Prevalence of 16S rRNA methylase genes among ß-lactamase-producing Enterobacteriaceae clinical isolates in Saudi Arabia.

BACKGROUND: Co production of 16S rRNA methylases gene and ß-Lactamase gene among Enterobacteriaceae isolates conferring resistance to both therapeutic options has serious implications for clinicians worldwide. METHODS: To study co existence of 16S rRNA methylases (armA, rmtA, rmtB, rmtC, rmtD, and npmA) and ß-Lactamase (blaTEM-1, blaSHV-12, blaCTX-M-14) genes, we screened all phenotypic positive ß-Lactamase producing enterobacteriaceae by polymerase chain reaction (PCR) targeting above genes. A total of 330 enterobacteriaceae strains were collected during study period out of that 218 isolates were identified phenotypically as ß-Lactamase producers, which include 50 (22.9%) Escherichia coli; 92 (42.2%) Klebsiella pneumoniae, 44 (20.2%), Citrobactor freundii and 32 (14.7%) Enterobacter spp. RESULTS: Among this 218, only 188 isolates harbored the resistant gene for ß-Lactamase production. Major ß-Lactamase producing isolates were blaTEM-1 type. 122 (56 %) isolates were found to produce any one of the 16S rRNA methylase genes. A total of 116 isolates co produced b-Lactamase and at least one 16S rRNA methylases gene Co production of armA gene was found in 26 isolates with rmtB and in 4 isolates with rmtC. The rmtA and rmtD genes were not detected in any of the tested isolates. Six isolates were positive for a 16S rRNA methylase gene alone. CONCLUSION: ß-Lactamase producing isolates appears to coexist with 16S rRNA methylase predominantly armA and rmtB genes in the same isolate. We conclude the major ß-Lactamase and 16S rRNA methylases co-producer was K. pneumoniae followed by E. coli. We suggest further work on evaluating other ß-lactamases types and novel antibiotic resistance mechanisms among Enterobacteriaceae.

Serological and molecular capsular typing, antibiotic susceptibility of Streptococcus pneumoniae isolates from invasive and non-invasive infections.

Streptococcus pneumoniae causes life threatening infections and necessitate for impediment and controlling disease; to conquer this, information is needed about serotype distribution and patterns of antibiotic resistance. The present study was to determine the serotype distribution of S. pneumoniae isolated from the entire age group individual and to correlate this distribution with susceptibility. Cases of pneumococcal infections have been reviewed for serotyping and antibiotic susceptibility. Out of 117 pneumococcal isolates 45 (39%) were penicillin-resistant, 84 (72%) were erythromycin-resistant and 100% were co-trimoxazole resistant. The most frequently isolated serotypes were 23F, 19F, 14, 6B, 5, 6A, 19A and 9V. PCV7, PCV10 and PCV13 coverage was 68%, 79%, 87%, respectively. Similarly, there was similarity in PCV7 coverage for non invasive isolates (64.5%) and invasive isolates (72.2%). The study state that common pneumococcal serotypes were present in similar ways as reported in literature. A continuous survey of pneumococcal infected population is requirement and necessity for success of vaccination.

Cytopathic effects of toxogenic strains of Helicobacter pylori on different cell lines.

PURPOSE: Many virulence factors are involved in the pathomechanism of infection caused by Helicobacter pylori. Toxins such as vacuolating cytotoxin, encoded by the vacA gene and the immunogenic protein cagA, encoded by the cagA gene (cytotoxin-associated gene) are major factors conferring the property of virulence. The current study is aimed at isolation of H. pylori and separation of its toxin from antral biopsies of patients. MATERIALS AND METHODS: The following cell lines were used to demonstrate the cytopathic effect (CPE) of the separated toxin: African green monkey kidney (Vero), baby hamster kidney, human lung carcinoma (LLC-MK2), and human epithelial. RESULTS: H. pylori was isolated from 27 out of 45 patients (60%) selected for the study. CPE of H. pylori toxin was highly significant on Vero cells than other cell lines used as it reached a high dilution titer of toxin (1/16) in 13 isolated strains (48.15%). No significant difference in CPE of toxin in different dilutions was detected among other cell lines used in different groups. H. pylori toxin could be detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis as a distinct band with a molecular weight ranging between 66 and 97 kDa and closely related to 87 kDa. CONCLUSION: H. pylori vacuolating cytotoxin plays a vital role in the pathogenesis of gastroduodenal diseases (gastritis, gastric ulcer, duodenal ulcer, and gastric cancer). The Vero cell lines were found to be the most suitable form of tissue culture when compared with other cell lines used in our study for demonstrating the activity of H. pylori toxin.

