Cronobacter Support
05-18-2009, 03:15 PM
1st International Conference on Cronobacter Poster Abstract 39
Genotypic and phenotypic characterisation of a collection of Enterobacter sakazakii isolates
Enterobacter sakazakii has been identified as the causative agent of serious neonatal infections, associated with high mortality rate. In most cases, powdered infant formula (PIF) has been identified as the source of infection. Recently, strains commonly referred as E. sakazakii were proposed to be classified in a new genus, Cronobacter. Since knowledge on this pathogen is still incomplete, it is recommended to type all isolates in order to favour epidemiological investigation and evaluate strain variability. In order to characterise a collection of isolates from various origins, we used a Pulse-Field Gel Electrophoresis technique (PFGE) developed in our laboratory. Relevant biochemical tests were also performed to classify strains into the different Cronobacter species. In order to compare growth characteristics, growth curves for each strain were determined in non selective brain heart infusion broth, at 25°C and 37°C, by measuring optical density using a spectrophotometer. Growth rate was estimated from the slope of the tangential line in mid-exponential phase. Results showed that PFGE technique seemed not to be suitable for establishing taxonomic relationships within Cronobacter genus, since we had difficulties to obtain coherent clustering of E. sakazakii strains using PFGE patterns. The majority of the strains belonged to Cronobacter sakazakii, which seemed to be the most commonly species distributed in environment of PIF production plants. Growth rates were homogenous within the genus, and no significant differences were observed between strains, according to their origin or species. This study did not allow to establish potential links between genotypic and phenotypic profiles. The high genetic heterogeneity observed could be opposed to the high homogeneity in growth behaviour, which is capital information for quantitative risk assessment studies. In order to have a more precise idea of the pathogen behaviour, further studies should be performed on lag phase distribution among the isolates.
Rabeb Beennour Miled, Annaelle Kerouanton, Thomas Meheut, Pierre Colin, Nathalie Gnanou-Besse
Agence française de sécurité sanitaire des aliments Laboratoire d’Etudes et de Recherches sur la Qualité des Aliments et sur les Procédés agro-alimentaires (AFSSA) LERQAP, 23 avenue du Général de Gaulle , 94706 Maisons Alfort cedex, France.
Genotypic and phenotypic characterisation of a collection of Enterobacter sakazakii isolates
Enterobacter sakazakii has been identified as the causative agent of serious neonatal infections, associated with high mortality rate. In most cases, powdered infant formula (PIF) has been identified as the source of infection. Recently, strains commonly referred as E. sakazakii were proposed to be classified in a new genus, Cronobacter. Since knowledge on this pathogen is still incomplete, it is recommended to type all isolates in order to favour epidemiological investigation and evaluate strain variability. In order to characterise a collection of isolates from various origins, we used a Pulse-Field Gel Electrophoresis technique (PFGE) developed in our laboratory. Relevant biochemical tests were also performed to classify strains into the different Cronobacter species. In order to compare growth characteristics, growth curves for each strain were determined in non selective brain heart infusion broth, at 25°C and 37°C, by measuring optical density using a spectrophotometer. Growth rate was estimated from the slope of the tangential line in mid-exponential phase. Results showed that PFGE technique seemed not to be suitable for establishing taxonomic relationships within Cronobacter genus, since we had difficulties to obtain coherent clustering of E. sakazakii strains using PFGE patterns. The majority of the strains belonged to Cronobacter sakazakii, which seemed to be the most commonly species distributed in environment of PIF production plants. Growth rates were homogenous within the genus, and no significant differences were observed between strains, according to their origin or species. This study did not allow to establish potential links between genotypic and phenotypic profiles. The high genetic heterogeneity observed could be opposed to the high homogeneity in growth behaviour, which is capital information for quantitative risk assessment studies. In order to have a more precise idea of the pathogen behaviour, further studies should be performed on lag phase distribution among the isolates.
Rabeb Beennour Miled, Annaelle Kerouanton, Thomas Meheut, Pierre Colin, Nathalie Gnanou-Besse
Agence française de sécurité sanitaire des aliments Laboratoire d’Etudes et de Recherches sur la Qualité des Aliments et sur les Procédés agro-alimentaires (AFSSA) LERQAP, 23 avenue du Général de Gaulle , 94706 Maisons Alfort cedex, France.