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In vitro assessment of virulence in Yersinia enterocolitica and related species
Abstract:
We have examined 136 isolates of Yersinia species, comprising 112 strains of Yersinia enterocolitica, 12 of Y. frederiksenii, 8 of Y. intermedia, and 5 of Y. kristensenii, for the presence of 40- to 50-megadalton virulence-associated plasmids and expression of the following plasmid-associated characteristics: Congo red pigmentation (CR), calcium dependence, autoagglutination, hydrophobicity, resistance to normal human serum, and pathogenicity in mice. All 136 strains yielded both pigmented (CR+) and nonpigmented (CR-) variants. Only CR+ variants, however, were virulent for iron-overloaded, desferrioxamine B-treated mice (R. M. Robins-Browne and J. K. Prpic, Infect. Immun. 47:744-779, 1985). Although the in vitro virulence-associated characteristics generally occurred together, each one could be expressed independently. Strains of Y. frederiksenii, Y. intermedia, and Y. kristensenii also expressed individual virulence-associated properties. Of 53 Y. enterocolitica strains which were virulent for iron-overloaded, desferrioxamine-treated mice, all but one expressed every virulence-associated characteristic. Several strains which were avirulent for mice, however, demonstrated these characteristics in various combinations. Because many Yersinia strains, particularly environmental isolates, carried plasmids of 40 to 50 megadaltons, detection of plasmids provided little information about bacterial pathogenicity unless virulence-associated properties were also sought. The best in vitro predictor of virulence was autoagglutination, followed by calcium dependence. Because only CR+ variants expressed virulence-associated determinants, Congo red pigmentation is useful for selecting potentially virulent strains.
Insights
Virulence in Yersinia species is linked to specific traits like Congo red pigmentation (CR+). Only CR+ variants showed pathogenicity in mice, making CR pigmentation a key indicator for identifying virulent Yersinia strains.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Yersinia species are known human pathogens.
- Virulence factors in Yersinia are often plasmid-mediated.
- Understanding Yersinia virulence is crucial for public health.
Purpose of the Study:
- To investigate the association between virulence-associated plasmids and phenotypic characteristics in Yersinia species.
- To evaluate the predictive value of in vitro characteristics for Yersinia pathogenicity in mice.
- To determine the role of Congo red pigmentation (CR) in identifying virulent Yersinia strains.
Main Methods:
- Examined 136 Yersinia isolates (Y. enterocolitica, Y. frederiksenii, Y. intermedia, Y. kristensenii).
- Assessed for 40-50 megadalton virulence plasmids and associated traits: CR pigmentation, calcium dependence, autoagglutination, hydrophobicity, serum resistance.
- Evaluated pathogenicity in iron-overloaded, desferrioxamine B-treated mice.
Main Results:
- All strains produced CR+ and CR- variants; only CR+ variants were virulent in mice.
- In vitro virulence traits generally co-occurred but could be expressed independently.
- Autoagglutination and calcium dependence were the best in vitro predictors of virulence.
- Detection of virulence plasmids alone provided limited information on pathogenicity.
Conclusions:
- Congo red pigmentation (CR+) is a reliable indicator for selecting potentially virulent Yersinia strains.
- Specific in vitro characteristics, particularly autoagglutination and calcium dependence, are valuable predictors of Yersinia pathogenicity.
- Virulence in Yersinia is complex, involving plasmid-associated traits that can be expressed variably.