Types Of Disinfectants Research Articles

Mechanism of oxidative damage in Escherichia coli caused by epigallocatechin gallate (EGCG) in the presence of calcium ions

Abstract Tea polyphenols can be developed into new types of disinfectants for drinking water. The antibacterial effect of epigallocatechin gallate (EGCG) on Escherichia coli (E. coli) in the presence of Ca2+ is affected by the Ca2+ concentration. The oxidative damage mechanism and oxidative damage process of EGCG in E. coli under the presence of Ca2+ were deeply analyzed under three aspects: reactive oxygen species (ROS), antioxidant system, and oxidative stress response in E. coli to provide a theoretical basis for the use of EGCG as a disinfectant in drinking water disinfection. EGCG leads to excessive production of superoxide anion in E. coli and the presence of Ca2+ promotes further imbalance of superoxide anion in E. coli; Ca2+ has little effect on EGCG hindering the scavenging of hydroxyl radicals in bacteria; EGCG can hinder the effect of antioxidant enzymes in E. coli, and Ca2+ has a particular regulatory effect on antioxidant enzymes, thus hindering the oxidative damage of EGCG to E. coli; Ca2+ can cause the expression of the oxyR and DPS genes, protect bacterial DNA, and prevent EGCG from damaging bacterial DNA. In the presence of a high concentration of Ca2+, it may activate the cell efflux pump through the soxS gene, resulting in E. coli resistance to EGCG.

The Efficacy of Three Types of Disinfectants on the Microbial Flora from the Surface of Impression Materials Used in Dentistry—In Vitro Study

During impressions, bacteria, viruses, and fungi remain on the impression material, representing a significant risk for the medical team (dentists, dental assistants, and laboratory technicians). Impression disinfectants have been introduced into dentistry to reduce the risk of cross-infection. This study was performed by examining the surface disinfection of five commonly used impression materials in prosthodontics: alginate-Tropicalgin (Zhermack®), condensation silicone-Zetaplus (Zhermack®), Oranwash L (Zhermack®); and addition silicone-Elite HD + Putty Soft (Zhermack®), Elite + Light Body (Zhermack®) after the disinfection with three disinfectants: Zeta 3 Soft (Zhermack®), Zeta 7 Spray (Zhermack®) and Zeta 7 Solution (Zhermack®). Before disinfection, the impression materials were contaminated with Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10213. Our results demonstrate the efficacy of the two examined specific disinfectants in reducing cross-infection risk. The surface disinfectant-spray is not adequate for impression disinfection. A high number of bacterial colonies were found on the surface of all impressions disinfected with this spray. The immersion-disinfection method effectively eliminates the risk of cross-infections (Kruskal–Wallis test showed a p < 0.001).

Use of Conductivity as a Tool for On-site Residue Management and Definition of Smart Cleanroom Regimes

Surface residues that result from the use of cleaning and disinfection products are becoming an increasing focus of regulators in the Cleanroom industry. Driven largely by the update to EU GMP Annex 1 [1] and best practice recommendation from the PDA Journal of Pharmaceutical Science and Technology [2], it is now recognized that residues need to be managed to avoid any risks they could present to safety or product quality. Residue management can be successfully achieved by selection and use of low residue disinfectants, through the frequency and choice of rinsing agent for removal, the use of the most suitable tools for physical removal like cleanroom specific mops, or a combination of all these factors. Unlike product contact surfaces [3], there is no clear guidance as to what level of residue may be acceptable on small or large cleanroom surfaces, or how they can be quantified. For this reason, most people still rely on judging a surface to be ‘visibly clean’. To improve detection and to quantify the level of residue on a cleanroom surface, a pragmatic method has been developed to measure residue anywhere on-site: Quantification of disinfectant residues by the use of conductivity. The method of quantification of disinfectant residues using conductivity has been verified in studies by measuring the residues derived from different disinfectant types, at various scales (from bench scale upwards) and various locations, and from laboratory to representative pharmaceutical manufacturing areas. Compared to the current ‘gold standard’ that has long been used for the assessment of residues – an individual’s judgment of ‘visually clean’ - the data from conductivity measurements can eliminate this subjective human appraisal and replace it with scientific assessment. Comparison of the visual analysis rating versus conductivity data also revealed that the human eye does indeed underestimate the actual levels of disinfectant residues remaining on surfaces in a cleanroom, resulting in potential impacts of risk to safety, contamination, time, and cost.

