Abstract: In this study, the sub-inhibitory concentrations (SICs) of citral on Cronobacter sakazakii were firstly determined. Then, the effect of citral at its SICs on the tolerance of C. sakazakii to desiccation, heat, osmotic pressure, acid and bile salt was investigated. The E-test? method was also used to detect the changes in the susceptibility of C. sakazakii to ampicillin and cefoxitin. Finally, the effects of citral on C. sakazakii genes related to environmental stress tolerance were analyzed at the transcription level by real-time RT-PCR. The results indicated that 31.250 μg/L citral had no effect on C. sakazakii growth. Thus, 31.250 and 15.625 μg/L were selected as SICs of citral. Citral at its SICs could significantly reduce the desiccation, heat, osmotic pressure, acid, and bile salt tolerance of C. sakazakii in a concentration-dependent way. In addition, the sensitivity of the bacterial cells to ampicillin and cefoxitin was enhanced after treatment with the SICs of citral. RT-PCR results showed that citral reduced the transcription levels of multiple genes associated with environmental stress tolerance in C. sakazakii. In conclusion, the environmental stresses tolerance and antibiotics susceptibility of C. sakazakii can be reduced significantly by citral. Citral has the potential to control C. sakazakii in food production and processing. This study provides new ideas for the control of foodborne pathogens by natural active substances.

Key words: Cronobacter sakazakii, citral, sub-inhibitory concentration, environmental stress tolerance, antibiotics