Formation mechanisms of viable but nonculturable bacteria through induction by light-based disinfection and their antibiotic resistance gene transfer risk: A review

Cai, Yiwei; Liu, Jianying; Li, Guiying; Wong, Po Keung; An, Taicheng

doi:10.1080/10643389.2021.1932397

Cited by 41 publications

(12 citation statements)

References 151 publications

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“…Bacterial cells in finished fermented products often appear as a mixture of healthy and vulnerable cell populations of altered states. For example, some of them enter a sublethal state, i.e., viable but non-culturable (VBNC), which are cells that exhibit and survive with a low level of activity for an extended period [ 10 , 11 , 12 ]. The current gold standard methods of evaluating probiotic viability rely mainly on enumerating bacterial growth, which fails to detect VBNC bacteria due to their vulnerability and difficulty in recovery for growth [ 13 ], leading to the underestimation of the probiotic viability in fermented products.…”

Section: Introductionmentioning

confidence: 99%

Rapid Detection of the Activity of Lacticaseibacillus Casei Zhang by Flow Cytometry

Wang

Dai

et al. 2023

Foods

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Food processing, e.g., freeze-drying, exerts strong pressure on bacteria in the food matrix, decreasing their viability/activity and even forcing them to become viable but unculturable (VBNC), which are often underestimated by traditional plate count. The strict standards of bacterial viability in probiotic products require accurate cell viability/activity enumeration. We developed a staining (5(6)-carboxyfluorescein diacetate succinimide ester, propidium iodide)-based flow cytometry rapid method for detecting the viability/activity of Lacticaseibacillus (Lb.) casei Zhang, a widely used probiotic in the dairy industry in China. We optimized the procedural and instrumental parameters for generating results comparable to that of standard plate counts. This method was also applied to freeze-dried Lb. casei Zhang, yielding 7.7 × 1011 CFU/g, which was non-significantly higher than the results obtained by plate count (6.4 × 1011 CFU/g), possibly due to the detection of VBNC cells in the freeze-dried powder. We anticipated that this method can be used for detecting lactic acid bacteria in other probiotic food/beverages.

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Section: Introductionmentioning

confidence: 99%

Rapid Detection of the Activity of Lacticaseibacillus Casei Zhang by Flow Cytometry

Wang

Dai

et al. 2023

Foods

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“…antibiotics) and easily bypass microbiological safety controls due to their lack of culturability, representing thus a potential threat for human health (Nowakowska and Oliver 2013;Li et al 2014). For instance, wastewater disinfection treatments can induce the VBNC state (Cai et al 2021). The reuse of such treated wastewater in agriculture and the lack of detection of VBNC cells, which is largely based on cultivation approach, represent a risk not only for the spread of pathogens but also of the antibiotic resistance genes (ARGs) the dormant cells may harbour (Cai et al 2021;Riva et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…For instance, wastewater disinfection treatments can induce the VBNC state (Cai et al 2021). The reuse of such treated wastewater in agriculture and the lack of detection of VBNC cells, which is largely based on cultivation approach, represent a risk not only for the spread of pathogens but also of the antibiotic resistance genes (ARGs) the dormant cells may harbour (Cai et al 2021;Riva et al 2020). Furthermore, we have to consider that a number of bacteria for open-field environmental applications are in most cases poorly characterized in relation to their potential VBNC state that may be induced under harsh conditions they may experience during their application in the field (Prakash et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Cell phenotype changes and oxidative stress response in Vibrio spp. induced into viable but non-culturable (VBNC) state

