Induction of Escherichia coli into a VBNC state through chlorination/chloramination and differences in characteristics of the bacterium between states

Chen, Sheng; Li, Xi; Wang, Yahong; Zeng, Jie; Ye, Chengsong; Li, Xianping; Guo, Lizheng; Zhang, Shenghua; Yu, Xin

doi:10.1016/j.watres.2018.05.055

Cited by 170 publications

(77 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…And the resuscitation was also influenced by the VBNC state induction conditions and also associated with bacterial vaccination algebra, the source of their own physiological characteristics. It is worth emphasizing that failing of resuscitation does not mean that the cells cannot be resuscitated in principle before suitable methods have been found ( Chen et al, 2018 ). VBNC E. coli O157:H7 may pose a potential health risk.…”

Section: Discussionmentioning

confidence: 99%

Induction of Viable but Nonculturable Escherichia coli O157:H7 by Low Temperature and Its Resuscitation

Wei

Zhao

2018

Front. Microbiol.

View full text Add to dashboard Cite

Viable but non-culturable (VBNC) cells are alive bacteria cells, but lose their culturability in conventional culture media, usually escape detection by the plate count method and pose a serious threat to food safety and public health. Therefore, it is urgent to study the VBNC status, and to provide theoretical basis and scientific basis for food processing and safety control caused by pathogenic microorganisms. In this study, Escherichia coli O157:H7 was induced to the VBNC state at two different temperatures (-20°C and 4°C) and its resuscitation and morphological changes under different nutritional conditions were studied. The initial inoculum of 2.1 × 107 CFU/mL E. coli O157:H7 cells were induced into the VBNC state in normal saline, distilled water, LB broth at -20 °C after 176, 160, 80 days, respectively. The results showed that E. coli O157:H7 reserved at -20°C, and LB culture medium were easier to enter VBNC state than others conditions, the cells still had metabolic activity and the cell morphology changed from the typical rod shape to short rod and the cell size decreased. The resuscitate ways including the direct warming resuscitation, gradual warming resuscitation, adding chemical substance resuscitation, and adding nutrients resuscitation were studied. The results showed that the optimal conditions of 5% Tween 80 and 3% Tween 80 acculated the resuscitation of E. coli O157:H7 VBNC state cells induced by low temperature LB medium and low temperature saline. E. coli O157:H7 VBNC state failed from resuscitation when incubating in LB broth, respectively using direct warming and adding nutrients substance. This study provides new insights into induction and resuscitation of VBNC E. coli O157:H7 and offers an approach for investigating the formation mechanism of VBNC foodborne pathogens in food safety.

show abstract

Section: Discussionmentioning

confidence: 99%

Induction of Viable but Nonculturable Escherichia coli O157:H7 by Low Temperature and Its Resuscitation

Wei

Zhao

2018

Front. Microbiol.

View full text Add to dashboard Cite

show abstract

“…In addition, a series of morphological and physiological changes occur when microorganisms enter the VBNC state. The morphological changes affect mainly cell size, cell wall composition and the cell membrane (Signoretto, 2000;Signoretto et al, 2002;Day and Oliver, 2004;Oliver, 2010;Chen et al, 2018). The physiological features of VBNC cells are mainly characterized by decreased metabolic activity, slow absorption of nutrients, potential pathogenicity, decreased gene expression and protein translation capacity, and increased resistance to antibiotics (Du et al, 2006;Li et al, 2014;Lin et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

