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Hu J, Wang R, Li S, Wu J, Qiang Z. Mechanisms of iopamidol transformation catalyzed by a copper corrosion product (c-Cu 2O) during peroxymonosulfate disinfection. JOURNAL OF HAZARDOUS MATERIALS 2024; 462:132821. [PMID: 37879278 DOI: 10.1016/j.jhazmat.2023.132821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 08/03/2023] [Accepted: 10/19/2023] [Indexed: 10/27/2023]
Abstract
Peroxymonosulfate (PMS) is an alternative disinfectant for drinking water. This study aimed to investigate the transformation of iopamidol (IPM) catalyzed by a main copper corrosion product (c-Cu2O) with PMS as a disinfectant. The observed pseudo-first-order constant (kobs) for the IPM degradation in the c-Cu2O/PMS system (0.033 min-1) was 3 times that in the CuO/PMS system (0.011 min-1). The quenching tests and the electron paramagnetic resonance (EPR) experiments indicate that O2•- and 1O2 contributed to IPM degradation in the c-Cu2O/ PMS system. The complexation of metastable Cu(II) with a PMS molecule polarized the OO bond and then facilitated the electron transfer from the PMS molecule to other PMS and O2 molecules, which directly and indirectly promoted the yield of O2•- and 1O2. The iodine balance indicated that 26.0% of initial TOI was converted to IO3-, and CHI3 only accounted for 0.6% of the residual TOI. In the c-Cu2O/PMS system, IPM conversion was started with amide C-N bond breakage, deiodination reaction and hydrogen abstraction. This study helps to better understand the conversion mechanisms of iodine-containing organic micropollutants when PMS is deployed as a disinfectant in copper pipes.
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Affiliation(s)
- Jun Hu
- College of Environment, Center for Membrane and Water Science & Technology, Zhe, jiang University of Technology, 18 Chao-wang Road, Hangzhou 310014, China; Innovation Research Center for Advanced Environmental Technology, Eco-industrial Innovation Institute ZJUT, 2 Rong-chang East Road, Quzhou 324400, China
| | - Ruiqi Wang
- College of Environment, Center for Membrane and Water Science & Technology, Zhe, jiang University of Technology, 18 Chao-wang Road, Hangzhou 310014, China
| | - Shangkun Li
- College of Environment, Center for Membrane and Water Science & Technology, Zhe, jiang University of Technology, 18 Chao-wang Road, Hangzhou 310014, China; Zhejiang Huanke Environmental Research Institute Co., Ltd., Hangzhou 311121, China
| | - Jun Wu
- College of Environment, Center for Membrane and Water Science & Technology, Zhe, jiang University of Technology, 18 Chao-wang Road, Hangzhou 310014, China.
| | - Zhimin Qiang
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco, Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing 100085, China
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Lee GH, Park SH, Song BM, Kim DM, Han HJ, Park JY, Jo YW, Hwang MY, Sim KT, Kang SM, Tark D. Comparative efficacy evaluation of disinfectants against severe acute respiratory syndrome coronavirus-2. J Hosp Infect 2023; 131:12-22. [PMID: 36183929 PMCID: PMC9639569 DOI: 10.1016/j.jhin.2022.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/20/2022] [Accepted: 09/20/2022] [Indexed: 01/25/2023]
Abstract
BACKGROUND Disinfection is one of the most effective ways to block the rapid transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Due to the prolonged coronavirus disease 2019 (COVID-19) pandemic, disinfectants have become crucial to prevent person-to-person transmission and decontaminate hands, clothes, facilities and equipment. However, there is a lack of accurate information on the virucidal activity of commercial disinfectants. AIM To evaluate the virucidal efficacy of 72 commercially available disinfectants constituting 16 types of ingredients against SARS-CoV-2. METHODS SARS-CoV-2 was tested with various concentrations of disinfectants at indicated exposure time points as recommended by the manufacturers. The 50% tissue culture infectious dose assay was used to calculate virus titre, and trypan blue staining and CCK-8 were used