Identification of a novel de novo mutation of CREBBP in a patient with Rubinstein-Taybi syndrome by targeted next-generation sequencing: a case report.

Rubinstein-Taybi syndrome (RSTS) is a rare autosomal dominant congenital disorder (prevalence, 1:125000-720000) characterized by broad thumbs and halluces, facial dysmorphism, psychomotor development delay, skeletal defects, abnormalities in the posterior fossa, and short stature. The purpose of this study was to use targeted exome sequencing to identify the genetic cause of RSTS in a 6.5-year-old girl presenting typical features of this condition. Targeted exome sequencing of the patient DNA revealed de novo transition c.1066C>T corresponding to a novel nonsense mutation p.Q356X in the CREB-binding protein gene, CREBBP, whose haploinsufficiency is responsible for 50% to 60% of the RSTS cases. Based on comparing the clinical manifestations of our patient with those of patients carrying similar mutations, we supposed that haploinsufficiency is the possible functional consequence of p.Q356X mutation by creation of a loss-of-function CREBBP allele due to a premature stop codon and RSTS phenotype. Our findings expand the spectrum of mutations associated with this condition.

Clonal dissemination of multilocus sequence type ST15 KPC-2-producing Klebsiella pneumoniae in Bulgaria.

A total of 36 consecutive clinical and two fecal-screening carbapenem-resistant Klebsiella pneumoniae isolates from two Bulgarian university hospitals (Varna and Pleven) were investigated. Susceptibility testing, conjugation experiments, and plasmid replicon typing were carried out. Beta-lactamases were characterized by isoelectric focusing, PCR, and sequencing. Clonal relatedness was investigated by RAPD and multilocus sequence typing (MLST). Most of the isolates demonstrated multidrug resistance profile. Amikacin and tigecycline retained good activity with susceptibility rates of 95 and 87%, respectively. The resistance rate to colistin was 63%. Six RAPD- and MLST-types were identified: the dominating MLST-type was ST15 (27 isolates), followed by ST76 (six isolates), and ST1350 (two isolates). ST101, ST258, and ST151 were detected once. All except one of the K. pneumoniae produced KPC-2, mostly in combination with CTX-M-15, while for one isolate (ST101) the enzymes OXA-48 and CTX-M-14 were found. All KPC-2-producing transconjugants revealed the presence of IncFII plasmid. The OXA-48- and CTX-M-14-producing isolate showed the presence of L/M replicon type. The dissemination of KPC-2-producing K.pneumoniae in Bulgaria is mainly due to the sustained spread of successful ST15 clone and to a lesser extent of ST76 clone. This is the first report of OXA-48 producing ST101 K. pneumoniae in Bulgaria.

Spectrum and frequencies of BRCA1/2 mutations in Bulgarian high risk breast cancer patients.

BACKGROUND: About 3885 women are diagnosed with breast cancer and 1285 die from the disease each year in Bulgaria. However no genetic testing to identify the mutations in high-risk families has been provided so far. METHODS: We evaluated 200 Bulgarian women with primary invasive breast cancer and with personal/ family history of breast cancer for the presence of unequivocally damaging germline mutations in BRCA1/2 using Sanger sequencing. RESULTS: Of the 200 patients, 39 (19.5 %) carried a disease predisposing mutation, including 28 (14 %) with a BRCA1 mutation and 11 (5.5 %) with a BRCA2 mutation. At BRCA1, 6 different mutations were identified, including 2 frameshifts, 1 nonsense and 1 missense that had been previously reported (c.5030_5033delCTAA, c.5263_5264insC, c.4603G > T, c.181 T > G), and 2 frameshifts, which were novel to this study (c.464delA, c.5397_5403delCCCTTGG). At BRCA2, 7 different frameshift mutations were identified, including 5 previously reported (5851_5854delAGTT, c.5946delT, c.5718_5719delCT, c.7910_7914delCCTTT,c.9098_9099insA) and 2 novel (c.8532_8533delAA, c.9682delA). A BRCA1 mutation was found in 18.4 % of women diagnosed with breast cancer at/or under the age of 40 compared to 11.2 % of women diagnosed at a later age; a BRCA2 mutation was found in 4 % of women diagnosed at/or under the age of 40 compared to 6.5 % of women diagnosed at a later age. A mutation was present in 26.8 % patients with a positive family history and in 14.4 % of women with a negative family history. The most prevalent mutation observed in 22 patients (11 %) was BRCA1 c.5263_5264insC, a known Slavic mutation with founder effect in Eastern European and AJ communities. Other recurrent mutations were BRCA2 c.9098-9099insA (2 %), BRCA1 c.181T > G (1 %) and BRCA2 c.5851_5854delAGTT (1 %). Notably, BRCA1 c.5263_5264insC represented 56 % of all mutations identified in this series. Of the 22 patients with BRCA1 c.5263_5264insC, 9 were diagnosed with early onset breast cancer, 11 with TNBCs, 4 with bilateral breast cancer, and 6 with both breast and ovarian cancer. CONCLUSIONS: This is the first comprehensive study of the BRCA1/2 mutation spectrum in Bulgaria and will assist the establishment of efficient protocols for genetic testing and individualized risk assessment for Bulgarian breast/ovarian cancer patients and healthy individuals at a high-risk.

