Examining Committee

Dr. Iris Joye, Chair
Dr. Keith Warriner, Advisor
Dr. Kari Dunfield, Advisory Committee Member
Dr. Lawrence Goodridge, Department Member

TITLE: THE FOOD SAFETY SIGNIFICANCE OF THE PERSISTER STATE WITHIN SHIGA-TOXIN
 PRODUCING ESCHERICHIA COLI 0157:H7

ABSTRACT:
The persister state is an induced dormancy and has previously been shown to provide cells with temporal antibiotic resistance. In the current study, it was found that the persister state was encountered in toxigenic shiga-toxin Escherichia coli O157:H7 and non-O157. Persister cells exhibited significantly greater tolerance to chlorine, ozone, peroxyacetic acid, and quaternary ammonium compounds, in addition to thermal stress. The revival of persister cells from dormancy depended on the duration of the incubation time post-antibiotic addition. Specifically, revival of persister cells 24 h post-ampicillin addition occurred upon enzymic degradation of the antibiotic.
Interestingly, residual ampicillin below the Minimum Inhibitory Concentration (MIC) could maintain the persister state. Persisters incubated for extended periods (8 days) following ampicillin addition eventually became non-culturable and could be revived by removing ampicillin. From the results it can be concluded that the persister state is significant to food safety although to what extent remains to be elucidated.