Leukopenic and Lethal Effects of Slime from Acinetobacter calcoaceticus

Intravenous and intraperitoneal injections of slime from Acinetobacter calcoaceticus TMS266 induced leukopenia and death in mice. The leukopenia was characterized by a decrease in neutrophil count , followed by death of mice. This decrease of leukocytes was profound and supposed to contribute to the enhancement of virulence of other bacteria such as Escherichia coli. In mice treated with sublethal doses of the slime, the slime could not show its capacity to reduce circulating leukocytes . Introduction Acinetobacter calcoaceticus has been isolated from patients with urinary tract infectionsu , pneumonia2), or septicemia3). Although Acinetobacter calcoaceticus infections have been studied in recent years , relatively little is known about the pathogenesis concerned4)5). Previous studies concerning the pathogenicity of Acinetobacter calcoaceticus have confirmed the role of slime of this bacterial species6)7) . It has been demonstrated that the slime produces antiphagocytic and lethal effects in mice . In this study, the slime-induced leukopenic and lethal effects were further characterized . Materials and Methods Organism. Acinetobacter calcoaceticus TMS266, originally isolated from a human clinical specimen, was supplied by Prof. S. Goto (School of Medicine, Toho University , Tokyo). Bacterial slime. Slime was obtained from the strain as indicated and was purified by methods described previously6). Slime was extracted with saline from 48-hours bacterial cultures grown on sheets of cellophane overlying brain heart infusion agar (Difco). The crude slime was precipitated with cold ethanol . After treatment with chloroform-i-amylalcohol, 0.1 N sodium hydroxide, and cethylpyridinium chloride, in that order, the purified slime was obtained. Chemical components of the slime were determined by methods described previously6). The slime had high contents of sugar , protein, and orcinol reaction-positive substances. Animals. Four-week-old male mice of ddY strain weighing 17 to 18g were used and were supplied with water and laboratory chow ad libitum. Animal challenge. Groups of ten mice were injected intravenously or intraperitoneally with 0.2ml of twofold dilutions of the slime. Animals were observed daily for up to five days and the LD50 value was estimated by the Probit method. Leukocyte counts. Leukocyte counts were made on peripheral blood samples collected retroorbitally . The results are presented in terms of average of five mice per group .