates. The highest effect of disinfectants was related to 5% sodium hypochlorite, and the least effect was 70% ethanol. EDTA increases the efficacy of selected disinfectants significantly. The highest prevalence of the efflux pump genes was related to SUG-E (95%) and Qac-E (91.7%), and, the qacE-Δ1 gene with 12.5%. The biofilm production rate was 91.3% among all isolates.ConclusionThe best and safest way to disinfect hospital floors and surfaces is to choose the right disinfectants, and learn how to use them properly. In this study, a mixture of disinfectants and EDTA had a significant effect on bactericidal activity. it was found that improper use of disinfectants, especially the use of sub-inhibitory dilutions, increases the resistance of bacteria to disinfectants.

Synthesis and broad-spectrum biocidal effect of novel gemini quaternary ammonium compounds

Since the discovery of antimicrobial agents, the misuse of antibiotics has led to the emergence of bacterial strains resistant to both antibiotics and common disinfectants like quaternary ammonium compounds (QACs). A new class, ’gemini’ QACs, which contain two polar heads, has shown promise. Octenidine (OCT), a representative of this group, is effective against resistant microorganisms but has limitations such as low solubility and high cytotoxicity. In this study, we developed 16 novel OCT derivatives. These compounds were subjected to in silico screening to predict their membrane permeation. Testing against nosocomial bacterial strains (G+ and G-) and their biofilms revealed that most compounds were highly effective against G+ bacteria, while compounds 7, 8, and 10–12 were effective against G- bacteria. Notably, compounds 6–8 were significantly more effective than OCT and BAC standards across the bacterial panel. Compound 12 stood out due to its low cytotoxicity and broad-spectrum antimicrobial activity, comparable to OCT. It also demonstrated impressive antifungal activity. Compound 1 was highly selective to fungi and four times more effective than OCT without its cytotoxicity. Several compounds, including 4, 6, 8, 9, 10, and 12, showed strong virucidal activity against murine cytomegalovirus and herpes simplex virus 1. In conclusion, these gemini QACs, especially compound 12, offer a promising alternative to current disinfectants, addressing emerging resistances with their enhanced antimicrobial, antifungal, and virucidal properties.

Assessing the reduction of microbial load in the intensive care unit of hospitals using Sanitizon solution

Background: The presence of microbial agents on different hospital surfaces is considered a harmful factor to health. The use of hypochlorous acid (HOCl) for health purposes has been evaluated in more than 50 countries. The present study aimed to assess the disinfection effect of Sanitizon solutions and common disinfectants (Sayasept HP and Sayasept 420) on the reduction of microbial load in Shohada-ye Ashayer Hospital, Khorram Abad. Materials and Methods: In this experimental study, 200 samples from intensive care units were prepared and studied in seven experimental groups (one control group and six different types of disincentives) in six different hospital departments. The samples were cultured on specific culture media. The results were analyzed using SPSS software (version 23). The germicidal power of disinfectants was investigated according to standard 10504 and diffusion method in agar. Results: The use of disinfectants caused a significant decrease in the microbial load compared to the control group. Disinfection solutions led to a decrease in the number of colonies from 113 to 12. Moreover, all disinfectants had germicidal and fungicidal power according to the standard (reduction of four logarithms of bacteria). The Sanitizon solution succeeded in removing all microorganisms and reducing more than seven logarithms of test microorganisms. Sanitizon caused a more marked reduction of gram-negative bacteria and fungi compared to other disinfectants. Conclusion: As evidenced by the results, Sanitizon can be used along with other common disinfectant products to clean surfaces. The intermittent use of disinfectants with different active substances reduces the probability of resistance in microorganisms.

Rapid discrimination of African swine fever virus nucleic acid and virions using BenzoNuclease

African swine fever (ASF) is an acute and severe infectious disease caused by the African Swine Fever Virus (ASFV). ASFV exhibits significant resistance and stability in the environment, which, coupled with its double-stranded DNA and large genome, predisposes it to contaminate laboratory samples. This characteristic can lead to false-positive results in swine farm settings even days after disinfection, as detectable through polymerase chain reaction (PCR) or real-time fluorescent quantitative PCR (qPCR) assays. To meet the demand for efficient clinical methods capable of discriminating between ASFV nucleic acid and ASFV virions, this study aims to ascertain the efficacy of the nuclease “BenzoNuclease” in distinguishing ASFV nucleic acid (ASFV-DNA) from ASFV virions. BenzoNuclease is a versatile nucleic acid enzyme with the capacity to degrade nearly all forms of DNA and RNA. Initially, this research established a highly sensitive general PCR detection method for ASFV. Subsequently, a positive control was constructed using the M13 bacteriophage to substitute for active ASFV, facilitating the development of an improved qPCR method. It is important to note that common disinfectants have the potential to deactivate BenzoNuclease. However, in an environment simulating actual production applications, residual disinfectants do not interfere with the enzymatic efficacy of BenzoNuclease, thus not affecting the detection capabilities of this method. Positive clinical samples from pig farms, upon testing with the improved method, revealed that three samples were positive, indicating the presence of viral particles, while the remaining samples were negative, indicating the presence of nucleic acids. This provides an additional new option for sample testing in pig farms.

