In Sweden, human cases of tularemia caused by Francisella tularensis holarctica are assumed to be... more In Sweden, human cases of tularemia caused by Francisella tularensis holarctica are assumed to be transmitted by mosquitoes, but how mosquito vectors acquire and transmit the bacterium is not clear. To determine how transmission of this bacterium occurs, mosquito larvae were collected in an area where tularemia is endemic, brought to the laboratory, and reared to adults in their original pond water. Screening of adult mosquitoes by real-time PCR demonstrated F. tularensis lpnA sequences in 14 of the 48 mosquito pools tested; lpnA sequences were demonstrated in 6 of 9 identifi ed mosquito species. Further analysis confi rmed the presence of F. tularensis holarctica-specifi c 30-bp deletion region sequences (FtM19inDel) in water from breeding containers and in 3 mosquito species (Aedes sticticus, Ae. vexans, and Ae. punctor) known to take blood from humans. Our results suggest that the mosquitoes that transmit F. tularensis holarctica during tularemia outbreaks acquire the bacterium already as larvae.
Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarct... more Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples (n = 341) and sediment samples (n = 245) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia. 6 International Journal of Microbiology Water B24 Water B33 F. tularensis subsp. novicida CIP 56.12 (AY928396) Water B13 Water B3 F. tularensis subsp. tularensis FSC 054 (AY968224) F. tularensis subsp. holarctica FSC 022 (AY968228) Water A24 Water B19 Water B4 F. tularensis subsp. mediasiatica FSC 147 (AJ698863) Water A4 F. tularensis subsp. holarctica FSC 090 (AJ698864) F. tularensis subsp. mediasiatica FSC 147 (AY968234) F. tularensis subsp. novicida FSC 040 (AY968237) F. tularensis subsp. tularensis FSC 043 (AJ698865) F. tularensis subsp. tularensis SchuS4 (AJ749949) F. tularensis subsp. holarctica LVS (AJ698866) F. tularensis subsp.
The Swedish Forum for Biopreparedness Diagnostics (FBD) is a network that fosters collaboration a... more The Swedish Forum for Biopreparedness Diagnostics (FBD) is a network that fosters collaboration among the 4 agencies with responsibility for the laboratory diagnostics of high-consequence pathogens, covering animal health and feed safety, food safety, public health and biodefense, and security. The aim of the network is to strengthen capabilities and capacities for diagnostics at the national biosafety level-3 (BSL-3) laboratories to improve Sweden's biopreparedness, in line with recommendations from the EU and WHO. Since forming in 2007, the FBD network has contributed to the harmonization of diagnostic methods, equipment, quality assurance protocols, and biosafety practices among the national BSL-3 laboratories. Lessons learned from the network include: (1) conducting joint projects with activities such as method development and validation, ring trials, exercises, and audits has helped to build trust and improve communication among participating agencies; (2) rotating the presidency of the network steering committee has fostered trust and commitment from all agencies involved; and (3) planning for the implementation of project outcomes is important to maintain gained competencies in the agencies over time. Contacts have now been established with national agencies of the other Nordic countries, with an aim to expanding the collaboration, broadening the network, finding synergies in new areas, strengthening the ability to share resources, and consolidating long-term financing in the context of harmonized European biopreparedness.
Francisella tularensis, a highly virulent bacteria that causes the zoonotic disease tularemia, is... more Francisella tularensis, a highly virulent bacteria that causes the zoonotic disease tularemia, is considered a potential agent of biological warfare and bioterrorism. Although the host range for several species within the Francisella is known, little is known about the natural reservoirs of various Francisella species. The lack of knowledge regarding the environmental fates of these pathogens greatly reduces the possibilities for microbial risk assessments. The greater wax moth (Galleria mellonella) is an insect of the order Lepidoptera that has been used as an alternative model to study microbial infection during recent years. The aim of this study was to evaluate G. mellonella as a model system for studies of human pathogenic and closely related opportunistic and non-pathogenic strains within the Francisella genus. The employed G. mellonella larvae model demonstrated differences in lethality between human pathogenic and human non-pathogenic or opportunistic Francisella species. The F. novicida, F. hispaniensis and F. philomiragia strains were significantly more virulent in the G. mellonella model than the strains of human pathogens F. t. holarctica and F. t. tularensis. Our data show that G. mellonella is a possible in vivo model of insect immunity for studies of both opportunistic and virulent lineages of Francisella spp., that produces inverse results regarding lethality in G. mellonella and incapacitating disease in humans. The results provide insight into the potential host specificity of F. tularensis and closely related members of the same genus, thus increasing our present understanding of Francisella spp. ecology.
