Extensive allelic variation among Francisella tularensis strains in a short-sequence tandem repeat region

Citation
A. Johansson et al., Extensive allelic variation among Francisella tularensis strains in a short-sequence tandem repeat region, J CLIN MICR, 39(9), 2001, pp. 3140-3146
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Clinical Immunolgy & Infectious Disease",Microbiology
Journal title
JOURNAL OF CLINICAL MICROBIOLOGY
ISSN journal
0095-1137 → ACNP
Volume
39
Issue
9
Year of publication
2001
Pages
3140 - 3146
Database
ISI
SICI code
0095-1137(200109)39:9<3140:EAVAFT>2.0.ZU;2-Y
Abstract
Members of the genus Francisella and the species F. tularensis appear to be genetically very similar despite pronounced differences in virulence and g eographic localization, and currently used typing methods do not allow disc rimination of individual strains. Here we show that a number of short-seque nce tandem repeat (SSTR) loci are present in F. tularensis genomes and that two of these loci, SSTR9 and SSTR16, are together highly discriminatory. L abeled PCR amplification products from the loci were identified by an autom ated DNA sequencer for size determination, and each allelic variant was seq uenced. Simpson's index of diversity was 0.97 based on an analysis of 39 no nrelated F. tularensis isolates. The locus showing the highest discriminati on, SSTR9, gave an index of diversity of 0.95. Thirty-two strains isolated from humans during five outbreaks of tularemia showed much less variation. For example, 11 of 12 strains isolated in the Ljusdal area, Sweden in 1995 and 1998 had identical allelic variants. Phenotypic variants of strains and extensively cultured replicates within strains did not differ, and, for ex ample, the same allelic combination was present in 55 isolates of the live- vaccine strain of F. tularensis and another one was present in all 13 isola tes of a strain passaged in animals. The analysis of short-sequence repeats of F. tularensis strains appears to be a powerful tool for discrimination of individual strains and may be useful for a detailed analysis of the epid emiology of this potent pathogen.