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Growth in mouse peritoneal macrophages of Yersinia pestis lacking established virulence determinants
Abstract:
Cultured mouse resident peritoneal macrophages were challenged with strains of Yersinia pestis differing only with respect to the absence of one or more of the virulence determinants established for the species. Guanine-auxotrophic (Pur-) yersiniae were unable to survive within the macrophages; exogenous hypoxanthine and guanosine permitted intracellular growth. This finding supports the idea that Pur- yersiniae are avirulent due to inability to obtain sufficient free purines in host tissues for growth and maintenance and indicates that net biosynthesis is necessary to counteract the intracellular microbicidal environment of macrophages. Yersiniae unable to pigment in medium containing the dye Congo red (Pgm-) or lacking either of the plasmids associated with the pesticin or calcium dependence virulence determinants (Pst- and Vwa-, respectively) were taken up as efficiently into macrophages and grew as well within these cells as did bacteria having all invasive virulence determinants intact. Opsonization with 100% homologous normal serum before infection of macrophages did not affect the ability of Pgm- or Vwa- Pgm- yersiniae to grow within macrophages. Accordingly, attributes independent of these virulence determinants mediate the survival and growth of yersiniae in serum and within resident macrophages, and components of the mammalian environment other than serum and macrophages must interact with Pgm-, Pst- and Vwa- yersiniae to cause their avirulence in vivo.
Insights
Yersinia pestis lacking purine synthesis cannot survive in macrophages unless given external purines. Other virulence factors are not essential for intracellular survival, suggesting different mechanisms contribute to Yersinia pestis virulence in vivo.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Yersinia pestis virulence is multifactorial, involving various determinants.
- Understanding bacterial survival mechanisms within host cells is crucial for pathogenesis research.
Purpose of the Study:
- To investigate the role of specific Yersinia pestis virulence determinants in intracellular survival within macrophages.
- To elucidate the mechanisms underlying Yersinia pestis avirulence in vivo.
Main Methods:
- Cultured mouse resident peritoneal macrophages were infected with Yersinia pestis strains lacking specific virulence determinants.
- Bacterial survival and growth were assessed intracellularly.
- The effect of exogenous purines and serum opsonization was evaluated.
Main Results:
- Guanine-auxotrophic (Pur-) Yersinia pestis strains failed to survive intracellularly without exogenous hypoxanthine and guanosine.
- Yersinia pestis strains lacking pigmenting (Pgm-) or specific plasmid-associated determinants (Pst-, Vwa-) showed efficient uptake and intracellular growth.
- Serum opsonization did not impact the intracellular survival of Pgm- or Vwa- Pgm- Yersinia pestis.
Conclusions:
- Intracellular survival of Yersinia pestis is dependent on purine biosynthesis, highlighting the importance of host purine availability.
- Virulence determinants like Pgm, Pst, and Vwa are not essential for Yersinia pestis survival and growth within macrophages.
- Factors beyond serum and macrophages in the mammalian environment likely contribute to the in vivo avirulence of Yersinia pestis strains lacking these determinants.