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Mazurkiewicz E, Lamch Ł, Wilk KA, Obłąk E. Anti-adhesive, anti-biofilm and fungicidal action of newly synthesized gemini quaternary ammonium salts. Sci Rep 2024; 14:14110. [PMID: 38898117 PMCID: PMC11187217 DOI: 10.1038/s41598-024-64859-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 06/13/2024] [Indexed: 06/21/2024] Open
Abstract
Newly synthesized gemini quaternary ammonium salts (QAS) with different counterions (bromide, hydrogen chloride, methylcarbonate, acetate, lactate), chain lengths (C12, C14, C16) and methylene linker (3xCH2) were tested. Dihydrochlorides and dibromides with 12 carbon atoms in hydrophobic chains were characterized by the highest biological activity against planktonic forms of yeast and yeast-like fungi. The tested gemini surfactants also inhibited the production of filaments by C. albicans. Moreover, they reduced the adhesion of C. albicans cells to the surfaces of stainless steel, silicone and glass, and slightly to polystyrene. In particular, the gemini compounds with 16-carbon alkyl chains were most effective against biofilms. It was also found that the tested surfactants were not cytotoxic to yeast cells. Moreover, dimethylcarbonate (2xC12MeCO3G3) did not cause hemolysis of sheep erythrocytes. Dihydrochlorides, dilactate and diacetate showed no mutagenic potential.
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Affiliation(s)
- Edyta Mazurkiewicz
- Department of Physico-Chemistry of Microorganisms, Faculty of Biological Sciences, University of Wrocław, Przybyszewskiego 63/77, 51-148, Wrocław, Poland
| | - Łukasz Lamch
- Department of Engineering and Technology of Chemical Processes, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370, Wrocław, Poland
| | - Kazimiera A Wilk
- Department of Engineering and Technology of Chemical Processes, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370, Wrocław, Poland
| | - Ewa Obłąk
- Department of Physico-Chemistry of Microorganisms, Faculty of Biological Sciences, University of Wrocław, Przybyszewskiego 63/77, 51-148, Wrocław, Poland.
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2
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Mikuni-Mester P, Robben C, Witte AK, Linke K, Ehling-Schulz M, Rossmanith P, Grunert T. Antimicrobial Ionic Liquids: Ante-Mortem Mechanisms of Pathogenic EPEC and MRSA Examined by FTIR Spectroscopy. Int J Mol Sci 2024; 25:4705. [PMID: 38731923 PMCID: PMC11083031 DOI: 10.3390/ijms25094705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 04/22/2024] [Accepted: 04/22/2024] [Indexed: 05/13/2024] Open
Abstract
Ionic liquids (ILs) have gained considerable attention due to their versatile and designable properties. ILs show great potential as antibacterial agents, but understanding the mechanism of attack on bacterial cells is essential to ensure the optimal design of IL-based biocides. The final aim is to achieve maximum efficacy while minimising toxicity and preventing resistance development in target organisms. In this study, we examined a dose-response analysis of ILs' antimicrobial activity against two pathogenic bacteria with different Gram types in terms of molecular responses on a cellular level using Fourier-transform infrared (FTIR) spectroscopy. In total, 18 ILs with different antimicrobial active motifs were evaluated on the Gram-negative enteropathogenic Escherichia coli (EPEC) and Gram-positive methicillin-resistant Staphylococcus aureus (MRSA). The results showed that most ILs impact bacterial proteins with increasing concentration but have a minimal effect on cellular membranes. Dose-response spectral analysis revealed a distinct ante-mortem response against certain ILs for MRSA but not for EPEC. We found that at sub-lethal concentrations, MRSA actively changed their membrane composition to counteract the damaging effect induced by the ILs. This suggests a new adaptive mechanism of Gram-positive bacteria against ILs and demonstrates the need for a better understanding before using such substances as novel antimicrobials.
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Affiliation(s)
- Patrick Mikuni-Mester
- Centre for Food Science and Veterinary Public Health, Unit of Food Microbiology, Clinical Department for Farm Animals and Food System Science, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria;
- FFoQSI—Austrian Competence Centre for Feed and Food Quality, Safety & Innovation, Technopark 1D, 3430 Tulln, Austria
| | - Christian Robben
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria;
| | - Anna K. Witte
- HTK Hygiene Technologie Kompetenzzentrum GmbH, Buger Str. 80, 96049 Bamberg, Germany;
| | - Kristina Linke
- ZuchtData EDV-Dienstleistungen GmbH, Dresdner Str. 89/18, 1200 Vienna, Austria;
| | - Monika Ehling-Schulz
- Centre of Pathobiology, Functional Microbiology Division, Department of Biological Sciences and Pathobiology, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria; (M.E.-S.); (T.G.)
| | - Peter Rossmanith
- Centre for Food Science and Veterinary Public Health, Unit of Food Microbiology, Clinical Department for Farm Animals and Food System Science, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria;
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria;
| | - Tom Grunert
- Centre of Pathobiology, Functional Microbiology Division, Department of Biological Sciences and Pathobiology, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria; (M.E.-S.); (T.G.)