Inactivation of Avian Influenza Viruses by Chemical Disinfectants and the Influence of Faecal Matter

Inactivation of avian influenza viruses (AIVs) using chemical disinfectants is an indispensable biosecurity measure during outbreaks. The efficiency of disinfection process depends on disinfectant type and presence or absence of organic matter. It is also not clear whether AIV pathotype could influence its tolerability to a given disinfectant. Here, we assessed the efficiency of formalin and caustic soda against high (H5N1) and low (H9N2) pathogenic AIVs in the presence and absence of wet faeces. Our results showed that the effectiveness of both disinfectants depends on the target virus with the low pathogenic H9N2 virus being generally more susceptible to disinfection than the high pathogenic H5N1 virus. Wet faeces slightly influenced disinfection action in a virus- and contact time- dependent manner. This study highlights the importance of eliminating faecal matter before initiating a disinfection process and indicates the influence of disinfectant type and AIVs pathotype when selecting the appropriate disinfectant.

THE INFLUENCE OF THE PREDECESSOR AND SOWING DATES ON THE DEVELOPMENT OF SEED INFECTION OF WINTER WHEAT VARIETIES IN THE CONDITIONS OF THE FOREST-STEPPE OF UKRAINE

THE INFLUENCE OF THE PREDECESSOR AND SOWING DATES ON THE DEVELOPMENT OF SEED INFECTION OF WINTER WHEAT VARIETIES IN THE CONDITIONS OF THE FOREST-STEPPE OF UKRAINE

Early and Delayed Effect of Cavity Disinfection with Chlorhexidine and Ozone on the Shear Bond Strength of Dentin to Glass Hybrid Restoration

Introduction: We aimed to evaluate the early and delayed effects of chlorhexidine (CHX) and ozone disinfection on the shear bond strength (SBS) of dentin to glass hybrid restoration. Methods: The occlusal surfaces of 60 extracted premolars were trimmed to obtain a flat dentinal surface and randomly divided into three groups, including distilled water (control), 2% CHX, and ozonized water. Each group was further subjected to a shear bond strength test after 24 hours and 3 months. Results: The overall model test (P < 0.001), disinfectant and time (P < 0.001), and time (P = 0.017) showed statistically significant differences among study groups. Yet, the type of disinfectant revealed a non-significant difference (P = 0.238). Post hoc tests showed SBS significantly decreasing over time in the control group (P < 0.001) while the difference between 24 hours and 3 months for the CHX (P = 0.880) and ozone (P = 0.983) groups was not significant. Conclusion: Within the inherent limitations of in vitro studies, it can be concluded that cavity disinfection with CHX and ozone before glass hybrid restoration had a significant effect on the stability of SBS to dentin over 3 months. The type of disinfectant revealed non-significant difference.

Optimizing In Vitro Surface Sterilization of Cyathea latebrosa Spore

Cyathea latebrosa is one of the lowland tree fern species found in Peninsular Malaysia. This fern species is highly demanded in ornamental landscaping. The in vitro cultures are an important tool for propagation which may contribute toward the reduction of over-exploitation. To overcome these problems, an effective spore surface disinfection protocol is crucial to allow the germination stage to be carried out. This studied had carried out three types of methods which are the packet method (PM), centrifuged method (CM), and soak method (SM) with difference percent of concentration (0, 0.1, 0.5, 1.0, 10 & 30) Mercury Chloride (HgCl2) and Sodium hypochlorite (NaOCl). In contrast, the method and concentration of disinfection affect germination. Our results showed that the soak method in both types of disinfection is a significant difference due to statistical analysis (MANOVA) which gives a positive effect on the germination of the spore. This method is efficient for sterilizing which spore loss is kept to a minimum and has a higher rate of germination (HgCl2-90% & NaOCl-80%). The optimum concentration of HgCl2 was 0.1%, then followed by 0.5% and 1.0%, while for NaOCl was 30%, 20%, and 10%.