to assess cell viability after 3-5 days of SARS-CoV-2 infection. FINDINGS This study found that disinfectants based on 83% ethanol, 60% propanol/ethanol, 0.00108-0.0011% sodium dichloroisocyanurate and 0.497% potassium peroxymonosulfate inactivated SARS-CoV-2 effectively and safely. Although disinfectants based on 0.05-0.4% benzalkonium chloride (BAC), 0.02-0.07% quaternary ammonium compound (QAC; 1:1), 0.4% BAC/didecyldimethylammonium chloride (DDAC), 0.28% benzethonium chloride concentrate/2-propanol, 0.0205-0.14% DDAC/polyhexamethylene biguanide hydrochloride (PHMB) and 0.5% hydrogen peroxide inactivated SARS-CoV-2 effectively, they exhibited cytotoxicity. Conversely, disinfectants based on 0.04-4% QAC (2:3), 0.00625% BAC/DDAC/PHMB, and 0.0205-0.14% and 0.0173% peracetic acid showed approximately 50% virucidal efficacy with no cytotoxicity. Citric acid (0.4%) did not inactivate SARS-CoV-2. CONCLUSION These results indicate that most commercially available disinfectants exert a disinfectant effect against SARS-CoV-2. However, re-evaluation of the effective concentration and exposure time of certain disinfectants is needed, especially citric acid and peracetic acid.
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Affiliation(s)
- G-H. Lee
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - S-H. Park
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - B-M. Song
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - D-M. Kim
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - H-J. Han
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - J-Y. Park
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea
| | - Y-W. Jo
- Division of Chemical Research, National Institute of Environmental Research, Incheon, Republic of Korea
| | - M-Y. Hwang
- Division of Chemical Research, National Institute of Environmental Research, Incheon, Republic of Korea
| | - K-T. Sim
- Division of Chemical Research, National Institute of Environmental Research, Incheon, Republic of Korea
| | - S-M. Kang
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea,Corresponding author. Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Republic of Korea
| | - D. Tark
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, Republic of Korea,Corresponding author. Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Republic of Korea
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An Evaluation of Sporicidal Treatments against Blown Pack Spoilage Associated Clostridium estertheticum and Clostridium gasigenes Spores. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12031663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Blown pack spoilage (BPS) occurs when meat is cross-contaminated with Clostridium estertheticum or Clostridium gasigenes spores, often from the meat processing environment. This study tested the efficacy of four sporicidal disinfectants commonly used in beef processing plants against C. estertheticum and C. gasigenes spores in a suspension test. D-values were obtained under model ‘clean’ (sterile distilled water, SDW) and ‘dirty’ (3 g/L bovine serum albumin, BSA) conditions. Mean concentration (log10 CFU/mL) were calculated from direct counts. The levels of dipicolinic acid (DPA), indicating damage to the core of these spores, was also monitored using a terbium (Tb)-DPA assay for treatment 1 (peracetic acid as the active ingredient) in SDW and BSA. In SDW sporicidal treatment 3 (containing peroxymonosulphate) was the most effective against C. estertheticum spores but under ‘dirty’ (BSA) conditions sporicidal treatments 1 and 2 were more effective. A similar pattern was obtained with C. gasigenes with treatment 3 being the most effective in SDW but treatment 2 (sodium hypochlorite as the active ingredient) being more effective in BSA. The lower DPA concentrations obtained in SDW versus BSA demonstrated the protective effect of organic matter. It was concluded that meat processors should use a 5% formulation containing sodium hypochlorite, sodium hydroxide and alkylamine oxide to eliminate BPS Clostridial spores in the abattoir.
