Genetic analysis identifies the SLC4A3 anion exchanger as a major gene for short QT syndrome.

BACKGROUND: A variant in the SLC4A3 anion exchanger has been identified as a novel cause of short QT syndrome (SQTS), but the clinical importance of SLC4A3 as a cause of SQTS or sudden cardiac death remains unknown. OBJECTIVE: The purpose of this study was to investigate the prevalence of potential disease-causing variants in SQTS patients using gene panels including SLC4A3. METHODS: In this multicenter study, genetic testing was performed in 34 index patients with SQTS. The pathogenicity of novel SLC4A3variants was validated in a zebrafish embryo heart model. RESULTS: Potentially disease-causing variants were identified in 9 (26%) patients and were mainly (15%) located in SLC4A3: 4 patients heterozygous for novel nonsynonymous SLC4A3 variants-p.Arg600Cys, p.Arg621Trp, p.Glu852Asp, and p.Arg952His-and 1 patient with the known p.Arg370His variant. In other SQTS genes, potentially disease-causing variants were less frequent (2× in KCNQ1, 1× in KCNJ2, and CACNA1C each). SLC4A3 variant carriers (n = 5) had a similar heart rate but shorter QT and J point to T wave peak intervals than did noncarriers (n = 29). Knockdown of slc4a3 in zebrafish resulted in shortened heart rate-corrected QT intervals (calculated using the Bazett formula) that could be rescued by overexpression of the native human SLC4A3-encoded protein (AE3), but neither by the mutated AE3 variants p.Arg600Cys, p.Arg621Trp, p.Glu852Asp nor by p.Arg952His, suggesting pathogenicity of these variants. Dysfunction in slc4a3/AE3 was associated with alkaline cytosol and shortened action potential of cardiomyocytes. CONCLUSION: In about a quarter of patients with SQTS, a potentially disease-causing variant can be identified. Nonsynonymous variants in SLC4A3 represent the most common cause of SQTS, underscoring the importance of including SLC4A3 in the genetic screening of patients with SQTS or sudden cardiac death.

Diagnostic Yield of Genetic Testing in Young Patients With Atrioventricular Block of Unknown Cause.

Background The cause of atrioventricular block (AVB) remains unknown in approximately half of young patients with the diagnosis. Although variants in several genes associated with cardiac conduction diseases have been identified, the contribution of genetic variants in younger patients with AVB is unknown. Methods and Results Using the Danish Pacemaker and Implantable Cardioverter Defibrillator (ICD) Registry, we identified all patients younger than 50 years receiving a pacemaker because of AVB in Denmark in the period from January 1, 1996 to December 31, 2015. From medical records, we identified patients with unknown cause of AVB at time of pacemaker implantation. These patients were invited to a genetic screening using a panel of 102 genes associated with inherited cardiac diseases. We identified 471 living patients with AVB of unknown cause, of whom 226 (48%) accepted participation. Median age at the time of pacemaker implantation was 39 years (interquartile range, 32-45 years), and 123 (54%) were men. We found pathogenic or likely pathogenic variants in genes associated with or possibly associated with AVB in 12 patients (5%). Most variants were found in the LMNA gene (n=5). LMNA variant carriers all had a family history of either AVB and/or sudden cardiac death. Conclusions In young patients with AVB of unknown cause, we found a possible genetic cause in 1 out of 20 participating patients. Variants in the LMNA gene were most common and associated with a family history of AVB and/or sudden cardiac death, suggesting that genetic testing should be a part of the diagnostic workup in these patients to stratify risk and screen family members.

Dilated cardiomyopathy caused by truncating titin variants: long-term outcomes, arrhythmias, response to treatment and sex differences.

BACKGROUND: Truncating variants in titin (TTNtv) are the most common cause of dilated cardiomyopathy (DCM). We evaluated the genotype-phenotype correlation in TTNtv-DCM, with a special focus on long-term outcomes, arrhythmias, response to treatment and sex-related presentation. METHODS: Data on patient characteristics and outcomes were collected retrospectively from electronic health records of patients genotyped at two Danish heart transplantation centres. RESULTS: We included 115 patients (66% men). At diagnosis of DCM, mean age was 46±13 years and left ventricular ejection fraction (LVEF) was 28%±13%. During a median follow-up of 7.9 years, 26% reached a composite outcome of left ventricular assist device implantation, heart transplantation or death. In 20% an arrhythmia preceded the DCM diagnosis. In total, 43% had atrial fibrillation (AF) and 23% had ventricular arrhythmias. Long-term left ventricular reverse remodelling (LVRR; LVEF increase ≥10% points or normalisation) was achieved in 58% and occurred more frequently in women (72% vs 51%, p=0.042).In multivariable proportional hazards analyses, occurrence of LVRR was a strong independent negative predictor of the composite outcome (HR: 0.05 (95% CI 0.02 to 0.14); p<0.001). Female sex independently predicted lower rates of ventricular arrhythmias (HR: 0.33 (95% CI 0.11 to 0.99); p=0.05), while the location of the TTNtv was not associated with cardiovascular outcomes. CONCLUSION: DCM caused by TTNtv presented in midlife and was associated with a high burden of AF and ventricular arrhythmias, which often preceded DCM diagnosis. Furthermore, LVRR occurred in a high proportion of patients and was a strong negative predictor of the composite outcome. Female sex was positively associated with occurrence of LVRR and longer event-free survival.

