Yang Wook Kim

IDENTIFICATION OF COAGULASE-NEGATIVE STAPHYLOCOCCI ISOLATED FROM CONTINUOUS AMBULATORY PERITONEAL DIALYSIS FLUID USING 16S RIBOSOMAL RNA, tuf, AND SodA GENE SEQUENCING

♦ Introduction: Coagulase-negative staphylococcus (CoNS) is the most common pathogen in continuous ambulatory peritoneal dialysis (CAPD)–associated peritonitis. There is no well-organized, standardized database for CoNS, and few studies have used gene sequencing in reporting species distribution in CAPD peritonitis. In the present study, we used 3 housekeeping genes to evaluate the prevalence of CoNS isolated from CAPD peritonitis episodes and to estimate the accuracy of, and the characteristic differences between, these genes for species identification. ♦ Methods: All 51 non-duplicated CoNS isolates obtained from CAPD peritonitis between April 2006 and May 2008 were used. The strains were identified by polymerase chain reaction and by direct sequencing using the 16S ribosomal RNA (rRNA), tuf, and sodA genes. We determined species distribution, and using selected databases, we analyzed the characteristics and diagnostic utility of the individual genes for species identification. ♦ Results: In GenBank (National Institutes of Health, Bethesda, MD, USA), we found 49 type or reference strains for CoNS 16S rRNA, 17 for tuf, and 46 for sodA, and we used those data for sequence-similarity comparisons with CAPD isolates. Among our 51 strains, S. epidermidis (66.7%) was the most common, followed by S. haemolyticus (11.8%), S. warneri (7.8%), S. caprae (5.9%), S. capitis (3.9%), and S. pasteuri (2.0%). For 1 strain, different species results were obtained with each gene. The identification rates with 16S rRNA, sodA, and tuf gene sequencing were 84.0%, 96.0%, and 92.2% respectively. The discrimination capability of 16S rRNA gene was lower in a few individual species, and for the sodA gene, the percentage similarity to sequences from reference strains was also lower. The tuf gene had excellent identification capacity, but relatively few type strains are available in public databases. The 16S rRNA gene did not discriminate between S. caprae and S. capitis. The sodA gene showed a similarity rate that was lower than that for sequences of the 16S rRNA gene. The tuf type strain sequences for S. caprae and S. pasteuri are not available in public databases. ♦ Conclusions: The sodA, tuf, and 16S rRNA genes were very useful for CoNS identification. Each has its own characteristics of similarity, discriminative power, and inclusion in databases.

Additional antihypertensive effect of magnesium supplementation with an angiotensin II receptor blocker in hypomagnesemic rats

Background/Aims Magnesium (Mg) is an essential element for vascular function and blood pressure regulation. Several studies have demonstrated that Mg concentration is inversely associated with blood pressure, and that Mg supplementation attenuates hypertension. The purpose of this study was to evaluate the effect of dietary Mg supplementation on the blood pressure effects of an angiotensin II receptor blocker (ARB) in hypomagnesemic rats. Methods Fifty male Sprague-Dawley rats were randomly divided into Mg-deficient (n = 30), normal diet plus Mg (n = 10), and control groups (n = 10). Mg-free, high-Mg, and normal-Mg diets were respectively fed to the rats. After 14 weeks, 10 of the 30 Mg-deficient rats were treated with Mg, 10 Mg-deficient rats received an ARB, and 10 Mg-deficient rats received an ARB plus Mg for 4 weeks. Results Systolic blood pressure was significantly higher in the Mg-deficient rats than in the control rats at week 14. Hypomagnesemic rats exhibited decreased systolic blood pressure after treatment with Mg, and systolic blood pressure showed a greater decrease after ARB treatment. Treatment with the ARB/Mg combination resulted in the greatest decrease in systolic blood pressure. Mg deficiency did not affect the serum angiotensin II level, but did increase the serum aldosterone concentration. Concomitant Mg/ARB supplementation significantly decreased the elevated serum aldosterone level in hypomagnesemic rats. Kidney tissues of the hypomagnesemic rats revealed mild to moderate inflammatory infiltrates. Mg and/or ARB treatment did not reverse the inflammatory reaction in the kidneys of hypomagnesemic rats. Conclusions Concurrent dietary Mg supplementation can enhance ARB-induced blood pressure reduction in rats with hypomagnesemic hypertension.

