INCIDENCE, SURVIVAL, AND GROWTH OF ENTEROBACTER-SAKAZAKII IN INFANT FORMULA

Enterobacter sakazakii has been implicated in a severe form of neonata l meningitis, Although studies have failed to identify an environmenta l source for the organism, dried infant formula has been implicated in outbreaks and sporadic cases of E. sakazakii meningitis. The high mor tality rate (50 to 75%), the severity of the infection in infants, and the lack of information on the incidence, survival, and growth of E. sakazakii in foods led to this study. Experiments were undertaken to d etermine the incidence of E. sakazakii in dried infant formula, the te mperature range for growth, and the growth characteristics of E. sakaz akii in reconstituted dried infant formula. Strains of E. sakazakii we re isolated from dried infant formula available on the Canadian retail market. The prevalence varied from 0 to 12% in samples from five diff erent companies. For both clinical and food isolates, minimum growth t emperatures of 5.5 to 8.0 degrees C were observed by using a temperatu re-gradient incubator. The potential growth of E. sakazakii was follow ed by using a mixture of food and clinical isolates in three different formulas incubated at 4, 10, and 23 degrees C. Average generation tim es were 40 min at 23 degrees C and 4.98 h at 10 degrees C. E. sakazaki i strains did not grow at 4 degrees C and began to die off during stor age at this temperature. The results of this study stress the importan ce of using aseptic methods and proper temperature control in the prep aration, use, and storage of dried infant formula.