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Sovijit W, Taesuji M, Rattanamas K, Punyadarsaniya D, Mamom T, Nguyen HT, Ruenphet S. In vitro cytotoxicity and virucidal efficacy of potassium hydrogen peroxymonosulfate compared to quaternary ammonium compound under various concentrations, exposure times and temperatures against African swine fever virus. Vet World 2021; 14:2936-2940. [PMID: 35017841 PMCID: PMC8743787 DOI: 10.14202/vetworld.2021.2936-2940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 10/13/2021] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND AIM The selection and proper application of disinfectants are crucial to the prevention of many diseases, so disinfectants must be evaluated before being used for the prevention of African swine fever (ASF). Three disinfectant products belonging to the group of potassium hydrogen peroxymonosulfates, product A and product B, and a quaternary ammonium compound called product C, were examined in vitro for host cell cytotoxicity and the efficacy of ASF virus inactivation. The study parameters included various concentrations, exposure times, temperatures, and degrees of cytotoxicity. MATERIALS AND METHODS Three disinfectant products were evaluated for cytotoxicity using primary porcine alveolar macrophage (PAM) cells at dilutions from 1:200 to 1:51,200. Disinfectants in concentrations of 1:200, 1:400, and 1:800 were prepared, the pH and the virucidal activity were tested. An equal volume of each dilution was mixed with the ASF virus and incubated at room temperature (20°C) or on ice (4°C) for 1 min, 5 min, or 30 min. Hemadsorption (HAD) or rosette formation was observed using an inverted microscope for 5 days after inoculation, and the virus titer was calculated as HAD50/mL. Each treatment and virus control were tested in triplicate, and the titers were reported as means and standard deviations. The reduction factor was used to measure inactivation. RESULTS Products A, B, and C at 1:400, 1:800, and 1:25,600 of dilution, respectively, did not show significant cytotoxic effects on PAM cells. Products A and B could inactivate ASF virus at 1:200 dilution within 5 min after exposure at 4°C. However, at 20°C, the exposure time had to be extended to 30 min to inactivate the virus. Product C could inactivate the virus at 1:400 dilution within 5 min under both temperature conditions, whereas at 1:800 dilution, the exposure time had to be extended to 30 min to completely inactivate the virus at 20°C. CONCLUSION All disinfectants could inactivate ASF virus in various concentrations, under appropriate exposure times and reaction temperatures, and there was no evidence of host cell cytotoxicity. For the control of ASF in pig farms, the appropriate concentration, ambient temperature, and contact time of these disinfectants should be taken into account.
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Affiliation(s)
- Watcharee Sovijit
- Department of Immunology and Virology, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok, Thailand
| | - Machimaporn Taesuji
- Department of Immunology and Virology, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok, Thailand
| | - Khate Rattanamas
- Department of Immunology and Virology, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok, Thailand
| | - Darsaniya Punyadarsaniya
- Department of Immunology and Virology, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok, Thailand
| | - Thanongsak Mamom
- Department of Pathology, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok, Thailand
| | - Hoa Thi Nguyen
- Key Laboratory of Veterinary Biotechnology, Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Sakchai Ruenphet
- Department of Immunology and Virology, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok, Thailand
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Zatorska B, Moser D, Diab-Elschahawi M, Ebner J, Lusignani LS, Presterl E. The effectiveness of surface disinfectants and a micellic H 2O 2 based water disinfectant on Candida auris. J Mycol Med 2021; 31:101178. [PMID: 34388399 DOI: 10.1016/j.mycmed.2021.101178] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 06/14/2021] [Accepted: 07/30/2021] [Indexed: 12/01/2022]
Abstract
BACKGROUND As infection control faces new challenges from emerging, multidrug resistant strains of the yeast Candida auris, this study was conducted in order to examine the efficacy of hospital surface disinfectants and a new water disinfectant against C. auris biofilm forms. METHODS We tested four reference strains of C. auris (NCPF8971, NCPF8977, NCPF8984, DSM21092) and one C. albicans strain (ATCC10231) against disinfectants based on ethanol (ETH), quaternary ammonium (QAC), a combination of glutaraldehyde, quaternary ammonium and surfactant (ALD) and potassium peroxymonosulfate (PP) as well as 3.4% H2O2 and 4.25% H2O2 alone. In addition, a micellic-based formulation containing 17% v/v hydrogene peroxide disinfectant (mH2O2) was tested. The efficacy of the disinfectants was measured in a 96-well plate using tetrazolium salt reduction (XTT) and the log10 reduction assay. RESULTS ETH and QAC displayed in clinically recommended concentrations more than 5log10 reduction and more than 80% XTT activity reduction for all of the Candida biofilms and planktonic cells. Only biofilms of C. auris NCPF8984 were additionally sensitive to all remaining disinfectants. All tested C. auris biofilms were sensitive to PP disinfectant and showed more than 5log10 reduction. However, the XTT assay showed a reduction of less than 80% for the PP disinfectant, indicating the presence of active but non-culturable cells. The 25% mH2O2 (corresponding to 4.25% H2O2) killed Candida biofilms after 1 minute.