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3
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Defeat undefeatable: ionic liquids as novel antimicrobial agents. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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4
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M. S. Costa F, Lúcia M. F. S. Saraiva M, L. C. Passos M. Ionic Liquids and Organic Salts with Antimicrobial Activity as a Strategy Against Resistant Microorganisms. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Navarro S, Sherman E, Colmer-Hamood JA, Nelius T, Myntti M, Hamood AN. Urinary Catheters Coated with a Novel Biofilm Preventative Agent Inhibit Biofilm Development by Diverse Bacterial Uropathogens. Antibiotics (Basel) 2022; 11:1514. [PMID: 36358169 PMCID: PMC9686518 DOI: 10.3390/antibiotics11111514] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 10/22/2022] [Accepted: 10/25/2022] [Indexed: 08/03/2023] Open
Abstract
Despite the implementation of stringent guidelines for the prevention of catheter-associated (CA) urinary tract infection (UTI), CAUTI remains one of the most common health care-related infections. We previously showed that an antimicrobial/antibiofilm agent inhibited biofilm development by Gram-positive and Gram-negative bacterial pathogens isolated from human infections. In this study, we examined the ability of a novel biofilm preventative agent (BPA) coating on silicone urinary catheters to inhibit biofilm formation on the catheters by six different bacterial pathogens isolated from UTIs: three Escherichia coli strains, representative of the most common bacterium isolated from UTI; one Enterobacter cloacae, a multidrug-resistant isolate; one Pseudomonas aeruginosa, common among patients with long-term catheterization; and one isolate of methicillin-resistant Staphylococcus aureus, as both a Gram-positive and a resistant organism. First, we tested the ability of these strains to form biofilms on urinary catheters made of red rubber, polyvinyl chloride (PVC), and silicone using the microtiter plate biofilm assay. When grown in artificial urine medium, which closely mimics human urine, all tested isolates formed considerable biofilms on all three catheter materials. As the biofilm biomass formed on silicone catheters was 0.5 to 1.6 logs less than that formed on rubber or PVC, respectively, we then coated the silicone catheters with BPA (benzalkonium chloride, polyacrylic acid, and glutaraldehyde), and tested the ability of the coated catheters to further inhibit biofilm development by these uropathogens. Compared with the uncoated silicone catheters, BPA-coated catheters completely prevented biofilm development by all the uropathogens, except P. aeruginosa, which showed no reduction in biofilm biomass. To explore the reason for P. aeruginosa resistance to the BPA coating, we utilized two specific lipopolysaccharide (LPS) mutants. In contrast to their parent strain, the two mutants failed to form biofilms on the BPA-coated catheters, which suggests that the composition of P. aeruginosa LPS plays a role in the resistance of wild-type P. aeruginosa to the BPA coating. Together, our results suggest that, except for P. aeruginosa, BPA-coated silicone catheters may prevent biofilm formation by both Gram-negative and Gram-positive uropathogens.