PEMBERDAYAAN KELOMPOK TANI TERNAK DI DESA CAMPLONG II, KABUPATEN KUPANG DALAM KERANGKA PENCEGAHAN PENYAKIT MENULAR PADA TERNAK MELALUI PEMANFAAT DISINFEKTAN YANG AMAN DAN TEPAT

Infectious diseases in livestock are a major issue in the global livestock industry. Kupang Regency is one of the livestock warehousing regions in NTT, and it also has issues every year owing to infectious diseases that target many species of livestock in the district, particularly cattle and pigs, which are the backbone of Kupang Regency. Recognizing the importance of livestock for the socioeconomic life of the local community and the magnitude of the effects that infectious diseases can have on livestock, one of the important strategic steps that must be taken is to empower livestock farmer groups in the effort to prevent infectious diseases in livestock, particularly in the safe and appropriate use of disinfectants. This community service was carried out at Camplong II Village, Kupang Regency, and three groups of livestock farmers from the village area participated. Counseling, interactive dialogues with livestock farmer groups, and demonstration on the use of appropriate and correct disinfectants were among the activities carried out. This activity revealed that many members of livestock farmer groups are still uninformed of the role and usage of disinfectants in the prevention of infectious diseases in their livestock. At the end of the program, the community learnt to distinguish different types of disinfectants and their applications in the farming managment.

1193. Disinfection of the Sink Drains to Reduce a Source of Serratia marcescens During Infection Outbreaks in a Neonatal Intensive Care Unit

Abstract Background Sink drains are known reservoirs of pathogens and have been associated with multiple nosocomial outbreaks. In this study, the distribution of Serratia marcescens was investigated within the sink environment of a NICU and in colonized or infected newborns. The effect of different types of drain disinfection on bacterial concentration and on the detection of Serratia marcescens in sink drains was also investigated. Methods Sink drains from a NICU were sampled: 20 drains sampled for 6 weeks in the first year and 28 drains sampled for 5 months in the second year. S. marcescens isolated from positive patients were collected. A high-throughput short sequence typing (HiSST) method was developed to identify S. marcescens and compare strains and environmental DNA from sink drains with 56 clinical strains from 5 nosocomial outbreaks. Five interventions were tested: self-disinfecting drains, hot water disinfection, chlorine disinfection, steam disinfection and hot tap water flushing. Bacterial concentration of samples was measured in culture and flow cytometry and the HiSST method was used to identify S. marcescens. Results During the first and second sampling campaigns, 40% and 60% of sink drain samples were positive for S. marcescens with a moderate genotype diversity (1 to 11 different STs). The genotype profile of the 56 clinical strains was heterogeneous (26 STs). Four distinct STs were retrieved in 8 sinks after detection in patients whereas 1 ST was detected in a sink before detection in patient. Some environmental and clinical strains were found in drains for up to a year after the first sampling campaign. Each tested drain intervention reduced culturable bacteria (4-8 log) and viable bacteria (2-3 log), except for chlorine. The self-disinfecting drains, hot water and steam disinfection were able to remove temporarily S. marcescens from the drains. Conclusion The high genotypic diversity of the clinical strains suggests diffuse sources of S. marcescens within the NICU likely to cause nosocomial infection outbreaks. The self-disinfecting drains, hot water and steam disinfection seem to be the best methods to reduce bacterial concentration in drains and eliminate S. marcescens in the short term, thus limiting the risk of pathogens spread from the sink environment to patients. Disclosures All Authors: No reported disclosures.

