ABSTRACT
Objective To analyze the serum polypeptide fingerprints of Enterococcus faecium (E. faecium) bloodstream infection in mice at different time points using matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-FOF MS), screen differential polypeptide peaks, and create a corresponding diagnostic model and look for new markers. Methods Ninety ICR mice were used to establish E. faecium bloodstream infection model (including 10 mice as normal control group with PBS injection, and 80 mice as the infection group with 1/2 LD50 E. faecium injection in a volume of 0.1 ml/10 g by the intravenous tail). Blood samples were collected at 8 time points (1, 3, 6, 12, 24, 48, 96 and 128 h), and tested for IL-1α, IL-1β and IL-6 detection. Serum samples were then purified with weak cation magnetic beads, the serum polypeptide profiling was recognized by MALDI-TOF MS and BioExplorer software between infection group and normal control group. Amino acid sequences of the candidate polypeptides were identified by nano-liquid chromatography electrospray ionization-tandem mass spectrometry (nano-LC/ESI–MS/MS). Results After infected with E. faecium, the mice showed abnormal behaviors compared with the normal control group, including listless and reduced activity; IL-1α was down-regulated, while IL-1β and IL-6 were up-regulated. A total of 102 polypeptide peaks were detected by fingerprints analysis. Screening on the basis of 5 times difference in content in both infection group and control group, 8 polypeptides were higher in infection group than those in control group (P<0.01), and 9 polypeptides were lower in infection group than those in control group (P<0.01). Combining five polypeptide peaks of m/z 1227.4, 1512.9, 4509.7, 5007.3 and 7816.7, the corresponding diagnostic model was established with accuracy rate of 80%, specificity of 76.6% and sensitivity of 83.3%. Identified by secondary mass spectrometry, polypeptide peaks m/z 1227.4 and 5007.3 were the fragment of β2microglobulin and complement C3, respectively. Conclusions MALDI-TOF MS combined with BioExplorer software, when used as a new method to study the E. faecium bloodstream infection, may find the differential polypeptides between infection group and control group, and can effectively establish a diagnostic model of bloodstream infection. β2-microglobulin and complement C3 are expected to become the new biomarkers for auxiliary diagnosis of bacterial bloodstream infection.
ABSTRACT
Objective To analyze the fingerprints of serum peptides in bloodstream infection induced by Candida albicans (C.albicans),with matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS),and establish the corresponding diagnostic model Methods To establish ICR mice model of C.albicans bloodstream infection,and collect the serum samples which were purified by weak cation exchange beads.The serum peptide finger printing was recognized by MALDITOF MS,and BioExplorer software was used for analysis between infection group and normal control group.Furthermore,the peptide fingerprints were analyzed between C.albicans infection group,Escherichia coli (E.coli) infection group and Staphylococcus aureus (S.aureus) infection group.Results Comparison between C.albicans infection group and normal control group,there were 135 polypeptide peaks,of which 5 polypeptides up-regulated,6 down-regulated and 7 up-regulated first and down-regulated afterwards.The diagnostic model was established by combination of 6 peaks (i.e.m/z 1610.9,1742.3,2666.4,2778.0,3345.1 and 4528.8),which possessed an accurate rate of 80.0％ in diagnosis of C.albicans infection.It was found by comprehensive comparison between C.albicans,E.coli and S.aureus infection groups that there were 5 polypeptides expressed collectively,i.e.m/z1513.8,2910.8,3538.1,3884.9 and 5007.3.Conclusions MALDI-TOF MS can be used to distinguish the C.albicans infection and normal polypeptide peaks.The collective polypeptides expressed in the infection groups can be further used to diagnose the infection.Establishment of corresponding diagnostic models may be helpful for early diagnosis of fungal bloodstream infection and provide a basis for reasonable clinical medication.
ABSTRACT
Objective To study the serum peptide fingerprint using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) technology,and find the different peaks with potential significance and establish the diagnosis model of Staphylococcus aureus and Escherichia coli bloodstream infection.Methods To establish ICR mice model of S.aureus and E.coli bloodstream infections,and collect serum samples.The serum samples were purified by weak cation exchange beads,the serum peptide fingerprint was recognized by using MALDI-TOF MS and BioExplorer software between infections group and normal control group.Results Compared with the normal control group,6 peptides were up-regulated,7 peptides downregulated and 8 peptides up-regulated first and then down-regulated in S.aureus infection group;And 5 peptides down-regulated,4 peptides down-regulated first and then up-regulated,and 8 peptides up-regulated first and then down-regulated in E.coli infection group.Conclusion MALDI-TOF MS combined with BioExplorer software may be used as a tool to study the serum peptides of S.aureus and E.coli bloodstream infection,effectively find significant peptides for establishing a diagnosis model of these two bacterial infections,and has a certain value for the diagnosis of bacterial bloodstream infection.