In recent years, an increasing diversity of species has been recognized within the family Francis... more In recent years, an increasing diversity of species has been recognized within the family Francisellaceae. Unfortunately, novel isolates are sometimes misnamed in initial publications or multiple sources propose different nomenclature for genetically highly similar isolates. Thus, unstructured and occasionally incorrect information can lead to confusion in the scientific community. Historically, detection of Francisella tularensis in environmental samples has been challenging due to the considerable and unknown genetic diversity within the family, which can result in false positive results. We have assembled a comprehensive collection of genome sequences representing most known Francisellaceae species/strains and restructured them according to a taxonomy that is based on phylogenetic structure. From this structured dataset, we identified a small number of genomic regions unique to F. tularensis that are putatively suitable for specific detection of this pathogen in environmental sam...
Francisella tularensis is the causative agent of the zoonotic disease tularemia. In Germany, most... more Francisella tularensis is the causative agent of the zoonotic disease tularemia. In Germany, most human infections are caused by contact with infected hares. The aim of this study was to characterize Francisella tularensis subsp. holarctica strains isolated from hares in Germany and to develop bioinformatics tools to analyze their genetic relatedness. In total, 257 German isolates—obtained mainly from hares (n = 233), other vertebrate animals, and ticks, but also from humans (n = 3)—were analyzed within this study. Publically available sequence data from 49 isolates were used to put our isolates into an epidemiological context and to compare isolates from natural foci and humans. Whole-genome sequences were analyzed using core-genome Multi-Locus-Sequence-Typing, canonical Single Nucleotide Polymorphism (SNP) typing and whole-genome SNP typing. An overall conformity of genotype clustering between the typing methods was found, albeit with a lower resolution for canonical single SNP ty...
Genes encoding extracellular p-lactamases of Streptomyces badius, Streptomyces cacaoi, Streptomyc... more Genes encoding extracellular p-lactamases of Streptomyces badius, Streptomyces cacaoi, Streptomyces fradiae and Streptomyces Zauendulae were cloned and mapped in Streptomyces liuiths. DNA sequence analysis of the plactamase genes revealed a high overall G + C content, ranging from 71 to 75 mol%, with a G + C content of 95 mol% at the third position of the codons for all four genes. The primary structure of the p-lactamases including their signal peptides was deduced. The four p-lactamases exhibited homology to each other and to class A plactamases from other bacterial genera. We suggest that Strepfomyces p-lactamases are representatives of a superfamily of genes, from which class A p-lactamases of Gram-negative bacteria may have evolved. P-lactamases of this genus. The genes for the fllactamases of S. badius, S. cacaoi and S. fradiae have been cloned previously in S. lividans (Jaurin et al., 1988a) and the DNA sequence encoding the S. cacaoi enzyme has been established (Forsman et al., 1989). Here we report the primary structure of p-lactamases of S. badius, S. fradiae and S. lavendulae, and show that Streptomyces p-lactamases are representatives of a superfamily of genes from Gram-positive bacteria, from which it is possible that class A /I-lactamases of Gram-negative bacteria have evolved. Methods Bacterial strains, plasmids, media and culture conditions. S. lividans 1326 (Lomovskaya et al., 1972) was used as the host for all Streptomyces 0001-5706 O 1990 SGM
Background: Tularaemia is a zoonotic disease caused by the bacterium Francisella tularensis. In G... more Background: Tularaemia is a zoonotic disease caused by the bacterium Francisella tularensis. In Germany, the disease is still rare (e.g. 34 human cases reported in 2015). There is a lack of data about the susceptibility of F. tularensis strains to antibiotics, because many cases are diagnosed using serological assays only. Objectives: The antibiotic susceptibility in vitro of F. tularensis subsp. holarctica strains isolated in Germany was assessed to determine whether the currently recommended empirical therapy is still adequate. Methods: A total of 128 F. tularensis strains were investigated that were collected between 2005 and 2014 