Molecular analysis of the Enterobacter sakazakii O-antigen gene locus

Centres for Food Safety and Food-borne Zoonomics, UCD Veterinary Sciences Centre, School of Agriculture, Food Science & Veterinary Medicine, Conway Institute of Biomolecular & Biomedical Research, School of Public Health & Population Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Institute for Food Safety & Hygiene, Vetsuisse Faculty, University of Zurich, CH-8057 Zurich, Switzerland

^* To whom correspondence should be addressed. Email: sfanning{at}ucd.ie.

	Abstract

Nucleotide polymorphism associated with the O-antigen encoding locus, rfb, in Enterobacter sakazakii was determined by PCR-RFLP analysis. Based on the analysis of these DNA profiles, 12 unique banding patterns were detected amongst a collection of 62 strains from diverse origins. Two common profiles were identified and designated as serotypes O:1 and O:2. DNA sequencing of the 12,500-bp region, flanked by galF and gnd, identified 11 open reading frames, all with the same transcriptional direction. Analysis of the proximal region of both sequences demonstrated remarkable heterogeneity. A polymerase chain reaction (PCR) assay targeting genes specific for the two prominent serotypes was developed, and applied for the identification of these strains recovered from food, environmental and clinical samples.