Benzalkonium Chloride Induces a VBNC State in Listeria monocytogenes

Noll, Matthias; Trunzer, Katharina; Vondran, Antje; Vincze, Szilvia; Dieckmann, Ralf; Dahouk, Sascha Al; Gold, C.S

doi:10.3390/microorganisms8020184

Cited by 30 publications

(41 citation statements)

References 31 publications

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“…Another aspect, however, that should be always also considered is the potential for bacterial cells surviving disinfection to enter the viable but not-culturable (VBNC) state, being thus unable to be enumerated by traditional plating methods, such as those here applied. As it seems, this is not a so rare phenomenon and has also been described for L. monocytogenes following the action of QAC disinfectants [ 64 , 65 ] and some EOs [ 66 ]. If this is indeed the case, the log reductions here recorded might be even lower.…”

Section: Discussionmentioning

confidence: 80%

Advanced Killing Potential of Thymol against a Time and Temperature Optimized Attached Listeria monocytogenes Population in Lettuce Broth

et al. 2021

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Fresh vegetables and salads are increasingly implicated in outbreaks of foodborne infections, such as those caused by Listeria monocytogenes, a dangerous pathogen that can attach to the surfaces of the equipment creating robust biofilms withstanding the killing action of disinfectants. In this study, the antimicrobial efficiency of a natural plant terpenoid (thymol) was evaluated against a sessile population of a multi-strain L. monocytogenes cocktail developed on stainless steel surfaces incubated in lettuce broth, under optimized time and temperature conditions (54 h at 30.6 °C) as those were determined following response surface modeling, and in comparison, to that of an industrial disinfectant (benzalkonium chloride). Prior to disinfection, the minimum bactericidal concentrations (MBCs) of each compound were determined against the planktonic cells of each strain. The results revealed the advanced killing potential of thymol, with a concentration of 625 ppm (= 4 × MBC) leading to almost undetectable viable bacteria (more than 4 logs reduction following a 15-min exposure). For the same degree of killing, benzalkonium chloride needed to be used at a concentration of at least 20 times more than its MBC (70 ppm). Discriminative repetitive sequence-based polymerase chain reaction (rep-PCR) also highlighted the strain variability in both biofilm formation and resistance. In sum, thymol was found to present an effective anti-listeria action under environmental conditions mimicking those encountered in the salad industry and deserves to be further explored to improve the safety of fresh produce.

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Section: Discussionmentioning

confidence: 80%

Advanced Killing Potential of Thymol against a Time and Temperature Optimized Attached Listeria monocytogenes Population in Lettuce Broth

et al. 2021

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“…Cell membrane integrity is an important hint to identify viable cells. Nevertheless, a combination of different staining methods to additionally measure the metabolic activity is necessary to identify cells in the VBNC state [ 68 , 69 , 70 ].…”

Section: Methodological Approaches For Antimicrobial Effectivity Tmentioning

confidence: 99%

“…All treatments showed a greater resistance for VBNC cells in contrast to cells in the exponential phase [ 68 ]. Noll et al [ 70 ] induced a VBNC state in Listeria ( L. ) monocytogenes using benzalkonium chloride and showed a reduced antimicrobial effectivity of benzalkonium chloride, ceftriaxone, gentamycin, linezolid, tetracycline, trimethoprim, and sulfamethoxazole against VBNCs in contrast to their parent cells using flow cytometry. During the study, benzalkonium chloride or the antibiotic substances did not influence the fluorescence properties of SYTO 9 ® or PI [ 70 ].…”

Section: Methodological Approaches For Antimicrobial Effectivity Tmentioning

confidence: 99%

“…Without the presence of cellular metabolism or energy, a cell (with the exception of spores) can be considered dead and therefore, it comes as no surprise, that these parameters have been widely used for the viability assessment of bacterial cells in the VBNC state. There have been efforts of using the uptake and subsequent degradation of fluorescent 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose (2-NBDG), which is comparable to glucose, to measure the active cell metabolism [ 70 , 165 ]. However, the vast majority of studies involving VBNC cells have used either the respiratory activity, or the presence/production of ATP as a measure to determine cell viability and will be the focus in the subsequent chapters.…”

Section: Methodological Approaches For Antimicrobial Effectivity Tmentioning

confidence: 99%

“…An example to measure the enzyme activity is described by Yoshioka et al [ 165 ] using the dye 2-NBDG. The fluorescent 2-NBDG molecule uptake into the cell is comparable to glucose and the green fluorescence signal degraded continuously by an active cell metabolism [ 70 , 165 ].…”

Section: Methodological Approaches For Antimicrobial Effectivity Tmentioning

confidence: 99%

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How to Evaluate Non-Growing Cells—Current Strategies for Determining Antimicrobial Resistance of VBNC Bacteria

et al. 2021

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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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