Ben Tall, U.S. Food and Drug Administration, Laurel, MD
Christopher Grim, U.S. Food and Drug Administration, Laurel, MD
Gopal Gopinath, U.S. Food and Drug Administration, Laurel, MD
Karen Jarvis, U.S. Food and Drug Administration, Laurel, MD
Michael Kotewicz, U.S. Food and Drug Administration, Laurel, MD
Karen Power, University College Dublin, Dublin, Ireland
Qiongqiong Yan, University College Dublin, Dublin, Ireland
Scott Jackson, NIST, Gaithersburg, MD
Isha Patel, U.S. Food and Drug Administration, Laurel, MD
Jayanthi Gangiredla, U.S. Food and Drug Administration, Laurel, MD
Mark Mammel, U.S. Food and Drug Administration, Laurel, MD
Venugopal Sathyamoorthy, U.S. Food and Drug Administration, Laurel, MD
Larisa Trach, U.S. Food and Drug Administration, Laurel, MD
Hannah Chase, U.S. Food and Drug Administration, Laurel, MD
Boram Lee, U.S. Food and Drug Administration, Laurel, MD
Seongeun Hwang, U.S. Food and Drug Administration, Laurel, MD
Franco Pagotto, Health Canada, Ottawa, Canada
Seamus Fanning, University College Dublin, Dublin, Ireland
Carol Iversen, University of Dundee, Dundee, Scotland
Angelika Lehner, University of Zurich, Zurich, Switzerland
Roger Stephan, University of Zurich, Zurich, Switzerland
Introduction: Cronobacter are opportunistic foodborne pathogens that cause meningitis, necrotizing enterocolitis, and septicemia, particularly among infants and elderly persons. Until recently, the genus was comprised of seven species:
C. sakazakii (Csak),
C. malonaticus (Cmal),
C. turicensis (Ctur),
C. dublinensis (Cdub),
C. muytjensii (Cmuy),
C. condimenti (Ccond), and
C. universalis (Cuni). All except for Ccond are established human pathogens. In 2013, three nonpathogenic species originally classified as
Enterobacter spp. (now named
C. helveticus,
C. pulveris, and
C. zurichensis) were included.
Purpose: Validation of the array was done by hybridizing DNA from sequenced strains represented on the array. Also, a study focusing on the interrogation of 122 Cronobacter and related strains was conducted to answer whether the microarray could be used as a food safety tool.
Methods: Comparative analysis of whole genome sequences from 17 Cronobacter strains led to the design of a custom Affymetrix DNA microarray. The array represents the pan genome for Cronobacter and species-specific features and contains 21,432 genes. For each gene, there are 11 probe pairs; each represented by a perfect match and corresponding mismatch probe. Hybridization intensities of these 25-mer probe pairs were used to determine the absence/presence of a gene.
Results: Results suggest that the identity of a Cronobacter isolate and its total gene content can be resolved. Furthermore, these results support the divergence of the genus from the most recent common ancestral species into two clusters, one consisting of Cdub-Cmuy and the other comprised of Csak-Cmal-Cuni-Ctur. Ccond was a distant outlier of the two larger clusters. Microarray interrogation of C. helveticus, C. pulveris and C. zurichensis strains support the hypothesis that these organisms taxonomically should not be considered as Cronobacter.
Significance: The current study establishes a powerful platform for further functional genomics research of this diverse group, an important prerequisite towards future development of countermeasures against this foodborne pathogen.
