Abstract
Molecular analysis of Francisella tularensis subsp. holarctica isolates from humans and animals revealed the presence of two subgroups belonging to the phylogenetic groups B.FTNF002-00 and B.13 in Switzerland. This finding suggests a broader spread of this group in Europe than previously reported. Until recently, only strains belonging to the Western European cluster (group B.FTNF002-00) had been isolated from tularaemia cases in Switzerland. The endemic strains belonging to group B.FTNF002-00 are sensitive to erythromycin, in contrast to the strains of the newly detected group B.13 that are resistant to this antibiotic. All the strains tested were susceptible to ciprofloxacin, streptomycin, gentamicin, nalidixic acid and chloramphenicol but showed reduced susceptibility to tetracycline when tested in a growth medium supplemented with divalent cations. The data show a previously undetected spread of group B.13 westwards in Europe, associated with changes in the antibiotic resistance profile relevant to treatment of tularaemia.
Highlights
Francisella tularensis is a Gram-negative bacterium causing the zoonotic disease tularaemia
All other strains (n=48) were identified here as F. tularensis subsp. holarctica, and 43 of them were determined as group B.FTNF002-00 (Table 1) [17], while five strains JF4830, JF5340, JF5370, JF5405 and JF5468 did not harbour the deletions specific to the group B.FTNF002-00 in the RD23 and Ft-M24 markers
Concerning the strains not belonging to group B.FTNF002-00, the three strains, JF5340, JF5370 and JF5405 isolated from two human patients and one hare between 2012 and 2013, shared the same variable-number tandem repeat (VNTR) profile, while strains JF4830, isolated in 2010 from a patient returning from a vacation in eastern Europe, and JF5468, isolated from a hare in 2013, revealed a distinct VNTR profile, with one variation in the Ft-M3 marker (Table 1)
Summary
Francisella tularensis is a Gram-negative bacterium causing the zoonotic disease tularaemia. The two clinically relevant subspecies are F. tularensis subsp. Only the latter subspecies is present in Europe. It is difficult to trace the source of infection [2]. Analyses of molecular genetic markers of the strains circulating in the environment provide valuable information on the dynamics of infection in people and in animals, and improve the knowledge of the biology of this bacterium. Genetic and phenotypic data are necessary to determine the most suitable antimicrobial substances to use to treat humans and animals [3,4,5,6,7,8]
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