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Affiliation(s)
- Stephany Navarro
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | | | - Jane A. Colmer-Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Medical Education, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Thomas Nelius
- Department of Urology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | | | - Abdul N. Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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6
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Gundolf T, Kalb R, Rossmanith P, Mester P. Bacterial Resistance Toward Antimicrobial Ionic Liquids Mediated by Multidrug Efflux Pumps. Front Microbiol 2022; 13:883931. [PMID: 35663893 PMCID: PMC9161554 DOI: 10.3389/fmicb.2022.883931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/27/2022] [Indexed: 11/13/2022] Open
Abstract
The effective elimination of foodborne pathogens through cleaning and disinfection measures is of great importance to the food processing industry. As food producers rely heavily on disinfectants to control pathogenic bacteria in their facilities, the increasing spread of tolerant, often even multidrug resistant, strains is of particular concern. In addition to efforts to prevent or at least reduce development and spread of strains resistant to disinfectants and sanitizers, there is an urgent need for new and effective antimicrobials. One new class of promising antimicrobials is ionic liquids (ILs), which have been reported to be effective against resistant strains as they interact with bacterial cells in multiple ways, but investigations of their effectivity against MDR bacteria or specific defense mechanisms are still limited. This study investigates the role of multidrug efflux pumps of the Resistance Nodulation-Division family (RND) on the resistance of bacterial pathogens Escherichia coli and Salmonella enterica serovar Typhimurium toward 10 antimicrobial active ILs. Results reveal that, while known structure–activity relationships (SARs), such as the side-chain effect, were found for all strains, antimicrobial ILs with one elongated alkyl side chain were significantly affected by the RND efflux pump, highlighting the importance of efflux pumps for future IL toxicity studies. In case of antimicrobial ILs with multiple side chains and different cationic head groups, two ILs were identified that were highly active against all investigated strains with little to no effect of the efflux pump. The results obtained in this study for RND efflux pumps can serve as a starting point for identifying and designing antimicrobial ILs as effective biocides against MDR bacteria.
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Affiliation(s)
- Tobias Gundolf
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, Unit for Food Microbiology, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Vienna, Austria
| | - Roland Kalb
- Proionic Production of Ionic Substances GmbH, Grambach, Austria
- Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Peter Rossmanith
- Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
- Unit for Food Microbiology, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Vienna, Austria
| | - Patrick Mester
- Unit for Food Microbiology, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Vienna, Austria
- *Correspondence: Patrick Mester,
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Guzmán L, Parra-Cid C, Guerrero-Muñoz E, Peña-Varas C, Polo-Cuadrado E, Duarte Y, Castro RI, Nerio LS, Araya-Maturana R, Asefa T, Echeverría J, Ramírez D, Forero-Doria O. Antimicrobial properties of novel ionic liquids derived from imidazolium cation with phenolic functional groups. Bioorg Chem 2021; 115:105289. [PMID: 34426154 DOI: 10.1016/j.bioorg.2021.105289] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 08/13/2021] [Accepted: 08/16/2021] [Indexed: 12/18/2022]
Abstract
Bacterial infections are nowadays among the major threats to public health worldwide. Thus, there is an urgent and increased need for new antimicrobial agents. As a result, the exploration of the antimicrobial properties of different substances including ionic liquids (ILs) has recently attracted great attention. The present work is aimed at evaluating how the addition of halogens and hydrophobic substituents on alkylimidazolium units of ILs as well as the increase in their chain lengths affects the antimicrobial properties of such ILs. After their synthesis, the antibacterial activities of these compounds against Pseudomona aeruginosa, Escherichia coli, and Staphylococcus aureus are determined by measuring their minimal inhibitory concentrations (MICs). Key features in ILs-membrane interactions are also studied using long-term all-atom molecular dynamics simulations (MDs). The results show that these ILs have good antibacterial activity against S. aureus, E. coli, and P. aeruginosa, with MIC values range from <7.81 to 62.50 μM. The antimicrobial property of tert-butyl N-methylphenolimidazolium salts (denoted as 8b and 8c) is particularly better with MIC values of < 7.81 μM. The antibacterial efficacy is also found to depend on the alkyl chain length and substituents on the phenolic ring. Finally, MDs done for ILs in a phosphatidylcholine (POPC) bilayer show key features in the mechanism of IL-induced membrane disruption, where the ILs are inserted as clusters into one side of the bilayer until saturation is reached. This insertion increases "leaflet strain" up to critical threshold, likely triggering the morphological disruption of the membranes in the microbes.
