Induction of viable but nonculturable Escherichia coli O157:H7 by high pressure CO2 and its characteristics

The viable but nonculturable (VBNC) state is a survival strategy adopted by many pathogens when exposed to harsh environmental stresses. In this study, we investigated for the first time that whether high pressure CO2 (HPCD), one of the nonthermal pasteurization techniques, can induce Escherichia co...

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Bibliographic Details
Published in:PloS one 2013-04, Vol.8 (4), p.e62388-e62388
Main Authors: Zhao, Feng, Bi, Xiufang, Hao, Yanling, Liao, Xiaojun
Format: Article
Language:English
Subjects:
Adaptation, Biological
Agriculture
Air Pressure
Bacteria
Biology
Carbon dioxide
Carbon Dioxide - metabolism
E coli
Electron microscopy
Engineering research
Environmental stress
Enzymatic activity
Enzyme Activation
Enzymes - metabolism
Epidemics
Escherichia coli
Escherichia coli O157 - physiology
Escherichia coli O157 - ultrastructure
Food production
Food safety
Food science
Fruits
Gene expression
Health risk assessment
High pressure
Medicine
Microorganisms
Pasteurization
Pathogens
pH effects
Plates (structural members)
Pressure
Resuscitation
Salmonella
Sodium chloride
Sonication
Sonication - adverse effects
Stress, Physiological
Temperature
Temperature effects
Temperature requirements
Vibrio
Vibrio parahaemolyticus
Vibrio vulnificus
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Summary:The viable but nonculturable (VBNC) state is a survival strategy adopted by many pathogens when exposed to harsh environmental stresses. In this study, we investigated for the first time that whether high pressure CO2 (HPCD), one of the nonthermal pasteurization techniques, can induce Escherichia coli O157:H7 into the VBNC state. By measuring plate counts, viable cell counts and total cell counts, E. coli O157:H7 in 0.85% NaCl solution (pH 7.0) was able to enter the VBNC state by HPCD treatment at 5 MPa and four temperatures (25°C, 31°C, 34°C and 37°C). Meanwhile, with the improvement of treatment temperature, the time required for E. coli O157:H7 to enter VBNC state would shorten. Enzymatic activities in these VBNC cells were lower than those in the exponential-phase cells by using API ZYM kit, which were also reduced with increasing the treatment temperature, but the mechanical resistance of the VBNC cells to sonication was enhanced. These results further confirmed VBNC state was a self-protection mechanism for some bacteria, which minimized cellular energetic requirements and increased the cell resistance. When incubated in tryptic soy broth at 37°C, the VBNC cells induced by HPCD treatment at 25°C, 31°C and 34°C achieved resuscitation, but their resuscitation capabilities decreased with increasing the treatment temperature. Furthermore, electron microscopy revealed changes in the morphology and interior structure of the VBNC cells and the resuscitated cells. These results demonstrated that HPCD could induce E. coli O157:H7 into the VBNC state. Therefore, it is necessary to detect if there exist VBNC microorganisms in HPCD-treated products by molecular-based methods for food safety.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0062388