in Germany from wild animals, ticks and humans. All isolates were genotyped using real-time PCR assays targeting canonical SNPs, and antibiotic susceptibility was tested using MIC test strips on agar plates. MIC values were interpreted using CLSI breakpoints. Results: The strains were susceptible to antibiotics commonly recommended for tularaemia therapy, i.e. aminoglycosides (MIC 90 values: gentamicin 1 mg/L; streptomycin 4.0 mg/L), tetracyclines (MIC 90 values: tetracycline 0.5 mg/L; doxycycline 1.5 mg/L) and quinolones (MIC 90 value: ciprofloxacin 0.064 mg/L). Chloramphenicol (MIC 90 value: 3.0 mg/L) may be of value in treatment of tularaemia meningitis. Ninety-four isolates were susceptible to erythromycin, which defines biovar I (genotypes B.4 and B.6); 34 were resistant (biovar II; genotype B.12). Conclusions: The F. tularensis isolates investigated in this study showed the typical antibiotic susceptibility pattern that was previously observed in other countries. Therefore, recommendations for empirical antibiotic therapy of tularaemia can remain unchanged. However, antibiotic susceptibility testing of clinical isolates should be performed whenever possible.
Here, we report a high-quality draft genome sequence of Francisella tularensis subsp. holarctica ... more Here, we report a high-quality draft genome sequence of Francisella tularensis subsp. holarctica strain 08T0073, isolated from the cadaver of a wild European hare (Lepus europaeus) found near Helmstedt, Lower Saxony, Germany, in 2007. In Germany, infected hares are a major source of tularemia in humans.
For many infections transmitting to humans from reservoirs in nature, disease dispersal patterns ... more For many infections transmitting to humans from reservoirs in nature, disease dispersal patterns over space and time are largely unknown. Here, a reversed genomics approach helped us understand disease dispersal and yielded insight into evolution and biological properties of Francisella tularensis, the bacterium causing tularemia. We whole-genome sequenced 67 strains and characterized by single-nucleotide polymorphism assays 138 strains, collected from individuals infected 1947-2012 across Western Europe. We used the data for phylogenetic, population genetic and geographical network analyses. All strains (n=205) belonged to a monophyletic population of recent ancestry not found outside Western Europe. Most strains (n=195) throughout the study area were assigned to a star-like phylogenetic pattern indicating that colonization of Western Europe occurred via clonal expansion. In the East of the study area, strains were more diverse, consistent with a founder population spreading from e...
A promoter-probe system, based on the arnpC fl-lactamase gene of Escherichia coli, has been devel... more A promoter-probe system, based on the arnpC fl-lactamase gene of Escherichia coli, has been developed for the isolation and characterization of transcriptional signals in the gram-positive bacterium Streptomyces lividans. The promoter-probe vector, denoted pJAS14, has the SLPI.2 replicon with a copy number of four-five plasmids per cell. It contains a unique BamHI site just in front of the ampC ribosome-binding site, and upstream of this BamHI site a transcriptional terminator signal that prevents readthrough transcription from plasmid-borne promoters has been inserted. Using pJAS14, we have shotgun cloned chromosomal DNA from S. lividans and S. lavendulae into the BamHI site, and isolated a number of promoter containing DNA fragments by the use of the chromogenic cephalosporin nitrocefin. On plates, we identified promoters of varying strengths and also with differences in nutritional and temporal expression. Using liquid cultures of S. lividans, it has been demonstrated that one promoter, denoted PI (SEP8), as well as the ampC gene orE. eoli, show activity corresponding to the vegetative growth of the cells. The PI (SEP8) promoter was shown to be expressed also in E. coli, and it initiates RNA synthesis at exactly the same nucleotides in both S. lividans and E. coli. The promoter shows good homology to the E. co]i promoter consensus sequence in both the-35 and-I0 regions. Thus, this promoter is a representative of the SEP (Streptomyces E. coli-type promoter) class of promoters recently described (Jaurin and Cohen 1985). This indicates that an S. lividans RNA polymerase recognizes the same sequence determinants and chooses the point of initiation of RNA synthesis in the same way as the corresponding E. coli enzyme.
