Abstract: Objective To study the cross-immune responses and epidemiological significance of three pathogenic Yersinia species to host rats. Methods The host animals of plague in Guangdong province, Rattus losea, R. tanezumi, and R. norvegicus, were immunized four times (2×10⁹, 3×10⁹, 6×10⁹, and 7×10⁹ cells/rat, respectively) with two strains of live Y. pseudotuberculosis and three strains of live Y. enterocolitica, respectively, and the control group of rats were set at the same time. Then the appropriate amount of Y. pestis EV₇₆ strain solution mixed with 0.3 ml of 0.30% ferric ammonium citrate solution was used for a challenge test to evaluate the presence or absence of cross-immune protection. The rates were compared by using χ² test or Fisher's exact test. Results Rattus losea:Y. pestis EV₇₆ strain was cultured at 28℃ and given at 2.5×10⁹ cells/rat in the challenge test; the mortality rate was 9.09% (2/22) for the Y. pseudotuberculosis immunization group, 31.25% (10/32) for the Y. enterocolitica immunization group, and 68.75% (22/32) for the control group, with significant differences among the Y. pseudotuberculosis immunization group, Y. enterocolitica immunization group, and the control group (χ²=18.793, P<0.001; χ²=9.000, P=0.003), but there was no significant difference between the Y. pseudotuberculosis immunization group and the Y. enterocolitica immunization group (χ²=2.533, P=0.112). Rattus tanezumi:Y. pestis EV₇₆ strain was cultured at 37℃ and given at 3.8×10⁹ cells/rat in the challenge test; the mortality rate was significantly lower in the Y. pseudotuberculosis immunization group than in the control group[18.18% (4/22) vs 91.30% (21/23), χ²=24.350, P<0.001]; there was no significant difference in mortality rate between the Y. enterocolitica immunization group and the control group[90.91% (30/33) vs 91.30% (21/23), χ²=0.000, P=1.000]; there was a significant difference in mortality rate between the Y. pseudotuberculosis immunization group and the Y. enterocolitica immunization group (χ²=29.580, P<0.001). Another group of R. tanezumi:Y. pestis EV₇₆ strain was cultured at 37℃ and given at 3×10⁹ cells/rat in the challenge test; the mortality rate was significantly different between the Y. enterocolitica immunization group and the control group[3.45% (1/29) vs 45.45% (5/11), P=0.004]. Rattus norvegicus:Y. pestis EV₇₆ strain was cultured at 37℃ and given at 3.5×10⁹ cells/rat in the challenge test; the mortality rate was significantly different between the Y. enterocolitica immunization group and the control group[3.70% (1/27) vs 61.11% (11/18), χ²=15.384,P<0.001]. Conclusion With effective immunity, Y. pseudotuberculosis can provide strong cross-immune protection against Y. pestis in host rats, and Y. enterocolitica can also provide a certain cross-immune protection.

Key words: Pathogenic Yersinia, Host rat, Cross-immunity, Mortality

摘要： 目的 研究3种致病性耶尔森菌对宿主鼠的交叉免疫反应及流行病学意义。方法 分别用2株假结核耶尔森菌（假结核菌）、3株小肠结肠炎耶尔森菌（小肠结肠炎菌）以活菌方式对广东省鼠疫宿主动物黄毛鼠、黄胸鼠和褐家鼠各免疫4次，每次菌量分别为20、30、60和70亿，同时设立对照组。然后用鼠疫耶尔森菌（鼠疫菌）EV₇₆株适量菌液混合0.30%枸橼酸铁铵溶液0.3 ml进行攻毒实验，观察是否有交叉免疫保护作用。率的比较采用χ²检验或Fisher精确概率法进行统计学处理。结果 黄毛鼠：鼠疫菌EV₇₆株28℃培养25亿攻毒，假结核菌免疫组（2/22，9.09%）、小肠结肠炎菌免疫组（10/32，31.25%）和对照组（22/32，68.75%）死亡率相比，差异均有统计学意义（χ² =18.793，P<0.001；χ²=9.000，P=0.003）。假结核菌免疫组和小肠结肠炎菌免疫组死亡率差异无统计学意义（χ²=2.533，P=0.112）。黄胸鼠：鼠疫菌EV₇₆株37℃培养38亿菌量攻毒，假结核菌免疫组（4/22，18.18%）与对照组（21/23，91.30%）死亡率相比，差异有统计学意义（χ²=24.350，P<0.001），小肠结肠炎菌免疫组（90.91%，30/33）与对照组死亡率差异无统计学意义（χ²=0.000，P=1.000），假结核菌免疫组与小肠结肠炎菌免疫组死亡率比较差异有统计学意义（χ²=29.580，P<0.001）。另一组黄胸鼠EV₇₆株37℃培养30亿攻毒，小肠结肠炎菌免疫组（1/29，3.45%）与对照组（5/11，45.45%）死亡率相比，差异有统计学意义（P=0.004）。褐家鼠：EV₇₆株37℃培养35亿攻毒，小肠结肠炎菌免疫组（1/27，3.70%）与对照组（11/18，61.11%）死亡率比较，差异有统计学意义（χ²=15.384，P<0.001）。结论 在有效免疫下，假结核菌对鼠类抵抗鼠疫菌侵袭有较强的交叉免疫保护作用，小肠结肠炎菌亦有一定的交叉免疫保护作用。

关键词: 致病性耶尔森菌, 宿主鼠, 交叉免疫, 死亡率