A C-terminal truncated mutation of licC attenuates the virulence of Streptococcus pneumoniae

LicC has been identified as a virulence factor of Streptococcus pneumoniae. However, its role in virulence is still not fully understood because deletion of licC is lethal for the bacterium. In this study, a mutant with 78-bp truncation at the C-terminus of licC was obtained from a signature-tagged mutagenesis (STM) library. The mutant was viable with a large reduction in enzymatic activity as CTP:phosphocholine cytidylyltransferase detected in vitro using a firefly luciferase assay. The mutation attenuated the adhesion and invasion of S. pneumoniae ST556 (serotype 19F) to epithelial cells by 72% and 80%, respectively, and increased the phagocytosis by macrophages for 16.5%, compared to the parental strain. When the mutation was introduced into the encapsulated D39 strain (serotype 2), it led to attenuated virulence in mouse models either by intranasal colonization or by intraperitoneal infection. In addition, the phosphocholine (PCho) on cell surface was decreased, and the choline binding proteins (CBPs) were impaired, which may explain the attenuated virulence of the mutant. These observations indicate that C-terminus of licC is accounted for the main activity of LicC in PCho metabolism and is essential for the virulence of S. pneumoniae, which provides a novel target for drug design against pneumococcal infection.     

晚期妊娠孕妇B群链球菌定植状况及妊娠结局分析

目的探讨妊娠晚期孕妇B群链球菌（GBS）定植情况、抗菌药物敏感性及妊娠结局。方法纳入2016年1月至2018年12月在东部战区总医院和南京医科大学第一附属医院妇产科定期产检的孕妇，于孕35~37周采用标准方法采集阴道及直肠拭子进行GBS培养，并对阳性标本分离的菌株进行药物敏感性试验。按培养结果分为GBS阳性组和GBS阴性组，阳性组按照产程中是否使用了抗菌药物治疗分为用药组与未用药组，比较不同组别妊娠结局的差异。结果共13 000名孕妇入组，GBS总体定植率为3.65%（475/13 000）。GBS在阴道中定植率为2.33%（303/13 000），在直肠中定植率为1.75%（227/13 000）。通过对直肠标本的采集检测，GBS阳性检出率增加了56.77%（172/303）。GBS每月的定植率有明显波动，3月份和10月份最高（均 P < 0.05）。475份GBS阳性标本对头孢曲松、万古霉素和利奈唑胺的敏感率为100%，对氨苄西林和青霉素的敏感率分别为97.26%和93.47%，而对左氧氟沙星、克林霉素、红霉素、四环素的耐药率较高，分别为30.11%、48.00%、52.21%和88.63%。GBS阳性组胎膜早破、产后出血、产褥期感染、新生儿肺炎、败血症发生率较GBS阴性组明显增高（均 P < 0.01）。产程中预防性使用抗菌药物的GBS阳性孕妇产褥期感染、新生儿感染及新生儿重症监护室入住率明显低于未使用抗菌药物的孕妇（ P < 0.05或 P < 0.01）。 结论妊娠晚期孕妇GBS定植率较低，无明显的季节性，通过补充直肠检测能提高GBS检出率。头孢曲松、氨苄西林和青霉素是目前预防和治疗GBS相关疾病的首选药物。GBS感染会明显增加母婴并发症的发生可能，产程中抗菌药物治疗可以改善母婴的结局。     

人猪链球菌感染致脑膜炎1例

本文报道一例猪链球菌感染所致脑膜炎病例。患者为屠宰工,主要症状为头痛、意识障碍,发热。因脑脊液中分离出猪链球菌而确诊。患者采用药敏试验敏感的万古霉素和青霉素治疗后痊愈出院。     

烤瓷表面抛光和上釉对其表面粗糙度及细菌黏附的影响

目的比较不同抛光方法对烤瓷表面粗糙度的影响,以及不同粗糙度烤瓷表面对口腔变异链球菌黏附的影响。方法采用原子力显微镜测量不同抛光方法对瓷表面粗糙度的影响,并通过细菌实验观察不同粗糙度的瓷表面对细菌黏附的影响。结果用抛光膏抛光或者上釉后,瓷面平整且有光泽。无论是表面粗糙度还是表面黏附的细菌数,橡皮轮组都大于抛光膏组和上釉组（P<0.05）。结论建议调改过的瓷表面进行抛光膏抛光或上釉以恢复瓷表面的光滑度和减少口腔致龋菌的黏附。     

