Prevalence and antibiotic resistance of bacteria isolated from the cerebrospinal fluid of neurosurgical patients at Peking Union Medical College Hospital.

Background: Postoperative central nervous system infections (PCNSIs) represent a serious complication, and the timely use of antibiotics guided by the identification of the causative pathogens and their antibiotic sensitivities is essential for treatment. However, there are little data regarding the prevalence of PCNSI pathogens in China. The aim of this study is to investigate the features of pathogens in patients with PCNSIs, which could help clinicians to choose the appropriate empirical antibiotic therapy. Methods: We retrospectively examined the positive CSF cultures in patients who underwent craniotomy between January 2010 and December 2015. We collected data, including demographic characteristics, type of neurosurgery, laboratory data, causative organisms and antimicrobial susceptibility testing results. Results: A total of 62 patients with 90 isolates out of 818 patients with 2433 CSF culture samples were available for data analysis. The estimated incidence and culture-positive rate of PCNSIs were approximately 0.9 and 7.5%, respectively. The predominant organism was coagulase-negative staphylococci, of which most were methicillin-resistant coagulase-negative staphylococci (MRCoNS). All were susceptible to vancomycin, linezolid, rifampicin and amoxicillin-clavulanate. Acinetobacter baumannii was the most frequent causative Gram-negative agent and was resistant to 12 out of 18 antimicrobials tested. The sensitivity rates for tigecycline and minocycline were only 40 and 33%, respectively. Conclusion: PCNSIs could lead to high mortality. Although the MRCoNS were the predominant organism, the management of Acinetobacter baumannii was a major clinical challenge with few effective antimicrobials in PCNSIs.

Protection of Nerve Injury with Exosome Extracted from Mesenchymal Stem Cell.

OBJECTIVE: To investigate the protective effect of Exosomes from human adipose-derived mesenchymal stem cells (hAMSCs) in neural injury induced by glutamate and its possible mechanism. METHODS: Characteristics of Exosomes from hAMSCs were identified by electron microscopy and Western blot analysis. Cytokines that might play a major role in the protective effect were tested by enzyme-linked immunosorbent assay (ELISA). The protective action of Exosome and its possible signaling pathway were researched by the in vitro neural injury induced by glutamate, including control group (without Glu), Glu group (dealing with Glu), Glu+Exo group (dealing with Glu +100 ng/ml Exo), Glu+Exo+Akt group (dealing with Glu+100 ng/ml Exo+10 µmol/L Akt), Glu+Exo+Erk group (dealing with 100 ng/ml Glu+100 ng/ml Exo+10 µmol/L Erk), and Glu+Exo+TrkB group (dealing with Glu+100 ng/ml Exo +10 µmol/L TrkB). RESULTS: Exosomes from hAMSCs had similar sizes to those isolated from other kinds of cells, and expressed the characteristic proteins such as CD63, CD81, HSP70, and HSP90. Cytokines that had neurotrophic effects on Exosomes were mainly insulin-like growth factor and hepatocyte growth factor, with the concentration being 9336.49±258.63 and 58,645.50±16,014.62, respectively; brain derived neurotrophic factor, nerve growth factor,and vascular endothelial growth factor had lower levels, with the concentration being 1928.25±385.47, 1136.94±5.99, and 33.34±9.43, respectively. MTS assay showed that the PC12 cell survival rates were 0.842±0.047, 0.306±0.024, 0.566±0.026, 0.461±0.016, 0.497±0.003, and 0.515±0.034 in the control group, Glu group, Glu+Exo group, Glu+Exo+Akt group, Glu+Exo+Erk group, and Glu+Exo+TrkB group; obviously, it was significantly lower in Glu group than in control group (P=0.02), significantly higher in Glu+Exo group than in Glu group (P=0.01), and significantly lower in Glu+Exo+Akt group than in Glu+Exo group (P=0.01). CONCLUSION: Exosomes secreted from hAMSCs have protective effect against neuron damage induced by glutamate, which may be mediated through activating the PI3/K-Akt signalling pathway.