Study on the resistant genes to carbapenems and epidemiological characterization of multidrug-resistant Acinetobacter baumannii isolates.

The purpose of this study was to examine the carbapenemase-encoding resistance genes and analyze homologous of multidrug-resistant Acinetobacter baumannii (MRAB) isolates from nosocomial infections. Seventy-six A. baumannii strains were collected from inpatients and object surface of devices in intensive care units from May 2008 to February 2011. Antibiotic susceptibility testing of 18 antimicrobial agents was performed. The presence of carbapenemase-encoding resistance genes was investigated by polymerase chain reaction. Genotyping and dendrogram analysis of A. baumannii strains from nosocomial infections were performed using the DiversiLab System. All of the 76 clinical A. baumannii isolates were shown multidrug resistance. The bla(OXA-23) gene was identified in the 76 MRAB strains, while bla(OXA-24), bla(OXA-58), VIM, IMP-1, IMP-4, SIM, and blaNDM-1 were absent in all. Twenty-four A. baumannii strains from the samples with nosocomial infections were classified into four unrelated groups and nine patterns. In conclusion, production of bla(OXA-23) in MRAB is one of the molecular mechanisms responsible for carbapenem resistance. The MRAB strains from unrelated groups show different drug resistance, but the homologous strains also have different drug resistance. Homologous analysis can provide scientific evidence for evaluation of epidemic status of nosocomial infection caused by MRAB.

[Establishment of protein fingerprint database of Salmonella paratyphi A using SELDI-TOF-MS].

AIM: To establish a protein fingerprint database of Salmonella paratyphi A by surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). METHODS: Thirty-six clinical bacterial isolates and 96 control bacteria isolates were collected and identified using 16S rDNA sequencing. Bacterial proteins were detected by SELDI-TOF-MS, and all protein fingerprints were analyzed by ProteinChip and Biomarker Wizard software. The analysis results were used to set up a classification tree model by means of BioMarker Patterns software. At the same time, the data were tested by a blinded validation. RESULTS: In the range of M(r); 3 000-20 000, we obtained 104 protein peaks, of which 90 were of statistical significance (P<0.01). A protein peak with mass-to-charge ratio(M/Z) 10 061.7 was chosen to establish the classification tree model of Salmonella paratyphi A, and the sensitivity and specificity of Salmonella paratyphi A diagnosis was 100% as shown by the blinded validation. CONCLUSION: The classification tree model of Salmonella paratyphi A can be not only established using SELDI-TOF-MS technology, but also used for the rapid identification of Salmonella paratyphi A.

Mechanism of simvastatin-induced K562 cell apoptosis.

Statins are being widely used for the therapy and prevention of several types of tumors, including human chronic myelogenous leukemia, but the underlying molecular mechanisms still remain unknown. Therefore, inhibition of cell proliferation, apoptosis and involved molecules were investigated in K562 cells after incubation with simvastatin.The results showed that simvastatin diminished K562 cell proliferation and induced apoptosis. At the same time, the level of reactive oxygen species (ROS) and intracellular calcium concentration increased. Furthermore, nitric oxide (NO) content and inducible NO synthase (iNOS) mRNA expression were significantly higher in the simvastatin-treated group than in the corresponding control group. The elevated ROS level and intracellular calcium concentration, enhanced mRNA expression of iNOS and total NO content might be responsible for the apoptotic and anti-proliferative effects of simvastatin in K562 cells.

Rapid identification of Staphylococcus aureus by surface enhanced laser desorption and ionization time of flight mass spectrometry.

Staphylococcus aureus (S. aureus), a vital nosocomial pathogen, is responsible for several diseases. With the increasing isolation rate in clinical specimens, rapid identification of this bacterial species is required. But present identification via conventional methods is time-consuming and lacks accuracy. The purpose of the current study was to evaluate the use of surface enhanced laser desorption ionization time of flight mass spectrometry (SELDI-TOF MS) for rapid identification of S. aureus. A total of 120 clinical isolates of S. aureus and 153 non-S. aureus species were identified by conventional methods, and the species nature of all staphylococci was further confirmed by 16S rDNA sequencing. All strains observed were analyzed by SELDI-TOF MS. An identification model for S. aureus was developed and validated by an artificial neural network. The model based on 6 protein peaks exhibited a sensitivity of 98.4% and specificity of 98.6%. This strategy has the potential for rapid identification of S. aureus.

In vitro and in vivo study of cell growth inhibition of simvastatin on chronic myelogenous leukemia cells.

BACKGROUND: Statins, a family of 3-hydroxy-3-methylglutaryl CoA (HMG CoA) reductase inhibitors, are being investigated for the therapy and prevention of cancers. Here we aimed to investigate the effects of simvastatin on chronic myelogenous leukemia (CML) cells in vitro and in vivo, and to elucidate the mechanisms. METHODS: Cell proliferation and cell cycle were measured after K562 cells were incubated with simvastatin, and differentially expressed genes were determined by oligonucleotide microarray. Changes of 2 genes obtained by oligonucleotide microarray were validated by real-time RT-PCR, and immunohistochemistry was performed to determine expression of proliferating cell nuclear antigen (PCNA). Finally, a xenograft tumor model was constructed to evaluate the effects of simvastatin in vivo. RESULTS: Simvastatin could inhibit K562 cell proliferation, and the inhibition rate was approximately 30% after treatment with 20 mumol/l simvastatin for 48 h. Cell cycle was arrested in G(1) phase, as shown by flow cytometry results. Fifteen downregulated, 9 upregulated cell cycle-related genes and decreased PCNA protein were observed in the presence of simvastatin. Furthermore, simvastatin exhibited impairment of xenograft tumor growth in nude mice and also blocked cell cycle in G(1) phase. CONCLUSION: Simvastatin can inhibit CML cell proliferation in vitro and in vivo, and its mechanisms might be involved in cell cycle regulation.

Human scFv antibody fragments specific for hepatocellular carcinoma selected from a phage display library.

AIM: To identify the scFv antibody fragments specific for hepatocellular carcinoma by biopanning from a large human naive scFv phage display library. METHODS: A large human naive scFv phage library was used to search for the specific targets by biopanning with the hepatocellular carcinoma cell line HepG2 for the positive-selecting and the normal liver cell line L02 for the counter-selecting. After three rounds of biopanning, individual scFv phages binding selectively to HepG2 cells were picked out. PCR was carried out for identification of the clones containing scFv gene sequence. The specific scFv phages were selected by ELISA and flow cytometry. DNA sequences of positive clones were analyzed by using Applied Biosystem Automated DNA sequencers 3 730. The expression proteins of the specific scFv antibody fragments in E.coli HB2151 were purified by the affinity chromatography and detected by SDS-PAGE, Western blot and ELISA. The biological effect of the soluble antibody fragments on the HepG2 cells was investigated by observing the cell proliferation. RESULTS: Two different positive clones were obtained and the functional variable sequences were identified. Their DNA sequences of the scFv antibody fragments were submitted to GenBank (accession nos: AY686498 and AY686499). The soluble scFv antibody fragments were successfully expressed in E.coli HB2151. The relative molecular mass of the expression products was about 36 ku, according to its predicted M(r) value. The two soluble scFv antibody fragments also had specific binding activity and obvious growth inhibition properties to HepG2 cells. CONCLUSION: The phage library biopanning permits identification of specific antibody fragments for hepatocellular carcinoma and affords experiment evidence for its immunotherapy study.