INVOLVEMENT OF BACTERICIDAL FACTORS FROM THROMBIN-STIMULATED PLATELETS IN CLEARANCE OF ADHERENT VIRIDANS STREPTOCOCCI IN EXPERIMENTAL INFECTIVE ENDOCARDITIS
INVOLVEMENT OF BACTERICIDAL FACTORS FROM THROMBIN-STIMULATED PLATELETS IN CLEARANCE OF ADHERENT VIRIDANS STREPTOCOCCI IN EXPERIMENTAL INFECTIVE ENDOCARDITIS
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DOI：
10.1128/iai.63.2.663-671.1995
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发表时间：
1995-02-01
影响因子：
3.1
通讯作者：
HESS, J
中科院分区：
文献类型：
--
作者：
DANKERT, J;VANDERWERFF, J;HESS, J
用凝血酶激活的血小板释放杀菌因子。我们研究了草绿色链球菌对这些杀菌因子的敏感性在感染性心内膜炎（IE）发展中的作用。通过使用实验性心内膜炎兔模型，对 10 种草绿色链球菌菌株的初始粘附和 IE 的发展进行了评估，这些菌株对凝血酶激活的血小板释放（释放的物质）的敏感性不同。六株菌株对这些释放物敏感，四株菌株对这些释放物具有抗性。测定用10(4)CPU静脉注射后5分钟和48小时定植的植被(VG)数量。攻击后 5 分钟，六种血小板释放敏感菌株的细菌定植的 VG 明显多于四种释放物抗性菌株的细菌 (P < 0.005)。在释放物敏感组菌株中，静脉接种后 5 分钟至 48 小时内定植的 VG 数量显着减少（P < 0.001）。对于释放抗性菌株没有观察到这种降低。结果，释放物敏感菌株和耐药菌株引起的 IE 最终发展没有显着差异。选择释放物敏感菌株I和释放物抗性菌株2进行更详细的实验。接种后5和30分钟以及2、4和48小时处死兔子。确定培养阳性 VG 的数量以及单个 VG 上粘附细菌的数量。每个菌株的 90% 感染剂量为 10(5) CFU。在低接种浓度（10(3) 和 10(4) CFU）下，与较高的攻击剂量相比，发现两种菌株的接种细菌中有更大比例粘附在 VG 上。在用菌株 1 攻击后的前 30 分钟内，培养物阳性 VG 的数量以及每个 VG 的贴壁细菌数量迅速减少，但在用菌株 2 攻击后则没有。用血小板释放敏感菌株 S224 和血小板释放抗性菌株 S182 进行的其他实验证实了用菌株 1 和 2 获得的数据，并表明释放敏感菌株随着时间的推移从 VG 中消失， 而释放抗性菌株仍然存在。用菌株 1 或 2 攻击 5 分钟后切除的 VG 进行的体外研究表明，释放物敏感菌株 1 的清除不是由补体杀菌活性或多形核细胞的表面吞噬作用引起的。粘附在切除的 VG 上的 I 株细菌细胞通过暴露于新鲜的凝固血液或凝血酶刺激的血小板悬浮液中释放的物质而被迅速清除。相比之下，粘附在 VG 上的菌株 2 细菌几乎不受这些处理的影响。这些数据有力地表明，血小板在凝血酶刺激下释放的杀菌因子参与了细菌粘附到 VG 后的早期清除过程。因此，IE的发生是草绿色链球菌粘附VGs和抵抗血小板释放的杀菌因子活性的综合结果。
Platelets activated with thrombin release bactericidal factors. We studied the role of the susceptibility of viridans streptococci to these bactericidal factors in the development of infective endocarditis (IE). By using the experimental endocarditis rabbit model, the initial adherence and the development of IE, were assessed for 10 viridans streptococcal strains differing in their susceptibilities to releasate (material released) from thrombin-activated platelets. Six strains were susceptible and four strains were resistant to these releasates. The numbers of vegetations (VGs) colonized at 5 min and 48 h after intravenous challenge with 10(4) CPU were determined. At 5 min after challenge, significantly more VGs were colonized with bacteria of the six platelet releasate-susceptible strains than with bacteria of the four releasate-resistant strains (P < 0.005). In the reIeasate-susceptible group of strains, the number of colonized VGs decreased significantly between 5 min and 48 h after intravenous inoculation (P < 0.001). Such a decrease was not observed with the releasate-resistant strains. As a result, the final developments of IE due to releasate-susceptible and -resistant strains were not significantly different. The releasate-susceptible strain I and the releasate-resistant strain 2 were selected for more detailed experiments. Rabbits were killed at 5 and 30 min and 2, 4, and 48 h after inoculation. The number of culture-positive VGs as well as the number of adherent bacteria on the individual VGs were determined. The 90% infective dose for each strain was 10(5) CFU. At low inoculum concentrations (10(3) and 10(4) CFU) a larger proportion of the inoculated bacteria of both strains was found to be adherent on VGs than at higher challenge doses. The number of culture-positive VGs as well as the number of adherent bacteria per VG decreased rapidly in the first 30 min after challenge with strain 1 but not after challenge with strain 2. Additional experiments with the platelet releasate-susceptible strain S224 and the platelet releasate-resistant strain S182 confirmed the data obtained with strains 1 and 2 and indicated that releasate-susceptible strains disappeared from the VGs with time, whereas releasate-resistant strains persisted. In vitro studies with VGs excised 5 min after challenge with strain 1 or 2 showed that clearance of the releasate-susceptible strain 1 was not caused by complement bactericidal activity or surface phagocytosis by polymorphonuclear cells. Bacterial cells of strain I adherent on excised VGs were rapidly cleared by exposure to fresh clotting blood or to releasates from thrombin-stimulated platelet suspensions. In contrast, strain 2 bacteria adherent on VGs were hardly affected by these treatments. These data strongly indicate that bactericidal factors released from platelets upon thrombin stimulation are involved in the clearance of bacteria early after their adherence to VGs. Therefore, development of IE is the combined result of the abilities of viridans streptococci to adhere to VGs and to resist the activity of platelet-released bactericidal factors.