应用电化学测菌法检测变形链球菌的初步探讨

目的:探讨应用电化学测菌法检测变形链球菌的可行性。方法:利用本课题组前期建立的电化学测菌法检测变形链球菌,记录检测参数,并将电化学测菌法的检测结果与细菌培养结果进行比较。结果:①微流芯片样本通道内层流形成时间为(3.17±0.16)min,从进样到获得稳定电阻抗数据的时间为(10.20±0.16)min。②当变形链球菌浓度为104～109cells/mL时,细菌浓度C的对数与系统阻抗值Z呈良好的线性关系(R2=0.98)。③与细菌培养的检测结果相比,电化学测菌法获得的细菌数多,差异有统计学意义(P<0.05)。④变形链球菌浓度为105cells/mL时,电化学测菌法检测值与细菌培养法检测值之间的线性函数关系式为:y=0.94x+0.32E4(R2=0.95),两种方法的检测值高度正相关(P=0.001<0.01)。结论:电化学测菌法能为变形链球菌的快速检测提供新的思路。     

Effect of Streptococcus sanguinis/Porphyromonas gingivalis single and combined biofilms upon platelet aggregation

Oral Diseases (2012) 18, 586–594 Objective: To assess the effect of two oral bacteria Streptococcus sanguinis and Porphyromonas gingivalis upon platelet aggregation. Materials and Methods: Streptococcus sanguinis, P. gingivalis, S. sanguniis + P. gingivalis were added to platelet‐rich plasma and platelet aggregation measured using a platelet aggregometer. Platelets were passed through a flow chamber with S. sanguinis, P. gingivalis or a biofilm of S. sanguinis and P. gingivalis coated with saliva. Platelet adhesion to the chamber was observed under a fluorescence microscope for 15 min. The positive control was platelets treated with adrenaline; the negative control was platelets treated with phosphate‐buffered saline. Results: The mean (± s.e.) aggregation magnitude of S. sanguinis and P. gingivalis was 77.7 ± 7.4% and 79.3 ± 9.9%, respectively. The aggregation magnitude of S. sanguinis + P. gingivalis was 51.3 ± 12.9%, which was significantly lower than that for S. sanguinis/P. gingivalis (P < 0.05). In the flow chamber system, platelets adhered to S. sanguinis/P.gingivalis respectively within 3 min, and reached a plateau at 5–15 min. Under the condition of the S. sanguinis‐ and P. gingivalis‐saliva biofilm, platelet adhesion to the biofilm was significantly reduced at 5–15 min (P < 0.05). Conclusions: In the static or dynamic flow system, platelets adhered to S. sanguinis or P. gingivalis. However, if S. sanguinis was mixed with P. gingivalis, the aggregation magnitude (%) was significantly reduced.     

变形链球菌ComCDE密度感应参与不同菌种的竞争

目的 研究口腔变形链球菌( S.mutans )ComCDE密度感应系统参与血链球菌(S.sanguinis)的相互竞争作用.方法 采用LIVE\DEAD BacLightTM荧光染色结合激光共聚焦显微镜,观察变形链球菌(简称变链菌)在CSP信号肽诱导下群体细菌自身死亡变化;通过荧光定量反转录聚合酶链反应(RT-PCR)测定细菌素以及细菌素免疫蛋白相关基因表达变化,分析变链菌ComCDE系统参与菌群生存竞争的调控机制.结果 在细菌竞争中,变形链球菌△comC、△comD 、△comE突变株失去不同菌种间的竞争力,无法抑制相邻Ssanguinis的正常生长;只有野生株保持竞争力,抑制相邻S.sanguinis生长,形成缺陷菌环.CSP信号肽诱导下,变链菌群体死菌/活菌率增高58.1％(P＜0.05);细菌素及免疫蛋白相关SMU.151、SMU.423、SMU.1913c基因分别升高23.3倍(P=0.00)、15.9倍(P＜0.05)、19.3倍(P＜0.05).结论 变形链球菌ComCDE密度感应系统调控变链菌的变链素及免疫蛋白产生、参与不同菌种间竞争生存.