Cronobacter Support
04-21-2009, 05:51 PM
1st International Conference on Cronobacter Poster Abstract 2
Comparison of virulence risk factors in Cronobacter and novel Enterobacter species
Ingestion of infant formula containing Cronobacter (Enterobacter sakazakii) has been associated with rare cases of neonatal infections. Cronobacter spp. are noted for their desiccation resistance and production of exopolysaccharide (EPS), factors which may allow them to persist in dry
environments. Some isolates can attach and invade epithelial cells and interact with macrophages in vitro. Three other recently described species (E. helveticus, E. turicensis and E. pulveris) are found in the same environmental niches as Cronobacter, including infant formula factories. However there has been no association of these species with neonatal illness. In this study, factors that may contribute to the infection of infants via infant formula are investigated in these novel species in comparison to Cronobacter isolates. Strains comprised 12 Cronobacter (representative of different geno- and phenotypes), 22 isolates from the novel Enterobacter spp. and 5 other Enterobacteriaceae. Biochemical and phenotypic assays were performed using conventional methods and included motility, siderophore, lactose fermentation, DNAse, esterase, gelatinase, mucinase, albuminase, elastase and haemolysin activity. Production of exopolysaccharide was scored semi-quantitatively based on colony size. Selected isolates were subjected to in vitro assays to determine the relative propensity to attach and invade human epithelial cells, persist in macrophages (24 and 48 h) and survive compliment mediated cytotoxity. The relative desiccation tolerance in dried milk powder was also determined over 6 months. The Enterobacter species lacked DNAse and siderophore activity. E. helveticus and E. turicensis were sensitive to compliment-mediated lysis and lacked gelatinase activity. Although the Enterobacter species were able to attach to epithelial cells they were less invasive than Cronobacter isolates, they were also unable to persist in macrophages. Although the production of EPS was variable among these species, Enterobacter isolates appear to be as desiccation resistant as Cronobacter isolates. Although the novel Enterobacter spp. appear to be adapted to exist in the same environments as Cronobacter, and are present at similar levels in infant foods, they appear to lack mechanisms involved in mammalian cell invasion and maintenance of systemic infection.
Carol Iversen1,2, Angelika Lehner1, Brendan Healy2, Séamus Fanning2 and Roger Stephan1
1Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zürich, CH-8057, Zürich, Switzerland. 2Centre for Food Safety, UCD Veterinary Sciences Centre, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
Comparison of virulence risk factors in Cronobacter and novel Enterobacter species
Ingestion of infant formula containing Cronobacter (Enterobacter sakazakii) has been associated with rare cases of neonatal infections. Cronobacter spp. are noted for their desiccation resistance and production of exopolysaccharide (EPS), factors which may allow them to persist in dry
environments. Some isolates can attach and invade epithelial cells and interact with macrophages in vitro. Three other recently described species (E. helveticus, E. turicensis and E. pulveris) are found in the same environmental niches as Cronobacter, including infant formula factories. However there has been no association of these species with neonatal illness. In this study, factors that may contribute to the infection of infants via infant formula are investigated in these novel species in comparison to Cronobacter isolates. Strains comprised 12 Cronobacter (representative of different geno- and phenotypes), 22 isolates from the novel Enterobacter spp. and 5 other Enterobacteriaceae. Biochemical and phenotypic assays were performed using conventional methods and included motility, siderophore, lactose fermentation, DNAse, esterase, gelatinase, mucinase, albuminase, elastase and haemolysin activity. Production of exopolysaccharide was scored semi-quantitatively based on colony size. Selected isolates were subjected to in vitro assays to determine the relative propensity to attach and invade human epithelial cells, persist in macrophages (24 and 48 h) and survive compliment mediated cytotoxity. The relative desiccation tolerance in dried milk powder was also determined over 6 months. The Enterobacter species lacked DNAse and siderophore activity. E. helveticus and E. turicensis were sensitive to compliment-mediated lysis and lacked gelatinase activity. Although the Enterobacter species were able to attach to epithelial cells they were less invasive than Cronobacter isolates, they were also unable to persist in macrophages. Although the production of EPS was variable among these species, Enterobacter isolates appear to be as desiccation resistant as Cronobacter isolates. Although the novel Enterobacter spp. appear to be adapted to exist in the same environments as Cronobacter, and are present at similar levels in infant foods, they appear to lack mechanisms involved in mammalian cell invasion and maintenance of systemic infection.
Carol Iversen1,2, Angelika Lehner1, Brendan Healy2, Séamus Fanning2 and Roger Stephan1
1Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zürich, CH-8057, Zürich, Switzerland. 2Centre for Food Safety, UCD Veterinary Sciences Centre, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.