Underlying the mechanisms of pathogen inactivation and regrowth in wastewater using peracetic acid-based disinfection processes: A critical review.

Peracetic acid (PAA) disinfection is an emerging wastewater disinfection process. Its advantages include excellent pathogen inactivation performance and little generation of toxic and harmful disinfection byproducts. The objective of this review is to comprehensively analyze the experimental data and scientific information related to PAA-based disinfection processes. Kinetic models and modeling frameworks are discussed to provide effective tools to assess pathogen inactivation efficacy. Then, the efficacy of PAA-based disinfection processes for pathogen inactivation is summarized, and the inactivation mechanisms involved in disinfection and the interactions of PAA with conventional disinfection processes are elaborated. Subsequently, the risk of pathogen regrowth after PAA-based disinfection process is clearly discussed. Finally, to address ecological risks related to PAA-based disinfection, its impact on the spread of antibiotic-resistant bacteria and the transfer of antibiotic resistance genes (ARGs) is also assessed. Among advanced PAA-based disinfection processes, ultraviolet/PAA is promising not only because it has practical application value but also because pathogen regrowth can be inhibited and ARGs transfer risk can be significantly reduced via this process. This review presents valuable and comprehensive information to provide an in-depth understanding of PAA as an alternative wastewater disinfection technology.

Comparing the susceptibility to sanitizers, biofilm-forming ability, and biofilm resistance to quaternary ammonium and chlorine dioxide of 43 Salmonella enterica and Listeria monocytogenes strains.

This study determined the susceptibility to sanitizers and biofilm-forming ability on stainless steel of 43 Salmonella enterica and Listeria monocytogenes strains. Besides, the biofilm resistance to sanitizers of four bacterial pathogen strains was evaluated. Four sanitizers commonly used in the food industry were tested: peracetic acid (PAA), chlorine dioxide (ClO2), sodium hypochlorite (SH), and quaternary ammonium compound (QAC). The susceptibility to sanitizers varied widely among the strains of both pathogens. On the other hand, the number of biofilm-associated cells on the stainless-steel surface was >5 log CFU/cm2 for all of them. Only one Salmonella strain and two L. monocytogenes strains stood out as the least biofilm-forming. The resistance of biofilms to sanitizers also varied among strains of each pathogen. Biofilms of L. monocytogenes were more susceptible to the disinfection process with ClO2 and QAC than those of Salmonella. However, no correlation was observed between the ability to form denser biofilm and increased sanitizer resistance. In general, chlorine compounds were more effective than other sanitizers in inactivating planktonic cells and biofilms.

Effect of micropollutants on disinfection byproducts and antibiotic resistance genes in drinking water in the process of biological activated carbon treatment.

The biofilm stress response of biological activated carbon (BAC) was investigated under prolonged exposure to sulfadiazine and 2,4-Dichlorophenoxyacetic acid, simulating complex emerging organic contaminants (EOCs) that are mainly involved in the formation of nitrogenous disinfection byproducts (N-DBPs) and antibiotic resistance genes (ARGs). Under trace complex EOCs condition (2 µg/L), N-DBP precursors and abundance of ARGs increased significantly in BAC effluent. The total formation potential of haloacetonitriles (HANs) and halonitromethanes (HNMs) was 751.47 ± 2.98 ng/L, which was much higher than the control group (440.67 ± 13.38 ng/L without EOCs). Similarly, the relative abundance of ARGs was more than twice that in the control group. The complex EOCs induce excessive extracellular polymeric substance secretion (EPS), thereby causing more N-DBP precursors and stronger horizontal gene transfer. Metagenome analysis revealed that functional amino acid and protein biosynthesis genes were overexpressed compared to the control group, causing more EPS to be secreted into the external environment. Complex EOCs promote Cobetia, Clostridium, and Streptomyces dominance, contributing to the production of N-DBP precursors and ARGs. For the first time, in addition to the direct hazards of the EOCs, this study successfully revealed the indirect water quality risks of complex EOCs from the microbial stress response during BAC treatment. Synergistic regulation of EOCs and microorganisms is important for tap water security.

