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Objective: Our purpose was to develop a mouse model of renal abscess to study the effect of extrauterine infection on preterm delivery., Methods: Escherichia coli or sterile medium was injected into the left kidney of 70 pregnant mice that had completed approximately 75% of gestation. Preterm delivery rates were recorded for various inocula. Kidney specimens were obtained and examined grossly and histologically for abscess formation., Results: Thirty-one of 51 animals (60.8%) infected with 1 x 10(5)-9 x 10(6) bacteria and none of 19 uninfected animals delivered prematurely (P < .001). Renal abscess was induced in 100% of mice receiving bacterial inoculation but in none receiving sterile medium., Conclusion: Kidney injection provides a reliable method for inducing renal abscess in pregnant mice. Renal abscess induces preterm delivery at a stable rate across a wide range of bacterial inocula. This model of extrauterine infection may be particularly useful in investigations of infection-induced preterm delivery.

We developed a murine model of kidney abscess by direct renal injection of either Escherichia coli (1 x 10(6) to 7 x 10(6) organisms) or sterile medium. Bacterial infection produced renal abscesses, bacteremia, and late-onset leukocytosis in all animals. Controls were unaffected. This model may be useful for the study of various sequelae of kidney infection.