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Infection in mouse peritoneal cavity with a pyrimidine-requiring mutant and naturally occurring Staphylococcus aureus
Abstract:
The lethal activity of a thymineless mutant of Staphylococcus aureus Wood 46 strain has been compared with that of three naturally occurring strains: parent Wood 46, Smith, and coagulase-negative SA-13. The thymineless mutant and the parent Wood 46 strain showed a sharp decline in culturable units from the peritoneal cavity in the first 4 hr after their injection. After 6 hr, that is, 2 hr before the mice began to die, the number of culturable units of the thymineless mutant was still declining, whereas that of the parent strain increased; for both strains, the number of units was still lower than that of the inoculum. Although the thymineless mutant, unlike the parent strain, was apparently unable to multiply in mouse peritoneal cavity, it killed mice at a similar rate. The highly virulent Smith strain known to multiply rapidly and the avirulent coagulase-negative SA-13 strain were used as additional controls. Under our experimental conditions, death of mice after the injection of the thymineless mutant in the peritoneal cavity did not seem to be due to bacterial multiplication but to toxicity, death being delayed by antitoxin. The pyrimidine-requiring auxotroph we used could be better material than killed bacteria to study some aspects of the lethal activity of S. aureus.
Insights
A thymineless Staphylococcus aureus mutant killed mice similarly to its parent strain, despite not multiplying. This suggests S. aureus toxicity, not just bacterial growth, contributes to lethal activity.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Immunology
Background:
- Staphylococcus aureus is a significant human pathogen.
- Understanding the mechanisms of S. aureus virulence is crucial for developing effective treatments.
- Bacterial multiplication and toxin production are key factors in pathogenesis.
Purpose of the Study:
- To compare the lethal activity of a thymineless mutant of Staphylococcus aureus with its parent strain and other natural isolates.
- To investigate the role of bacterial multiplication versus toxicity in S. aureus-mediated lethality.
- To evaluate the potential of a pyrimidine-requiring auxotroph as a model for studying S. aureus lethal activity.
Main Methods:
- Comparison of a thymineless mutant and parent strain of Staphylococcus aureus Wood 46 in a mouse model.
- Inoculation into the peritoneal cavity and monitoring of culturable bacterial units over time.
- Assessment of mouse survival rates and the effect of antitoxin on mortality.
- Inclusion of highly virulent (Smith) and avirulent (SA-13) S. aureus strains as controls.
Main Results:
- The thymineless mutant and parent strain showed an initial decline in culturable units.
- The thymineless mutant did not multiply in the peritoneal cavity, unlike the parent strain.
- Both strains killed mice at a similar rate, suggesting toxicity plays a significant role.
- Antitoxin administration delayed death, further supporting the role of toxicity.
Conclusions:
- Lethality of Staphylococcus aureus in this model is not solely dependent on bacterial multiplication.
- Toxicity of the bacteria, potentially mediated by toxins, contributes significantly to the lethal outcome.
- A pyrimidine-requiring auxotroph may serve as a valuable tool for studying S. aureus toxicity, potentially offering advantages over killed bacteria.