Cronobacter Support
05-12-2009, 07:13 PM
1st International Conference on Cronobacter Poster Abstract 27
Isolation and characterisation of Cronobacter from infant food
Cronobacter are a causative agent of illness in premature and low birth weight neonates and transmission has been associated with infant formula. In this study Cronobacter isolated from baby food samples were assessed for their virulence potential. A total of 20 different baby foods were tested for the presence of Enterobacteriaceae using the ISO TS 22964. Isolates were identified using ID32E (bioMerieux) and confirmed as Cronobacter by rt-PCR. The Cronobacter isolates were speciated using biochemical tests and 16S rRNA sequencing and were typed using PFGE. The virulence characteristics of the isolates were assessed using a macrophage survival assay and PCR assays to detect selected virulence markers. The antibiotic resistance profiles were also determined. Other Enterobacteriaceae isolates from infant foods were used for comparative purposes, including a Salmonella Ealing isolate previously implicated in an outbreak of neonatal infection. Of the Cronobacter isolates obtained, 4 were found to be Cronobacter turicensis and 3 were Cronobacter sakazakii. Using PFGE, the C. turicensis isolates clustered together but were distinct from E866, the type strain of this species. The C. sakazakii isolates also clustered together within one band difference, however were also distinct from the type strain of this species (ATCC 29544). All isolates were resistant to erythromycin but sensitive to the other antibiotics tested with the exception of one isolate that was resistant to cephalothin. All the Cronobacter isolates were positive for the presence of ompA, tolC and phoP. However using these primer sets, only the C. turicensis isolates were positive for acrA and only the C. sakazakii isolates were positive for phoQ. Persistence in macrophages was evident at 24 h after phagocytosis for all the Cronobacter isolates. However at 48 h none of the C. sakazakii isolates were recovered in contrast to continued persistence of the C. turicensis isolates. In comparison Salmonella Ealing isolated from infant formula in 1985 showed proliferation at 24 h and persistence up to 72 h. In conclusion, Enterobacteriaceae including Cronobacter spp. can be isolated from baby foods. These Cronobacter strains may harbor potential virulence genes and posses the ability to persist in macrophages. However, few cases of Cronobacter infections have been reported in children older than 3 months and no epidemiological evidence exists to suggest that ingestion of baby foods containing low levels of Enterobacteriaceae are a health concern.
Orla Condell, Brendan Healy, Stephen O’Brien, Shane Cooney, Séamus Fanning, Carol Iversen
Centres for Food Safety & Food-borne Zoonomics. UCD Veterinary Sciences Centre, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
Isolation and characterisation of Cronobacter from infant food
Cronobacter are a causative agent of illness in premature and low birth weight neonates and transmission has been associated with infant formula. In this study Cronobacter isolated from baby food samples were assessed for their virulence potential. A total of 20 different baby foods were tested for the presence of Enterobacteriaceae using the ISO TS 22964. Isolates were identified using ID32E (bioMerieux) and confirmed as Cronobacter by rt-PCR. The Cronobacter isolates were speciated using biochemical tests and 16S rRNA sequencing and were typed using PFGE. The virulence characteristics of the isolates were assessed using a macrophage survival assay and PCR assays to detect selected virulence markers. The antibiotic resistance profiles were also determined. Other Enterobacteriaceae isolates from infant foods were used for comparative purposes, including a Salmonella Ealing isolate previously implicated in an outbreak of neonatal infection. Of the Cronobacter isolates obtained, 4 were found to be Cronobacter turicensis and 3 were Cronobacter sakazakii. Using PFGE, the C. turicensis isolates clustered together but were distinct from E866, the type strain of this species. The C. sakazakii isolates also clustered together within one band difference, however were also distinct from the type strain of this species (ATCC 29544). All isolates were resistant to erythromycin but sensitive to the other antibiotics tested with the exception of one isolate that was resistant to cephalothin. All the Cronobacter isolates were positive for the presence of ompA, tolC and phoP. However using these primer sets, only the C. turicensis isolates were positive for acrA and only the C. sakazakii isolates were positive for phoQ. Persistence in macrophages was evident at 24 h after phagocytosis for all the Cronobacter isolates. However at 48 h none of the C. sakazakii isolates were recovered in contrast to continued persistence of the C. turicensis isolates. In comparison Salmonella Ealing isolated from infant formula in 1985 showed proliferation at 24 h and persistence up to 72 h. In conclusion, Enterobacteriaceae including Cronobacter spp. can be isolated from baby foods. These Cronobacter strains may harbor potential virulence genes and posses the ability to persist in macrophages. However, few cases of Cronobacter infections have been reported in children older than 3 months and no epidemiological evidence exists to suggest that ingestion of baby foods containing low levels of Enterobacteriaceae are a health concern.
Orla Condell, Brendan Healy, Stephen O’Brien, Shane Cooney, Séamus Fanning, Carol Iversen
Centres for Food Safety & Food-borne Zoonomics. UCD Veterinary Sciences Centre, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.