Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass stra... more Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strains of diverse pathogenicity: YE biotypes 1B and 2-5 are considered pathogenic, whereas biotype 1A is in general considered nonvirulent. Also YE-like species, which can sometimes be misidentified as YE, are considered nonvirulent. Methods: In order to study differences in clinical picture caused by different YE types and their possible sources a casecontrol study was conducted in 2006. In this case-control study, 295 case-patients with YE or YE-like finding and their 758 controls responded to the questionnaire about symptoms and possible sources of infection. Results: Strains of pathogenic YE bio/serotypes 3-4/O:3 or 2/O:9 were found in 18%, YE biotype 1A in 65 % and YE-like strains of 17 % of the patients. Patients infected with the strains of pathogenic YE bio/serotypes were younger and had fever more often than those with BT 1A who suffered more from vomiting. Symptoms of reactive art...
Yersinia enterocolitica is a foodborne bacterium that causes gastroenteritis and post-infectious ... more Yersinia enterocolitica is a foodborne bacterium that causes gastroenteritis and post-infectious complications, such as reactive arthritis, in humans. Y. enterocolitica species is divided into six biotypes, which differ in their ability to cause illness. The Y. enterocolitica incidence in Finland has been among the highest in the EU, but there has been little information on the occurrence of different Y. enterocolitica biotypes. In this thesis Y. enterocolitica strains isolated from Finnish patients were characterised and the symptoms and sources of infections were analysed in a case-control study. The majority of clinical isolates of Y. enterocolitica were found to belong to biotype 1A, the status of which as a true pathogen is controversial. Furthermore, the study investigated the microbiological identification and molecular typing methods for Y. enterocolitica. The MLVA method was found to be appropriate for investigating foodborne outbreaks. This study adds to the understanding ...
Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass stra... more Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strains of diverse pathogenicity: YE biotypes 1B and 2-5 are considered pathogenic, whereas biotype 1A is in general considered nonvirulent. Also YE-like species, which can sometimes be misidentified as YE, are considered nonvirulent. Methods: In order to study differences in clinical picture caused by different YE types and their possible sources a casecontrol study was conducted in 2006. In this case-control study, 295 case-patients with YE or YE-like finding and their 758 controls responded to the questionnaire about symptoms and possible sources of infection. Results: Strains of pathogenic YE bio/serotypes 3-4/O:3 or 2/O:9 were found in 18%, YE biotype 1A in 65% and YE -like strains of 17% of the patients. Patients infected with the strains of pathogenic YE bio/serotypes were younger and had fever more often than those with BT 1A who suffered more from vomiting. Symptoms of reactive arth...
Proceedings of the National Academy of Sciences, 2014
Significance Our past understanding of pathogen evolution has been fragmented because of tendenci... more Significance Our past understanding of pathogen evolution has been fragmented because of tendencies to study human clinical isolates. To understand the evolutionary trends of pathogenic bacteria though, we need the context of their nonpathogenic relatives. Our unique and detailed dataset allows description of the parallel evolution of two key human pathogens: the causative agents of plague and Yersinia diarrhea. The analysis reveals an emerging pattern where few virulence-related functions are found in all pathogenic lineages, representing key “foothold” moments that mark the emergence of these pathogens. Functional gene loss and metabolic streamlining are equally complementing the evolution of Yersinia across the pathogenic spectrum.
One chromosomal virulence marker of Yersinia is the gene ail, which encodes Ail, an outer membran... more One chromosomal virulence marker of Yersinia is the gene ail, which encodes Ail, an outer membrane protein that promotes attachment and invasion. A high correlation has been found between the ail gene and the virulence of Yersinia. Here, we report two Yersinia enterocolitica biotype 1A strains that are usually nonpathogenic and carry the ail gene. The ail gene sequences of biotype 1A strains displayed similarity to the bioserotype 1B/O:8 strain 8081. The finding suggests that ail-based detection methods for Y. enterocolitica alone are insufficient to detect real pathogenic strains.
