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Experimental Proteus mirabilis burn surface infection
Abstract:
We established a human burn isolate of Proteus mirabilis as an experimental pathogen. Infliction of a nonfatal scald injury (30%) rendered rats highly susceptible to lethal surface infection with this isolate. Dose-response experiments indicated that the lethal inoculation dose (50%) was less than 10(3) organisms per square centimeter. Histopathologically, surface colonization was followed by progressive growth with subsequent invasion of viable tissue. The invasion was not characterized by the perivascular or perineural lesions observed in experimental Pseudomonas burn sepsis. Bacteriologic examinations showed moribund animals to be bacteremic with the test strain and to have wound biopsy counts exceeding 10(6) organisms per gram of tissue. The role of bacterial motility as a virulence factor in this surface infection was investigated. Substrains selected for loss of subsurface spreading in soft agar lost virulence. This model of burn infection with a member of the Enterobacteriaceae should be used to evaluate topical and parenteral antimicrobial agents needed for the control of wound infections caused by such agents.
Insights
This study shows that Proteus mirabilis causes lethal burn wound infections in rats. Bacterial motility is crucial for virulence, highlighting a new model for testing antimicrobial agents against Enterobacteriaceae wound infections.
Area of Science:
- Microbiology
- Pathogen Research
- Infectious Diseases
Background:
- Burn wound infections pose significant clinical challenges.
- Enterobacteriaceae, including Proteus mirabilis, are common causes of hospital-acquired infections.
- Understanding pathogen virulence factors is crucial for developing effective treatments.
Purpose of the Study:
- To establish a rat model for experimental burn wound infection using a human isolate of Proteus mirabilis.
- To investigate the role of bacterial motility as a virulence factor in this infection model.
- To validate the model for evaluating antimicrobial agents against Enterobacteriaceae wound infections.
Main Methods:
- Induction of scald injury in rats followed by surface inoculation with Proteus mirabilis.
- Dose-response experiments to determine lethal inoculation doses.
- Histopathological examination of infected tissues.
- Investigation of bacterial motility using substrains with altered spreading capabilities.
Main Results:
- A non-fatal scald injury significantly increased susceptibility to lethal Proteus mirabilis surface infection.
- The lethal dose (50%) was less than 10^3 organisms/cm^2.
- Infection progressed from surface colonization to tissue invasion, without specific perivascular/perineural lesions.
- Bacteremia and high bacterial counts (>10^6 organisms/g) were observed in moribund animals.
- Loss of bacterial motility (subsurface spreading) correlated with reduced virulence.
Conclusions:
- Proteus mirabilis can act as an experimental pathogen causing lethal burn wound infections in rats.
- Bacterial motility is a key virulence factor in this burn wound infection model.
- This model is suitable for evaluating topical and parenteral antimicrobial agents for Enterobacteriaceae-related wound infections.