Cardiac conduction abnormalities in a mouse model of Lyme borreliosis.

BACKGROUND: Borrelia Burgdorferi (BB) induces cardiac conduction abnormalities in infected humans. Mice models of Lyme disease have been developed, however their electrophysiologic (EP) properties of conduction are unknown. METHODS: Seventy-six C3H/J mice (BB infected and age- and gender-matched controls) underwent blinded in vivo EP studies. In a first phase of the study, 40 male C3H/J mice were divided into 2 groups: Group (A) mice were infected at age 3 (weeks) and studied at 5, and Group (B) mice were infected at 9 and studied at 11. In a second phase, 36 female mice were divided into 2 groups: Group (C) mice were infected at 3 weeks and studied at 5, and Group (D) mice were infected at 3 and studied at 11. RESULTS: Infected mice of group (A) and (C) had wider QRS complexes (21.0+/-1.6 versus 17.3+/-1.3ms, p< or =0.0001 and 20.3+/-2.1 versus 18.5+/-1.7, p = 0.05, respectively) compared to the healthy controls (HC). Infected mice of group (B) and group (D) were similar to the HC. In all groups, the presence of conduction abnormalities correlated very closely with the amount of inflammation on pathology. CONCLUSION: This study describes the first EP mouse model of Lyme carditis. C3H/J mice exhibit conduction abnormalities that are reversible 8 weeks after inoculation, closely paralleling the resolution of inflammation on pathology. This model can be a valuable tool in the developing and testing of new modalities for the prevention and treatment of Lyme carditis.

Improving survival from sudden cardiac arrest: the role of the automated external defibrillator.

CONTEXT: Sudden cardiac death is a major public health problem in the United States, and improving survival after out-of-hospital cardiac arrest has been the subject of intense study. Early defibrillation has been shown to be critical to improving survival. Use of automated external defibrillators (AEDs) has become an important component of emergency medical systems, and recent advances in AED technology have allowed expansion of AED use to nontraditional first responders and the lay public. OBJECTIVES: To examine advancements in AED technology, review the impact of AEDs on time to defibrillation and survival, and explore the future role of AEDs in the effort to improve survival following sudden cardiac arrest. DATA SOURCES: MEDLINE was searched for articles from 1966 through December 2000 (Medical Subject Headings: electric countershock, heart arrest, resuscitation, emergency medical services; keywords: automatic external defibrillator, automated external defibrillator, public access defibrillation). Reference lists of relevant articles, news releases, and product information from manufacturers were also reviewed. STUDY SELECTION: Initial MEDLINE search produced 4816 articles, from which 101 articles were selected for referencing based on having been published in a peer-reviewed journal and on relevance to the subject of the manuscript as determined by all 5 authors. DATA EXTRACTION: All studies were critically reviewed for relevance, accuracy, and quality of data and study design by all authors. DATA SYNTHESIS: Recent advances in AED technology and design have resulted in marked simplification of AED operation, improvements in accuracy and effectiveness, and reductions in cost. Use of AEDs by first responders and laypersons has reduced time to defibrillation and improved survival from sudden cardiac arrest in several communities. Initial studies of the cost-effectiveness of AED use in comparison with other commonly used treatments are favorable. CONCLUSION: The AED represents an efficient method of delivering defibrillation to persons experiencing out-of-hospital cardiac arrest and its use by both traditional and nontraditional first responders appears to be safe and effective. The rapidly expanding role of AEDs in traditional emergency medical systems is supported by the literature, and initial studies of public access to defibrillation offer hope that further improvements in survival after sudden cardiac death can be achieved.

Use of correlation waveform analysis in discrimination between anterograde and retrograde atrial electrograms during ventricular tachycardia.

INTRODUCTION: Discriminating between ventricular tachycardia (VT) with 1:1 ventriculoatrial association and sinus tachycardia can be difficult, even when assisted by intracardiac tracings. In this study, we used a new computer algorithm to perform correlation waveform analyses on intracardiac atrial electrograms to help distinguish between VT and sinus tachycardia. METHODS AND RESULTS: Electrophysiologic studies of 28 patients (22 men; age 66 +/- 14 years) with inducible VT and mean ejection fraction of 37% +/- 16% were analyzed. A template of an intracardiac high right atrial electrogram was obtained during sinus rhythm (SR). Atrial electrograms during SR and VT were compared with the template using the new algorithm, and correlation coefficients (rho) were generated. The correlation coefficient of SR beats with the template was 96.4% +/- 3.4%. During VT with AV dissociation and persistent SR, rho was 94.5% +/- 3.7% (P = NS). During VT with 1:1 retrograde conduction, rho was 70.6% +/- 11.3% (P < 0.0001). At a cutoff of 85%, rho had positive and negative predictive values of 99% and 96%, respectively. CONCLUSION: Our findings indicate that the new algorithm can reliably separate between anterograde and retrograde atrial activation during VT. It can, therefore, discriminate between sinus tachycardia and VT with 1:1 ventriculoatrial conduction and may be useful in preventing inappropriate shocks from dual chamber defibrillators.