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Affiliation(s)
- Beata Zatorska
- Department of Hospital Hygiene and Infection Control, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Doris Moser
- Department of Cranio-Maxillofacial and Oral Surgery, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Magda Diab-Elschahawi
- Department of Hospital Hygiene and Infection Control, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Julia Ebner
- Department of Hospital Hygiene and Infection Control, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Luigi Segagni Lusignani
- Department of Hospital Hygiene and Infection Control, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Elisabeth Presterl
- Department of Hospital Hygiene and Infection Control, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria.
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McSharry S, Koolman L, Whyte P, Bolton D. Investigation of the Effectiveness of Disinfectants Used in Meat-Processing Facilities to Control Clostridium sporogenes and Clostridioides difficile Spores. Foods 2021; 10:foods10061436. [PMID: 34205779 PMCID: PMC8234884 DOI: 10.3390/foods10061436] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 05/28/2021] [Accepted: 06/17/2021] [Indexed: 11/26/2022] Open
Abstract
Spore-forming bacteria are a major concern for the food industry as they cause both spoilage and food safety issues. Moreover, as they are more resistant than vegetative cells, their removal from the food processing environment may be difficult to achieve. This study investigated the efficacy of the ten most commonly used disinfectant agents (assigned 1–10), used at the recommended concentrations in the meat industry, for their ability to eliminate Clostridium sporogenes and Clostridioides difficile spores. Test-tube based suspension assays suggested that disinfectants 2 (10% v/v preparation of a mixture of hydrogen peroxide (10–30%), acetic acid (1–10%) and peracetic acid (1–10%)), 7 (4% w/v preparation of a mixture of peroxymonosulphate (30–50%), sulphamic acid (1–10%) and troclosene sodium (1–10%)) and 10 (2% v/v preparation of a mixture of glutaraldehyde (10–30%), benzalkonium chloride (1–10%)) were the most effective formulations. D-values for these ranged from 2.1 to 8.4 min at 20 °C for the target spores. Based on these findings, it is recommended that these disinfectants are used to control Clostridium spores in the meat plant environment.
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Affiliation(s)
- Siobhán McSharry
- Teagasc Food Research Centre, Ashtown, 15 Dublin, Ireland; (S.M.); (L.K.)
- School of Veterinary Medicine, University College Dublin, Belfield, 4 Dublin, Ireland;
| | - Leonard Koolman
- Teagasc Food Research Centre, Ashtown, 15 Dublin, Ireland; (S.M.); (L.K.)
| | - Paul Whyte
- School of Veterinary Medicine, University College Dublin, Belfield, 4 Dublin, Ireland;
| | - Declan Bolton
- Teagasc Food Research Centre, Ashtown, 15 Dublin, Ireland; (S.M.); (L.K.)