Chlorine dioxide may be an alternative to acidification and chlorination for drinking water chemical disinfection in dairy beef bulls

Alternative water disinfectants to chlorination need to be identified because its effectiveness is limited by water pH and potentially carcinogen by−products resulted from chlorination and organic compound reaction. The first study aimed to evaluate the effect of different drinking water chemical disinfection treatments on water quality, its potential hazard effects on animal health, water and feed consumption, and apparent total tract digestibility in dairy beef bulls fed high-concentrate diets. For 224 days, 24 Holstein bulls (176 ± 16.3 kg BW, and 149 ± 5.8 days of age) were individually assigned to one of four treatments with different drinking water chemical disinfectants: without disinfection (CTR); acidification and chlorination (ACCHL; 0.65 mL/L H3PO4 and 0.14 mL/L NaClO 15%); hydrogen peroxide (PER; 0.15 mL/L); and chlorine dioxide (DIO; 2.50 mL/L). Data were analysed with a mixed-effects model. Treatments affected the chemical characteristics of the water: in ACCHL, pH was 6.60 and free residual chlorine was 0.75 mg/L; in PER, H2O2 was 10.6 mg/L; and in DIO, ClO2 was 0.52 mg/L. Water physicochemical quality parameters in all treatments were below maximal thresholds established for safe water consumption by the Water Safety Royal Decree (RD 140/2003). In addition, the total coliform count of treated waters was reduced (P = 0.01) compared with CTR; moreover, ACCHL and DIO treatments were more effective in reducing total coliform count than PER. Dry matter intake tended (P = 0.07) to increase in DIO compared with CTR. Treatments did not affect blood parameters nor apparent total tract digestibility. The second study aimed to evaluate the potential benefit on animal performance of two drinking water disinfectants under commercial conditions in dairy beef crossbred Holstein bulls fed high-concentrate diets. Ninety-six animals (307 ± 4.4 kg BW, and 224 ± 1.8 days of age) were allocated to six pens for 140 days and assigned to one of two treatments: ACCHL, most common water disinfectant, and DIO. Data were analysed with a mixed-effects model. Water total coliform count and water consumption were similar between treatments. Concentrate intake was greater (P = 0.02) in ACCHL for the last 14 study days. Growth performance and carcass quality were similar between treatments. In summary, acidification and chlorination, H2O2, and ClO2 as drinking water disinfectants in dairy beef bulls had good disinfecting activity without detrimental effects on health and nutrient digestibility, and performance.

Efficient trihalomethane quantification in drinking water for minimally-equipped water treatment plants labs

Chlorine is a common disinfectant used in water treatment. However, its reaction with organic matter can lead to the formation of harmful byproducts, such as trihalomethanes (THMs), which are potentially carcinogenic. To address this issue, the aim of this work was to enhance a colorimetric method capable of quantifying THMs in drinking water through UV/Vis Spectrophotometry, using cost-effective equipment, and validate this methodology for the first time according to established validation protocols. The method’s innovation involved replacing the solvent pentane with the more common hexane, along with adjusting the heating ramp, elucidating the mechanisms involved in the process. This method involves the reaction between THMs, pyridine, and NaOH to produce a colored compound, which is then monitored through molecular absorption spectroscopy in the visible region. The method was thoroughly validated, achieving a limit of detection of 13.41 μg L−1 and a limit of quantification of 40.65 μg L−1. Recovery assays ranged from 86.1 % to 90.7 %, demonstrating high accuracy. The quality of the linear fit for the analytical curve exceeded R2 > 0.98. The method was applied to real samples, revealing concentrations ranging from 13.58 to 55.46 μg L−1, all way below the legal limit in Brazil (Maximum Contaminant Levels (MCL) = 100 μg L−1). This cost-effective and straightforward method is suitable for integration into water treatment plant laboratories.

UV-C light-activated gallic acid and ultrasound: A novel approach for reducing enteropathogens inoculated in lettuce (Lactuca sativa L.)

The effect of UV-C light-activated gallic acid (AGA) alone or combined with ultrasound (US) on the inactivation of E. coli and S. Typhimurium inoculated in aqueous solution and lettuce was studied. The contact time (0–30 min) and AGA concentration (0.05–0.25 M) were evaluated against microorganisms inoculated in aqueous solutions. At selected conditions, the combined effect of AGA and US process was evaluated against microorganisms inoculated in lettuce leaves; samples were taken from washing peptone water and the surface of lettuce using a cotton swab. The microbial inactivation of AGA in lettuce was described using the Monod model, which adequately reproduces the inactivation kinetics (R > 0.96). In aqueous solutions, 10 min of contact time and 0.15 M and 0.25 M of AGA were required to reduce more than 5 log reduction of S. Typhimurium and E. coli, respectively. In lettuce, the E. coli showed higher resistance than S. Typhimurium to the AGA treatment, obtaining a maximum microbial reduction (4.33 ± 0.17 log reduction) using washing peptone water as a sampling method and AGA plus US process. Moreover, the AGA treatment combined with the US process presented a higher microbial inactivation compared to a common disinfectant (colloidal silver). Therefore, it is possible to indicate that AGA combined with the US may be an adequate alternative to reduce enteropathogens in lettuce.

