臨床分離Citrobacter freundiiの病原性に関する研究

Abstract

Clinical and experimental studies were performed using Citrobacter freundii organisms which were isolated from urine specimens of in- and out-patients who visited our Department between January 1980 and July 1981. Specimens from other clinics were examined similarly for comparison. The results are summarized as follows; (1) Most of the C. freundii isolated at our hospital were from urine specimens (80%). At our department, C. freundii tended to be isolated at a higher frequency as the years passed (in-patients, from 18.4% (1980) to 19.0% (1981); out-patients, from 4.1% (1980) to 6.4% (1981)). (2) Examination by the disc method showed the C. freundii organisms to be sensitive to AMK and PL, but to be resistant to 9 other drugs, especially β-lactam antibiotics. Examination by the MIC method showed the same organisms to be highly sensitive to PPA, FOM and GM, as well as CMX (aβ-lactam antibiotic). (3) Phenol coefficients of Hibitane and Osvan to C. freundii were not particularly, different from those obtained for the Enterobacteriaceae. (4) Experimental urinary tract infection was produced by 12 strains of C. freundii in female ddY mice by injection into exposed urinary bladder. The mortality ratio in the bladder infection was calculated at 5 days after inoculation of bacilli. Strain No.l2 and No.53 induced a relatively high mortality ratio (100% mortality at an infection dose of 5.0×10[5] CFU/mouse and 7.0 X 10[5] CFU/mouse, respectively). Rates of recovery of the organisms from kidney and urinary bladder of the infected mice were high (In the case of No.12, the recovery rate was 100% when the organisms of 5.0x 10[4] CFU/mouse were inoculated; similarly 100% recovery was attained when the No.53 organisms of 7.0×10[3] CFU/mouse were inoculated). (5) Histopathologically, the infected kidney showed a severe inflammatory reaction associated with abscess formation and necrosis of medulla, pelvis and papilla. The overall pictures were of typical acute pyelonephritis.