BIOFILM FORMATION BY ENTEROBACTER SAKAZAKII GROWN IN ARTIFICIAL BROTH AND INFANT MILK FORMULA ON PLASTIC SURFACE

Abstract

ABSTRACT Biofilm‐forming characteristics of 72 different Enterobacter sakazakii strains on plastic surface were tested. And the influence of the artificial growth medium and infant milk formula (IMF) was also determined. Quantification of biofilm formation was performed with medium including brain heart infusion broth, nutrient broth, tryptic soy broth, 1/20 diluted tryptic soy broth (1/20‐TSB) and differently diluted IMF on plastic microtiter plates. According to the result, reconstituted IMF was the more effective medium for biofilm formation than artificial medium. At normal IMF concentration, 56 strains produced biofilm (77.8%) but most suitable artificial medium and 1/20‐TSB; 12 strains produced biofilm (16.7%). These results indicated that the IMF offers more opportunities of biofilm formation on plastic surface. Therefore, all bottles and equipment should be effectively cleaned for preventing biofilm formation by IMF and E. sakazakii.PRACTICAL APPLICATIONS E. sakazakii could produce biofilm and protect the cells from being affected by disinfectants. It is also more difficult to wash such bacteria off from the surface they attached with biofilm and the chance of cross‐contamination could increase. The ability of biofilm formation could be influenced by different strains and also the growing media. By this study, we observed that IMF is the most effective media for biofilm formation among all the other media tested. Since IMF is the most important vehicle and source of E. sakazakii, it is important to surely clean and disinfect all the processing facilities in the factory and all the utensils, bottles, or teats used for IMF preparation. As biofilm would be formed when contact time increased, it is recommended not to sit the feeding bottles with IMF for a prolonged time to prevent biofilm formation and therefore minimize the opportunity of E. sakazakii infection.