Design spherical particles of potassium peroxymonosulfate compound salt with high stability and good powder properties via an agglomeration-dissolution mechanism

With the outbreak of COVID-19, disinfection protection has become a necessary measure to prevent infection. As a new type of disinfectant, potassium peroxymonosulfate compound salt (PMS) has the advantages of good bactericidal effect, non-toxicity, high safety and stability. However, the current PMS products with irregular particle shapes lead to poor flowability, high hygroscopicity, poor stability of reactive oxygen species (ROS) and serious caking problems. In this work, an agglomeration-dissolution mechanism was designed to prepare spherical PMS particles with large size (>300 μm) and high sphericity (up to 90%), effectively addressing the above problems. Shaping (dissolution and abrasion) is the key to improving sphericity, which is mainly controlled by the design of the heating mode, residence time and stirring rate. Compared with the irregular PMS particles, the large spherical particles present better flowability (angle of repose decreased by 35.80%, Carr's index decreased by 64.29%, Hausner's ratio decreased by 19.14%), lower hygroscopicity (decreased by 38.0%), lower caking ratio (decreased by 84.50%), and higher stability (the monthly loss of ROS was reduced by 61.68%). The agglomeration-dissolution mechanism demonstrates the crystallization, agglomeration, dissolution and abrasion process of inorganic salt crystals, providing an opportunity to prepare high-end inorganic crystal materials with high-quality morphologies.

COMPARATIVE ANTIMICROBIAL ACTIVITY OF SEVEN DISINFECTANTS MARKETTED IN LAGOS AGAINST CLINICAL BACTERIA ISOLATES

Antimicrobial effects of seven disinfectants were studied against a wide range of clinical bacterial isolates using Agar dilution method to determine the minimum inhibitory concentration (MIC). The active compounds of the disinfectants according to their manufacturer were D1-(Chloroxylenol 4.8% w/v), D2-(Chlorhexidinegluconate 0.3g and Centrimide 3.0% w/v), D3- (Centrimide 3.0% w/v and Chlorhexidinegluconate 0.3g), D4- (Dichloroxylenol 2% w/v), D5- (Sodium hypochlorite 3.85% m/v) and D6- (Halogenated phenol 0.68% and Sodium salicylate 0.052%). The test organisms were clinical isolates of Escherichia coli, Staphylococcus aureus and Salmonella enterica serotype Typhi. The MICs of the disinfectants ranges from 0.003%v/v to 2.5%v/v. This study showed that some of the disinfectants tested have strong bactericidal effect against the clinical bacteria isolates while others were less effective. Results also revealed that D2 which is made of Chlorhexidinegluconate 0.3g and centrimide 3.0% w/v has the greatest antibacterial activity. Likewise, antibacterial effects of the disinfectants are not only dependent on the types of disinfectant but also on their concentrations

The Effect of Hypochlorous Acid Disinfectant on the Reproduction of Details and Surface Hardness of Type III Dental Stone.

Introduction Gypsum products have been used for many years in dentistry. They are used to make casts that are used in different dental laboratory procedures. It is considered a source of contamination because it comes in contact with blood and saliva that are found on dental impressions. Because it is difficult to make sure that every impression brought to the dental laboratory has been cleanedand because cleaning impressionsis a complicated process that can lead to problems because of the way impression materials are made, cleaning the cast has become a key part of preventing infections. For this study, we used two ways (immersion and spray) to apply a hypochlorous acid (HOCl) disinfectant solutionto type III dental stone to see how they affected the stone's surface hardness and its ability to show surface details accurately. Materials and methods A total of 100 samples of type III dental stone, 50 samples for each test, which include the reproduction of detailtest and surface hardness test, were prepared and randomly divided into five groups, 10 samples for each test group, which include group A (control), group B (immersion in 200 ppm HOCl disinfectant for five minutes), group C (spraying with 200 ppm HOCl disinfectant for five minutes), group D (immersion in 0.6% sodium hypochlorite (NaOCl) disinfectant for five minutes), and group E (spraying with 0.6% NaOCl disinfectant for five minutes). Results The results showed that all the samples had met the reproduction of detailtest requirement after disinfection with HOCl, while a significant reduction in the surface hardness of type III stone samples was also shown. Conclusion The less undesirable effects of HOCl disinfectant solution on the surface hardness of type III dental stone when compared to sodium hypochlorite, as well as the absence of adverse effects on detail reproduction, made the HOCl disinfectant solution a good choice for dentists and dental laboratory personnel for cast disinfection and contamination control.