The Association of Cell Division Regulated by DicC With the Formation of Viable but Non-culturable Escherichia coli O157:H7

et al. 2019

View full text Add to dashboard Cite

The viable but non-culturable (VBNC) state, in which bacteria fail to grow on routine culture media but are actually alive, has been widely recognized as a strategy adopted by bacteria to cope with stressful environments. However, little is known regarding the molecular mechanism of VBNC formation. Here, we aimed to elucidate the specific roles of cell division regulatory proteins and the cell growth rate during VBNC Escherichia coli O157:H7 formation. We have previously found that expression of dicC is reduced by 20.08-fold in VBNC E. coli O157:H7 compared to non-VBNC cells. Little is known about DicC except that it, along with DicA, appears to act as a regulator of cell division by regulating expression of the cell division inhibitor DicB. First, our results showed that the VBNC cell number increased in the dicC mutant as well as the DicA-overexpressing strain but decreased in the DicC-overexpressing strain induced by high-pressure carbon dioxide, acid, and H 2 O 2. Furthermore, the growth rates of both the DicA-overexpressing strain and the dicC mutant were higher than that of the control strain, while DicCoverexpressing strain grew significantly more slowly than the vector strain. The level of the dicB gene, regulated by dicA and dicC and inhibiting cell division, was increased in the DicC-overexpressing strain and decreased in the dicC mutant and DicAoverexpressing strain, which was consistent with the growth phenotypes. In addition, the dwarfing cell morphology of the dicC mutant and DicA-overexpressing strain were observed by SEM and TEM. Taken together, our study demonstrates that DicC negatively regulates the formation of the VBNC state, and DicA enhances the ability of cells to enter the VBNC state. Besides, the cell growth rate and dwarfing cell morphology may be correlated with the formation of the VBNC state.

show abstract

“…Phe et al [28] also observed an alteration in fluorescence of E. coli cells exposed to sodium hypochlorite at a concentration >3 µmol•L −1 of chlorine. The difference between fluorescing cells (viable + compromised), obtained by flow cytometry, and culturable cells, obtained by CFU assay, point out to the presence of possible VBNC cells [29] (Figure 3). There is no formation of VBNC cells only to a concentration of 100 mg•L −1 of free chlorine ( Figure 3) though this will probably be possible with an intermediate concentration between 50 and 100 mg•L −1 .…”

Section: Resultsmentioning

confidence: 98%

Evaluation by Flow Cytometry of Escherichia coli Viability in Lettuce after Disinfection

et al. 2019

View full text Add to dashboard Cite

Foodborne outbreaks due to the consumption of ready-to-eat vegetables have increased worldwide, with Escherichia coli (E. coli) being one of the main sources responsible. Viable but nonculturable bacteria (VBNC) retain virulence even after some disinfection procedures and constitute a huge problem to public health due to their non-detectability through conventional microbiological techniques. Flow cytometry (FCM) is a promising tool in food microbiology as it enables the distinction of the different physiological states of bacteria after disinfection procedures within a short time. In this study, samples of lettuce inoculated with E. coli were subject to disinfection with sodium hypochlorite at free chlorine concentrations of 5, 10, 25, 50, and 100 mg·L−1 or with 35% peracetic acid at concentrations of 5, 10, 25, and 50 mg·L−1. The efficiency of these disinfectants on the viability of E. coli in lettuce was evaluated by flow cytometry with LIVE/DEAD stains. Results from this study suggest that FCM can effectively monitor cell viability. However, peracetic acid is more effective than sodium hypochlorite as, at half the concentration, it is enough to kill 100% of bacteria and always induces a lower percentage of VBNC. Finally, we can conclude that the recommended levels of chemical disinfectants for fresh fruit and vegetables are adequate when applied in lettuce. More importantly, it is possible to ensure that all cells of E. coli are dead and that there are no VBNC cells even with lower concentrations of those chemicals. These results can serve as guidance for lettuce disinfection, improving quality and the safety of consumption.

show abstract

Induction of Escherichia coli into a VBNC state through chlorination/chloramination and differences in characteristics of the bacterium between states

Cited by 170 publications

References 38 publications

Induction of Viable but Nonculturable Escherichia coli O157:H7 by Low Temperature and Its Resuscitation

Induction of Viable but Nonculturable Escherichia coli O157:H7 by Low Temperature and Its Resuscitation

The Association of Cell Division Regulated by DicC With the Formation of Viable but Non-culturable Escherichia coli O157:H7

Evaluation by Flow Cytometry of Escherichia coli Viability in Lettuce after Disinfection

Contact Info

Product

Resources

About