The Journal of antimicrobial chemotherapy, Oct 21, 2016
We analysed diverse strains of Francisella tularensis subsp. holarctica to assess if its division... more We analysed diverse strains of Francisella tularensis subsp. holarctica to assess if its division into biovars I and II is associated with specific mutations previously linked to erythromycin resistance and to determine the distribution of this resistance trait across this subspecies. Three-hundred and fourteen F. tularensis subsp. holarctica strains were tested for erythromycin susceptibility and whole-genome sequences for these strains were examined for SNPs in genes previously associated with erythromycin resistance. Each strain was assigned to a global phylogenetic framework using genome-wide canonical SNPs. The contribution of a specific SNP to erythromycin resistance was examined using allelic exchange. The geographical distribution of erythromycin-resistant F. tularensis strains was further investigated by literature search. There was a perfect correlation between biovar II strains (erythromycin resistance) and the phylogenetic group B.12. Only B.12 strains had an A → C SNP a...
Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Umeå... more Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Umeå, from Streptomyces cacaoi. Genes blaL and blaU were found to differ largely in their nucleotide sequences, although the encoded proteins both belonged to the class A of beta-lactamases (active-site serine penicillinases). DNA-hybridization and polymerase chain reaction assays have now demonstrated that both blaL and blaU genes were present in the S. cacaoi strains used in Liège and in Umeå.
In Sweden, human cases of tularemia caused by Francisella tularensis holarctica are assumed to be... more In Sweden, human cases of tularemia caused by Francisella tularensis holarctica are assumed to be transmitted by mosquitoes, but how mosquito vectors acquire and transmit the bacterium is not clear. To determine how transmission of this bacterium occurs, mosquito larvae were collected in an area where tularemia is endemic, brought to the laboratory, and reared to adults in their original pond water. Screening of adult mosquitoes by real-time PCR demonstrated F. tularensis lpnA sequences in 14 of the 48 mosquito pools tested; lpnA sequences were demonstrated in 6 of 9 identifi ed mosquito species. Further analysis confi rmed the presence of F. tularensis holarctica-specifi c 30-bp deletion region sequences (FtM19inDel) in water from breeding containers and in 3 mosquito species (Aedes sticticus, Ae. vexans, and Ae. punctor) known to take blood from humans. Our results suggest that the mosquitoes that transmit F. tularensis holarctica during tularemia outbreaks acquire the bacterium already as larvae.
Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarct... more Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples (n = 341) and sediment samples (n = 245) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia. 6 International Journal of Microbiology Water B24 Water B33 F. tularensis subsp. novicida CIP 56.12 (AY928396) Water B13 Water B3 F. tularensis subsp. tularensis FSC 054 (AY968224) F. tularensis subsp. holarctica FSC 022 (AY968228) Water A24 Water B19 Water B4 F. tularensis subsp. mediasiatica FSC 147 (AJ698863) Water A4 F. tularensis subsp. holarctica FSC 090 (AJ698864) F. tularensis subsp. mediasiatica FSC 147 (AY968234) F. tularensis subsp. novicida FSC 040 (AY968237) F. tularensis subsp. tularensis FSC 043 (AJ698865) F. tularensis subsp. tularensis SchuS4 (AJ749949) F. tularensis subsp. holarctica LVS (AJ698866) F. tularensis subsp.
