ENTEROCOCCUS-FAECALIS AGGRAVATES PYELONEPHRITIS CAUSED BY PSEUDOMONAS-AERUGINOSA IN EXPERIMENTAL ASCENDING MIXED URINARY-TRACT INFECTION INMICE

Mixed urinary tract infection was: caused: by simultaneous inoculation or 10(4) CFU each of Enterococcus faecalis TN2005 and Pseudomonas aer uginosa P9 into the bladders of CBA/J mice. Both organisms proliferate d in the kidneys, and viable cell counts of E. faecalis TN2005 reached a peak level of 4.1 x 10(5) CFU per pair of kidneys within the first 24 h, while P. aeruginosa P9 counts increased more slowly. The number of P. aeruginosa P9 cells peaked at 8.3 x 10(6) CFU per pair of kidney s 5 days after infection. Five days after mixed infection, infiltratio n of neutrophils into the renal pelvis and renal medulla was observed. Immunohistochemical staining revealed the presence of E. faecalis ant igen in the renal medulla. P. aeruginosa antigen was detected mainly i n the renal pelvis 5 days after infection and in the renal medulla as well as the renal pelvis 14 days after infection. Mixed infection indu ced pyelonephritis within 5 days after mixed infection, while it was n ot observed until 14 days after infection with P. aeruginosa P9 alone. P. aeruginosa P9 inoculated together with E. faecalis. TN2005 was mor e resistant to eradication from the kidneys by by beta-lactam antibiot ics than P. aeruginosa P9 inoculated alone. These results suggest that E. faecalis TN2005 invades the renal medulla first in mixed urinary t ract infection and induces histological changes which lead to aggravat ion of the pyelonephritis caused by P. aeruginosa P9.