The temperature-dependent kinetics and bacteria regrowth by performic acid and sodium hypochlorite disinfection.

Sodium hypochlorite (NaOCl) has been widely used as a disinfectant in water and wastewater treatment, because of its high efficiency and low cost, whereas the bio-toxicity of its disinfection byproducts (DBPs) raised great concern. Performic acid (PFA) produces less DBPs and shows strong oxidation abilities. In this study, the effect of temperature on NaOCl and PFA disinfection as well as bacteria regrowth were evaluated. First, the inactivation of Escherichia coli, Staphylococcus aureus, and Bacillus subtilis by NaOCl and PFA at 4 and 20 °C, detected by cell cultured-based plate counting were fitted to kinetic models, and the predicted CTs were calculated. The results showed that NaOCl was more effective than PFA for E. coli and S. aureus inactivation, and the temperature was positively correlated to disinfection. Second, bacteria regrowth was evaluated at different temperatures (4 and 20 °C) of disinfection and storage. The results showed that the bacteria inactivated by NaOCl regrew prominently, especially for those inactivated at 4 and stored at 4 °C, probably through the mechanism of reactivation of viable but non-culturable (VBNC) bacteria. PFA was superior in suppressing bacteria regrowth, and it may be used as an alternate disinfectant in water treatment in cold environment.

A comparative evaluation of antimicrobial property of traditional and three alternative disinfectants on irreversible hydrocolloid impressions: An in vitro study.

Aim: The aim was to compare the efficacy of various herbal disinfectants on irreversible hydrocolloid impressions and to investigate the effectiveness of three herbal disinfectants and a chemical disinfectant against particular pathogens. Settings and Design: In vitro -a comparative study. Materials and Methods: The following methodology was followed to achieve the objectives. Four maxillary impressions were made for each selected patient with irreversible hydrocolloid impression material. The predisinfection swabs were taken from impression sites of teeth 17, 13, 27, and 23 (FDI system of tooth numbering). The impressions were immersed in all four different disinfectants such as 2% glutaraldehyde, Aloe vera solution, 50% neem oil, and apple vinegar solution, then the postdisinfection swabs were taken from the same sites 17,13,27,23 and then cultured onto sheep blood agar and examined for growth, and colony forming units (CFUs) of Streptococcus viridans, Streptococcus mutans, Streptococcus sanguis, and Actinomyces viscosus. The comparative analysis was done for the predisinfection and postdisinfection values in each study group. Statistical Analysis Used: Descriptive analysis, Kruskal Wallis test, Mann Whitney post hoc test, Wilcoxon signed rank test. Results: The results revealed that the mean CFUs of S. viridans, S. mutans, S. sanguis, and A. viscosus during postdisinfection samples were statistically significant when compared to predisinfection samples. Multiple comparison of the mean CFUs of all 4 microorganisms in the control group and in 50% Neem oil group was significantly lesser compared to A. vera and Apple Vinegar group. Conclusion: CFUs of S. viridans, S. mutans, S. sanguis, and A. viscosus significantly decreased in the 50% neem oil group as well as the control group. As a result, 50% Neem oil was a viable option for disinfecting alginate impressions.

Benzalkonium chloride forces selective evolution of resistance towards antibiotics in Salmonella enterica serovar Typhimurium.