The Swedish Forum for Biopreparedness Diagnostics (FBD) is a network that fosters collaboration a... more The Swedish Forum for Biopreparedness Diagnostics (FBD) is a network that fosters collaboration among the 4 agencies with responsibility for the laboratory diagnostics of high-consequence pathogens, covering animal health and feed safety, food safety, public health and biodefense, and security. The aim of the network is to strengthen capabilities and capacities for diagnostics at the national biosafety level-3 (BSL-3) laboratories to improve Sweden's biopreparedness, in line with recommendations from the EU and WHO. Since forming in 2007, the FBD network has contributed to the harmonization of diagnostic methods, equipment, quality assurance protocols, and biosafety practices among the national BSL-3 laboratories. Lessons learned from the network include: (1) conducting joint projects with activities such as method development and validation, ring trials, exercises, and audits has helped to build trust and improve communication among participating agencies; (2) rotating the presidency of the network steering committee has fostered trust and commitment from all agencies involved; and (3) planning for the implementation of project outcomes is important to maintain gained competencies in the agencies over time. Contacts have now been established with national agencies of the other Nordic countries, with an aim to expanding the collaboration, broadening the network, finding synergies in new areas, strengthening the ability to share resources, and consolidating long-term financing in the context of harmonized European biopreparedness.
Francisella tularensis, a highly virulent bacteria that causes the zoonotic disease tularemia, is... more Francisella tularensis, a highly virulent bacteria that causes the zoonotic disease tularemia, is considered a potential agent of biological warfare and bioterrorism. Although the host range for several species within the Francisella is known, little is known about the natural reservoirs of various Francisella species. The lack of knowledge regarding the environmental fates of these pathogens greatly reduces the possibilities for microbial risk assessments. The greater wax moth (Galleria mellonella) is an insect of the order Lepidoptera that has been used as an alternative model to study microbial infection during recent years. The aim of this study was to evaluate G. mellonella as a model system for studies of human pathogenic and closely related opportunistic and non-pathogenic strains within the Francisella genus. The employed G. mellonella larvae model demonstrated differences in lethality between human pathogenic and human non-pathogenic or opportunistic Francisella species. The F. novicida, F. hispaniensis and F. philomiragia strains were significantly more virulent in the G. mellonella model than the strains of human pathogens F. t. holarctica and F. t. tularensis. Our data show that G. mellonella is a possible in vivo model of insect immunity for studies of both opportunistic and virulent lineages of Francisella spp., that produces inverse results regarding lethality in G. mellonella and incapacitating disease in humans. The results provide insight into the potential host specificity of F. tularensis and closely related members of the same genus, thus increasing our present understanding of Francisella spp. ecology.
In recent years, an increasing diversity of species has been recognized within the family Francis... more In recent years, an increasing diversity of species has been recognized within the family Francisellaceae. Unfortunately, novel isolates are sometimes misnamed in initial publications or multiple sources propose different nomenclature for genetically highly similar isolates. Thus, unstructured and occasionally incorrect information can lead to confusion in the scientific community. Historically, detection of Francisella tularensis in environmental samples has been challenging due to the considerable and unknown genetic diversity within the family, which can result in false positive results. We have assembled a comprehensive collection of genome sequences representing most known Francisellaceae species/strains and restructured them according to a taxonomy that is based on phylogenetic structure. From this structured dataset, we identified a small number of genomic regions unique to F. tularensis that are putatively suitable for specific detection of this pathogen in environmental sam...
Francisella tularensis is the causative agent of the zoonotic disease tularemia. In Germany, most... more Francisella tularensis is the causative agent of the zoonotic disease tularemia. In Germany, most human infections are caused by contact with infected hares. The aim of this study was to characterize Francisella tularensis subsp. holarctica strains isolated from hares in Germany and to develop bioinformatics tools to analyze their genetic relatedness. In total, 257 German isolates—obtained mainly from hares (n = 233), other vertebrate animals, and ticks, but also from humans (n = 3)—were analyzed within this study. Publically available sequence data from 49 isolates were used to put our isolates into an epidemiological context and to compare isolates from natural foci and humans. Whole-genome sequences were analyzed using core-genome Multi-Locus-Sequence-Typing, canonical Single Nucleotide Polymorphism (SNP) typing and whole-genome SNP typing. An overall conformity of genotype clustering between the typing methods was found, albeit with a lower resolution for canonical single SNP ty...
