Inactivation behaviors of selected bacteria in ultraviolet-C-treated human breast milk

Abstract

Abstract This study determined the inactivation behaviors, which include inactivation pattern, sublethal injury development, and inactivation kinetic parameters of selected bacteria in UV-C treated human breast milk. Multi strain mixtures of Salmonella enterica, Escherichia coli O157:H7, non-pathogenic E. coli , Pseudomonas aeruginosa , Listeria monocytogenes, and a lone strain of Staphylococcus aureus were inoculated into donated breast milk prior to UV-C inactivation studies. Results showed that the test organisms exhibited two types of inactivation patterns, making it difficult to directly compare UV-C resistance. S. enterica and non-pathogenic E. coli exhibited a monophasic log-linear inactivation pattern within the 60-min UV-C treatment period. All other challenge organisms exhibited a biphasic inactivation pattern characterized by a faster initial log linear inactivation, followed by a slower inactivation tailing. Sublethal injury rates were small in all test organisms except for S. aureus , which developed total sublethal injury throughout the UV-C exposure. Despite the injury rates, S. aureus had the least total population reduction (2.63 log CFU) after the 60-min treatment, while S. enterica had the greatest reduction (3.88 log CFU). The inactivation behaviors established in this work provide baseline information in the development of a UV-C pasteurization equipment and process for breast milk.