Doctoral Dissertations

Date of Award

5-2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Food Science and Technology

Major Professor

Francis Ann Draughon

Committee Members

P. Michael Davidson, Arnold Saxton, Doris D’Souza

Abstract

Enterobacter sakazakii is considered an emerging opportunistic pathogen associated with sporadic life-threatening bacterial infections in neonates linked to the compsumption of contaminated infant formula [Stoll et al., 2004]. In 2001 a neonate fatal infection associated with the presence of E. sakazakii in infant formula occurred in the neonatal intensive care unit (NICU) of the University of Tennessee Hospital [Himelright et al., 2002], as a result of this outbreak, the hospital made several policy changes and requested the Food Safety Center of Excellence of University of Tennessee to analyze the growth pattern of this microorganism at the conditions maintained in the hospital. The objective of this study was to analize E. sakazakii growth profile during preparation and administration of formula, as well as E. sakazakii tolerance to chlorine sanitizers widely used in hospital settings.Our results showed that if the starting temperature of the formula at the time of administration was 6 oC, the formula reached 25 oC in a period of four hours. Once contaminated formula reach 25 oC the generation times can decrease to less than one hour. We also noted that cells organized in colonies or in contact with solid surfaces had a higher resistance to chlorine sanitizers than those of planktonic cells, this phenomena could be explained by the expression of genes triggered by the physical contact between cell and surface.

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