Identification and characterization of microorganisms isolated from noncompliant or atypical dairy products in Canada

Despite good manufacturing practices and rigorous cleaning and sanitizing procedures established in dairy processing plants, microbiological contamination remains the main cause of products being non-compliant and/or atypical and hence not fit for human consumption. The objective of this study was to isolate, identify and characterize bacteria, yeasts and molds associated with substandard dairy products in Canada and to create a collection of reference isolates. In addition to conventional microbiological characterization, each isolate was tested for biofilm-forming ability and susceptibility to heat, antimicrobial agents, and common industrial disinfectants. Among the 105 microbial strains isolated from pasteurized milk, cream, and cheese samples, 24 bacterial isolates, belonging mainly to the genus Pseudomonas, were shown to be moderate or strong biofilm producers in 96-well plates and highly resistant to peracetic acid (100 ppm, 5 min contact time) and sodium hypochlorite (70 ppm, 5 min contact time). In addition, 56 bacterial isolates, including Acinetobacter baumannii, Enterobacter bugandensis, Klebsiella pneumoniae and Pseudomonas spp., were found resistant to ampicillin, fosfomycin and/or ceftriaxone, while 14 others, such as Bacillus spp. and Macrococcus spp., withstood a heat treatment equivalent to low-temperature long-time pasteurization (63°C for 30 min). This descriptive study provides new information on potential problematic microorganisms in dairies and will guide the development of novel control strategies intended to prevent and reduce microbiological contamination and the associated economic losses.

Influence of physical and water quality parameters on residual chlorine decay in water distribution network

Chlorine is the most common disinfectant in drinking water distribution practice. World Health Organization recommends 0.2–5.0 mg/l of residual chlorine in drinking water. This paper analyzed influence of physical and water quality parameters on chlorine decay in drinking water distribution. Principal component analysis, directed tree and regression were used to investigate influence of these parameters on chlorine from water treatment plant to water consumption points. Results show that initial chlorine, electrical conductivity and distance explain 62 % of chlorine decay with estimated error of 0.045 mg/l. The decision-tree feature importance scores of initial chlorine and electrical conductivity were 0.47 and 0.23 respectively. The combined feature importance scores of physical parameters of distance (0.09), pipe diameter (0.06), flow velocity (0.03), pressure (0.02) and travel time (0.046) were less than that for initial chlorine concentration (0.47) alone. These results show that conventional chlorination at water treatment plants removes largely fast inorganic reactants leaving traces of slow organic reactants as the dominant secondary contaminants in water distribution system. The key policy recommendation is to use water quality parameters more than physical parameters in order to enable water utility managers maintain residual chlorine within safe public health standards.

Disinfection of Water by Chlorine, Peracetic Acid, Ultraviolet and Solar Radiations: A Review

Disinfection is an essential step during water treatment to ensure the microbiological safety of water for human consumption, and over time, it has been improved and better understood. In this context, this review provides a compilation of information, new insights, and perspectives on the main microorganisms present in supply water, their basic structures, and mechanisms of disinfection via chlorine, peracetic acid (PAA), ultraviolet (UV) radiation and solar disinfection (SODIS). Chlorine is the most common chemical disinfectant, however, there is the formation of toxic by-products, which has stimulated the use of non-chlorinated disinfection methods, such as PAA, UV and SODIS. The main advantages of PAA reported in the literature are its high disinfecting power, the non-formation of toxic/carcinogenic by-products, its ability to generate radicals, such as CH3C(O)O●, HO● and HOO● with or without the use of electromagnetic radiation or thermal energy. The generation of radicals is one of the most used mechanisms to explain the oxidation process during disinfection, which, also prompted studies to use radiation for catalyzing the formation of these radicals. Consequently, physical disinfection processes, such as UV irradiation and SODIS have received significant attention because, in addition to having the ability to damage the RNA (Ribonucleic Acid) and DNA (Deoxyribonucleic Acid) of microorganisms causing their inactivation, these processes also promote the formation of radicals through reactive species that are ubiquitous in natural water. Therefore, the review will be important for studies focused on the process of water disinfection by advanced oxidized processes, especially those that use PAA combined with UV or SODIS.

Catabolism of germinant amino acids is required to prevent premature spore germination in Bacillus subtilis.

Many bacterial species produce dormant cells called endospores, which are not killed by antibiotics or common disinfection practices. Endospores pose critical challenges in the food industry, where endospore contaminations cause food spoilage, and in hospitals, where infections by pathogenic endospore formers threaten the life of millions every year. Endospores lose their resistance properties and can be killed easily when they germinate and exit dormancy. We have discovered that the enzymes that break down the amino acids alanine and valine are critical for the production of stable endospores. If these enzymes are absent, endospores germinate as they are formed or shortly thereafter in response to alanine, which can initiate the germination of many different species' endospores, or to valine. By blocking the activity of alanine dehydrogenase, the enzyme that breaks down alanine and is not present in mammals, it may be possible to inactivate endospores by triggering premature and unproductive germination.