Validation of an NGS Approach for Diagnostic BRCA1/BRCA2 Mutation Testing.

BACKGROUND AND OBJECTIVE: Pathogenic mutations in BRCA1/2 tumor suppressor genes increase the lifetime risk for developing breast and ovarian cancer. The aim of the present study was to evaluate the sensitivity and specificity of the Ion Torrent PGM™ for diagnostic mutation screening of BRCA1/2 genes. METHODS: In the current study we included a cohort of 58 Bulgarian high-risk breast cancer patients to validate a next-generation sequencing approach for diagnostic mutation screening of the BRCA1/2 genes using the Ion Torrent Personal Genome Machine® (PGM™) platform. We have also optimized the workflow by comparing two different library preparation methods and using three software packages: NextGENE, Torrent Suite variantCaller, and Samtools/BCFtools to achieve detection of all variants with high specificity and sensitivity. RESULTS: We have validated a quick and accurate diagnostic test, with an overall specificity of 95.9% and sensitivity of up to 100%, which can be the first method of choice, followed by confirmation of the identified variants by Sanger sequencing. Our results prove that the Ion AmpliSeq™ BRCA1/2 Community Panel used with the PGM™ platform, and coupled with our variant selection pipeline, is able to detect all sequence variants discovered by Sanger sequencing. CONCLUSION: The application of the new test which outperforms the classical approach in turn-around time and price will have great impact in the clinical practice to identify the mutation carriers and guide the better personalized treatment of the patients, as well as to contribute for the improved prophylaxis in hereditary breast and ovarian cancer families.

Dominance of multidrug-resistant Denmark(14)-32 (ST230) clone among Streptococcus pneumoniae serotype 19A isolates causing pneumococcal disease in Bulgaria from 1992 to 2013.

A pneumococcal conjugate vaccine (PCV10) was introduced in Bulgarian national immunization program since April 2010. Clonal composition based on pulsed-field gel electrophoresis and multilocus sequence typing genotyping of 52 serotype 19A Streptococcus pneumoniae isolates was analyzed. These were invasive and respiratory isolates collected between 1992 and 2013 from both children (78.8% <5 years) and adults with pneumococcal infections. Multidrug resistance was found in 82.7% of all 19A isolates. The most prevalent genotype (63.5%) among serotype 19A pneumococcal strains was the multidrug-resistant clonal complex CC230, which is a capsular switched variant of the Denmark(14)-32 (ST230) global clone. The most frequent sequence type (ST) was ST230 (48.1%) and together with four other closely related STs (15.4%), belonging to ST1611, ST276, ST7466, and ST2013, which were single- and double-locus variants; they were included in the main CC230. The disappearance of highly drug-resistant ST663 clone and emergence of new clones as CC320 and CC199 was also observed among the rest 19A isolates. A comparison of clonal composition between invasive and noninvasive isolates did not show a great genetic diversity among both kinds of isolates. Continuous surveillance of serotype 19A population following the introduction of PCV10 is essential to evaluate the impact of the vaccine on the epidemiology of this serotype.