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- Nielsen, Karen L., et al.
(författare)
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Fitness cost : a bacteriological explanation for the demise of the first international methicillin-resistant Staphylococcus aureus epidemic
- 2012
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 67:6, s. 1325-1332
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Tidskriftsartikel (refereegranskat)abstract
- Denmark and several other countries experienced the first epidemic of methicillin-resistant Staphylococcus aureus (MRSA) during the period 196575, which was caused by multiresistant isolates of phage complex 83A. In Denmark these MRSA isolates disappeared almost completely, being replaced by other phage types, predominantly only penicillin resistant. We investigated whether isolates of this epidemic were associated with a fitness cost, and we employed a mathematical model to ask whether these fitness costs could have led to the observed reduction in frequency. Bacteraemia isolates of S. aureus from Denmark have been stored since 1957. We chose 40 S. aureus isolates belonging to phage complex 83A, clonal complex 8 based on spa type, ranging in time of isolation from 1957 to 1980 and with varyous antibiograms, including both methicillin-resistant and -susceptible isolates. The relative fitness of each isolate was determined in a growth competition assay with a reference isolate. Significant fitness costs of 215 were determined for the MRSA isolates studied. There was a significant negative correlation between number of antibiotic resistances and relative fitness. Multiple regression analysis found significantly independent negative correlations between fitness and the presence of mecA or streptomycin resistance. Mathematical modelling confirmed that fitness costs of the magnitude carried by these isolates could result in the disappearance of MRSA prevalence during a time span similar to that seen in Denmark. We propose a significant fitness cost of resistance as the main bacteriological explanation for the disappearance of the multiresistant complex 83A MRSA in Denmark following a reduction in antibiotic usage.
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- Ostergaard, Henrik, et al.
(författare)
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Prolonged half-life and preserved enzymatic properties of factor IX selectively PEGylated on native N-glycans in the activation peptide
- 2011
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 118:8, s. 2333-2341
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Tidskriftsartikel (refereegranskat)abstract
- Current management of hemophilia B entails multiple weekly infusions of factor IX (FIX) to prevent bleeding episodes. In an attempt to make a longer acting recombinant FIX (rFIX), we have explored a new releasable protraction concept using the native N-glycans in the activation peptide as sites for attachment of polyethylene glycol (PEG). Release of the activation peptide by physiologic activators converted glycoPEGylated rFIX (N9-GP) to native rFIXa and proceeded with normal kinetics for FXIa, while the Km for activation by FVIIa-tissue factor (TF) was increased by 2-fold. Consistent with minimal perturbation of rFIX by the attached PEG, N9-GP retained 73%-100% specific activity in plasma and whole-blood-based assays and showed efficacy comparable with rFIX in stopping acute bleeds in hemophilia B mice. In animal models N9-GP exhibited up to 2-fold increased in vivo recovery and a markedly prolonged half-life in mini-pig (76 hours) and hemophilia B dog (113 hours) compared with rFIX (16 hours). The extended circulation time of N9-GP was reflected in prolonged correction of coagulation parameters in hemophilia B dog and duration of effect in hemophilia B mice. Collectively, these results suggest that N9-GP has the potential to offer efficacious prophylactic and acute treatment of hemophilia B patients at a reduced dosing frequency. (Blood. 2011; 118(8): 2333-2341)
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- Riihijarvi, Sari, et al.
(författare)
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High serum vascular endothelial growth factor level is an adverse prognostic factor for high-risk diffuse large B-cell lymphoma patients treated with dose-dense chemoimmunotherapy
- 2012
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Ingår i: European Journal of Haematology. - : Wiley. - 1600-0609 .- 0902-4441. ; 89:5, s. 395-402
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Tidskriftsartikel (refereegranskat)abstract
- Objectives To determine whether serum vascular endothelial growth factor (s-VEGF) levels and VEGF gene expression in tumor tissue predict survival of diffuse large B-cell lymphoma (DLBCL) patients treated with chemoimmunotherapy. Methods VEGF levels were measured in serum samples from 102 patients <65yrs with high-risk DLBCL using a quantitative sandwich enzyme immunoassay technique. Exon array data set of tumor tissues from 32 patients was concurrently used to determine VEGF-A exon and gene expression. All patients were treated in a Nordic phase II study with six dose-dense chemoimmunotherapy courses followed by systemic central nervous system prophylaxis. Results After a median follow-up time of 40months, 3-yr progression-free survival (PFS) was inferior in patients with high s-VEGF levels compared to those with low levels (59% vs. 83%, P=0.005). The relative risk of progression or relapse was 3.1-fold (95% confidence interval 1.346.91, P=0.008). The predictive capacity of s-VEGF levels on PFS was most pronounced in the DLBCLs of non-germinal center subtype. In contrast to serum data, VEGF mRNA expression in the lymphoma tissue did not predict outcome, and no correlation was found between s-VEGF levels and lymphoma VEGF expression. Conclusion Pretreatment s-VEGF level is a predictor of PFS after chemoimmunotherapy and may help to further stratify high-risk DLBCL patients into low- and high-risk groups.
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