The attachment strength of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes to beef surface was evaluated. The effect of bacterial attachment strength on inactivation by HDP treatment was studied. Bacterial attachment was defined as loosely attached (analyzed first by running diluent over the beef cubes) and strongly attached (analyzed again rinsed cubes by pummeling for 2 min in diluent) to the beef surface. Most attachment of these three pathogens occurred within 10 min. There was no significant difference in attachment strength of pathogens during the first 30 minutes exposure time. Strongly attached bacteria to beef surface were inactivated by HDP at a greater rate and the reduction was significant for all three bacteria (0.52, 0.37, and 0.43 log10 CFU/g for E. coli O157:H7,
S. Typhimurium, and L. monocytogenes, respectively). No clear indications were obtained for sub-lethal damage of microorganisms surviving the HDP treatment. These findings disclose that HDP treatment is more lethal to pathogenic bacteria strongly attached to beef surface compared to those planktonic or loosely attached cells.