BACKGROUND: Although food-grade disinfectants are extensively used worldwide, it has been reported that the long-term exposure of bacteria to these compounds may represent a selective force inducing evolution including the emergence of antibiotic resistance. However, the mechanism underlying this correlation has not been elucidated. This study aims to investigate the genomic evolution caused by long-term disinfectant exposure in terms of antibiotic resistance in Salmonella enterica Typhimurium. METHODS: S. Typhimurium isolates were exposed to increasing concentrations of benzalkonium chloride (BAC) and variations of their antibiotic susceptibilities were monitored. Strains that survived BAC exposure were analyzed at whole genome perspective using comparative genomics, and Sanger sequencing-confirmed mutations in ramR gene were identified. Next, the efflux activity in ramR-mutated strains shown as bisbenzimide accumulation and expression of genes involved in AcrAB-TolC efflux pump using quantitative reverse transcriptase PCR were determined. RESULTS: Mutation rates of evolved strains varied from 5.82 × 10-9 to 5.56 × 10-8, with fold increase from 18.55 to 1.20 when compared with strains evolved without BAC. Mutations in ramR gene were found in evolved strains. Upregulated expression and increased activity of AcrAB-TolC was observed in evolved strains, which may contribute to their increased resistance to clinically relevant antibiotics. In addition, several indels and point mutations in ramR were identified, including L158P, A37V, G42E, F45L, and R46H which have not yet been linked to antimicrobial resistance. Resistance and mutations were stable after seven consecutive cultivations without BAC exposure. These results suggest that strains with sequence type (ST) ST34 were the most prone to mutations in ramR among the three STs tested (ST34, ST19, ST36). CONCLUSIONS: This work demonstrated that disinfectants, specifically BAC forces S. Typhimurium to enter a specific evolutionary trajectory towards antibiotic resistance illustrating the side effects of long-term exposure to BAC and probably also to other disinfectants. Most significantly, this study provides new insights in understanding the emergence of antibiotic resistance in modern society.

Impact of clonal lineages on susceptibility of Staphylococcus lugdunensis to chlorhexidine digluconate and chloride benzalkonium.

BACKGROUND: Little is known about susceptibility of Staphylococcus lugdunensis to antiseptics. The objective of this study was to evaluate, at the molecular and phenotypic level, the susceptibility of 49 clinical S. lugdunensis strains (belonging to the seven clonal complexes [CCs] defined by multilocus sequence typing) to two antiseptics frequently used in healthcare settings (chlorhexidine digluconate [CHX] and chloride benzalkonium [BAC]). RESULTS: The minimum inhibitory concentrations (MICs), by broth microdilution method, varied for BAC from 0.25 mg/L to 8 mg/L (MIC50 = 1 mg/L, MIC90 = 2 mg/L) and for CHX from 0.5 mg/L to 2 mg/L (MIC50 = 1 mg/L, MIC90 = 2 mg/L). The BAC and CHX minimum bactericidal concentrations (MBCs) varied from 2 mg/L to 8 mg/L (MBC50 = 4 mg/L, MBC90 = 8 mg/L) and from 2 mg/L to 4 mg/L (MBC50 and MBC90 = 4 mg/L), respectively. A reduced susceptibility to CHX (MIC = 2 mg/L) was observed for 12.2% of the strains and that to BAC (MIC ≥ 4 mg/L) for 4.1%. The norA resistance gene was detected in all the 49 isolates, whereas the qacA gene was rarely encountered (two strains; 4.1%). The qacC, qacG, qacH, and qacJ genes were not detected. The two strains harboring the qacA gene had reduced susceptibility to both antiseptics and belonged to CC3. CONCLUSION: The norA gene was detected in all the strains, suggesting that it could belong to the core genome of S. lugdunensis. S. lugdunensis is highly susceptible to both antiseptics tested. Reduced susceptibility to BAC and CHX was a rare phenomenon. Of note, a tendency to higher MICs of BAC was detected for CC3 isolates. These results should be confirmed on a larger collection of strains.

Inactivation of human coronaviruses using an automated room disinfection device.

The emergence of more virulent and epidemic strains of viruses, especially in the context of COVID-19, makes it more important than ever to improve methods of decontamination. The objective of this study was to evaluate the potential of on-demand production of chlorine species to inactivate human coronaviruses. The commercial prototype disinfection unit was provided by Unipolar Water Technologies. The Unipolar device generates active chlorine species using an electrochemical reaction and dispenses the disinfectant vapour onto surfaces with an aspirator. The minimum effective concentration and exposure time of disinfectant were evaluated on human hepatoma (Huh7) cells using 50% tissue culture infectious dose (TCID50) assay and human coronavirus 229E (HCoV-229E), a surrogate for pathogenic human coronaviruses. We showed that chlorine species generated in the Unipolar device inactivate HCoV-229E on glass surfaces at ≥ 400 parts per million active chlorine concentration with a 5 min exposure time. Here, inactivation refers to the inability of the virus to infect the Huh7 cells. Importantly, no toxic effect was observed on Huh7 cells for any of the active chlorine concentrations and contact times tested.

