Reyes L, Steiner D A, Hutchison J, Crenshaw B, Brown M B
Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville 32611-0880, USA.
Comp Med. 2000 Dec;50(6):622-7.
Mycoplasma pulmonis is a natural pathogen of the respiratory and genital tracts of rats. Differential susceptibility and severity of the respiratory form of the disease, known as murine respiratory mycoplasmosis (MRM), exist between rat strains. We now report that specific rat strains vary in susceptibility to genital tract infection and pregnancy outcome.
Specific-pathogen-free (SPF) female F344, LEW, Wistar (WIS) and Sprague Dawley (SD) rats were intravaginally inoculated with 3 x 10(7) colony-forming units (CFU) of M. pulmonis strain X1048 or sterile diluent, and allowed to breed at 10 days after inoculation. Pregnant dams and pups were necropsied within 24 hours of parturition. At necropsy, culture for M. pulmonis was performed on dam and pups, and adverse effects on pregnancy outcome were assessed by determination of the incidence of infertility, fetal resorption, stillbirths, changes in litter size, and pup birth weight. Blood from dams was collected prior to inoculation and at time of necropsy for measurement of IgM and IgG antibodies to M. pulmonis.
At time of necropsy, WIS (50%) and SD (60%) dams had a higher frequency of M. pulmonis culture positivity in the genital tract than did LEW (22.2%) and F344 (17.6%) dams. Dams that were still infected with M. pulmonis at time of necropsy had various complications. The SD rats had the greatest degree of adverse effects on pregnancy outcome, which were: infertility, decreased litter size (P < or = 0.01), decreased pup birth weight (P < or = 0.01), increased frequency of resorptions, stillbirths (P < or = 0.05), and the highest rate of pup pulmonary infection (23.1%) (P < or = 0.001). Despite a 50% colonization rate, WIS dams were the least adversely affected. The WIS pups born from M. pulmonis. infected dams had slight decrease in birth weight, and only 6% had pulmonary infections. The LEW infected dams developed infertility and lower numbers of liveborn pups without evidence of vertical transmission. The F344 infected dams had lower numbers of liveborn pups that were smaller than their control counterparts, and none had pulmonary infections. None of the animals had detectable IgM and IgG antibodies to M. pulmonis before inoculation. At time of necropsy, all animals inoculated with M. pulmonis developed significantly (P < or = 0.001) higher amounts of M. pulmonis IgG and IgM antibodies, with SD rats developing the highest amounts (P < or = 0.005).
Both F344 and LEW rats are more resistant to vaginal inoculation with M. pulmonis than are WIS and SD rats. However, only SD dams suffered severe adverse effects on pregnancy outcome. The SD dams also had the greatest IgM and IgG antibody response to M. pulmonis. Our studies clearly indicate differences among rat strains in their susceptibility to vaginal inoculation with M. pulmonis and in secondary complications associated with infection. This system may be a useful model for determining host-specific factors that influence the outcome of natural mycoplasmal infections of the genital tract.
肺支原体是大鼠呼吸道和生殖道的天然病原体。大鼠品系之间存在对称为鼠呼吸道支原体病（MRM）的呼吸道疾病形式的易感性和严重程度差异。我们现在报告特定大鼠品系对生殖道感染和妊娠结局的易感性有所不同。
将无特定病原体（SPF）的雌性F344、LEW、Wistar（WIS）和Sprague Dawley（SD）大鼠经阴道接种3×10⁷肺支原体X1048菌株的菌落形成单位（CFU）或无菌稀释液，并在接种后10天允许其交配。在分娩后24小时内对怀孕母鼠和幼崽进行尸检。尸检时，对母鼠和幼崽进行肺支原体培养，并通过测定不育率、胎儿吸收、死产、窝仔数变化和幼崽出生体重来评估对妊娠结局的不良影响。在接种前和尸检时采集母鼠血液，用于检测抗肺支原体的IgM和IgG抗体。
尸检时，WIS（50%）和SD（60%）母鼠生殖道中肺支原体培养阳性频率高于LEW（22.2%）和F344（17.6%）母鼠。尸检时仍感染肺支原体的母鼠出现了各种并发症。SD大鼠对妊娠结局的不良影响程度最大，包括：不育、窝仔数减少（P≤0.01）、幼崽出生体重降低（P≤0.01）、吸收和死产频率增加（P≤0.05），以及幼崽肺部感染率最高（23.1%）（P≤0.001）。尽管定植率为50%，但WIS母鼠受到的不良影响最小。由感染肺支原体的WIS母鼠所生的幼崽出生体重略有降低，只有6%发生肺部感染。感染的LEW母鼠出现不育，活产幼崽数量减少，无垂直传播证据。感染的F344母鼠活产幼崽数量较少，且比对照幼崽小，无一发生肺部感染。接种前所有动物均未检测到抗肺支原体的IgM和IgG抗体。尸检时，所有接种肺支原体的动物抗肺支原体IgG和IgM抗体量均显著升高（P≤0.001），其中SD大鼠抗体量最高（P≤0.005）。
F344和LEW大鼠比WIS和SD大鼠对经阴道接种肺支原体更具抵抗力。然而，只有SD母鼠的妊娠结局受到严重不良影响。SD母鼠对肺支原体的IgM和IgG抗体反应也最强。我们的研究清楚地表明，大鼠品系在经阴道接种肺支原体的易感性以及与感染相关的继发并发症方面存在差异。该系统可能是确定影响生殖道自然支原体感染结局的宿主特异性因素的有用模型。