Benign lipid envelope of the heart simulating a pericardial hematoma.

The hallmark of diagnosing a pericardial effusion by echocardiography is the presence of relatively sonolucent space outside of the cardiac structures. The location, size, mobility, and consistency of the pericardial space determined by echocardiography are considered to be reliable markers for defining pericardial processes. In certain clinical scenarios, however, it may be difficult to differentiate fluid from other pericardial processes, notably subepicardial adipose tissue. This case of a 76-year-old woman, who presented with possible cardiac tamponade after permanent pacemaker implantation, demonstrates some of the potential pitfalls in the diagnosis of pericardial space abnormalities.

Cardiac arrhythmias in the athlete.

Cardiac arrhythmias in the athlete are a frequent cause for concern. Some arrhythmias may be benign and asymptomatic, but others may be life threatening and a sign that serious cardiovascular disease is present. Physicians often are consulted with regard to arrhythmias, or symptoms consistent with arrhythmias, in athletes. Sinus bradyarrhythmias are common and even expected in athletes. These bradyarrhythmias are rarely a cause for concern. Heart block is unusual and merits a thorough workup. Atrial fibrillation may be more common in the athlete. Supraventricular tachycardias other than atrial fibrillation generally warrant consideration of radiofrequency ablation for cure of the tachyarrhythmia. Ventricular arrhythmias in the athlete generally occur in the setting of structural heart disease that is genetically determined (hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, anomalous coronary arteries) or acquired (coronary artery disease, myocarditis, idiopathic dilated cardiomyopathies). In these conditions, the arrhythmia generally is life threatening. Ventricular arrhythmias that occur in the athlete without structural heart disease are not thought to be life threatening. Athletes with structural heart disease and syncope and those with exertional syncope merit a complete evaluation.

Effect of low estrogen states in healthy women on dispersion of ventricular repolarization.

Our data show that although estrogen does not seem to affect the QT interval in healthy women, it significantly decreases the QT dispersion. This finding could provide an explanation to the gender differences in susceptibility to ventricular arrhythmias, besides the difference in the incidence of coronary artery disease.

ECG Findings in Active Patients: Differentiating the Benign From the Serious.

ECGs and cardiac rhythms of normal athletes can vary widely. The heightened vagal tone from athletic conditioning can result in variant ECG findings that may mimic serious disorders. ECG patterns of long-QT syndrome, arrhythmogenic right ventricular dysplasia, Wolff-Parkinson-White syndrome, and hypertrophic cardiomyopathy signal the need for further evaluation, therapy, and possible participation restriction. Radiofrequency ablation may be appropriate when symptomatic supraventricular arrhythmias or Wolff-Parkinson-White syndrome is present. Further research is needed to effectively distinguish normal ECG changes in the athlete from changes that underlie cardiac disease. Improvements in identifying athletes at risk of serious or life-threatening arrhythmias are also needed.

Predictors of ventricular tachycardia recurrence in 100 patients receiving tiered therapy defibrillators.

BACKGROUND AND HYPOTHESIS: Programmed electrical stimulation (PES) is a time-honored diagnostic tool in patients with ventricular tachyarrhythmias. The response to PES can be used to assess efficacy of pharmacologic or electrical therapy, as well as to obtain prognostic information. Reproducible induction of ventricular tachycardia with invasive electrophysiologic testing, or stimulation through defibrillator lead systems, can help optimize antiarrhythmic drug therapy and device programming during clinical follow-up. METHODS: We present our experience with 100 patients who had inducible sustained monomorphic ventricular tachycardia (SMVT) during invasive PES at baseline, and received a third-generation implantable cardioverter-defibrillator (ICD) alone, or in combination with antiarrhythmic drug therapy. Noninvasive programmed stimulation (NIPS) was performed prior to hospital discharge in 61 patients. RESULTS: The inducibility of SMVT was concordant between the invasive study and NIPS in a subgroup of 40 (82%) patients who had invasive PES on the same drug regimen. During a mean follow-up of 16 months, there were 12 nonarrhythmic deaths and recurrence of spontaneous SMVT in 36 (40%) of the surviving patients. Using a Cox proportional hazards model, the following variables were associated with early arrhythmia recurrence: persistent inducibility of SMVT during the NIPS session (relative risk 11, range 2.6-47); induction of SMVT with a cycle length > 280 ms during invasive baseline PES (2.5, 1.2-5) and presence of prior inferior myocardial infarction (2.1, 1-4.2). Timing to initial recurrence of spontaneous tachycardia was unaffected by other clinical variables or concomitant antiarrhythmic drug use. CONCLUSION: Programmed electrical stimulation techniques offer insight into the patterns of spontaneous ventricular tachycardia recurrence and have significant practical utility in the management of patients receiving third-generation ICDs.

