Han Chul Son

pncA mutations in clinical Mycobacterium tuberculosis isolates from Korea

BackgroundPyrazinamide (PZA) is among the first-line drugs for the treatment of tuberculosis. In vitro, it kills semidormant mycobacteria only at low pH. The purpose of this study was to compare PZA resistance with pyrazinamidase (PZase) activity and the genotype to better understand the molecular basis of PZA resistance and to expand the profile of pncA mutations worldwide.ResultsOf the 28 tested strains of Mycobacterium tuberculosis, 6 were susceptible to PZA and positive for PZase activity and had no pncA mutations. Twenty-one strains were resistant to PZA and negative for PZase activity and had mutations in the pncA gene, including 15 point mutations, 5 insertions, and 2 deletions. One strain had no mutation in the pncA gene, even though it was resistant to PZA and negative for PZase activity. Three isolates had adenine to guanine point mutations in the -11 upstream region, making this the most common type of pncA mutations in this study, with at least two different RFLP patterns.ConclusionThese data help in the understanding of the molecular basis of PZA resistance. An adenine to guanine point mutation in the -11 upstream region was the most common type of pncA mutation in our isolates. The results of pncA mutation analyses should be carefully interpreted for epidemiologic purposes.

Evaluation of the Sysmex UF-100 Urine Cell Analyzer as a Screening Test to Reduce the Need for Urine Cultures for Community-Acquired Urinary Tract Infection

We evaluated the UF-100 flow cytometer (TOA Medical Electronics, Kobe, Japan) as a screening test for community-acquired urinary tract infection (UTI) to reduce the need for bacterial cultures. By comparing the test results for 330 urine samples with quantitative urine cultures, we established cutoff criteria for the UF-100. To rule out hospital-acquired UTI, all urine samples were from new patients who had not been admitted to a hospital within the previous month. Abacterial cutoff value of 3,000/microL provided the best discrimination for community-acquired UTI, with a sensitivity of 94.4% and a specificity of 73.4%compared with urine culture. It was possible to forgo 58.2% of cultures with only 4 false-negative results. With a bacterial cutoff value of 1,500/microL, the sensitivity improved to 100%, but the specificity declined to 49.8%, and only 38.5% of cultures could be avoided without any false-negative results. Screening with the UF-100 for community-acquired UTI is acceptable for routine use. It would improve the efficiency of the routine microbiology laboratory, and unnecessary antibiotic prescriptions could be reduced.

Recurrent Self-Limited Fungemia Caused by Yarrowia lipolytica in a Patient with Acute Myelogenous Leukemia

ABSTRACT Yarrowia lipolytica is a weakly pathogenic yeast that is rarely isolated from the blood. We observed transient recurrent catheter-related fungemia attributable to this organism in a leukemic patient. The fungemia and accompanying fever subsided spontaneously. The data suggest that it might be possible to withhold specific treatment for Y. lipolytica fungemia even in an immunocompromised patient.

Tetraploid acute promyelocytic leukemia with double t(15;17) and PML/RARA rearrangements detected by fluorescence in situ hybridization analysis

Acute promyelocytic leukemia (APL) is characterized by a serious hemorrhagic syndrome, unique morphologic findings, and its response to retinoids. Tetraploidy is a very rare chromosomal abnormality in acute myelocytic leukemia. This report presents a unique case of APL with a tetraploid clone characterized by two t(15;17) without other chromosomal changes, as well as PML/RARA rearrangements confirmed fluorescence in situ hybridization. The morphology of the blast cells was that of the classic M3 subtype, but the mean blast size exceeded that of control APL cases with diploidy. A chromosomal study revealed a 92,XXXX,t(15;17)(q22;q21)x2 karyotype in all 20 metaphase spreads. Despite all-trans-retinoic acid (ATRA) treatment and chemotherapy, leukemic cells persisted in the blood, and the patient died of an intracranial hemorrhage on the 16th day after admission.