Evaluation of compressed sodium chloride on the inactivation of SARS-CoV-2 and surrogates.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes the global COVID-19 pandemic. Limited studies have been performed on various types of disinfectants utilized to control the spread of this highly contagious virus. This study aimed to investigate the inactivation of SARS-CoV-2 using compressed sodium chloride (CSC) surface. A real-time reverse transcriptase quantitative PCR (RT-qPCR) assay was used to evaluate the effectiveness of CSC on the disintegration of viral RNA in a time dependent manner. The effects of CSC on viral infectivity were determined using a TCID50 assay of a surrogate virus, hCoV-229E, in MRC-5 cell culture. The results demonstrated that CSC achieved a 2 to 3- log10 reduction of viral genomic RNA for a laboratory strain of hCoV-229E, and clinical samples of hCoV-229E and hCoV-OC43. A 3 to 4-log10 reduction was observed for SARS-CoV-2 (RdRp and E gene) suggesting that a CSC surface could effectively disintegrate the SARS-CoV-2 RNA genome. CSC was observed to have a 6 log10 inactivation of infectious hCoV-229E using cell culture after 5 minutes of exposure compared to the control, indicating good disinfection efficacy of a CSC surface against virus.

Comparison of two different antiseptics regarding intracutaneous microbial load after preoperative skin cleansing in total knee and hip arthroplasties

Periprosthetic infections (PPIs) are a serious concern in total knee and hip arthroplasty, and they have an increasing incidence. To prevent PPI, preoperative skin disinfection, as a key element of antisepsis, represents an important part of infection prevention. However, no specific antiseptic agent is endorsed by the relevant guidelines. The purpose of this retrospective, not randomized study was to investigate the difference in the residual bacteria load between an approved antiseptic with an alcohol-based solution with additional benzalkonium chloride (BAC) and an alcohol-based solution with additional octenidine dihydrochloride (OCT) at two different time periods. In 200 consecutive patients with total knee or hip arthroplasty, skin samples from the surgical sites were collected after skin disinfection with BAC (100 g solution contain: propan-2-ol 63.0 g, benzalkonium chloride 0.025 g) or OCT (100 g solution contain: octenidine dihydrochloride 0.1 g, propan-1-ol, 30.0 g, propan-2-ol 45.0 g) (100 patients per group). Following the separation of cutis and subcutis and its processing, culture was performed on different agar plates in aerobic and anaerobic environments. In the case of bacteria detection, the microbial identification was determined by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), and the number of contaminated samples was compared between the groups. Additionally, multiple regression analysis was performed to examine the effect of the type of disinfectant, BMI, age, sex, rheumatoid arthritis, diabetes mellitus, skin disorders, smoking status, and localization of skin samples on positive bacteria detection. A total of 34 samples were positive for bacteria in the BAC group, while only 17 samples were positive in the OCT group (p = 0.005). Disinfectant type was the only significant parameter in the multiple regression analysis (p = 0.006). A significantly higher contamination rate of the subcutis was shown in the BAC group compared to the OCT group (19 vs. 9, p = 0,003). After the change from BAC to OCT in preoperative skin cleansing in the hip and knee areas, the number of positive cultures decreased by 50%, which might have been caused by a higher microbicidal activity of OCT. Therefore, the use of OCT in preoperative cleansing may reduce the risk of PPI in hip and knee surgery. Randomized controlled trials are required to confirm the effect and to evaluate if it reduces the risk of PPI.

Efficacy of Five Disinfectant Products Commonly Used in Pig Herds against a Panel of Bacteria Sensitive and Resistant to Selected Antimicrobials.