European Journal of Clinical Microbiology & Infectious Diseases, 2009
This study investigated the prevalence of Yersinia enterocolitica (YE) bio/serotypes and YE-like ... more This study investigated the prevalence of Yersinia enterocolitica (YE) bio/serotypes and YE-like species in clinical stool specimens. The special aim was to find the best methods for accurate identification of YE species and, further, pathogenic strains among YE isolates. Of the 41,848 specimens cultured in ten laboratories during a 12-month period, 473 Yersinia strains were isolated from 462 patients. The strains were identified by 21 biochemical tests, serotyping, colony morphology, as well as by 16S rRNA and gyrB gene sequencing. The most prevalent Yersinia findings were YE biotype 1A (64% of the strains) and pathogenic bio/serotype 4/O:3 (16%). The cold-enrichment increased the number of all isolates, and 25% of the bio/serotype 4/O:3 and 2/O:9 strains were only found by cold-enrichment. In routine diagnostic laboratories, 50% of the YE-like species were identified as YE and in 26% the identification differed from that of the reference laboratory. The microscopic colony identification on CIN agar with positive CR-MOX test, combined with several biochemical tests, identified reliably the pathogenic YE bioserotypes and most YE BT 1A strains, but some strains of the YE-like species were so heterogenic that gene sequencing was the only way to identify them.
Background Y. enterocolitica biotype (BT) 1A strains are often isolated from human clinical sampl... more Background Y. enterocolitica biotype (BT) 1A strains are often isolated from human clinical samples but their contribution to disease has remained a controversial topic. Variation and the population structure among the clinical Y. enterocolitica BT 1A isolates have been poorly characterized. We used multi-locus sequence typing (MLST), 16S rRNA gene sequencing, PCR for ystA and ystB, lipopolysaccharide analysis, phage typing, human serum complement killing assay and analysis of the symptoms of the patients to characterize 298 clinical Y. enterocolitica BT 1A isolates in order to evaluate their relatedness and pathogenic potential. Results A subset of 71 BT 1A strains, selected based on their varying LPS patterns, were subjected to detailed genetic analyses. The MLST on seven house-keeping genes (adk, argA, aroA, glnA, gyrB, thrA, trpE) conducted on 43 of the strains discriminated them into 39 MLST-types. By Bayesian analysis of the population structure (BAPS) the strains clustered co...
Background Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strai... more Background Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strains of diverse pathogenicity: YE biotypes 1B and 2-5 are considered pathogenic, whereas biotype 1A is in general considered nonvirulent. Also YE-like species, which can sometimes be misidentified as YE, are considered nonvirulent. Methods In order to study differences in clinical picture caused by different YE types and their possible sources a case-control study was conducted in 2006. In this case-control study, 295 case-patients with YE or YE-like finding and their 758 controls responded to the questionnaire about symptoms and possible sources of infection. Results Strains of pathogenic YE bio/serotypes 3-4/O:3 or 2/O:9 were found in 18%, YE biotype 1A in 65% and YE -like strains of 17% of the patients. Patients infected with the strains of pathogenic YE bio/serotypes were younger and had fever more often than those with BT 1A who suffered more from vomiting. Symptoms of reactive arthri...
A practically important phenomenon, resulting in the loss of the original flagellar phenotype (ge... more A practically important phenomenon, resulting in the loss of the original flagellar phenotype (genotype) of bacteria, is described in the Escherichia coli H17 type strain P12b possessing two distinct genes for H17 and H4 flagellins, respectively. By PCR, sequencing, and phylogenetic investigation, the H17 gene (originally expressed) was considered a new non-fliC flagellin gene and assigned flnA, while the H4 gene (originally cryptic) was reaffirmed as fliC. H17 and H4 flagella differed morphologically. The phenomenon consisted in the replacement of H17 cells by H4 cells during subculturing through certain semisolid media and resulted from the excision of flnA (H17) entirely or in part. The substitution rate depended on the density and nutrient composition of media and reached 100% even after a single passage through 0.3% LB agar. Such phenomenon can lead to an unexpected loss of original H17 phenotype. Our review of the literature showed that the loss of the original flagellar genotype (phenotype) of P12b has occurred in some laboratories while the authors continued to consider their cultures H17. We showed how to distinguish these alternative flagellin genotypes using popular fliC primers. Attention was also paid to possible discrepancies between serological and molecular results in flagellar typing of E. coli.
Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass stra... more Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strains of diverse pathogenicity: YE biotypes 1B and 2-5 are considered pathogenic, whereas biotype 1A is in general considered nonvirulent. Also YE-like species, which can sometimes be misidentified as YE, are considered nonvirulent. Methods: In order to study differences in clinical picture caused by different YE types and their possible sources a casecontrol study was conducted in 2006. In this case-control study, 295 case-patients with YE or YE-like finding and their 758 controls responded to the questionnaire about symptoms and possible sources of infection. Results: Strains of pathogenic YE bio/serotypes 3-4/O:3 or 2/O:9 were found in 18%, YE biotype 1A in 65 % and YE-like strains of 17 % of the patients. Patients infected with the strains of pathogenic YE bio/serotypes were younger and had fever more often than those with BT 1A who suffered more from vomiting. Symptoms of reactive art...
Yersinia enterocolitica is a foodborne bacterium that causes gastroenteritis and post-infectious ... more Yersinia enterocolitica is a foodborne bacterium that causes gastroenteritis and post-infectious complications, such as reactive arthritis, in humans. Y. enterocolitica species is divided into six biotypes, which differ in their ability to cause illness. The Y. enterocolitica incidence in Finland has been among the highest in the EU, but there has been little information on the occurrence of different Y. enterocolitica biotypes. In this thesis Y. enterocolitica strains isolated from Finnish patients were characterised and the symptoms and sources of infections were analysed in a case-control study. The majority of clinical isolates of Y. enterocolitica were found to belong to biotype 1A, the status of which as a true pathogen is controversial. Furthermore, the study investigated the microbiological identification and molecular typing methods for Y. enterocolitica. The MLVA method was found to be appropriate for investigating foodborne outbreaks. This study adds to the understanding ...
Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass stra... more Background: Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strains of diverse pathogenicity: YE biotypes 1B and 2-5 are considered pathogenic, whereas biotype 1A is in general considered nonvirulent. Also YE-like species, which can sometimes be misidentified as YE, are considered nonvirulent. Methods: In order to study differences in clinical picture caused by different YE types and their possible sources a casecontrol study was conducted in 2006. In this case-control study, 295 case-patients with YE or YE-like finding and their 758 controls responded to the questionnaire about symptoms and possible sources of infection. Results: Strains of pathogenic YE bio/serotypes 3-4/O:3 or 2/O:9 were found in 18%, YE biotype 1A in 65% and YE -like strains of 17% of the patients. Patients infected with the strains of pathogenic YE bio/serotypes were younger and had fever more often than those with BT 1A who suffered more from vomiting. Symptoms of reactive arth...
Proceedings of the National Academy of Sciences, 2014
Significance Our past understanding of pathogen evolution has been fragmented because of tendenci... more Significance Our past understanding of pathogen evolution has been fragmented because of tendencies to study human clinical isolates. To understand the evolutionary trends of pathogenic bacteria though, we need the context of their nonpathogenic relatives. Our unique and detailed dataset allows description of the parallel evolution of two key human pathogens: the causative agents of plague and Yersinia diarrhea. The analysis reveals an emerging pattern where few virulence-related functions are found in all pathogenic lineages, representing key “foothold” moments that mark the emergence of these pathogens. Functional gene loss and metabolic streamlining are equally complementing the evolution of Yersinia across the pathogenic spectrum.
One chromosomal virulence marker of Yersinia is the gene ail, which encodes Ail, an outer membran... more One chromosomal virulence marker of Yersinia is the gene ail, which encodes Ail, an outer membrane protein that promotes attachment and invasion. A high correlation has been found between the ail gene and the virulence of Yersinia. Here, we report two Yersinia enterocolitica biotype 1A strains that are usually nonpathogenic and carry the ail gene. The ail gene sequences of biotype 1A strains displayed similarity to the bioserotype 1B/O:8 strain 8081. The finding suggests that ail-based detection methods for Y. enterocolitica alone are insufficient to detect real pathogenic strains.
