Experimental Proteus mirabilis burn surface infection
A. T. McManus, C. G. McLeod Jr and A. D. Mason Jr
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.