et al. 2023

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Purpose Aquatic bacteria of the genus Vibrio include animal and human pathogens. The occurrence of Vibrio-related diseases has been associated with the current climate change-driven increase of sea surface temperature. Vibrio spp. can enter into the viable but non-culturable (VBNC) state, as a consequence of starvation in seawater at low temperatures. In such physiological state, Vibrio cells are no longer culturable on standard media agar plates but can resuscitate if incubated at 30 °C prior to plating, retaining virulence. Since limited information is available on regards to this topic, in this work, we characterized the phenotypic changes of four Vibrio spp. strains (one laboratory strain and three environmental isolates) in cold seawater microcosms, investigating the relationship between resuscitation and a hydrogen peroxide-induced oxidative stress. Methods Cell phenotypic changes and the effect of hydrogen peroxide and/or catalase addition to the medium were studied on VBNC and resuscitated cells by flow cytometry in microcosm experiments, paralleled by culturability experiments by plating. Results The cells of all the Vibrio strains changed their phenotype upon the induction of the VBNC state resulting in cell dwarfing and decrease in DNA quantity, losing the ability to grow on solid media. These features were partially or totally reverted when the cells were treated for resuscitation. Hydrogen peroxide at concentrations as low as 0.007 mM prevented resuscitation and a prolonged exposure to hydrogen peroxide at concentrations far under those inhibiting the growth of log-phase cells permanently damaged VBNC cells, which could not be resuscitated. However, the potential of culturability of VBNC cells could be preserved, at least for a part of the population, by plating the cells in the presence of catalase. The study also showed that during the resuscitation process, the cells gradually increased their resistance to hydrogen peroxide. Conclusions The timing and mode of induction of the VBNC state, as well as cell resuscitation and response to hydrogen peroxide, differed among Vibrio strains, indicating that induction and resuscitation from dormancy could vary in the context of species belonging to a single genus.

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“…However, the strong spectral dependence and low efficiency in light absorption limit the inactivation performance of the SODIS system. Notably, it has been reported that many microorganisms are known to enter into a viable but nonculturable (VBNC) state during physical or chemical disinfection processes, including SODIS. − They cannot be cultured with the standard plate counting method but can retain cellular integrity, self-repair ability, and virulence. − Biohazards in the VBNC state in drinking water have been largely overlooked, and they pose potential health threats to human health. Great efforts have been made to improve treatment devices and/or enhance the photothermal/photocatalytic reactivities to enhance the SODIS process.…”

Section: Introductionmentioning

confidence: 99%

Flower Pollen-Based Photosensitization Process for Enhanced Solar Disinfection of Drinking Water: Reactor Design and Inactivation Mechanisms

Tang

Yin

et al. 2022

ACS EST Eng.

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Solar disinfection (SODIS) is a chemical-free, low-cost, and user-friendly approach to achieving Sustainable Development Goal No. 6 (SDG 6). Herein, a natural flower pollen-based photosensitizer was fabricated in a facile way and used to enhance the conventional SODIS process. Complete inactivation of five biohazards (Escherichia coli K-12, Spingopyxis sp. BM1-1, Bacillus subtilis spores, Enterococcus faecalis, and tetracycline-resistant E. coli) at their culturable or viable but nonculturable states was achieved by both batch reactors and a flow-through reactor with a standing separation–recycling system. Herein, microorganisms adhered to the photosensitizer’s surface due to electrostatic attraction and topological interactions. The photosensitizer induced the localized heating effect under solar irradiation, and a portion of microorganisms was inactivated by the photothermal effect. Meanwhile, abundant reactive species (•OH and 1O2) were generated and contributed to the photocatalytic inactivation of microorganisms. Synergism between the photothermal and photocatalytic processes enhanced the destruction of cell membranes and the penetration of reactive species. A comprehensive inactivation pathway was proposed and verified. The findings suggested that the natural flower pollen-based photosensitization process is promising to enhance the SODIS for effective disinfection, which assists rural and underdeveloped areas in achieving SDG 6.

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Formation mechanisms of viable but nonculturable bacteria through induction by light-based disinfection and their antibiotic resistance gene transfer risk: A review

Cited by 41 publications

References 151 publications

Rapid Detection of the Activity of Lacticaseibacillus Casei Zhang by Flow Cytometry

Rapid Detection of the Activity of Lacticaseibacillus Casei Zhang by Flow Cytometry

Cell phenotype changes and oxidative stress response in Vibrio spp. induced into viable but non-culturable (VBNC) state

Flower Pollen-Based Photosensitization Process for Enhanced Solar Disinfection of Drinking Water: Reactor Design and Inactivation Mechanisms

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