Cronobacter Support
06-03-2009, 04:16 PM
1st International Conference on Cronobacter Poster Abstract 52
Osmo-tolerance of Enterobacter sakazakii strains using Phenotype Micro-Array analysis
E. sakazakii is a food-borne pathogen associated with a rare form of neonatal meningitis, sepsis and necrotizing enterocolitis (NEC), resulting in a high mortality rate (40%-80%) in newborns and infants. The mode of transmission associated with E. sakazakii is generally powdered infant milk formula, which has a water activity (aw) of ca 0.2. The lowest aw at which proliferation of most pathogens is limited, occurs at 0.8 however, bacteria have been shown to survive in conditions of much lower moisture availability. This study seeks to assess the ability of 12 E. sakazakii strains to grow in a range different osmolytes. The effect of water activity on the growth of twelve strains of E. sakazakii was investigated using multiple osmotic solutes arranged in a commercial high-throughput phenotype micro-array plate 9 (Biolog, Inc). Stationary phase cells were suspended in the IF-10a base inoculating solution and transferred in 100μl aliquots to individual wells. Tetrazolium dye was used as a measure of the respiratory activity of the cells, an indicator of metabolic activity. The experiment was conducted at 37°C for 48 hours. The results for respiratory activity were plotted against time to produce the growth profiles for each strain. Analysis of the 12 strains revealed considerable variation in growth in different osmolytes at varying concentrations. Notable, E. sakazakii strains were most severely inhibited by sodium benzoate (20 -200 mM), followed by urea (2- 7 %) and sodium formate (1- 6 %). The strains were least inhibited by sodium sulfate (2-5 %), ethylene glycol (5 -20 %), sodium phosphate pH 7 and ammonium sulphate (20 –200 mM). An inverse relationship was observed between the remaining osmolytes (e.g. NaCl, 1 -10 %) and respiratory activity. Of the 12 E sakazakii strains, NCTC08155 was the most resistant isolate followed by, E789, ES104 This study also found E901P, E787 and ATCC 29544 to the most sensitivity to low aw. This study shows that while E. sakazakii is relatively resistant to osmotic stress when compared with other strains of the Enterobacteriaceae, this capacity depends largely on the strain used and the osmolytes against which it is tested.
Jenna M. 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.
Osmo-tolerance of Enterobacter sakazakii strains using Phenotype Micro-Array analysis
E. sakazakii is a food-borne pathogen associated with a rare form of neonatal meningitis, sepsis and necrotizing enterocolitis (NEC), resulting in a high mortality rate (40%-80%) in newborns and infants. The mode of transmission associated with E. sakazakii is generally powdered infant milk formula, which has a water activity (aw) of ca 0.2. The lowest aw at which proliferation of most pathogens is limited, occurs at 0.8 however, bacteria have been shown to survive in conditions of much lower moisture availability. This study seeks to assess the ability of 12 E. sakazakii strains to grow in a range different osmolytes. The effect of water activity on the growth of twelve strains of E. sakazakii was investigated using multiple osmotic solutes arranged in a commercial high-throughput phenotype micro-array plate 9 (Biolog, Inc). Stationary phase cells were suspended in the IF-10a base inoculating solution and transferred in 100μl aliquots to individual wells. Tetrazolium dye was used as a measure of the respiratory activity of the cells, an indicator of metabolic activity. The experiment was conducted at 37°C for 48 hours. The results for respiratory activity were plotted against time to produce the growth profiles for each strain. Analysis of the 12 strains revealed considerable variation in growth in different osmolytes at varying concentrations. Notable, E. sakazakii strains were most severely inhibited by sodium benzoate (20 -200 mM), followed by urea (2- 7 %) and sodium formate (1- 6 %). The strains were least inhibited by sodium sulfate (2-5 %), ethylene glycol (5 -20 %), sodium phosphate pH 7 and ammonium sulphate (20 –200 mM). An inverse relationship was observed between the remaining osmolytes (e.g. NaCl, 1 -10 %) and respiratory activity. Of the 12 E sakazakii strains, NCTC08155 was the most resistant isolate followed by, E789, ES104 This study also found E901P, E787 and ATCC 29544 to the most sensitivity to low aw. This study shows that while E. sakazakii is relatively resistant to osmotic stress when compared with other strains of the Enterobacteriaceae, this capacity depends largely on the strain used and the osmolytes against which it is tested.
Jenna M. 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.