European Journal of Clinical Microbiology & Infectious Diseases, 2009
This study investigated the prevalence of Yersinia enterocolitica (YE) bio/serotypes and YE-like ... more This study investigated the prevalence of Yersinia enterocolitica (YE) bio/serotypes and YE-like species in clinical stool specimens. The special aim was to find the best methods for accurate identification of YE species and, further, pathogenic strains among YE isolates. Of the 41,848 specimens cultured in ten laboratories during a 12-month period, 473 Yersinia strains were isolated from 462 patients. The strains were identified by 21 biochemical tests, serotyping, colony morphology, as well as by 16S rRNA and gyrB gene sequencing. The most prevalent Yersinia findings were YE biotype 1A (64% of the strains) and pathogenic bio/serotype 4/O:3 (16%). The cold-enrichment increased the number of all isolates, and 25% of the bio/serotype 4/O:3 and 2/O:9 strains were only found by cold-enrichment. In routine diagnostic laboratories, 50% of the YE-like species were identified as YE and in 26% the identification differed from that of the reference laboratory. The microscopic colony identification on CIN agar with positive CR-MOX test, combined with several biochemical tests, identified reliably the pathogenic YE bioserotypes and most YE BT 1A strains, but some strains of the YE-like species were so heterogenic that gene sequencing was the only way to identify them.
Background Y. enterocolitica biotype (BT) 1A strains are often isolated from human clinical sampl... more Background Y. enterocolitica biotype (BT) 1A strains are often isolated from human clinical samples but their contribution to disease has remained a controversial topic. Variation and the population structure among the clinical Y. enterocolitica BT 1A isolates have been poorly characterized. We used multi-locus sequence typing (MLST), 16S rRNA gene sequencing, PCR for ystA and ystB, lipopolysaccharide analysis, phage typing, human serum complement killing assay and analysis of the symptoms of the patients to characterize 298 clinical Y. enterocolitica BT 1A isolates in order to evaluate their relatedness and pathogenic potential. Results A subset of 71 BT 1A strains, selected based on their varying LPS patterns, were subjected to detailed genetic analyses. The MLST on seven house-keeping genes (adk, argA, aroA, glnA, gyrB, thrA, trpE) conducted on 43 of the strains discriminated them into 39 MLST-types. By Bayesian analysis of the population structure (BAPS) the strains clustered co...
Background Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strai... more Background Yersinia enterocolitica (YE) is the causative agent of yersiniosis. YE encompass strains of diverse pathogenicity: YE biotypes 1B and 2-5 are considered pathogenic, whereas biotype 1A is in general considered nonvirulent. Also YE-like species, which can sometimes be misidentified as YE, are considered nonvirulent. Methods In order to study differences in clinical picture caused by different YE types and their possible sources a case-control study was conducted in 2006. In this case-control study, 295 case-patients with YE or YE-like finding and their 758 controls responded to the questionnaire about symptoms and possible sources of infection. Results Strains of pathogenic YE bio/serotypes 3-4/O:3 or 2/O:9 were found in 18%, YE biotype 1A in 65% and YE -like strains of 17% of the patients. Patients infected with the strains of pathogenic YE bio/serotypes were younger and had fever more often than those with BT 1A who suffered more from vomiting. Symptoms of reactive arthri...
A practically important phenomenon, resulting in the loss of the original flagellar phenotype (ge... more A practically important phenomenon, resulting in the loss of the original flagellar phenotype (genotype) of bacteria, is described in the Escherichia coli H17 type strain P12b possessing two distinct genes for H17 and H4 flagellins, respectively. By PCR, sequencing, and phylogenetic investigation, the H17 gene (originally expressed) was considered a new non-fliC flagellin gene and assigned flnA, while the H4 gene (originally cryptic) was reaffirmed as fliC. H17 and H4 flagella differed morphologically. The phenomenon consisted in the replacement of H17 cells by H4 cells during subculturing through certain semisolid media and resulted from the excision of flnA (H17) entirely or in part. The substitution rate depended on the density and nutrient composition of media and reached 100% even after a single passage through 0.3% LB agar. Such phenomenon can lead to an unexpected loss of original H17 phenotype. Our review of the literature showed that the loss of the original flagellar genotype (phenotype) of P12b has occurred in some laboratories while the authors continued to consider their cultures H17. We showed how to distinguish these alternative flagellin genotypes using popular fliC primers. Attention was also paid to possible discrepancies between serological and molecular results in flagellar typing of E. coli.
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Papers by Leila Sihvonen