S80 Abstracts / Journal of Clinical Virology 70 (2015) S1–S126 Abstract No: 1501 Presentation at ESCV 2015: Poster 2 The study of resistance of human cytomegalovirus to ganciclovir in patients after alogeneic transplantation of haematopoietic stem cells Stepanova Vlasta 1 , L. Pliskova 2 , E. Vejrazkova 3 , R. Kutova 2 , P. Hubacek 4 , M. Fajfr 1 1 Inst. of Clin. Microbiology, University Hospital and Faculty of Medicine, Charles University, Hradec, Czech Republic 2 Inst. of Clin. Biochemistry and Diagnostics, University Hospital and Faculty of Medicine, Charles University, Hradec, Czech Republic 3 Clinic of Internal Diseases, Department of Clin. Haematology, University Hospital and Faculty of Medicine, Charles University, Hradec, Czech Republic 4 Clinic of Paediatric Haematology and Oncology, Inst. of Medical Microbiology of University Hospital, Czech Republic Aim: To analyze the relation between clinical resistance to gan- ciclovir (GCV) therapy and isolated cytomegalovirus (CMV) strain and identify the mutation coding GCV resistance in patients after alogeneic hematopoietic stem cell transplantation (HSCT) treated with GCV. Background: Treatment failure is defined as a persistent DNAemia or increasing CMV load after 2 weeks of GCV treatment. CMV resistance to GCV is most frequently caused by mutation in UL 97 gene and develops mostly within 2–3 months after HSCT. Ganciclovir-resistant CMV strain is confirmed by genotype test- ing. Methods: The group of 68 retrospectively followed patients after HSCT in 2012–2014 (34 males, 34 females, median age 53 years), 40 of them (58.8%) treated with GCV for CMV reactiva- tion with clinical disease. The frequency of blood collection was in noncomplicated course once a weak up to day 100 after HSCT and then according to clinical status of patient. Sequence anal- ysis was performed only in patients with suspected resistence to GCV. CMV viremia was determined by quantitative real-time PCR from full peripheral blood – DNA extraction performed by QIAamp DNA Mini Kit (Qiagen), quantitative DNA determination by CMV RG PCR (Qiagen) with 500 cp/ml as the quantification cut off and 100 cp/ml as the detection cut off. Positive CMV DNA samples were stored at −20 ◦ C for additional testing and deter- mination of mutation time development. The sequence analysis determined UL 97 and UL 54 genes parts, extracted sequences were compared with the reference CMV strain AD169 using the home designed program for detection of differencies by auto- matical search of mutations and polymorphisms of CMV in UL 97 and UL 54. This program detects the conformity and displays the differences in sequenced DNA. The results were compared with the reference datebase of CMV mutations and polymor- phisms. Results: Treatment failure with persistant viraemia occurred in 7 patients. Ganciclovir-resistance based on coding mutation was detected only in 2 patients (mutations L595F and M460I in gene UL 97). Another mutation (N510S in gene UL 97) was found in 1 patient with recurrent CMV replication although he did not meet the criteria for clinical treatment failure. In 5 patients the cause of treatment failure was different. Conclusion: The low incidence of drug resistant CMV isolates in our patients in relatively common clinical treatment failure sug- gests that slower viral clearance is likely more frequently different from UL 97 and UL 54 genes mutation development. http://dx.doi.org/10.1016/j.jcv.2015.07.187 Abstract No: 1506 Presentation at ESCV 2015: Poster 2 Interim analysis of study of kinetics of CMV-DNA load in whole blood and plasma samples of allogeneic hematopoietic stem cell transplant (HSCT) recipients T. Lazzarotto 1 , L. Gabrielli 1 , R. Cavallo 2 , G. Piccirilli 1 , A. Piralla 3 , A. Chiereghin 1 , G. Campanini 3 , M. Furione 3 , C. Costa 2 , F. Sidoti 2 , G. Bianco 2 , P. Paba 4 , C.F. Perno 4 , F. Baldanti 3 , AMCLI – Infections in Transplant Working Group (GLaIT) 1 O.U. of Microbiology, Laboratory of Virology, Policlinico S. Orsola Malpighi, University of Bologna, Italy 2 O.U. of Microbiology and Virology, Laboratory of Virology, Policlinico Città della Salute e della Scienza di Torino, University of Turin, Italy 3 Molecular Virology Unit, Microbiology and Virology Department, Fondazione IRCCS Policlinico San Matteo, University of Pavia, Italy 4 O.U. of Molecular Virology, Policlinico Fondazione Tor Vergata, Università Tor Vergata, Roma, Italy Background: The quantification of cytomegalovirus (CMV)- DNA is a cornerstone in the management of CMV disease in hematopoietic stem cell transplant (HSCT) recipients. However, major discrepancies among transplantation centers in testing methods, type of blood samples, frequency and thresholds for initiating preemptive therapy are obstacles for a standardized diagnostic and therapeutic approach. This retrospective non- interventional multicentre cohort study aimed at analyzing the kinetics of CMV-DNA in whole blood (WB) and plasma samples from HSCT recipients and allow the identification of DNA cut-off values for pre-emptive therapy for both blood compartments. Methods: From March to December 2014, we enrolled 67 allo- geneic HSCT actively CMV infected recipients (18 paediatric, 49 adult). We analyzed a total of 74 episodes of active CMV infection and tested a mean of 10 sequential samples of WB and 10 sequential plasma samples per episode. A total of 1138 serial samples of WB and plasma were retrospectively processed with the artus ® CMV QS-RGQ kit and QIAsymphony SP/AS instruments (QIAGEN). Results. A correlation between CMV DNA levels in WB and in plasma was demonstrated by regression analysis: we analyzed all 1138 samples (r = 0.84) and 620 samples with a positive and quantified value of CMV-DNA (r = 0.73). To compare the kinetics of CMV-DNA in the two blood specimens, CMV DNA in WB was used as a reference and T0 was set at the time of CMV DNA peak in WB. For each patient, the CMV DNA levels in WB and plasma were then stratified over 5 weeks before and after the WB peak time. Peak CMV DNA levels in WB mostly coincided with peak levels in plasma, however different kinetics in the two types of specimens were observed. Before reaching a peak, CMV DNA levels in plasma was 1 log lower than whole blood, while after the peak CMV DNA levels in plasma showed a slower decline. Conclusions: In HSCT patients, the determination of CMV DNA in both blood matrices was able to provide univocal information on the kinetics of viral replication. The identification of the pre- emptive therapy cut-off was safe to use for both WB and plasma