Objections to the transfer of Francisella novicida to the subspecies rank of Francisella tularensis.

International Journal of Systematic and Evolutionary Microbiology (Impact Factor: 2.8). 08/2010; 60(Pt 8):1717-8; author reply 1718-20. DOI: 10.1099/ijs.0.022830-0
Source: PubMed


Available from: Anders Johansson, Jun 03, 2015
1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Francisella tularensis, the etiologic agent of tularemia and a Class A Select Agent, is divided into three subspecies and multiple subpopulations that differ in virulence and geographic distribution. Given these differences, there is a need to rapidly and accurately determine if a strain is F. tularensis and, if it is, assign it to subspecies and subpopulation. We designed TaqMan real-time PCR genotyping assays using eleven single nucleotide polymorphisms (SNPs) that were potentially specific to closely related groups within the genus Francisella, including numerous subpopulations within F. tularensis species. We performed extensive validation studies to test the specificity of these SNPs to particular populations by screening the assays across a set of 565 genetically and geographically diverse F. tularensis isolates and an additional 21 genetic near-neighbor (outgroup) isolates. All eleven assays correctly determined the genetic groups of all 565 F. tularensis isolates. One assay differentiates F. tularensis, F. novicida, and F. hispaniensis from the more genetically distant F. philomiragia and Francisella-like endosymbionts. Another assay differentiates F. tularensis isolates from near neighbors. The remaining nine assays classify F. tularensis-confirmed isolates into F. tularensis subspecies and subpopulations. The genotyping accuracy of these nine assays diminished when tested on outgroup isolates (i.e. non F. tularensis), therefore a hierarchical approach of assay usage is recommended wherein the F. tularensis-specific assay is used before the nine downstream assays. Among F. tularensis isolates, all eleven assays were highly sensitive, consistently amplifying very low concentrations of DNA. Altogether, these eleven TaqMan real-time PCR assays represent a highly accurate, rapid, and sensitive means of identifying the species, subspecies, and subpopulation of any F. tularensis isolate if used in a step-wise hierarchical scheme. These assays would be very useful in clinical, epidemiological, and/or forensic investigations involving F. tularensis.
    PLoS ONE 09/2014; 9(9):e107964. DOI:10.1371/journal.pone.0107964 · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The highly infectious bacteria, Francisella tularensis, colonize a variety of organs and replicate within both phagocytic as well as non-phagocytic cells, to cause the disease tularemia. These microbes contain a conserved cluster of important virulence genes referred to as the Francisella Pathogenicity Island (FPI). Two of the most characterized FPI genes, iglC and pdpA, play a central role in bacterial survival and proliferation within phagocytes, but do not influence bacterial internalization. Yet, their involvement in non-phagocytic epithelial cell infections remains unexplored. To examine the functions of IglC and PdpA on bacterial invasion and replication during epithelial cell infections, we infected liver and lung epithelial cells with F. novicida and F. tularensis 'Type B' Live Vaccine Strain (LVS) deletion mutants (ΔiglC and ΔpdpA) as well as their respective gene complements. We found that deletion of either gene significantly reduced their ability to invade and replicate in epithelial cells. Gene complementation of iglC and pdpA partially rescued bacterial invasion and intracellular growth. Additionally, substantial LAMP1-association with both deletion mutants was observed up to 12 h suggesting that the absence of IglC and PdpA caused deficiencies in their ability to dissociate from LAMP1-positive Francisella Containing Vacuoles (FCVs). This work provides the first evidence that IglC and PdpA are important pathogenic factors for invasion and intracellular growth of Francisella in epithelial cells, and further highlights the discrete mechanisms involved in Francisella infections between phagocytic and non-phagocytic cells.
    PLoS ONE 08/2014; 9(8):e104881. DOI:10.1371/journal.pone.0104881 · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background. Francisella novicida is a rare cause of human illness despite its close genetic relationship to Francisella tularensis, the agent of tularemia. During April-July 2011, 3 inmates at a Louisiana correctional facility developed F. novicida bacteremia; 1 inmate died acutely. Methods. We interviewed surviving inmates; reviewed laboratory, medical, and housing records; and conducted an environmental investigation. Clinical and environmental samples were tested by culture, real-time polymerase chain reaction (PCR), and multigene sequencing. Isolates were typed by pulsed-field gel electrophoresis (PFGE). Results. Clinical isolates were identified as F. novicida based on sequence analyses of the 16S ribosomal RNA, pgm, and pdpD genes. PmeI PFGE patterns for the clinical isolates were indistinguishable. Source patients were aged 40-56 years, male, and African American, and all were immunocompromised. Two patients presented with signs of bacterial peritonitis; the third had pyomyositis of the thigh. The 3 inmates had no contact with one another; their only shared exposures were consumption of municipal water and of ice that was mass-produced at the prison in an unenclosed building. Swabs from one set of ice machines and associated ice scoops yielded evidence of F. novicida by PCR and sequencing. All other environmental specimens tested negative. Conclusions. To our knowledge, this is the first reported common-source outbreak of F. novicida infections in humans. Epidemiological and laboratory evidence implicate contaminated ice as the likely vehicle of transmission; liver disease may be a predisposing factor. Clinicians, laboratorians, and public health officials should be aware of the potential for misidentification of F. novicida as F. tularensis.
    Clinical Infectious Diseases 06/2014; 59(6). DOI:10.1093/cid/ciu430 · 9.42 Impact Factor