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

Abstract

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.

Quorum-Sensing Regulation of Antimicrobial Resistance in Bacteria

“…In recent years, the discovery of microbial quorum-sensing systems has provided new hope for studying the regulatory mechanism of drug resistance mechanisms and overcoming drug resistance. The results show that the quorum-sensing system regulates various cellular processes of microorganisms, such as pathogenic gene expression, toxin production and extracellular polysaccharide synthesis, and plays an important regulatory role in the process of drug efflux pumps and the formation of microbial biofilms [38][39][40]. According to different self-inducible molecules, bacterial QS systems are divided into three types.…”

Detection and Quantification Methods for Viable but Non-culturable (VBNC) Cells in Process Wash Water of Fresh-Cut Produce: Industrial Validation

“…Under these conditions, cells can persist for extended periods without division, called dormancy or a viable but non-culturable (VBNC) state. The VBNC state has been defined as a survival strategy, where bacteria cannot grow on routine culture media but are alive and capable of renewing metabolic activity (Zhao et al, 2017;Dong et al, 2020). Recently, Dong et al (2020) demonstrated that cells in the VBNC state go through different changes, including morphological and compositional variations, which allow them to have a higher resistance to chemical and physical stresses.…”

Induction of Escherichia coli O157:H7 into a viable but non‐culturable state by high temperature and its resuscitation

“…Exposure to various stresses can induce E. coli the VBNC state (Li et al, 2014), including low temperature (Wei and Zhao, 2018;Zhong and Zhao, 2019) and high temperature (Noor, 2015;Bruhn-Olszewska et al, 2018). Escherichia coli O157: H7, a foodborne pathogen of major concern to public health, has been associated with numerous outbreaks of haemorrhagic colitis and haemolytic uremic syndrome worldwide (Vidovic and Korber, 2016).…”