Experimental infection of immunocompromised mice with Achromobacter xylosoxidans.

The natural resistance of mice to Achromobacter (A.) xylosoxidans was decreased to 1/80 by a single dose of 250 mg of cylophosphamide (CY) per kg intraperitoneally. When mice were infected with 1 X 10(9) A. xylosoxidans, the numbers of organisms in the liver, spleen, kidneys, lungs and heart blood reached to more than 10(6) per g at 6 hr after infection, and then decreased to less than 10(4) at 96 hr after infection. However, in the CY-treated mice, the numbers of organisms in these organs began to increase rapidly at 6 hr after infection and exceeded 10(9) per g at 48 hr when the mice died. Seventeen of 18 immunocompromised mice and 23 of 24 normal mice which were infected with 1 to 2 X 10(9) organisms of A. xylosoxidans, respectively, were still living until 4 weeks after infection when they were killed and examined. Thirteen of the 33 surviving mice which were examined for bacteriological assay were chronically infected with A. xylosoxidans, some in the spleen, others in the kidney, lung, brain and/or heart blood but none were infected in the liver. Most of the infected and surviving mice had produced an antibody against A. xylosoxidans and its titer was higher in the bacteriologically "cured" group than in the chronically infected one. All surviving mice were resistant to the 2nd challenge with a lethal dose of A. xylosoxidans even when they received an effective dose of CY. The surviving mice showed activated cellular immunity and rather depressed humoral immunity as compared with normal mice or the mice which were infected with killed A. xylosoxidans.