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Affiliation(s)
- Luis Guzmán
- Departamento de Bioquímica Clínica e Inmunohematología, Facultad de Ciencias de la Salud, Universidad de Talca, P.O. Box 747, Talca 3460000, Chile
| | - Cristóbal Parra-Cid
- Departamento de Bioquímica Clínica e Inmunohematología, Facultad de Ciencias de la Salud, Universidad de Talca, P.O. Box 747, Talca 3460000, Chile
| | - Etiennette Guerrero-Muñoz
- Instituto de Química de Recursos Naturales, Universidad de Talca, P.O. Box 747, Talca 3460000, Chile
| | - Carlos Peña-Varas
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, El Llano Subercaseaux, 2801-Piso 6, Santiago, Chile
| | - Efraín Polo-Cuadrado
- Instituto de Química de Recursos Naturales, Laboratorio de Síntesis Orgánica, Universidad de Talca, Casilla 747, Talca 3460000, Chile
| | - Yorley Duarte
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Ricardo I Castro
- Carrera de Ingeniería en Construcción e Instituto de Ciencias Químicas Aplicadas, Multidisciplinary Agroindustry Research Laboratory, Universidad Autónoma de Chile, Talca, Chile
| | - Luz Stella Nerio
- Universidad de la Amazonia, Programa de Química, Calle 17 Diagonal 17 Carrera 3F, Florencia, Colombia
| | - Ramiro Araya-Maturana
- Instituto de Química de Recursos Naturales, Universidad de Talca, P.O. Box 747, Talca 3460000, Chile
| | - Tewodros Asefa
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854, United States; Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, United States
| | - Javier Echeverría
- Departamento de Ciencias del Ambiente, Facultad de Química y Biología, Universidad Santiago de Chile, Santiago, Chile
| | - David Ramírez
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, El Llano Subercaseaux, 2801-Piso 6, Santiago, Chile
| | - Oscar Forero-Doria
- Departamento de Ciencias del Ambiente, Facultad de Química y Biología, Universidad Santiago de Chile, Santiago, Chile.
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8
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Vereshchagin AN, Frolov NA, Egorova KS, Seitkalieva MM, Ananikov VP. Quaternary Ammonium Compounds (QACs) and Ionic Liquids (ILs) as Biocides: From Simple Antiseptics to Tunable Antimicrobials. Int J Mol Sci 2021; 22:6793. [PMID: 34202677 PMCID: PMC8268321 DOI: 10.3390/ijms22136793] [Citation(s) in RCA: 77] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 12/13/2022] Open
Abstract
Quaternary ammonium compounds (QACs) belong to a well-known class of cationic biocides with a broad spectrum of antimicrobial activity. They are used as essential components in surfactants, personal hygiene products, cosmetics, softeners, dyes, biological dyes, antiseptics, and disinfectants. Simple but varied in their structure, QACs are divided into several subclasses: Mono-, bis-, multi-, and poly-derivatives. Since the beginning of the 20th century, a significant amount of work has been dedicated to the advancement of this class of biocides. Thus, more than 700 articles on QACs were published only in 2020, according to the modern literature. The structural variability and diverse biological activity of ionic liquids (ILs) make them highly prospective for developing new types of biocides. QACs and ILs bear a common key element in the molecular structure-quaternary positively charged nitrogen atoms within a cyclic or acyclic structural framework. The state-of-the-art research level and paramount demand in modern society recall the rapid development of a new generation of tunable antimicrobials. This review focuses on the main QACs exhibiting antimicrobial and antifungal properties, commercial products based on QACs, and the latest discoveries in QACs and ILs connected with biocide development.
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Affiliation(s)
- Anatoly N. Vereshchagin
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991 Moscow, Russia; (N.A.F.); (K.S.E.); (M.M.S.)
| | | | | | | | - Valentine P. Ananikov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991 Moscow, Russia; (N.A.F.); (K.S.E.); (M.M.S.)
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Morpholinium-based ionic liquids show antimicrobial activity against clinical isolates of Pseudomonas aeruginosa. Res Microbiol 2021; 172:103817. [PMID: 33741516 DOI: 10.1016/j.resmic.2021.103817] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 03/02/2021] [Accepted: 03/04/2021] [Indexed: 11/22/2022]
Abstract
Pseudomonas aeruginosa is a multi-drug resistant (MDR) pathogen. It is classified by WHO as one of the most life-threatening pathogens causing nosocomial infections. Some of its clinical isolates and their subpopulations show high persistence to many antibiotics that are recommended by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Thus, there is a need for non-traditional classes of antibiotics to fight the increasing threat of MDR P. aeruginosa. Ionic liquids (IL) are one such promising class of novel antibiotics. We selected four strains of P. aeruginosa and studied the growth inhibition and other effects of 12 different ILs. We used the well-characterized P. aeruginosa PAO1 (ATCC 15692) as model strain and compared it to three other isolates from chronic lung infection (LES B58), skin burn infection (UCBPP-PA14) and keratitis infection (39016), respectively. The ILs consisted of either 4,4-didecylmorpholinium [Dec2Mor]+ or 4-decyl-4-ethylmorpholinium [DecEtMor]+ cations combined with different anions. We found that the ILs with 4,4-didecylmorpholinium [Dec2Mor]+ cations most effectively inhibited bacterial growth as well as reduced strain fitness and virulence factor production. Our results indicate that these ILs could be used to treat P. aeruginosa infections.
