Behavior and changes in cell morphology of Escherichia coli O157:H7 in liquid medium and skim milk in the presence of caffeine

The objective of this study was to investigate the antibacterial effect of caffeine on the behavior and changes in cell morphology of E. coli O157:H7 in a liquid medium and in skim milk. The inhibitory effect of caffeine at different concentrations was determined by inoculating E. coli O157:H7 in laboratory medium and skim milk samples. Samples were incubated at 37°C for 48 h, and E. coli O157:H7 population was enumerated. Our results showed that caffeine significantly (P < 0.05) inhibited the growth of E. coli O157:H7 in laboratory medium and milk samples. A greater than 3.0 log CFU ml-1 inhibition was observed in milk containing 5.0 g/L caffeine within 12 h of incubation. Moreover, using flow cytometry, marked changes in the morphology of E. coli O157:H7 were also observed. Caffeine has potential as an antimicrobial agent and could be used as an effective natural additive to improve the safety of food products. © 2013 Taylor & Francis.