Genes encoding extracellular p-lactamases of Streptomyces badius, Streptomyces cacaoi, Streptomyc... more Genes encoding extracellular p-lactamases of Streptomyces badius, Streptomyces cacaoi, Streptomyces fradiae and Streptomyces Zauendulae were cloned and mapped in Streptomyces liuiths. DNA sequence analysis of the plactamase genes revealed a high overall G + C content, ranging from 71 to 75 mol%, with a G + C content of 95 mol% at the third position of the codons for all four genes. The primary structure of the p-lactamases including their signal peptides was deduced. The four p-lactamases exhibited homology to each other and to class A plactamases from other bacterial genera. We suggest that Strepfomyces p-lactamases are representatives of a superfamily of genes, from which class A p-lactamases of Gram-negative bacteria may have evolved. P-lactamases of this genus. The genes for the fllactamases of S. badius, S. cacaoi and S. fradiae have been cloned previously in S. lividans (Jaurin et al., 1988a) and the DNA sequence encoding the S. cacaoi enzyme has been established (Forsman et al., 1989). Here we report the primary structure of p-lactamases of S. badius, S. fradiae and S. lavendulae, and show that Streptomyces p-lactamases are representatives of a superfamily of genes from Gram-positive bacteria, from which it is possible that class A /I-lactamases of Gram-negative bacteria have evolved. Methods Bacterial strains, plasmids, media and culture conditions. S. lividans 1326 (Lomovskaya et al., 1972) was used as the host for all Streptomyces 0001-5706 O 1990 SGM
Background: Tularaemia is a zoonotic disease caused by the bacterium Francisella tularensis. In G... more Background: Tularaemia is a zoonotic disease caused by the bacterium Francisella tularensis. In Germany, the disease is still rare (e.g. 34 human cases reported in 2015). There is a lack of data about the susceptibility of F. tularensis strains to antibiotics, because many cases are diagnosed using serological assays only. Objectives: The antibiotic susceptibility in vitro of F. tularensis subsp. holarctica strains isolated in Germany was assessed to determine whether the currently recommended empirical therapy is still adequate. Methods: A total of 128 F. tularensis strains were investigated that were collected between 2005 and 2014 in Germany from wild animals, ticks and humans. All isolates were genotyped using real-time PCR assays targeting canonical SNPs, and antibiotic susceptibility was tested using MIC test strips on agar plates. MIC values were interpreted using CLSI breakpoints. Results: The strains were susceptible to antibiotics commonly recommended for tularaemia therapy, i.e. aminoglycosides (MIC 90 values: gentamicin 1 mg/L; streptomycin 4.0 mg/L), tetracyclines (MIC 90 values: tetracycline 0.5 mg/L; doxycycline 1.5 mg/L) and quinolones (MIC 90 value: ciprofloxacin 0.064 mg/L). Chloramphenicol (MIC 90 value: 3.0 mg/L) may be of value in treatment of tularaemia meningitis. Ninety-four isolates were susceptible to erythromycin, which defines biovar I (genotypes B.4 and B.6); 34 were resistant (biovar II; genotype B.12). Conclusions: The F. tularensis isolates investigated in this study showed the typical antibiotic susceptibility pattern that was previously observed in other countries. Therefore, recommendations for empirical antibiotic therapy of tularaemia can remain unchanged. However, antibiotic susceptibility testing of clinical isolates should be performed whenever possible.
Here, we report a high-quality draft genome sequence of Francisella tularensis subsp. holarctica ... more Here, we report a high-quality draft genome sequence of Francisella tularensis subsp. holarctica strain 08T0073, isolated from the cadaver of a wild European hare (Lepus europaeus) found near Helmstedt, Lower Saxony, Germany, in 2007. In Germany, infected hares are a major source of tularemia in humans.