- Correspondence: ; Tel.: +353-0-1-805-9539
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Miyaoka Y, Kabir MH, Hasan MA, Yamaguchi M, Shoham D, Murakami H, Takehara K. Virucidal activity of slightly acidic hypochlorous acid water toward influenza virus and coronavirus with tests simulating practical usage. Virus Res 2021; 297:198383. [PMID: 33705798 DOI: 10.1016/j.virusres.2021.198383] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 02/21/2021] [Accepted: 03/04/2021] [Indexed: 10/22/2022]
Abstract
Slightly acidic hypochlorous acid waters (SAHWs) with pH of 5.2-5.8 containing different concentrations of free available chlorine - 62, 119, 220, 300, and 540 ppm (SAHW-62, -119, -220, -300, and -540, respectively) - were evaluated for their virucidal activity toward a low pathogenic H7N1 avian influenza virus (AIV) and an infectious bronchitis virus (IBV) in suspension, abiotic carrier, and direct spray tests, with the presence of organic materials. In the carrier test, the dropping and wiping techniques were performed toward viruses on carriers. In the suspension test, SAHW-62 could decrease the viral titer of both AIV and IBV by more than 1000 times within 30 s. With the dropping technique, IBV on carriers showed high resistance to SAHW, while AIV on plastic carrier was inactivated to an effective level (≧3 log virus reduction) within 1 min. With the wiping technique, SAHW-62 could inactivate both AIV and IBV on wiped plastic carriers to an effective level within 30 s. However, SAHW-220 could not inactivate IBV in the wiping rayon sheet to an effective level. In the direct spray test, sprayed SAHW-300 within 10 min, and SAHW-540 within 20 min, inactivated AIV and IBV on the rayon sheets to undetectable level, respectively. Our study indicates that the usage of wipes with SAHW could remove viruses from plastic carriers, while viruses remained in the wipes. Besides, a small volume of sprayed SAHW was effective against the viruses on the rayon sheets for daily cleaning in the application area. The findings we obtained concerning IBV might basically be applicable in relation to SARS-CoV-2, given the resemblance between the two viruses.
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Affiliation(s)
- Yu Miyaoka
- Laboratory of Animal Health, Cooperative Division of Veterinary Sciences, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Md Humayun Kabir
- Laboratory of Animal Health, Cooperative Division of Veterinary Sciences, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Md Amirul Hasan
- Laboratory of Animal Health, Cooperative Division of Veterinary Sciences, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Makiko Yamaguchi
- Laboratory of Animal Health, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Dany Shoham
- Bar-Ilan University, Begin-Sadat Center for Strategic Studies, Ramat Gan, 5290002, Israel
| | - Harumi Murakami
- Laboratory of Animal Health, Cooperative Division of Veterinary Sciences, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan; Laboratory of Animal Health, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Kazuaki Takehara
- Laboratory of Animal Health, Cooperative Division of Veterinary Sciences, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan; Laboratory of Animal Health, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
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Osland AM, Vestby LK, Nesse LL. The Effect of Disinfectants on Quinolone Resistant E. coli (QREC) in Biofilm. Microorganisms 2020; 8:microorganisms8111831. [PMID: 33233591 PMCID: PMC7699778 DOI: 10.3390/microorganisms8111831] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 11/18/2020] [Indexed: 12/18/2022] Open
Abstract
The aim of disinfection is to reduce the number of microorganisms on surfaces which is a challenge due to biofilms. In the present study, six quinolone resistant Escherichia coli (QREC) strains with three different biofilm matrix compositions were included to assess the log10 colony forming units (CFU) reduction effect of three disinfectants at various exposure times on biofilm of different ages and morphotypes. Biofilm was formed on stainless steel coupons for two and five days before transferred to tubes with Virocid 0, 25%, VirkonS 1%, and TP990 1% and left for various exposure times. The biofilms were scraped off and serial dilutions were spread on blood agar plates where colony forming units (CFU) were counted. A mean log10 CFU reduction ≥4 was seen on two-day-old biofilm with VirkonS and Virocid (30 min) but not on five-day old biofilm. TP990 did not display sufficient effect under the conditions tested. The bactericidal effect was inferior to that reported on planktonic bacteria. The findings of this study should be considered when establishing both disinfectant routines and standard susceptibility tests, which further should accommodate E. coli biofilms and not only Pseudomonas as is the case today.
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