Lactoferrin as an antimicrobial against Salmonella enterica and Escherichia coli O157:H7 in raw milk

Improper storage conditions or processing of milk leads to potential spoilage and illness, due in part to temperature abuse, allowing bacteria present to grow and spoil the product. However, certain proteins naturally found in raw milk, such as lactoferrin, have reported antibacterial properties. The levels of lactoferrin required to effectively inhibit growth of pathogens have not been investigated thoroughly. This study aimed to examine various concentrations of lactoferrin as a potential biopreservative and as an antimicrobial against the common dairy pathogens Salmonella enterica and Escherichia coli O157:H7. Minimum inhibitory concentration assays were conducted on raw bovine milk in which the bacteria were exposed to varying concentrations of lactoferrin. In the raw milk system, the growth of E. coli O157:H7 was significantly decreased at levels greater than 14.05 mg/mL lactoferrin based on the reduction of tetrazolium salts. For S. enterica, only lactoferrin concentrations at or above 112.5 mg/mL in the milk resulted in reduced growth. Taken together, these results indicate that lactoferrin may have biopreservative potential. To fully examine the practicality and effectiveness of lactoferrin as an antimicrobial additive, a similar study should be conducted using additional (gram-positive) pathogens, such as Bacillus cereus and Listeria monocytogenes. If effective, lactoferrin could prolong the shelf life of dairy products and help reduce the incidence of foodborne illnesses in developing countries with limited refrigeration capability.