Antimicrobial Activity and Possible Mechanism of Action of Citral against Cronobacter sakazakii

PLoS One. 2016 Jul 14;11(7):e0159006. doi: 10.1371/journal.pone.0159006. eCollection 2016.

Abstract

Citral is a flavor component that is commonly used in food, beverage and fragrance industries. Cronobacter sakazakii is a food-borne pathogen associated with severe illness and high mortality in neonates and infants. The objective of the present study was to evaluate antimicrobial effect of citral against C. sakazakii strains. The minimum inhibitory concentration (MIC) of citral against C. sakazakii was determined via agar dilution method, then Gompertz models were used to quantitate the effect of citral on microbial growth kinetics. Changes in intracellular pH (pHin), membrane potential, intracellular ATP concentration, and membrane integrity were measured to elucidate the possible antimicrobial mechanism. Cell morphology changes were also examined using a field emission scanning electron microscope. The MICs of citral against C. sakazakii strains ranged from 0.27 to 0.54 mg/mL, and citral resulted in a longer lag phase and lower growth rate of C. sakazakii compared to the control. Citral affected the cell membrane of C. sakazakii, as evidenced by decreased intracellular ATP concentration, reduced pHin, and cell membrane hyperpolarization. Scanning electron microscopy analysis further confirmed that C. sakazakii cell membranes were damaged by citral. These findings suggest that citral exhibits antimicrobial effect against C. sakazakii strains and could be potentially used to control C. sakazakii in foods. However, how it works in food systems where many other components may interfere with its efficacy should be tested in future research before its real application.

MeSH terms

  • Acyclic Monoterpenes
  • Adenosine Triphosphate / analysis
  • Anti-Bacterial Agents / pharmacology*
  • Cronobacter sakazakii / chemistry
  • Cronobacter sakazakii / drug effects*
  • Hydrogen-Ion Concentration
  • Membrane Potentials / drug effects
  • Microbial Sensitivity Tests
  • Microscopy, Electron, Scanning
  • Monoterpenes / pharmacology*

Substances

  • Acyclic Monoterpenes
  • Anti-Bacterial Agents
  • Monoterpenes
  • Adenosine Triphosphate
  • citral

Grants and funding

This work was supported in part by New Century Excellent Talent Support Plan (NCET-13-0488), the Twelve-five Science and Technology Support Program (No.2015BAD16B08), National Natural Science Foundation of China (31301498), International Collaboration Partner Plan (A213021203) in Northwest A&F University and Special Fund for Sino-US Joint Research Center for Food Safety (A200021501).