Short QTc interval in males with klinefelter syndrome-influence of CAG repeat length, body composition, and testosterone replacement therapy.

BACKGROUND: Klinefelter syndrome (KS) is a sex chromosomal aneuploidy (47,XXY) affecting 1/660 males. Based on findings in Turner syndrome, we hypothesized that electrocardiogram (ECG) abnormalities would be present in males with KS. OBJECTIVE: To investigate ECGs in males with KS and compare with controls. METHODS: Case control study of 62 males with KS and 62 healthy males matched on age. The primary outcome parameter was a difference in the ECG presentation between the two groups. The ECGs were analyzed by one blinded examiner (intraobserver variability 0.2-2.1%). The QT-interval was measured using "teach-the-tangent" method excluding the U-wave. QTc was calculated using Bazett's equation, Hodges' equation, and a linear regression model. Body mass index, abdominal fat, and muscle mass as well as sex hormone levels were secondary parameters. The prevalence of mutations in genes related to short QT syndrome was determined in participants with a QTc < 330 ms. RESULTS: Compared to controls, the QTc-interval was shorter (P = 0.02-0.06) in males with KS depending on the applied correction method. QTc was shortest among testosterone (T)-treated males with KS, while untreated and thus hypogonadal KS had QTc interval comparable to controls. No mutations in genes related to short QT syndrome were found. CONCLUSION: We found short QTc interval in males with KS, with further shortening of the QTc interval by T. These results suggest that genes on the X chromosome could be involved in regulation of the QTc interval and that T treatment may aggravate this mechanism.

Comparison of the Abbott RealTime CT new formulation assay with two other commercial assays for detection of wild-type and new variant strains of Chlamydia trachomatis.

In an analytical-method comparison study of clinical samples, the Abbott RealTime CT new formulation assay (m2000 real-time PCR), consisting of a duplex PCR targeting different parts of the cryptic plasmid in Chlamydia trachomatis, was compared both with version 2 of the Roche Cobas TaqMan CT assay, comprising a duplex PCR for a target in the cryptic plasmid and the omp1 gene, and with the Gen-Probe Aptima Combo 2 assay (AC2) targeting the C. trachomatis 23S rRNA molecule. First-catch urine samples from Sweden were tested in Malmö, Sweden, for C. trachomatis with the m2000 real-time PCR assay and with an in-house PCR for the new variant C. trachomatis strain with a deletion in the cryptic plasmid. Aliquots of the urine samples were sent to Aarhus, Denmark, where they were further examined with the TaqMan CT and AC2 assays. A positive prevalence of 9.1% (148/1,632 urine samples examined) was detected according to the combined reference standard. The sensitivities and specificities of the three assays were as follows: for the Abbott m2000 assay, 95.3% (141/148) and 99.9% (1,483/1,485), respectively; for the Roche TaqMan assay, 82.4% (122/148) and 100.0% (1,485/1,485); and for the Gen-Probe AC2 assay, 99.3% (147/148) and 99.9% (1,484/1,485). The plasmid mutant strain was detected in 24% (36/148) of the C. trachomatis-positive samples. There is a difference in sensitivity between the new formulations of the Abbott and the Roche assays, but both assays detected the wild-type and new variant C. trachomatis strains equally well.

Typing Chlamydia trachomatis: from egg yolk to nanotechnology.

A historical review is provided of the various methods used for half a century to differentiate and type Chlamydia trachomatis strains. Typing of C. trachomatis is an important tool for revealing transmission patterns in sexual networks, and enabling association with clinical manifestations and pathogenicity. Serotyping using the major outer membrane protein (MOMP) has been the mainstay of epidemiological work for several decades. However, the development of nucleic acid amplification techniques (NAAT) and easy access to sequencing have shifted the focus from MOMP serotypes to omp1 genotypes. However, insufficient epidemiological resolution is achieved by characterization of both MOMP and omp1. This calls for new high-resolution genotyping methods applying for example a multilocus variable number tandem repeat assay (MLVA) or multilocus sequence typing (MLST). The futuristic nanotechnology already seems at hand to further simplify and automate the high-resolution genotyping method based on NAAT and sequencing of various targets in the C. trachomatis genome. Thereby, a high throughput can be achieved and more epidemiological information can be obtained. However, it is important to realize that culture of C. trachomatis may still be needed to detect and characterize new variants of C. trachomatis.

Eight-plex PCR and liquid-array detection of bacterial and viral pathogens in cerebrospinal fluid from patients with suspected meningitis.