Antimicrobial-induced Electrolyte and Acid-Base Disturbances

Antimicrobials are one of the most widely prescribed classes of therapeutic agents. Although adverse effects of antimicrobials are generally minimal and reversible, serious sequelae can sometimes remain, such as unusual forms of renal failure, acid base disturbance and electrolyte abnormalities. Many antimicrobials, especially vancomycin or aminoglycosides, are associated with development of acute renal failure caused by acute tubular necrosis, allergic acute interstitial nephritis, or vasculitis. Besides, some antimicrobial agents can cause serious fluid and electrolyte imbalance. To prevent these serious consequences, early recognition and correction of their harmful renal and electrolyte effects are required.

Confronting Practical Problems for Initiation of On-line Hemodiafiltration Therapy

Conventional hemodialysis, which is based on the diffusive transport of solutes, is the most widely used renal replacement therapy. It effectively removes small solutes such as urea and corrects fluid, electrolyte and acid-base imbalance. However, solute diffusion coefficients decreased rapidly as molecular size increased. Because of this, middle and large molecules are not removed effectively and clinical problem such as dialysis amyloidosis might occur. Online hemodiafiltration which is combined by diffusive and convective therapies can overcome such problems by removing effectively middle and large solutes. Online hemodiafiltration is safe, very effective, economically affordable, improving session tolerance and may improve the mortality superior to high flux hemodialysis. However, there might be some potential limitations for setting up online hemodiafiltaration. In this article, we review the uremic toxins associated with dialysis, definition of hemodiafiltration, indication and prescription of hemodiafiltration and the limitations of setting up hemodiafiltration.

Coombs Negative Autoimmune Hemolytic Anemia in Crohn’s Disease

Patient: Female, 41 Final Diagnosis: Coombs negative autoimmune hemolytic anemia Symptoms: Dark urine • dizziness • dyspnea Medication: — Clinical Procedure: Immunoradiometric assay for RBC-IgG Specialty: Hematology Objective: Rare disease Background: Anemia is a common, important extraintestinal complication of Crohn’s disease. The main types of anemia in patients with Crohn’s disease are iron deficiency anemia and anemia of chronic disease. Although patients with Crohn’s disease may experience various type of anemia, autoimmune hemolytic anemia (AIHA) in patients with Crohn’s disease, especially Coombs-negative AIHA, is very rare. Case Report: A 41-year-old woman with Crohn’s disease presented to our emergency room (ER) with dark urine, dizziness, and shortness of breath. The activity of Crohn’s disease had been controlled, with Crohn’s disease activity index (CDAI) score below 100 point. On physical examination, the patient had pale conjunctivae and mildly icteric sclerae. Serum bilirubin was raised at 3.1 mg/dL, lactate dehydrogenase (LDH) level was 1418 U/L and the haptoglobin level was <3 mg/dL. Results of direct and the indirect Coombs tests were all negative. We then measured the RBC-IgG to evaluate the possibility of Coombs-negative AIHA. The result revealed that RBC-IgG level was 352 IgG molecules/cell, with the cut-off value at 78.5 IgG molecules/cell. Conclusions: We report a case of Coombs-negative AIHA in a patient with Crohn’s disease with chronic anemia, diagnosed by red blood cell-bound immunoglobulin G (RBC-IgG) and treated with steroids therapy.

Population Pharmacokinetic Analysis of Doripenem after Intravenous Infusion in Korean Patients with Acute Infections

ABSTRACT We investigated the population pharmacokinetics (PK) of doripenem in Korean patients with acute infections and determined an appropriate dosing regimen using a Monte Carlo simulation for predicting pharmacodynamics (PD). Patients (n = 37) with a creatinine clearance (CLCR) of 20 to 50 ml/min or >50 ml/min who received a 250-mg or 500-mg dose of doripenem over the course of 1 h every 8 h, respectively, were included in this study. Blood samples were taken predosing and 0 h, 0.5 h, and 4 to 6 h after the fourth infusion. A nonlinear mixed-effect modeling tool was used for the PK analysis and pharmacodynamic simulation; doripenem PK were well described by a one-compartment model. The population mean values of the body weight (WT)-normalized clearance (CL/WT) and the body weight-normalized volume of distribution (V/WT) were 0.109 liter/h/kg of body weight (relative standard error, 9.197%) and 0.280 liter/kg (relative standard error, 9.56%), respectively. Doripenem CL was significantly influenced by CLCR. The proposed equation to estimate doripenem CL in Korean patients was CL/WT = 0.109 × WT × (CLCR/57)0.688, where CL/WT is in liters per hour per kilogram. CL in Korean patients was expected to be lower than that in Caucasian patients, regardless of renal function. The Monte Carlo simulation showed that 90% attainment of target PK/PD magnitudes could be achieved with the usual dosing regimens when the MIC was ≤1 mg/liter. However, prolonged infusions (4 h) should be considered, especially when patients have augmented renal function and for patients infected with pathogens with a high MIC. Our results provide an individualized doripenem dosing regimen for patients with various renal functions and for patients infected with bacteria with decreased susceptibility.