Transcriptomic and phenotype analysis revealed the role of rpoS in stress resistance and virulence of a novel ST3355 ESBL-producing hypervirulent Klebsiella pneumoniae isolate.

Introduction: An extended-spectrum beta-lactamase (ESBL)-hypervirulent Klebsiella pneumoniae (HvKP) strain HKE9 was isolated from the blood in an outpatient. Methods: The effect of the global regulatory factor RpoS on antimicrobial resistance, pathogenicity, and environmental adaptability was elucidated. Results: HKE9 is a novel ST3355 (K20/O2a) hypervirulent strain with a positive string test and resistant to cephems except cefotetan. It has a genome size of 5.6M, including two plasmids. CTX-M-15 was found in plasmid 2, and only ompk37 was found in the chromosome. HKE9 could produce bacterial siderophores, and genes of enterobactin, yersiniabactin, aerobactin, and salmochelin have been retrieved in the genome. As a global regulatory factor, knockout of rpoS did not change antimicrobial resistance or hemolytic phenotype while increasing the virulence to Galleria mellonella larvae and showing higher viscosity. Moreover, rpoS knockout can increase bacterial competitiveness and cell adhesion ability. Interestingly, HKE9-M-rpoS decreased resistance to acidic pH, high osmotic pressure, heat shock, and ultraviolet and became sensitive to disinfectants (H2O2, alcohol, and sodium hypochlorite). Although there were 13 Type 6 secretion system (T6SS) core genes divided into two segments with tle1 between segments in the chromosome, transcriptomic analysis showed that rpoS negatively regulated T4SS located on plasmid 2, type 1, and type 3 fimbriae and positively regulate genes responsible for acidic response, hyperosmotic pressure, heat shock, oxidative stress, alcohol and hypochlorous acid metabolism, and quorum sensing. Discussion: Here, this novel ST3355 ESBL-HvKP strain HKE9 may spread via various clonal types. The important regulation effect of rpoS is the enhanced tolerance and resistance to environmental stress and disinfectants, which may be at the cost of reducing virulence and regulated by T4SS.

Evaluation of a novel surface-coating formulation with time-extended antimicrobial activity for healthcare environment disinfection.

BACKGROUND: The importance of environmental contamination in the transmission of pathogens among hospitalized patients is universally recognized, and disinfection of surfaces is a widely accepted modality for reducing healthcare-associated infections. Nevertheless, hospital disinfection is still suboptimal. In this study, we evaluated the sustained effects of the novel formulation OxiLast™ which extends the antimicrobial effects of chlorine-based disinfectants. METHODS: In an experimental lab phase, PVC surfaces were coated with OxiLast™ and then inoculated with representative Gram-positive and Gram-negative pathogenic bacteria. Cells were recovered at different contact times (5, 15, 30 min) to assess the reduction in bacterial counts compared to uncoated surfaces and also subject to various challenges to assess robustness. A similar methodology was then applied in an unoccupied hospital room to evaluate the sustained effect of OxiLast™ on high-touch surfaces. RESULTS: OxiLast™ demonstrated notable activity against the range of bacterial strains tested with ≥ 4 log10 reduction in bacterial counts observed for up to seven days following one surface application, for various strains and contact times. Similar results were observed following challenges such as simulated abrasion of coated surfaces, organic contamination or successive inoculations. The results were confirmed in a simulated patient care environment. CONCLUSIONS: The addition of OxiLast™ to common chlorine-based disinfectants has shown a substantial and sustained reduction in bacterial pathogen counts for up to 7 days following one application. The consistent results in the laboratory and hospital are promising and should be tested in a real-life clinical scenario.

Suitable Disinfectants with Proven Efficacy for Genetically Modified Viruses and Viral Vectors.