For many infections transmitting to humans from reservoirs in nature, disease dispersal patterns ... more For many infections transmitting to humans from reservoirs in nature, disease dispersal patterns over space and time are largely unknown. Here, a reversed genomics approach helped us understand disease dispersal and yielded insight into evolution and biological properties of Francisella tularensis, the bacterium causing tularemia. We whole-genome sequenced 67 strains and characterized by single-nucleotide polymorphism assays 138 strains, collected from individuals infected 1947-2012 across Western Europe. We used the data for phylogenetic, population genetic and geographical network analyses. All strains (n=205) belonged to a monophyletic population of recent ancestry not found outside Western Europe. Most strains (n=195) throughout the study area were assigned to a star-like phylogenetic pattern indicating that colonization of Western Europe occurred via clonal expansion. In the East of the study area, strains were more diverse, consistent with a founder population spreading from e...
A promoter-probe system, based on the arnpC fl-lactamase gene of Escherichia coli, has been devel... more A promoter-probe system, based on the arnpC fl-lactamase gene of Escherichia coli, has been developed for the isolation and characterization of transcriptional signals in the gram-positive bacterium Streptomyces lividans. The promoter-probe vector, denoted pJAS14, has the SLPI.2 replicon with a copy number of four-five plasmids per cell. It contains a unique BamHI site just in front of the ampC ribosome-binding site, and upstream of this BamHI site a transcriptional terminator signal that prevents readthrough transcription from plasmid-borne promoters has been inserted. Using pJAS14, we have shotgun cloned chromosomal DNA from S. lividans and S. lavendulae into the BamHI site, and isolated a number of promoter containing DNA fragments by the use of the chromogenic cephalosporin nitrocefin. On plates, we identified promoters of varying strengths and also with differences in nutritional and temporal expression. Using liquid cultures of S. lividans, it has been demonstrated that one promoter, denoted PI (SEP8), as well as the ampC gene orE. eoli, show activity corresponding to the vegetative growth of the cells. The PI (SEP8) promoter was shown to be expressed also in E. coli, and it initiates RNA synthesis at exactly the same nucleotides in both S. lividans and E. coli. The promoter shows good homology to the E. co]i promoter consensus sequence in both the-35 and-I0 regions. Thus, this promoter is a representative of the SEP (Streptomyces E. coli-type promoter) class of promoters recently described (Jaurin and Cohen 1985). This indicates that an S. lividans RNA polymerase recognizes the same sequence determinants and chooses the point of initiation of RNA synthesis in the same way as the corresponding E. coli enzyme.
The Journal of antimicrobial chemotherapy, Oct 21, 2016
We analysed diverse strains of Francisella tularensis subsp. holarctica to assess if its division... more We analysed diverse strains of Francisella tularensis subsp. holarctica to assess if its division into biovars I and II is associated with specific mutations previously linked to erythromycin resistance and to determine the distribution of this resistance trait across this subspecies. Three-hundred and fourteen F. tularensis subsp. holarctica strains were tested for erythromycin susceptibility and whole-genome sequences for these strains were examined for SNPs in genes previously associated with erythromycin resistance. Each strain was assigned to a global phylogenetic framework using genome-wide canonical SNPs. The contribution of a specific SNP to erythromycin resistance was examined using allelic exchange. The geographical distribution of erythromycin-resistant F. tularensis strains was further investigated by literature search. There was a perfect correlation between biovar II strains (erythromycin resistance) and the phylogenetic group B.12. Only B.12 strains had an A → C SNP a...
Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Umeå... more Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Umeå, from Streptomyces cacaoi. Genes blaL and blaU were found to differ largely in their nucleotide sequences, although the encoded proteins both belonged to the class A of beta-lactamases (active-site serine penicillinases). DNA-hybridization and polymerase chain reaction assays have now demonstrated that both blaL and blaU genes were present in the S. cacaoi strains used in Liège and in Umeå.
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Papers by Mats Forsman