Thrombotic thrombocytopenic purpura triggered by influenza A virus subtype H1N1 infection

We report a case of acquired thrombotic thrombocytopenic purpura (TTP) triggered by influenza A virus subtype H1N1 infection. In December 2010, a 27-year-old man was diagnosed with pneumonia from influenza A virus infection at a local clinic. Two days later, he was admitted to our hospital because of a worsening condition and unexplained thrombocytopenia. The influenza A virus subtype H1N1 real-time polymerase chain reaction test was positive. The patient had typical clinical signs of TTP, thus he was diagnosed with TTP. He received treatment with oseltamivir and high dose methylprednisolone. Plasma exchange therapy was started daily at a 1.5 dose volume of his whole blood. After the 17th plasma exchange therapy, the symptoms and abnormal laboratory results had recovered to normal. Finally, 47 days after admission, the patient had recovered completely and was discharged. This case suggests that the influenza A virus subtype H1N1 infection may have triggered acquired TTP.

Elecsys Hepatitis B Surface Antigen Quantitative Assay: Performance Evaluation and Correlation with Hepatitis B Virus DNA during 96 Weeks of Follow-up in Chronic Hepatitis B Patients

Background Treatment for chronic hepatitis B aims to suppress virus replication and virus sequestration in hepatocytes. Covalently closed circular (ccc) DNA is the template for transcription of viral genes and is responsible for viral persistence. However, limited data are available for quantification of hepatitis B surface antigen (HBsAg) in Korea. Methods We evaluated the Elecsys HBsAg II quant assay (Roche Diagnostics, USA) for within-run, between-run, and between-day precisions, linearity, carryover, and clinical specificity. In total, 156 serum samples were evaluated for correlation between HBsAg and hepatitis B virus (HBV) DNA. Serial samples were obtained from 10 patients at 0, 12, 24, 48, 72, and 96 weeks during follow-up. Results The assay detected HBsAg in a linear range of 0.5-48,696 IU/mL. Within-run, between-run, and between-day CVs were 2.9-4.1%, 0-1.5%, and 1.5-4.9%, respectively. Cross-reactivity between potentially interfering substances was absent, and the carryover rate was 0.00002%. The correlation of measurements between the Elecsys assay and HBV DNA PCR was weak (r=0.438, P=0.002). For predicting virologic response, cutoff values of 10,275 IU/mL and 3,846 IU/mL at 12 and 24 weeks after treatment initiation showed positive predictive values of 77.1% and 85% and negative predictive values of 84.6% and 50%, respectively. Conclusions The Elecsys HBsAg II quant assay showed good performance for precision, linearity, carryover rate, and specificity. HBsAg level at baseline, 12 weeks, and 24 weeks after treatment initiation can predict virologic response, and the assay can be used for HBsAg quantification in clinical practice.

Reduction of Contamination of Mycobacterial Growth Indicator Tubes with a Modified Antimicrobial Combination

ABSTRACT Culture in the fluorimetric Mycobacteria Growth Indicator Tube (MGIT) treated with a combination of vancomycin, amphotericin B, and nalidixic acid (VAN) showed growth of most strains of 31 mycobacterial species with a less-than-1-day delay. The results were similar to those in the MGIT with polymyxin B, amphotericin B, nalidixic acid, trimethoprim, and azlocillin, but with respiratory specimens, the MGIT with VAN showed a lower contamination rate with no change in the detection rate or time.

Evaluation of recombinant factor VIIa treatment for massive hemorrhage in patients with multiple traumas.

Background Recent studies and case reports have shown that recombinant factor VIIa (rFVIIa) treatment is effective for reversing coagulopathy and reducing blood transfusion requirements in trauma patients with life-threatening hemorrhage. The purpose of this study is to evaluate the effect of rFVIIa treatment on clinical outcomes and cost effectiveness in trauma patients. Methods Between January 2007 and December 2010, we reviewed the medical records of patients who were treated with rFVIIa (N=18) or without rFVIIa (N=36) for life-threatening hemorrhage due to multiple traumas at the Emergency Department of Pusan National University Hospital in Busan, Korea. We reviewed patient demographics, baseline characteristics, initial vital signs, laboratory test results, and number of units transfused, and then analyzed clinical outcomes and 24-hr and 30-day mortality rates. Thromboembolic events were monitored in all patients. Transfusion costs and hospital stay costs were also calculated. Results In the rFVIIa-treated group, laboratory test results and clinical outcomes improved, and the 24-hr mortality rate decreased compared to that in the untreated group; however, 30-day mortality rate did not differ between the groups. Thromboembolic events did not occur in both groups. Transfusion and hospital stay costs in the rFVIIa-treated group were cost effective; however, total treatment costs, including the cost of rFVIIa, were not cost effective. Conclusions In our study, rFVIIa treatment was shown to be helpful as a supplementary drug to improve clinical outcomes and reduce the 24-hr mortality rate, transfusion and hospital stay costs, and transfusion requirements in trauma patients with life-threatening hemorrhage.