Viral disinfection is important for medical facilities, the food industry, and the veterinary field, especially in terms of controlling virus outbreaks. Therefore, standardized methods and activity levels are available for these areas. Usually, disinfectants used in these areas are characterized by their activity against test organisms (i.e., viruses, bacteria, and/or yeasts). This activity is usually determined using a suspension test in which the test organism is incubated with the respective disinfectant in solution to assess its bactericidal, yeasticidal, or virucidal activity. In addition, carrier methods that more closely reflect real-world applications have been developed, in which microorganisms are applied to the surface of a carrier (e.g., stainless steel frosted glass, or polyvinyl chloride (PVC)) and then dried. However, to date, no standardized methods have become available for addressing genetically modified vectors or disinfection-resistant oncolytic viruses such as the H1-parvovirus. Particularly, such non-enveloped viruses, which are highly resistant to disinfectants, are not taken into account in European standards. This article proposes a new activity claim known as "virucidal activity PLUS", summarizes the available methods for evaluating the virucidal activity of chemical disinfectants against genetically modified organisms (GMOs) using current European standards, including the activity against highly resistant parvoviridae such as the adeno-associated virus (AAV), and provides guidance on the selection of disinfectants for pharmaceutical manufacturers, laboratories, and clinical users.

African Swine Fever: Transmission, Spread, and Control through Biosecurity and Disinfection, Including Polish Trends.

African swine fever is a contagious disease, affecting pigs and wild boars, which poses a major threat to the pig industry worldwide and, therefore, to the agricultural economies of many countries. Despite intensive studies, an effective vaccine against the disease has not yet been developed. Since 2007, ASFV has been circulating in Eastern and Central Europe, covering an increasingly large area. As of 2018, the disease is additionally spreading at an unprecedented scale in Southeast Asia, nearly ruining China's pig-producing sector and generating economic losses of approximately USD 111.2 billion in 2019. ASFV's high resistance to environmental conditions, together with the lack of an approved vaccine, plays a key role in the spread of the disease. Therefore, the biosecurity and disinfection of pig farms are the only effective tools through which to prevent ASFV from entering the farms. The selection of a disinfectant, with research-proven efficacy and proper use, taking into account environmental conditions, exposure time, pH range, and temperature, plays a crucial role in the disinfection process. Despite the significant importance of ASF epizootics, little information is available on the effectiveness of different disinfectants against ASFV. In this review, we have compiled the current knowledge on the transmission, spread, and control of ASF using the principles of biosecurity, with particular attention to disinfection, including a perspective based on Polish experience with ASF control.

The impact of potassium peroxymonosulphate and chlorinated cyanurates on biofilms of Stenotrophomonas maltophilia: effects on biofilm control, regrowth, and mechanical properties.

The activity of two chlorinated isocyanurates (NaDCC and TCCA) and peroxymonosulphate (OXONE) was evaluated against biofilms of Stenotrophomonas maltophilia, an emerging pathogen isolated from drinking water (DW), and for the prevention of biofilm regrowth. After disinfection of pre-formed 48 h-old biofilms, the culturability was reduced up to 7 log, with OXONE, TCCA, and NaDCC showing more efficiency than free chlorine against biofilms formed on stainless steel. The regrowth of biofilms previously exposed to OXONE was reduced by 5 and 4 log CFU cm-2 in comparison to the unexposed biofilms and biofilms exposed to free chlorine, respectively. Rheometry analysis showed that biofilms presented properties of viscoelastic solid materials, regardless of the treatment. OXONE reduced the cohesiveness of the biofilm, given the significant decrease in the complex shear modulus (G*). AFM analysis revealed that biofilms had a fractured appearance and smaller bacterial aggregates dispersed throughout the surface after OXONE exposure than the control sample. In general, OXONE has been demonstrated to be a promising disinfectant to control DW biofilms, with a higher activity than chlorine. The results also show the impact of the biofilm mechanical properties on the efficacy of the disinfectants in biofilm control.

DBP-FP change of biofilm in drinking water distribution system induced by sequential UV and chlorine disinfection: Effect of UV dose and influencing mechanism.

