Cronobacter Support
06-03-2009, 05:18 PM
1st International Conference on Cronobacter Poster Abstract 53
Thermal death kinetics of Enterobacter sakazakii at 60°C in Reconstituted infant formula milk
E. sakazakii, a unique species defined in 1980, has been implicated as the causative agent in a rare but severe form of neonatal meningitis, with Infant Formula Milk (IFM) being implicated as the mode of transmission. Despite the high temperatures (72 – 200ºC) used during the production of IFM, E. sakazakii, may still be recovered at low levels in the finished product. This study aims to compare the D-values of a number of Ent sakazakii strains at 60ºC. Ten E. sakazakii strains (7 clinical, 2 environmental and 1 food isolate) were used to assess heat resistance using rubber sealed thin walled glass tubes. Stationary cells were suspended in IFM, divided into 1 ml aliquots and heated at 60°C for up to 180 minutes. Duplicate tubes for each time point were removed from the water-bath at one min intervals, cooled on ice and samples were plated on Tryptone Soya Agar (Oxoid, Basingstoke, England) using spread plate technique. The duplicate experiments were carried out on three separate occasions. Results, Log cfu/ml, were graphed against time and D-values (time required for a 1 log reduction to occur) were calculated using the graphical regions demonstrating first order kinetics. The resultant D-values ranged from 0.71 to 2.51 min. This is comparable with those previously reported (2.5 min) for 60ºC. Previous literature has stated that E. sakazakii strains possessing a KT protein tend to have a higher D-value than those without. However, no significant difference (p>0.05) was observed between the KT+ strains and KT-strains, in this study. Extensive tailing of curves was observed in this study which may be explained by cell exposure to increasing temperatures during testing (heat-up times), resulting in increased resistance to subsequent thermal conditions. Such heat resistance therefore, poses a greater risk to the health of infants should reconstitution of IFM not follow WHO recommendations, using water at 70ºC. For this reason, a thorough understanding of the thermal death kinetics of E. sakazakii in IFM is essential.
Jenna Warby, Ciara Walsh, Séamus Fanning and Amalia Scannell
College of Life Sciences,School of Agriculture, Food Science & Veterinary Medicine, UCD Agriculture and Food Science Centre, UCD, Dublin, Belfield, Dublin 4, Ireland.
Thermal death kinetics of Enterobacter sakazakii at 60°C in Reconstituted infant formula milk
E. sakazakii, a unique species defined in 1980, has been implicated as the causative agent in a rare but severe form of neonatal meningitis, with Infant Formula Milk (IFM) being implicated as the mode of transmission. Despite the high temperatures (72 – 200ºC) used during the production of IFM, E. sakazakii, may still be recovered at low levels in the finished product. This study aims to compare the D-values of a number of Ent sakazakii strains at 60ºC. Ten E. sakazakii strains (7 clinical, 2 environmental and 1 food isolate) were used to assess heat resistance using rubber sealed thin walled glass tubes. Stationary cells were suspended in IFM, divided into 1 ml aliquots and heated at 60°C for up to 180 minutes. Duplicate tubes for each time point were removed from the water-bath at one min intervals, cooled on ice and samples were plated on Tryptone Soya Agar (Oxoid, Basingstoke, England) using spread plate technique. The duplicate experiments were carried out on three separate occasions. Results, Log cfu/ml, were graphed against time and D-values (time required for a 1 log reduction to occur) were calculated using the graphical regions demonstrating first order kinetics. The resultant D-values ranged from 0.71 to 2.51 min. This is comparable with those previously reported (2.5 min) for 60ºC. Previous literature has stated that E. sakazakii strains possessing a KT protein tend to have a higher D-value than those without. However, no significant difference (p>0.05) was observed between the KT+ strains and KT-strains, in this study. Extensive tailing of curves was observed in this study which may be explained by cell exposure to increasing temperatures during testing (heat-up times), resulting in increased resistance to subsequent thermal conditions. Such heat resistance therefore, poses a greater risk to the health of infants should reconstitution of IFM not follow WHO recommendations, using water at 70ºC. For this reason, a thorough understanding of the thermal death kinetics of E. sakazakii in IFM is essential.
Jenna Warby, Ciara Walsh, Séamus Fanning and Amalia Scannell
College of Life Sciences,School of Agriculture, Food Science & Veterinary Medicine, UCD Agriculture and Food Science Centre, UCD, Dublin, Belfield, Dublin 4, Ireland.