The growth profile, thermotolerance and biofilm formation of Enterobacter sakazakii grown in infant formula milk

Aims: To study the growth, thermotolerance and biofilm formation of the emergent pathogen Enterobacter sakazakii in infant formula milk (IFM). Methods and Results: The temperature range, death kinetics and biofilm formation of E. sakazakii were determined using impedance microbiology and conventional methods. In IFM the organism grew as low as 6degreesC and optimally at 37-43degreesC. In faecal coliform tests, 23% of strains (n = 70) produced gas from lauryl sulphate broth (LSB) at 44degreesC after 48 h incubation. Three strains failed to grow in LSB at any of the temperatures. The D-value of cells suspended in IFM was determined between 54 and 62degreesC. The resultant z-value was 5.7degreesC. The organism was able to adhere and grow on latex, polycarbonate, silicon and to a lesser extent stainless steel. Conclusions: Enterobacter sakazakil, was able to grow at refrigeration temperatures and on infant-feeding equipment. The thermotolerance of the organism was similar to other Enterobacteriaceae and should be killed during standard pasteurization treatment. Significance and Impact of the Study: Enterobacter sakazakii, has been associated with infant meningitis through consumption of contaminated IFM. Enterobacter sakazakii is able to grow in IFM during storage at refrigeration temperatures and attach to infant-feeding equipment, which may become reservoirs of infection.