Survival and Growth of Enterobacter sakazakii on Fresh-Cut Fruits and Vegetables and in Unpasteurized Juices as Affected by Storage Temperature

Abstract

Enterobacter sakazakii is an emerging foodborne pathogen that has caused illnesses and deaths in infants and elderly immunocompromised adults. Outbreaks of E. sakazakii infection have been associated with infant formulas, but the documented presence of this pathogen in a wide variety of ready-to-eat foods, including lettuce and other raw vegetables, makes it important to learn more about its behavior in these environments. We investigated the survival and growth characteristics of E. sakazakii on fresh-cut apple, cantaloupe, strawberry, watermelon, cabbage, carrot, cucumber, lettuce, and tomato and in juices prepared from these fruits and vegetables. Produce and juices were inoculated with E. sakazakii at 2 to 3 log CFU/g and 1 to 2 log CFU/ml, respectively, and stored at 4, 12, or 25°C. Populations either did not change or gradually decreased in fresh-cut produce and juices stored at 4°C but grew at 12°C on fresh-cut apple, cantaloupe, watermelon, cucumber, and tomato and in all juices except apple, strawberry, cabbage, and tomato juices. All fresh-cut fruits and vegetables except strawberry supported growth of E. sakazakii at 25°C. Growth occurred in all juices except apple, strawberry, and cabbage juices, followed by decreases in population to <1 CFU/ml after 48 to 72 h, which coincided with decreases in pH and an increase in the population of lactic acid bacteria. Increases in total counts occurred in all juices except strawberry juice stored at 25°C and apple and strawberry juices stored at 12°C. Total counts increased in cantaloupe, carrot, cucumber, and lettuce juices stored at 4°C. Populations of molds and yeasts increased in apple and tomato juices stored at 25°C but decreased to <1 CFU/ml in cabbage, lettuce, and cucumber juices. Further characterization of the behavior of E. sakazakii on fresh produce and in unpasteurized juice as affected by commercial packaging and handling practices is needed.