We here report on the development of a novel multiplex PCR with product detection in a Luminex 100 suspension array system. The assay covers the nine most important bacterial and viral pathogens found in Danish meningitis patients. The microorganisms include Neisseria meningitidis, Streptococcus pneumoniae, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Streptococcus agalactiae, herpes simplex virus types 1 and 2, and varicella-zoster virus. The study was based on 1,187 samples, of which 55 were found to be positive by PCR. The assay was found to have an excellent sensitivity and an excellent specificity compared to the results of a "gold standard," defined by routine laboratory tests, for the two most important pathogens, S. pneumoniae (95 and 99.1%, respectively) and N. meningitidis (100 and 99.7%, respectively). The method provides a valuable supplement to the traditional microscopy and culture of cerebrospinal fluid (CSF) samples in a routine diagnostic setting, and results can be available within 1 workday. The method is suitable for use for the initial screening and identification of nine important microorganisms in CSF samples from patients with suspected meningitis. Compared to microscopy and culture of CSF, this rapid and sensitive method will support physicians with the selection of the appropriate antimicrobial agents and the initiation of timely treatment in the absence of live microorganisms in the CSF.

Comparison of Gen-probe transcription-mediated amplification, Abbott PCR, and Roche PCR assays for detection of wild-type and mutant plasmid strains of Chlamydia trachomatis in Sweden.

The clinical performance of two nucleic acid amplification assays targeting the cryptic plasmid and two assays targeting rRNA molecules in Chlamydia trachomatis was examined. First-catch urine samples from Malmoe, Sweden, were tested for C. trachomatis with the Abbott real-time PCR assay m2000 and an in-house PCR for the new variant strain of C. trachomatis with a deletion in the cryptic plasmid. Aliquots of the urine samples were sent to Aarhus, Denmark, and further examined with the Roche COBAS Amplicor CT (RCA) PCR, the Gen-Probe Aptima Combo 2 assay (AC2) targeting the C. trachomatis 23S rRNA, and the Aptima C. trachomatis assay (ACT) targeting the 16S rRNA molecule. A positive prevalence of 9% (163/1,808 urine samples examined) was detected according to the combined reference standard. The clinical sensitivity and specificity of the four assays were as follows: for ACT, 100% (163/163) and 99.9% (1,643/1,645), respectively; for AC2, 100% (163/163) and 99.6% (1,640/1,645); for m2000, 68.7% (112/163) and 99.9% (1,644/1,645); for RCA, 63.8% (104/163) and 99.9% (1,643/1,645). The two Gen-Probe assays detected all mutant strains characterized by the in-house PCR as having the deletion in the cryptic plasmid, whereas the Roche and the Abbott PCRs targeting the plasmid were both unable to detect the plasmid mutant. The difference in clinical sensitivity between the plasmid PCR assays m2000 and RCA, on the one hand, and the rRNA assays AC2 and ACT, on the other, could be attributed almost exclusively to the presence of the plasmid mutant in about one-quarter of the Chlamydia-positive samples examined.

Broad-range PCR as a supplement to culture for detection of bacterial pathogens in patients with a clinically diagnosed spinal infection.

We aimed to evaluate broad-range PCR and subsequent sequencing compared to conventional culture in the diagnosis of spinal infection. The method was a prospective study of all patients admitted to Aarhus University Hospital for surgery during a 12-months period with a clinically diagnosed infection of the spine. Samples from patients undergoing surgery for non-infectious causes (malignancy etc.) were included as control group. Specimens were submitted to conventional culture and molecular investigation with 16S rRNA gene amplification and sequence analysis. 38 patients were included in the study (clinically diagnosed spinal infections=18; non-infectious diseases=20). The specificity was excellent for both culture and PCR (95% and 100%, respectively). A true culture positive result was obtained in 50% of patients (9/18) and 61% was positive (11/18) by broad-range PCR. When combined, culture and PCR allowed for a microbiological diagnosis in 72% of patients (13/18). A positive culture was found only in patients treated < or =7 d compared to < or =16 d for PCR. However, PCR and culture result were equally negatively affected by duration of treatment. The combination of culture and broad-range PCR substantially adds to the number of microbiological diagnoses obtained, and improves the clinician's opportunity to tailor therapy to individual patients.

Clonal spread of Staphylococcus aureus with reduced susceptibility to oxacillin in a dermatological hospital unit.

In November 2000, we became aware of isolates of Staphylococcus aureus with borderline resistance to oxacillin (BORSA) from patients in the Department of Dermatology, Aarhus University Hospital. The objective was to describe the isolates phenotypically and genotypically and to assess possible transmission routes in order to intervene and prevent further spread. Clonality of the isolates was confirmed by pulsed field gel electrophoresis. Several breaches in infection control procedures were revealed suggesting both direct and indirect transmission between patients. Defective skin barriers, high carrier rates of S. aureus in dermatological patients and high consumption rates of dicloxacillin in the department might facilitate transmission. Following improvement of the general infection control measures, and after reassessment of the antibiotic policy in the department, the outbreak has disappeared.

Different polymerase chain reaction-based analyses for culture-negative endocarditis caused by Streptococcus pneumoniae.

Two cases of culture-negative infective endocarditis caused by Streptococcus pneumoniae are presented. Conventional bacteriological methods were compared with 2 different polymerase chain reaction (PCR)-based analyses: PCR amplification with primers specific for S. pneumoniae, and broad-range PCR followed by sequencing. PCR-based analyses can be a valuable supplement to traditional bacteriological analyses.