Analysis of intracardiac electrograms showing monomorphic ventricular tachycardia in patients with implantable cardioverter-defibrillators.

Ventricular tachycardia (VT) initiation and its relation to various clinical factors was studied by reviewing intracardiac electrograms from patients with implantable cardioverter-defibrillators. Events were divided into (1) sudden onset without preceding ventricular premature complexes (VPCs), (2) extrasystolic onset with VPCs, or (3) paced, depending on the type and morphology of the last 5 beats before initiation of VT. Prematurity index, sinus rate, cycle length, and presence of short-long-short sequence for each episode was noted. A total of 268 episodes of VT among 52 patients were analyzed. Extrasystolic initiation was the most frequent pattern (177; 66%) followed by sudden onset (75; 28%) and paced (16; 6%). Among extrasystolic onset, 99 episodes (56%) were due to multiple VPCs and 149 episodes (84%) had different VPC morphology than the subsequent VT. Among pacing-induced VT, 13 of 16 episodes were due to inappropriate pacing due to undersensing of prior R waves. Sudden-onset episodes were slower (mean cycle length 383+/-97 ms) than extrasystolic (mean cycle length 336+/-88 ms, p = 0.002) and paced (mean cycle length 313+/-85 ms, p = 0.01) onset. Patients in the sudden-onset group had better left ventricular ejection fraction (33+/-15%) than the extrasystolic (29+/-11%, p<0.001) and paced (28+/-14%, p<0.01) groups. Extrasystolic onset with multiple, late coupled VPCs was the most common pattern of VT initiation and was associated with lower ejection fraction. Sudden-onset initiation was more common with better preserved systolic function.

Connexin40-deficient mice exhibit atrioventricular nodal and infra-Hisian conduction abnormalities.

INTRODUCTION: Previous electrophysiologic investigations have described AV conduction disturbances in connexin40 (Cx40)-deficient mice. Because expression of Cx40 occurs predominantly in the atria and His-Purkinje system of the mouse heart, the AV conduction disturbances were thought to be secondary to disruption in His-Purkinje function. However, the lack of a His-bundle electrogram recording in the mouse has limited further investigation of the importance of Cx40. Using a novel technique to record His-bundle recordings in Cx40-deficient mice, we define the physiologic importance of deficiencies in Cx40. METHODS AND RESULTS: Ten Cx40-/- mice and 11 Cx40+/+ controls underwent a blinded, in vivo, closed chest electrophysiology study at 9 to 12 weeks of age. In the Cx40-/- mice, the PR interval was significantly longer compared with Cx40+/+ mice (44.6+/-6.4 msec vs 36.0+/-4.1 msec, P = 0.002). Not only the HV interval (14.0+/-3.0 msec vs 10.4+/-1.2 msec, P = 0.003) but also the AH interval (33.2+/-4.8 msec vs 27.1+/-3.7 msec, P = 0.006), AV Wenckebach cycle lengths, and AV nodal effective and functional refractory periods were prolonged in Cx40-/- compared with Cx40+/+ mice. CONCLUSION: Cx40-deficient mice exhibit significant delay not only in infra-Hisian conduction, as would be expected from the expression of Cx40 in the His-Purkinje system but also in the electrophysiologic parameters that reflect AV nodal conduction. Our data suggest a significant role of Cx40 in atrionodal conduction and/or in proximal His-bundle conduction.

Effect of saline irrigation flow rate on temperature profile during cooled radiofrequency ablation.

