ABSTRACT
We present TaqMan-minor groove binding (MGB) assays for an SNP that separates the Yersinia pestis strain CO92 from all other strains and for another SNP that separates North American strains from all other global strains.
Subject(s)
Bacterial Typing Techniques/methods , Yersinia pestis/classification , Yersinia pestis/isolation & purification , Alleles , DNA, Bacterial/analysis , DNA, Bacterial/genetics , Genotype , North America , Polymorphism, Single Nucleotide/genetics , Reproducibility of Results , Time Factors , Yersinia pestis/geneticsABSTRACT
The causative agent of tularemia, Francisella tularensis, is a formidable biologic agent that occurs naturally throughout North America. We examined genetic and spatial diversity patterns among 161 US F. tularensis isolates by using a 24-marker multiple-locus variable-number tandem repeat analysis (MLVA) system. MLVA identified 126 unique genotypes. Phylogenetic analyses showed patterns similar to recently reported global-scale analyses. We observed clustering by subspecies, low genetic diversity within F. tularensis subsp. holarctica, and division of F. tularensis subsp. tularensis into 2 distinct subpopulations: A.I. and A.II. The 2 F. tularensis subsp. tularensis subpopulations also represent geographically distinct groups; A.I. occurs primarily in the central United States, and A.II. occurs primarily in the western United States. These spatial distributions are correlated with geographic ranges of particular vectors, hosts of tularemia, and abiotic factors. These correlates provide testable hypotheses regarding ecologic factors associated with maintaining tularemia foci.
Subject(s)
Francisella tularensis/genetics , Francisella tularensis/isolation & purification , Tularemia/epidemiology , Tularemia/microbiology , Animals , Francisella tularensis/classification , Geography , Phylogeny , United States/epidemiologyABSTRACT
Francisella tularensis is found in a wide variety of hosts and extrahost environments, making culture recovery a diagnostic challenge. Here we demonstrate improved recovery times and good sensitivity (90%) when cultures were inoculated on the site of an investigation using fresh tissues. For contaminated specimens, antibiotic supplementation of enriched cysteine heart agar blood culture medium improved recovery of F. tularensis by 81.1%. For transport of tissues, immediate freezing yielded culture recovery rates as high as 94%.
