title: Characterization of putative virulence genes on the related RepFIB plasmids harbored by Cronobacter spp.
abstract: Cronobacter spp. are emerging neonatal pathogens that cause meningitis, sepsis, and necrotizing enterocolitis. The genus Chronobacter consists of six species: C. sakazakii, C. malonaticus, C. muytjensii, C. turicensis, C. dublinensis, and Cronobacter genomospecies group 1. Whole-genome sequencing of C. sakazakii BAA-894 and C. turicensis z3032 revealed that they harbor similarly sized plasmids identified as pESA3 (131 kb) and pCTU1 (138 kb), respectively. In silico analysis showed that both plasmids encode a single RepFIB-like origin of replication gene, repA, as well as two iron acquisition systems (eitCBAD and iucABCD/iutA). In a chrome azurol S agar diffusion assay, it was demonstrated that siderophore activity was associated with the presence of pESA3 or pCTU1. Additionally, pESA3 contains a cpa (Cronobacter plasminogen activator) gene and a 17-kb type 6 secretion system (T6SS) locus, while pCTU1 contains a 27-kb region encoding a filamentous hemagglutinin gene (fhaB), its specifc transporter gene (fhaC), and associated putative adhesins (FHA locus), suggesting that these are virulence plasmids. In a repA-targeted PCR assay, 97% of 229 Cronobacter species isolates were found to possess a homologous RepFIB plasmid. All repA PCR-positive strains were also positive for the eitCBAD and iucABCD/iutA iron acquisition systems. However, the presence of cpa, T6SS, and FHA loci depended on species, demonstrating a strong correlation with the presence of virulence traits, plasmid type, and species. These results support the hypothesis that these plasmids have evolved from a single archetypical plasmid backbone through the cointegration, or deletion, of specific virulence traits in each species.
authors.affiliation: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Franco
authors.forename: L
authors.initials: L
authors.lastname: Hu
authors.forename: C J
authors.initials: CJ
authors.lastname: Grim
authors.forename: G
authors.initials: G
authors.lastname: Gopinath
authors.forename: V
authors.initials: V
authors.lastname: Sathyamoorthy
authors.forename: K G
authors.initials: KG
authors.lastname: Jarvis
authors.forename: C
authors.initials: C
authors.lastname: Lee
authors.forename: J
authors.initials: J
authors.lastname: Sadowski
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.forename: M H
authors.initials: MH
authors.lastname: Kothary
authors.forename: B A
authors.initials: BA
authors.lastname: McCardell
authors.forename: B D
authors.initials: BD
authors.lastname: Tall
mesh_terms: D016000:Cluster Analysis; D003470:Culture Media / Q000737:chemistry; D004265:DNA Helicases / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004755:Enterobacteriaceae / Q000235:genetics* / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D010957:Plasmids; D017422:Sequence Analysis, DNA; D017262:Siderophores / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D026901:Membrane Transport Proteins; D017262:Siderophores; D015534:Trans-Activators; D037521:Virulence Factors; C045264:replication initiator protein; D007501:Iron; D004265:DNA Helicases