Renal Infarction Caused by Isolated Spontaneous Renal Artery Intramural Hematoma

Patient: Male, 46 Final Diagnosis: Renal infarction Symptoms: Flank pain Medication: — Clinical Procedure: CT Specialty: Nephrology Objective: Rare disease Background: Acute renal infarction is an uncommon condition resulting from an obstruction or a decrease in renal arterial blood flow. Isolated spontaneous renal artery intramural hematoma is a rare cause of renal infarction. Case Report: A 46-year-old healthy man presented to our emergency room because of sudden onset of severe right flank pain. An enhanced abdominal computed tomography scan showed a low-attenuated lesion in the lateral portion of the right kidney but no visible thromboembolisms in the main vessels. Computed tomography angiography revealed acute infarction resulting from intramural hematoma of the anterior segmental artery of the right kidney, with distal occlusion. Conclusions: The rarity and non-specific clinical presentation of renal infarction often lead to a delayed diagnosis that may result in impaired renal function. Clinical suspicion is important in the early diagnosis, and intramural hematoma of the renal artery should be considered the cause of renal infarction even in healthy patients without pre-disposing factors.

Population Pharmacokinetic Analysis of Meropenem After Intravenous Infusion in Korean Patients With Acute Infections

PURPOSE The aim of this study was to investigate the population pharmacokinetic (PK) profile of meropenem in Korean patients with acute infections. METHODS The study included 37 patients with a creatinine clearance ≤50 or >50 mL/min who received a 500- or 1000-mg dose of meropenem, respectively, infused intravenously over 1 hour every 8 hours. Blood samples were collected before and at 1, 1.5, and 5 hours after the start of the fourth infusion. The population PK analysis was conducted by using nonlinear mixed effect modeling software (NONMEM). Monte-Carlo simulations were performed to identify optimal dosing regimens. FINDINGS Thirty-seven subjects completed the study. Meropenem PK variables were well described by using a one-compartment model. The typical values (relative SE) for weight-normalized clearance (CL) and Vd were 0.266 L/h/kg (12.29%) and 0.489 L/kg (11.01%), respectively. Meropenem CL was significantly influenced by the serum creatinine level, which explained 11% of the interindividual CK variability. The proposed equation to estimate meropenem CL in Korean patients was as follows: CL (L/h) = 0.266 × weight × [serum creatinine/0.74]-1.017. The simulation results indicate that the current meropenem dosing regimen may be suboptimal in patients infected with normal or augmented renal function. IMPLICATIONS Prolonged infusions of meropenem over at least 2 hours should be considered, especially in patients with augmented renal function and those infected with pathogens for which the minimum inhibitory meropenem concentration is >1 μg/mL. Our results suggest an individualized meropenem dosing regimen for patients with abnormal renal function and those infected with pathogens with decreased in vitro susceptibility.

Polyomavirus Nephropathy in Native Kidneys of an Immunocompetent Individual

Patient: Male, 34 Final Diagnosis: Poliomavirus nephropathy Symptoms: Renal disfunction Medication: — Clinical Procedure: Renal biopsy Specialty: Nephrology Objective: Rare disease Background: Polyomavirus nephropathy has emerged as an important cause of graft loss in kidney transplant recipients. Polyomavirus rarely affects the native kidneys of an immunocompetent individual. Until now, polyomavirus nephropathy in native kidneys of an immunocompetent individual has not been reported, as far as we know. Case Report: A 34-year-old man was transferred from a local clinic to be evaluated for the cause of azotemia. Serum creatinine was 2.85 mg/dL. We performed renal biopsy to identify the cause of azotemia. The result of kidney biopsy was consisted to polyomavirus nephropathy. Conclusions: We report the first case of polyomavirus nephropathy in native kidneys of an immunocompetent individual.

Successfully treated isolated renal artery pseudoaneurysm in a patient with Behçet's disease

Renal artery aneurysms and pseudoaneurysms are an uncommon clinical problem with a low incidence rate. They are abnormal dilatations of the vessel lumen with some different natures. However, the rupture of an aneurysm and pseudoaneurysm is the most dreaded complication because it causes death of the patient. There are many causes of renal artery aneurysm and pseudoaneurysm, including Behçets disease; however, renal involvement in Behçets disease is less frequent. We report a case of renal artery pseudoaneurysm induced by Behçets disease and treated successfully with coil embolization. A 56-year-old woman with Behçets disease presented with an incidental left renal artery pseudoaneurysm measuring 18 mm. We successfully performed endovascular treatment with coil embolization instead of surgical treatment.