Biofilm formation on enteral feeding tubes by Cronobacter sakazakii, Salmonella serovars and other Enterobacteriaceae.

WHO (2007) recommended that to reduce microbial risks, powdered infant formula should be reconstituted with water at temperatures >70 degrees C, and that such feeds should be used within 2h of preparation. However, this recommendation does not consider the use of enteral feeding tubes which can be in place for more than 48h and can be loci for bacterial attachment. This study determined the extent to which 29 strains of Cronobacter sakazakii, Salmonella serovars, other Enterobacteriaceae and Acinetobacter spp. can adhere and grow on enteral feeding tubes composed of polyvinyl chloride and polyurethane. The study also included silver-impregnated tubing which was expected to have antibacterial activity. Bacterial biofilm formation by members of the Enterobacteriaceae was ca. 10(5)-10(6) cfu/cm after 24h. Negligible biofilm was detected for Acinetobacter gensp. 13; ca. 10 cfu/cm, whereas Cr. sakazakii strain ATCC 12868 had the highest biofilm cell density of 10(7) cfu/cm. Biofilm formation did not correlate with capsule production, and was not inhibited on silver-impregnated tubing. Bacteria grew in the tube lumen to cell densities of 10(7)cfu/ml within 8h, and 10(9)cfu/ml within 24h. It is plausible that in vivo the biofilm will both inoculate subsequent routine feeds and as the biofilm ages, clumps of cells will be shed which may survive passage through the neonate's stomach. Therefore biofilm formation on enteral feeding tubes constitutes a risk factor for susceptible neonates.

Genotypic and phenotypic analysis of Enterobacter sakazakii strains from an outbreak resulting in fatalities in a neonatal intensive care unit in France.

In 1994, an outbreak of Enterobacter sakazakii infections occurred in a neonatal intensive care unit in France from 5 May to 11 July. During the outbreak, 13 neonates were infected with E. sakazakii, resulting in 3 deaths. In addition, four symptomless neonates were colonized by E. sakazakii. The strains were subjected to 16S rRNA gene 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, attributed to E. sakazakii infection, during this period. However, 16S rRNA gene sequence analysis revealed that the organism was Enterobacter 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 formula and unfinished formula. However, no pulsotypes matched the E. sakazakii strain 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 beta-lactamase activity. It is possible that E. sakazakii strains differ in their pathogenicities, as shown by the range of symptoms associated with each pulsotype.