Evaluation of ARCHITECT HCV core antigen assay.

BACKGROUND Hepatitis C virus (HCV) core antigen (Ag) levels are known to be well correlating with HCV RNA levels, and may be used as an alternative marker of HCV replication for monitoring the response to HCV treatment. However, the low sensitivity of HCV core Ag assay has been an obstacle for clinical use. In this study, recently developed ARCHITECT HCV Ag assay (Abbott Laboratories, USA) was evaluated for analytical performance and clinical usefulness. METHODS A total of 109 sera from HCV infected patients including various genotypes of HCV (1b, 2, 2a/2c, 2b, and 3a) and 20 sera from healthy donors were used for evaluating the sensitivity, precision, and linearity of the HCV core Ag assay. The cross reactivity with HIV, hepatitis B virus and myeloma proteins (N=5, each) and correlation with HCV RNA PCR assay were also evaluated. RESULTS The sensitivity of the HCV core Ag assay was 97.2% (106/109) and there were no false positive results and cross reactivity. The within-run, between-run and between-day CVs were 3.0%, 2.5% and 3.0%, respectively. The levels of HCV core antigen showed a good correlation with those of HCV RNA quantification (r=0.940). The HCV Ag assay showed an excellent linearity in the range from 0.63 to 17,114 fmol/L (r=0.999). CONCLUSIONS The ARCHITECT HCV Ag assay was good in sensitivity, precision, and linearity and its results well correlated with HCV RNA levels. This assay could be used as a good marker of viral replication for monitoring the therapy response in chronically HCV infected patients.

Rapid Extraction of DNA using Ion Exchange Resin for Early Detection ofMycobacterium tuberculosis by the Polymerase Chain Reaction

연구배경: 본 연구는 결핵의 조기검출을 위하여, PCR을 이용하는데 있어서의 중요한 문제점의 하나인 임상검체로부터 결핵균을 분리 방법을 개선하여, 교차오염의 가능성을 최소화하고 PCR에 의한 결핵균의 DNA검출을 보다 쉽고 안전하게 실시하여 대량의 검체를 처리해야하는 일상 임상검사법으로 정착시키고자 하는데 그 목적이 있다. 방법: 다양한 방법으로 DNA를 검출하여 동일한 방법으로 PCR을 수행하여 이차 PCR 산물의 전기영동 결과를 AFB도말 및 배양검사 결과와 함께 비교하여 감수성, 특이성, 양성예측도 및 음성예측도의 항목으로 비교분석하였다. 실험 1은 Proteinase K 처리후 phenol로 추출하는 방법과 Chelex 100 이온교환 수지를 이용한 InstaGene법을 100예에서 비교하였으며, 실험 2에서는 Microwave 처리후 원침 상청액을 직접 시용하는 방법과 Chelex 100 이온교환 수지를 이용한 InstaGene 법을 98예에서 비교하였다. 결과: 세 DNA 분리법으로 실시한 PCR결과에서 모두 특이성과 양성예측도가 매우 낮았다. 실험 1에서 Proteinase K 법에 의한 경우 보다 Insta Gene을 이용한 경우에 약 20% 높은 감수성과 10%~20% 높은 음성예측도를 보이고 있으며, 특이성은 2%~8% 낮고, 양성예측도는 2.5%~4% 높은 것으로 나타났다. 실험 2에서는 Microwave법과 Insta Gene을 이용한 경우에 거의 비슷한 결과를 보였다. 결론: 결핵진단시 PCR을 위한 객담검체에서의 DNA 분리시에 Microwave법과