Fate of Enterobacter sakazakii attached to or in biofilms on stainless steel upon exposure to various temperatures or relative humidities.
Survival of Enterobacter sakazakii dried on the surface of stainless steel and exposed to 43% relative humidity, as affected by temperature, was studied. Populations of E. sakazakii (7.4 to 8.6 log CFU per coupon) on coupons dried for 2 h at 22 degrees C decreased significantly (P < or = 0.05) at 4, 25, and 37 degrees C within 10, 3, and 1 day(s), respectively, but the pathogen remained viable for up to 60 days. At a given storage temperature and time, reductions were significantly greater when cells had been suspended in water rather than in infant formula before drying. Formation of biofilm by E. sakazakii on stainless steel immersed in M9 medium, which contains minimal concentrations of nutrients, and infant formula at 25 degrees C and subsequent survival of cells at 25 degrees C as affected by exposure to 23, 43, 68, 85, and 100% relative humidity were investigated. Some of the cells in these biofilms survived under all test relative humidities for up to 42 days. The overall order of survival as affected by relative humidity was 100 > 23 = 43 = 68 > 85% relative humidity, regardless of the medium in which the biofilm was formed. Reduction in viability of cells was significantly greater in biofilm that had formed in M9 medium than in biofilm formed in infant formula. Results indicate that infant formula provides protection for attached cells, as well as cells in biofilm, against lethality on exposure to desiccation. These results are useful when predicting the survival characteristics of E. sakazakii on stainless steel surfaces in processing and preparation kitchen environments.
Graduate School of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-791, Republic of Korea.
Hoikyung
H
Kim
Jihyun
J
Bang
Larry R
LR
Beuchat
Jee-Hoon
JH
Ryu
D001422:Bacterial Adhesion / Q000502:physiology; D018441:Biofilms / Q000254:growth & development*; D015169:Colony Count, Microbial; D044083:Cronobacter sakazakii / Q000502:physiology*; D003470:Culture Media; D004866:Equipment Contamination / Q000517:prevention & control*; D005506:Food Contamination / Q000517:prevention & control*; D005516:Food Microbiology; D006801:Humans; D006813:Humidity; D041943:Infant Formula; D013193:Stainless Steel; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
D003470:Culture Media; D013193:Stainless Steel