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How to Evaluate Non-Growing Cells-Current Strategies for Determining Antimicrobial Resistance of VBNC Bacteria. Antibiotics (Basel) 2021; 10:antibiotics10020115. [PMID: 33530321 PMCID: PMC7912045 DOI: 10.3390/antibiotics10020115] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/19/2021] [Accepted: 01/22/2021] [Indexed: 12/17/2022] Open
Abstract
Thanks to the achievements in sanitation, hygiene practices, and antibiotics, we have considerably improved in our ongoing battle against pathogenic bacteria. However, with our increasing knowledge about the complex bacterial lifestyles and cycles and their plethora of defense mechanisms, it is clear that the fight is far from over. One of these resistance mechanisms that has received increasing attention is the ability to enter a dormancy state termed viable but non-culturable (VBNC). Bacteria that enter the VBNC state, either through unfavorable environmental conditions or through potentially lethal stress, lose their ability to grow on standard enrichment media, but show a drastically increased tolerance against antimicrobials including antibiotics. The inability to utilize traditional culture-based methods represents a considerable experimental hurdle to investigate their increased antimicrobial resistance and impedes the development and evaluation of effective treatments or interventions against bacteria in the VBNC state. Although experimental approaches were developed to detect and quantify VBNCs, only a few have been utilized for antimicrobial resistance screening and this review aims to provide an overview of possible methodological approaches.
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Robben C, Witte AK, Schoder D, Stessl B, Rossmanith P, Mester P. A Fast and Easy ATP-Based Approach Enables MIC Testing for Non-resuscitating VBNC Pathogens. Front Microbiol 2019; 10:1365. [PMID: 31258524 PMCID: PMC6587809 DOI: 10.3389/fmicb.2019.01365] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 05/31/2019] [Indexed: 12/14/2022] Open
Abstract
Many bacteria enter the viable but non-culturable (VBNC) state to maximize resources and increase their tolerance to harmful conditions to cope with environmental stress, which has been described for a plethora of important human and foodborne pathogens. VBNC pathogens can potentially present a serious risk to human health as they are invisible to routine microbiological culture-based methods. Of high importance is the increased tolerance to antibiotics or disinfectant measures while in the VBNC state. The greatest remaining challenge for such investigations is the lack of an appropriate, cost-effective multi-species screening method due to experimental constraints. In this study, we investigated if de novo ATP production of cells in the VBNC state is a suitable indicator for overall cell viability that can be utilized to determine the minimum ATP inhibitory concentration (MAIC) of antibiotics and other antimicrobials. To validate this approach, heat-stress time-kill experiments were performed with both culturable and VBNC cells. We developed a comprehensive experimental setup and demonstrated the applicability of this VBNC–MIC assay for testing the tolerance of 12 strains of 4 important bacterial species (Escherichia coli, Bacillus cereus, Pseudomonas aeruginosa, and Listeria monocytogenes) in the VBNC state to eight important antimicrobials including four different antibiotics. We confirmed that bacteria in the VBNC state were resistant to all tested antibiotics (ampicillin, imipenem, ciprofloxacin, and gentamicin) and additionally insensitive to disinfectants (benzalkonium chloride and trioctylmethylammonium chloride) and preservatives (bronopol and sodium azide). These data emphasize the need for further research regarding the characteristics of bacterial pathogens in the VBNC state and present the advantages and high-throughput capabilities of ATP determinations to investigate tolerance of VBNC pathogens to antimicrobials. The presented method should be helpful in order to identify appropriate countermeasures, treatments, or disinfectants when confronted with bacterial pathogens in the VBNC state.
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Affiliation(s)
- Christian Robben
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, Department of Farm Animal and Public Health in Veterinary Medicine, Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria
| | - Anna Kristina Witte
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, Department of Farm Animal and Public Health in Veterinary Medicine, Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria
| | - Dagmar Schoder
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, Department of Farm Animal and Public Health in Veterinary Medicine, Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria.,Department of Farm Animal and Public Health in Veterinary Medicine, Institute of Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria
| | - Beatrix Stessl
- Department of Farm Animal and Public Health in Veterinary Medicine, Institute of Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria
| | - Peter Rossmanith
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, Department of Farm Animal and Public Health in Veterinary Medicine, Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria.,Department of Farm Animal and Public Health in Veterinary Medicine, Institute of Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria
| | - Patrick Mester
- Christian Doppler Laboratory for Monitoring of Microbial Contaminants, Department of Farm Animal and Public Health in Veterinary Medicine, Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria
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