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ABSTRACTThe antimicrobial activity of the intraurethrally administered probiotic Lactobacillus caseistrain Shirota againstEscherichia coliin a murine urinary tract infection (UTI) model was examined. UTI was induced by intraurethral administration ofEscherichia colistrain HU-1 (a clinical isolate from a UTI patient, positive for type 1 and P fimbriae), at a dose of 1 × 106to 2 × 106CFU in 20 μl of saline, into a C3H/HeN mouse bladder which had been traumatized with 0.1 N HCl followed immediately by neutralization with 0.1 N NaOH 24 h before the challenge infection. Chronic infection with the pathogen at 106CFU in the urinary tract (bladder and kidneys) was maintained for more than 3 weeks after the challenge, and the number of polymorphonuclear leukocytes and myeloperoxidase activity in the urine were markedly elevated during the infection period. A single administration of L. caseiShirota at a dose of 108CFU 24 h before the challenge infection dramatically inhibited E. coligrowth and inflammatory responses in the urinary tract. Multiple daily treatments with L. caseiShirota during the postinfection period also showed antimicrobial activity in this UTI model. A heat-killed preparation ofL. caseiShirota exerted significant antimicrobial effects not only with a single pretreatment (100 μg/mouse) but also with multiple daily treatments during the postinfection period. The otherLactobacillusstrains tested, i.e., L. fermentumATCC 14931T, L. jenseniiATCC 25258T, L. plantarumATCC 14917T, and L. reuteriJCM 1112T, had no significant antimicrobial activity. Taken together, these results suggest that the probiotic L. caseistrain Shirota is a potent therapeutic agent for UTI.

ABSTRACTWe examined colonization patterns of Shiga toxin-producingEscherichia coli(STEC), concentrations of Shiga toxins (Stxs) and specific immunoglobulin A (lgA) against Stxs and STEC bacterial cell surface antigen in various portions of the gastrointestinal tract in an infant rabbit infection model. After inoculation of 3-day-old infant rabbits with STEC strain 89020087 at low doses (∼103CFU/body), numbers of colonizing STEC bacteria and concentrations of Stxs in the intestine increased dramatically and the animals developed diarrhea within a couple of days after infection. Daily administration ofLactobacillus caseifrom the day of birth dramatically decreased the severity of diarrhea and lowered STEC colonization levels in the gastrointestinal tract 100-fold day 7 after infection. Both Stx1 and Stx2 concentrations in the intestines and histological damage to the intestinal mucus induced by STEC infection were decreased by the administration of L. casei. Examination of the concentrations of volatile fatty acids and pH of the intestinal contents revealed that the protective effect of L. caseiadministration against STEC infection was not due to fermented products such as lactic acid in the gastrointestinal tract. Administration ofL. caseiincreased levels of lgAs against Stx1, Stx2, and formalin-killed STEC cells in the colon approximately two-, four-, and threefold, respectively, compared with those of the untreated controls by day 7 after infection. These results suggest that administration ofL. caseistrain Shirota enhances the local immune responses to STEC cells and Stxs and leads to elimination of STEC and thus decreases Stx concentrations in the intestines.

The effect of fermented skim milk (FSM) by Lactobacillus caseistrain Shirota on plasma lipids in hamsters was examined. Hamsters fed on cholesterol-free and -enriched diets containing 30% FSM had lower levels of plasma triglyceride than those fed on the control diet. In the experiment with the cholesterol-enriched diet-fed hamsters, the plasma triglyceride level was suppressed by FSM at concentrations of 10% to 30%. Unfermented milk tended to lower the level of triglyceride, but not significantly. The plasma cholesterol concentration was not affected by an FSM and unfermented skim milk supplement to the diet. L. caseistrain Shirota grew well in the presence of mixed lipid micelles containing bile acid, but did not have the ability to remove cholesterol from the culture broth. These results indicate that FSM lowered the plasma triglyceride level in hamsters.

We evaluated the properties of recombinant staphyloki-nase in comparison with those of tissue-type plasminogen activator (t-PA) and streptokinase (SK). The presence of fibrin(ogen) fragment FCB-2 in the reaction mixture increased plasminogen activation by staphylokinase more than 20-fold. Such characteristics are similar to those of t-PA. On the other hand, SK was not affected by the presence of FCB-2. The thrombolytic properties of staphy-lokinase were studied in a system consisting of a radioactive human plasma clot (125l-fibrinogen-labeled) suspended in the circulating citrated plasma. Significant thrombolysis (50% in 3 hours) was obtained with 2 μg/mL of staphyloki-nase and 4.45 μg/mL t-PA, as compared with 12  μ g/ml. for SK. The relative molar potency of staphylokinase, calculated from the molecular weight, was about two times more effective than that of SK, but about half of that of t-PA. Systemic fibrinolytic activation and fibrinogen break-down was not observed with staphylokinase or t-PA, but was observed with SK. The thrombolytic efficiency of staphylokinase, which was calculated as the ratio of the degree of thrombolysis/the degree of fibrinogenolysis, was about five times greater than that of SK, and about half of that of t-PA. These findings suggest that staphylokinase has higher specific thrombolytic properties and lesser fibrinogenolytic properties than those of SK.