Standardization of a model of E. coli-pyelonephritis in rats

The validity of preclinical testing of antibiotics in animal experiments is highly dependent on the quality and, especially, the standardizability of the infection model. Some of the factors associated with standardization of the acute phases of infection are demonstrated for experimental pyelonephritis in female albino Wistar rats after transuretheral infection. The renal bacterial count and infection rate are correlated to the volume and bacterial concentration of the instilled E. coli suspension. Strains of albino Wistar rats from different breeding institutions show differing resistance to the infection. E. coli pyelonephritis establishes more easily in female Wistar rats of strain Han: WIST than in strain Bor: WIST. Following dissection of the animals, the infected kidneys can be stored for at least 4 weeks at -30 degrees C or in liquid nitrogen, because the bacterial counts remain constant. However, in frozen renal homogenates the bacterial counts fall rapidly. During the first 4 post-infection days the bacterial content of the kidneys is relatively constant. The period 30-72 h post infection is especially suitable for therapeutic studies.