Genotypic and phenotypic analysis of Enterobacter sakazakii strains from a fatal outbreak in a neonatal intensive care unit in France

School of Biomedical and Natural Sciences, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK; Laboratoire de Microbiologie et Génetique Moléculaires, UMR 5100 CNRS et Université Paul Sabatier Toulouse III, 118 route de Narbonne, 31062 Toulouse cedex 9, FRANCE

^* To whom correspondence should be addressed. Email: Stephen.forsythe{at}ntu.ac.uk.

	Abstract

In 1994, an outbreak of Enterobacter sakazakii infections in France occurred in a neonatal intensive care unit from 5th May to 11th July. During the outbreak, 13 neonates were infected with E. sakazakii resulting in three deaths. In addition, four symptomless neonates were colonised by E. sakazakii. The strains were subjected to 16S rDNA sequence analysis, genotyped using pulsed-field gel electrophoresis, and phenotyped for a range of enzyme activities. E. sakazakii was isolated from various anatomical sites, reconstituted formula and an unopened can of powdered infant formula. A fourth neonate died from septic shock during this period and was attributed to E. sakazakii infection. However, 16S rRNA gene sequence analysis revealed it was E. cloacae.

There were three pulsotypes of E. sakazakii associated with infected neonates, and three neonates were infected by more than one genotype. One genotype matched isolates from unused prepared feed and unfinished feed. However, no pulsotypes matched the E. sakazakii recovered from an unopened can of powdered infant formula. One pulsotype was associated with the three fatal cases, and two of these isolates had extended spectrum -lactamase activity. It is possible that E. sakazakii strains vary in their pathogenicity, as shown by the range of symptoms associated with each pulsotype.