Simple SummaryAntimicrobial resistance (AMR) is a growing concern worldwide in both human and veterinary medicine. Biosecurity and the ability to limit bacterial contamination on farms are crucial in the fight against disease, including AMR bacteria. This study aimed to investigate whether the recommended concentrations of five commercial disinfectants (A to E) were sufficient to inhibit growth and inactivate a panel of bacterial strains, including some that carry multidrug resistance to selected antimicrobials. The effectiveness of each disinfectant was expressed as the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The results indicate that the type of disinfectant and its concentration influence the inhibitory and bactericidal efficacy. The glutaraldehyde/quaternary ammonium-compound-based (disinfectant D) and chlorocresol-based products (disinfectant B) were the most effective in this study. Varying results were observed for the other compounds, depending on the bacterial species tested. The iodine-based (disinfectant C) and potassium-peroxymonosulfate-based (disinfectant A) products were less able to inhibit or inactivate the bacteria. The disinfectant products were less effective against the strains of E. coli with different phenotypic profiles of antimicrobial resistance compared to sensitive strains.The growing threat of antimicrobial resistance worldwide has led to an increasing concern in the human, veterinary, and environmental fields, highlighting the need for strategies to effectively control bacterial contamination. Correct biosecurity practices, including the appropriate use of disinfectants, play a crucial role in controlling bacterial contamination. This study aimed to verify whether the recommended concentrations defined according to the Defra General Orders concentration (GO, published by the UK Department for Environment, Food and Rural Affairs’ disinfectant-approval scheme) of five commercial disinfectant preparations (peroxygen-based, phenol-based, two halogen-releasing agents, and glutaraldehyde/quaternary ammonium compound-based; disinfectants A to E, respectively) were sufficient to inhibit growth and inactivate selected bacterial strains, including some that carry known phenotypic patterns of multidrug resistance. The effectiveness of each disinfectant was expressed as the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values, determined by the broth-microdilution method. The results indicate that the type of disinfectant and its concentration influence the inhibitory and bactericidal efficacy. The glutaraldehyde/quaternary ammonium compound-based (disinfectant D) and chlorocresol-based products (disinfectant B) were the most effective, and the GO concentration was bactericidal in all the strains tested. The efficacy of the other compounds varied, depending on the bacterial species tested. The GO concentrations were at least able to inhibit the bacterial growth in all the products and bacterial strains tested. A greater tolerance to the compounds was observed in the strains of E. coli with multidrug-resistance profiles compared to the strains that were sensitive to the same antimicrobials.

Efektivitas Didecyldimethylammonium Chloride 2.5% dan Chlorine 0.5% terhadap Pertumbuhan Staphylococcus aureus dan Klebsiella pneumoniae di Ruang Operasi

This study aims to determine the effectiveness of the disinfection of 0.5% chlorine and 2.5% didecyldimethylammonium chloride against Staphylococcus aureus and Klebsiella pneumoniae in the operating room. The method used is a quasi-experimental post-only group design with a total sample of 40 samples of the operating room environment. The results showed no difference between the two types of disinfectants, namely didecyldimethylammonium chloride 2.5% and chlorine 0.5% in reducing the number of bacteria (p-value 0.373) and both were able to reduce the number of Staphylococcus aureus and Klebsiella pneumoniae. In conclusion, both disinfectants effectively reduced Staphylococcus aureus and Klebsiella pneumoniae on operating room surfaces.
 Keywords: Didecyldimethylammonium Chloride Disinfection, Chlorine, Bacterial Growth, Operating Room

Inhibición de la actividad metanogénica acetoclástica para diferentes desinfectantes usados en el lavado de equipo en la industria farmacéutica

The pharmaceutical industry uses different types of disinfectants in the washing processes of different equipment, which become part of the wastewaters generated in the production processes. The nature of these compounds can diminish the biodegradability of the effluents; hence, this is an important issue to consider during the design and operation of treatment processes. This study establishes the kinetic parameters for three commercial disinfectants, using anaerobic sludges as inoculum. The doses for the active principle (quaternary salt) that yield a 50% reduction of the methanogenic inoculum were 1.6X10-3 kg · m-3 for benzalkonium, 8.4X10-3 kg · m-3 for bactium, and 154X10-3 kg · m-3 for anibac. The three disinfectants induced a mixed-type inhibition on the anaerobic biodegradability of sodium acetate, the main precursor of methanogenesis during anaerobic digestion.