INTRODUCTION: Cooled radiofrequency ablation has been developed clinically for the treatment of ventricular tachycardia. Although clinical studies employ a constant saline flow rate for cooling, we hypothesized that varying the flow rates might optimize the temperature profile at depth. METHODS: In excised ovine left ventricle, we compared the temperature profile from a catheter tip electrode thermocouple to those placed at depths of 0.0 mm, 1.0 mm, and 2.0 mm. We compared the following settings: 20 Watts without flow, 20 Watts with 0.3 cc/sec flow, 20 Watts with 0.5cc/sec flow, and 70C surface temperature without flow (temperature control). RESULTS: The temperatures decreased from 77.5 +/-10.5 degrees C, 91.7+/-6.3 degrees C, 65.5 +/- 11.8 degrees C, and 52.5 +/- 11.8 degrees C at 20W without saline irrigation at the tip, 0.0mm, 1.0mm, and 2.0 mm, respectively, to 33.0+/-1.4 degrees C, 63.4 +/- 7.0 degrees C, 57.1+/-5.8 degrees C, 49.9+/-5.8 degrees C+ at 20W with 0.5 ml/sec flow (*p<0.01, +p = 0.09). The lesion volumes were 79.6mm3 for 20W without flow, 64.1 mm3 for 20W with 0.3 ml/sec flow, 47.5 mm3 for 20W with 0.5 ml/sec flow, and 28.6 mm3 for temperature control. CONCLUSIONS: We conclude that 1) the temperature profile greatly depends upon the rate of saline flow for cooling; 2) at high flow rates, the 0.0 mm and 1.0 mm temperatures are similar; 3) even at high irrigation rates, lesion size is greater than for temperature control; 4) the tip temperature significantly underestimates the surface temperature and improved methods of measuring temperature are needed.

Safety and efficacy of a steerable temperature monitoring microwave catheter system for ventricular myocardial ablation.

INTRODUCTION: Radiofrequency current delivered during cardiac ablation is limited by a rise in impedance secondary to coagulum formation on the ablation electrode. Microwave antennas continue to deliver energy despite the presence of coagulum; thus, temperature control of the ablation electrode may be even more important for microwave than for radiofrequency ablations to avoid thromboembolic risks. The purpose of this study was to test the safety and efficacy of an ablation system utilizing a feedback control system to maintain a fixed target temperature for creating lesions with multiple applications of microwave energy. METHODS AND RESULTS: Microwave ablation was assessed using an 8.5-French catheter at 2 to 4 sites in 11 dogs. Microwave energy delivery was performed for 60 seconds three times at the same site. Power was regulated using a feedback control mechanism to maintain a target temperature of 75 degrees C. Ambulatory ECG monitoring was performed before and after ablation to assess arrhythmia occurrence. After follow-up, the dogs were euthanized, and lesion dimensions measured after fixation. The mean power applied to achieve the target temperature of 75 degrees C was 9.3+/-44 W. The mean depth of the lesions was 8.8+/-4.2 mm. The mean volume of the lesions was 304+/-240 mm3. Forty-four percent of the lesions were transmural. No endocardial thrombus was found. Ventricular tachycardia was observed acutely but resolved after 1 week. CONCLUSION: Temperature feedback control systems for microwave ablation using a temperature-controlled system is feasible for myocardial ablation and creates uniform and large lesions; however, such large lesions can be acutely proarrhythmic.

Microwave ablation using a spiral antenna design in a porcine thigh muscle preparation: in vivo assessment of temperature profile and lesion geometry.

INTRODUCTION: Theoretical studies have suggested that microwave energy can increase the depth of heating compared with radiofrequency energy. A spiral microwave antenna design may have advantages over previous designs using smaller designs because the resulting power deposition pattern is considerably larger than the catheter diameter. We tested the efficacy of a spiral antenna using microwave energy in a porcine thigh muscle preparation. METHODS AND RESULTS: In five anesthetized pigs, the thigh muscle was exposed and bathed in heparinized bovine blood (36 degrees to 37 degrees C). A helical microwave catheter with a fiberoptic thermometer attached to the distal end was positioned perpendicular to the thigh muscle. The antenna-tissue interface and tissue temperatures at depths of 3.0 and 6.0 mm were measured. A 915-MHz microwave generator delivered energy at one of three power outputs (50, 100, or 150 W) for 60 seconds. Seventy lesions were created: 50 W (n = 23), 100 W (n = 24), and 150 W (n = 23). The mean depths at 50, 100, and 150 W were 4.3 +/- 1.8 mm, 7.2 +/- 1.7 mm, and 9.4 +/- 0.9 mm, respectively. Lesion depth (R = 0.96, P = 0.05), maximum surface dimension (R = 0.99, P = 0.06), and volume (R = 0.99, P = 0.04) were closely correlated to the power applied. CONCLUSION: Power is an important determinant of lesion size using a spiral microwave antenna. A novel, spiral microwave antenna design can create lesions of significant depth that may be applicable for the ablative therapy of ventricular tachycardia.