The issue of biofilm-related disinfection byproducts (DBPs) in drinking water distribution system (DWDS) has garnered significant attention. This study sought to examine the changes in biofilm-originated halogenated DBP formation potential (biofilm DBP-FP) in simulated continuous-flow DWDSs subjected to sequential UV and chlorine disinfection (UV-Cl2) treatments with varying UV doses and to propose the underlying mechanism. The formation potential of trihalomethanes (THMs), haloacetic acids (HAAs), and the total organic halogen (TOX, X = Cl and Br) produced by biofilm were measured. Results showed that the biofilm TOCl-FP was at a minimum with a UV dose of 80 mJ/cm2, corresponding to the lowest amounts of protein and polysaccharides in the extracellular polymeric substances (EPS). Sphingobium, Methylobacterium, and Sphingomonas played a crucial role in protein and polysaccharide biosynthesis. Bacterial community composition characterization together with metabolic function analysis indicated that dominant bacteria varied and metabolic function shifted due to UV-Cl2 disinfection, with Alphaproteobacteria increasing in relative abundance and Bacteroidia showing the opposite trend with increasing UV doses. Correlation analysis suggested that the UV-Cl2 disinfection process led to changes in the water matrix, including organics, inorganics, bacteria, and components that provide environmental pressure for the biofilm. These changes ultimately influenced the properties of the biofilm EPS, which had a direct impact on biofilm DBP-FP.

Formation of halonitromethanes from glycine during LED-UV265/chlorine disinfection.

LED-UV265/chlorine is a promising alternative disinfection technology that emits mono-wavelength light for high germicidal efficiency. Halonitromethanes (HNMs) are highly cytotoxic and genotoxic disinfection byproducts that can be formed during LED-UV265/chlorine disinfection. Thus, this work aimed to investigate the HNMs formation from glycine (Gly) during LED-UV265/chlorine disinfection. The results indicated that the concentrations of chlorinated-HNMs (Cl-HNMs) increased first and then decreased as the reaction proceeded. Besides, the effects of operating parameters (UV intensity, free chlorine dosage, and pH) and coexisting ions (Cu2+ and Br-) on HNMs formation were investigated. It was found that the formation concentrations of Cl-HNMs increased with the increase of LED-UV265 intensity and free chlorine dosage but decreased with increased pH. The presence of Cu2+ promoted the formation of Cl-HNMs. The total concentration of HNMs (at 3 min) with adding 1.5 mg/L Cu2+ was 30.90% higher than that without Cu2+. Notably, nine species of HNMs were detected after adding Br-, and the total concentrations of HNMs were enhanced. Moreover, Cl-HNMs were gradually transformed into brominated (chlorinated)-HNMs and brominated-HNMs as Br- concentration increased. According to the findings, the possible formation mechanism of HNMs from Gly during LED-UV265/chlorine disinfection was deduced. Finally, it was demonstrated that the formation laws of HNMs from Gly in real water samples were basically consistent with those in simulated water. Insights obtained in this study help to comprehend the HNMs formation from Gly and provide strategies for controlling the production of HNMs during LED-UV265/chlorine disinfection.

Tomato Brown Rugose Fruit Virus: Survival and Disinfection Efficacy on Common Glasshouse Surfaces.

Tomato brown rugose fruit virus (ToBRFV) is a contact-transmitted tobamovirus affecting many tomato growing regions of the world. This study investigated the effects of different glasshouse surfaces on the survival of the virus; the efficacy of different disinfectants; and heat treatment against ToBRFV (surfaces included steel, aluminium, hard plastic, polythene, glass and concrete). A bioassay followed by ELISA was used to check virus viability. ToBRFV survived for at least 7 days on all surfaces tested and on some for at least 6 months. The virus survived for over two hours on hands and gloves. Hand washing was shown to be unreliable for the removal of the virus. Glutaraldehyde and quaternary ammonium compound disinfectants were effective at one hour on all surfaces. Some other disinfectants were effective at one hour of contact time, on all surfaces except concrete. Sodium hypochlorite was partially effective against ToBRFV, even on concrete. A 5 min soak of plastic trays in water at 90 °C was effective at denaturing ToBRFV; however, 5 min at 70 °C was not. Heating infected sap showed the thermal inactivation point to be 90 °C, confirming the hot water treatment results and showing that deactivation was due to the heat treatment and not a washing effect of the water.