Use of a door handle disinfection system to reduce the risks associated with microbial loads on fomites in a healthcare setting

Pathogenic organisms, including those that are multidrug resistant, can survive for extended periods of time on surfaces. Numerous studies show that contaminated hand-touch sites, such as door handles, pose a serious risk for onward transfer to patients. To compare microbial levels on the handles of ten frequently used door locations, with and without a door handle disinfection system in place, in a busy rehabilitation unit consisting of two wards at the National Orthopaedic Hospital, Dublin. A door handle disinfection system (Handle Hygiene®), utilizing an atomizing pump (non-aerosol), automatically delivered a pulse of disinfectant to a door handle each time the door was used. Microbial levels on the handles of frequently used door locations were monitored over a 16-week period, to compare microbial loads with and without a door handle disinfection system in place. Samples of two disinfectant types, Steri-7 (broad-spectrum disinfectant) and Dew (hypochlorous acid), were used in the study. Levels of ≤2.5cfu/cm2 were recorded on 93% of samples collected where a door handle disinfection system was in use, with 66% of samples showing no microbes recovered. Where a level of >2.5cfu/cm2 was recorded, the door handle disinfection system reduced this to a negligible level by the time the next sample was taken, compared with several days where no system was in place. Door handle disinfection systems offer an effective solution to reducing microbial levels on frequently touched door handles, as an automated solution with minimal additional costs.

Impact of pipe material, operation, and disinfectant on cold water plumbing microbiology

AbstractThis study examined the effects of pipe materials, pipe diameters, frequency of use, and disinfectant types on the water quality microbiology in experimental pipe rack systems. Two pipe rack systems were installed in buildings in Colorado (CO) and Pennsylvania (PA) and sampled for 8–9 months of operation, respectively, under simulated high and low use conditions. Opportunistic premise plumbing pathogens including Legionella pneumophila, nontuberculous mycobacteria, Pseudomonas aeruginosa, and free‐living amoebae (FLA) were the target organisms. Disinfectant type (free chlorine vs. chloramine) and use frequency (flushed every 12 h vs. weekly) had the greatest impact on bulk water microbiology. Under low use conditions, neither system had detectable disinfectant residual but under high use, residual was detected. Heterotrophic plate count bacteria predominated in the free chlorine system while nontuberculous mycobacteria were predominant in the chloraminated system. P. aeruginosa and FLA were not detected in the free chlorine system and legionellae were not detected in either system.

Chloramine Prevents Manganese Accumulation in Drinking Water Pipes Compared to Free Chlorine by Simultaneously Inhibiting Abiotic and Biotic Mn(II) Oxidation

The oxidation of residual Mn(II) in finished water can lead to MnOx deposit formation in drinking water pipes. Previous work has illustrated that microbes readily cause Mn deposit build-up in nondisinfected pipes. Here, we investigated how disinfectant type and dose affected Mn(II) oxidation and MnOx accumulation through long-term pipe experiments using water produced by a full-scale water treatment plant. The results showed that Mn(II) oxidation initiated quickly in the new pipes chlorinated with 1.0 mg/L free chlorine. After 130 days of MnOx accumulation, 100 μg/L Mn(II) in water could drop to 1.0 μg/L within 1.5 h, resulting from autocatalytic Mn(II) oxidation and Mn(II) adsorption by MnOx deposits accumulated on pipe walls. In contrast to chlorination, chloramination (1.0 mg/L Cl2) caused almost no MnOx accumulation during the entire study period. The underlying mechanism was probably that monochloramine inhibited microbial Mn(II) oxidation without causing significant abiotic Mn(II) oxidation like free chlorine. A low free chlorine dose (0.3 mg/L) also reduced Mn deposit formation by mass but to a lesser extent than chloramination. After disinfection (chlorination or chloramination) was discontinued for days, biotic Mn(II) oxidation occurred, and this process was inhibited again once disinfection was resumed. In addition, Fe(III) of 200 μg/L enhanced the stability of MnOx accumulated on pipe surfaces, while humic acid induced MnOx deposit resuspension. Overall, this study highlighted the regulating role of disinfectants in MnOx formation and provided insights into developing appropriate disinfection strategies for Mn deposit control.