Response mechanisms of pipe wall biofilms in water supply networks under different disinfection strategy pressures and the effect of mediating halogenated acetonitrile formation.

Residual chlorine and biofilm coexistence is inevitable in drinking water transmission and distribution networks. Understanding the microbial response and its mediated effects on disinfection byproducts under different categories of residual chlorine stress is essential to ensure water safety. The aim of our study was to determine the response of pipe wall biofilms to residual chlorine pressure in chlorine and chloramine systems and to understand the microbially mediated effects on the formation and migration of haloacetonitriles (HANs), typical nitrogenous disinfection byproducts. According to the experimental results, the biofilm response changes under pressure, with significant differences noted in morphological characteristics, the extracellular polymeric substances (EPS) spatial structure, bacterial diversity, and functional abundance potential. Upon incubation with residual chlorine (1.0 ± 0.2 mg/L), the biofilm biomass per unit area, EPS, community abundance, and diversity increased in the chloramine group, and the percentage of viable bacteria increased, potentially indicating that the chloramine group provides a richer variety of organic matter precursors. Compared with the chloramine group, the chlorination group exhibited increased haloacetonitrile formation potential (HANFP), with Rhodococcus (43.2%) dominating the system, whereas the prediction abundance of metabolic functions was advantageous, especially with regard to amino acid metabolism, carbohydrate metabolism, and the biodegradation and metabolism of foreign chemicals. Under chlorine stress, pipe wall biofilms play a stronger role in mediating HAN production. It is inferred that chlorine may stimulates microbial interactions, and more metabolites (e.g., EPS) consume chlorine to protect microbial survival. EPS dominates in biofilms, in which proteins exhibit greater HANFP than polysaccharides.

Determining the efficacy of disinfectants at nucleic acid degradation.

AIMS: Nucleic acids, particularly antibiotic resistance genes, are commonly found on surfaces within healthcare environments, with levels not reducing following cleaning. Within the UK, there are no regulations for testing disinfectants against nucleic acids. METHODS AND RESULTS: A series of commonplace in vitro methods were used to determine disinfectant-induced physical and functional damage to various nucleic acids; RNA (10 µg), genomic DNA (2 µg), and plasmids (1 µg). Using these methods, the optimal residence time (10 minutes) and working concentration (10%) were determined for a new disinfectant. Furthermore, comparison of disinfectants with different active ingredients including lactic acid (LA), sodium hydroxide (NaOH), chloroxylenol (PCMX), and quaternary ammonium compounds (QACs), were compared to controls. All disinfectants showed greater degradation by gel electrophoresis of genomic DNA and RNA than of purified plasmids. Functional analysis using quantitative polymerase chain reaction (qPCR) and polymerase chain reaction (PCR) demonstrated that no disinfectant tested (apart from control) could damage DNA to the level where PCR amplification was not possible, and only the NaOH reagent could achieve this for RNA. CONCLUSIONS: The set of methods described herein provides a platform for future standardization and potential regulation regarding monitoring cleaning solutions for their activity against nucleic acids.

Systematic analyses identify modes of action of ten clinically relevant biocides and antibiotic antagonism in Acinetobacter baumannii.

Concerns exist that widespread use of antiseptic or disinfectant biocides could contribute to the emergence and spread of multidrug-resistant bacteria. To investigate this, we performed transposon-directed insertion-site sequencing (TraDIS) on the multidrug-resistant pathogen, Acinetobacter baumannii, exposed to a panel of ten structurally diverse and clinically relevant biocides. Multiple gene targets encoding cell envelope or cytoplasmic proteins involved in processes including fatty acid biogenesis, multidrug efflux, the tricarboxylic acid cycle, cell respiration and cell division, were identified to have effects on bacterial fitness upon biocide exposure, suggesting that these compounds may have intracellular targets in addition to their known effects on the cell envelope. As cell respiration genes are required for A. baumannii fitness in biocides, we confirmed that sub-inhibitory concentrations of the biocides that dissipate membrane potential can promote A. baumannii tolerance to antibiotics that act intracellularly. Our results support the concern that residual biocides might promote antibiotic resistance in pathogenic bacteria.