Clinical Usefulness of the QMAC-dRAST System for AmpC β-lactamase-Producing Enterobacterales / 대한임상미생물학회지

Background@#Rapid antimicrobial susceptibility testing (RAST) is important for the appropriate treatment of bloodstream infections. The QMAC-dRAST system (QuantaMatrix Inc., Korea) can directly perform RAST using positive blood culture samples with microscopic imaging. This study aimed to evaluate the performance of the QMAC-dRAST system for AmpCβ-lactamase-producing Enterobacterales. @*Methods@#Eighty isolates (20 Morganella morganii, 20 Serratia marcescens, 10 Klebsiella aerogenes, 10 Enterobacter cloacae, and 20 Citrobacter freundii) and 14 antimicrobial agents were included in the antimicrobial susceptibility testing (AST). The performance of the QMAC-dRAST system was evaluated by simulating the clinical blood culturing process. We conducted a comparative evaluation of the QMAC-dRAST and Vitek 2 systems (bioMérieux Inc., France). Broth microdilution tests were performed as the reference method to resolve any discrepancies in the AST results between the two systems. @*Results@#For 20 M. morganii and 20 S. marcescens, the categorical agreement (CA) between the QMAC-dRAST and Vitek 2 systems increased from 55.4% to 83.8% after AST algorithm optimization. Moreover, the discrepancy rates decreased as follows: from 19.1% to 5.4% very major errors (VME), from 38.3% to 4.3% major errors (ME), and from 14.6% to 12.1% minor errors (mE) for the QMAC-dRAST system compared to the Vitek 2 system. For all 80 tested isolates, the QMAC-dRAST system showed 93.0% CA, 1.7% VME, 2.3% ME, and 4.9% mE. @*Conclusion@#The QMAC-dRAST system was comparable to the Vitek 2 system after AST algorithm optimization for AmpC β-lactamase-producers, which are major pathogens and require time to express the enzyme. However, further modifications of the AST algorithm are still warranted.

Detection of Intestinal Protozoa in Korean Patients Using BD MAX Enteric Parasite Panel and Seegene Allplex Gastrointestinal Parasite Assay

Background@#Intestinal protozoan infection is one of the main causes of gastrointestinal diseases. Protozoa are usually detected by direct smear microscopy, concentration techniques, or special stains; however, these techniques are labor-intensive and require well-trained technicians. Therefore, molecular techniques involving polymerase chain reaction (PCR) have been developed to satisfy the need for unbiased and rapid analytical methods with high sensitivity and specificity. In this study, the BD MAXTM Enteric Parasite Panel (EPP) (Becton, Dickinson and Company, USA), designed to detect Cryptosporidium parvum and/or hominis, Giardia lamblia, and Entamoeba histolytica, and the AllplexTM Gastrointestinal Parasite Assays (AGPA) (Seegene Inc., Korea), designed to detect Cryptosporidium species, G. lamblia, E. histolytica, Blastocystis hominis, Dientamoeba fragilis, and Cyclospora cayetanensis were compared to determine whether any of these assays could become a useful tool for detecting intestinal protozoan infections in Korea. @*Methods@#We investigated 295 fecal samples using EPP and AGPA. Then we confirmed the positive results with the conventional and nested PCR. Consistent detection by conventional PCR, nested PCR, and one of the multiplex panels was considered “true positive.” @*Results@#Out of 295 samples, 17 were true positives for B. hominis and 2 were true positives for E. histolytica. EPP detected parasites in only two samples owing to its design; however, its true positive detection rate was 100% (2/2). AGPA detected parasites in 24 samples with 79.2% (19/24) true positives. @*Conclusions@#The incidence of protozoan, especially B. hominis, infection may be more prevalent than expected. AGPA could be an effective tool for screening protozoan infections.

Transfusion in RhD Mismatch Hematopoietic Stem Cell Transplantation / 대한수혈학회지

In some cases, hematopoietic stem cell transplants (HSCT) show differences in the D antigen. In previous studies, there have been few cases of de novo anti-D alloimmunization, and even rarer cases of serious side effects or the outcomes. De novo anti-D alloimmunization has been reported to occur more frequently in minor D mismatch than in major D mismatch. For the RhD type of blood components, RhD-negative type is recommended in transfusion in RhD mismatch HSCT without anti-D in donors and recipients. But in situations of insufficient RhD-negative blood supply, this study suggests that the RhD type of blood components depends on the patients’ RhD type before transplantation, and it depends on the donors’ RhD type after transplantation, and an RhD-positive platelet transfusion may be available.

Performance of Modified-EUCAST Rapid Direct Antimicrobial Susceptibility Testing on Clinical Urine Samples / 대한임상미생물학회지

Background@#The rapid antimicrobial susceptibility testing (AST) performed on urine samples would guide the adequate choice of antibiotics for obtaining better treatment outcomes in patients. Our study aimed to evaluate the performance of the modified-EUCAST (European Committee on Antimicrobial Susceptibility Testing) rapid direct AST on urine samples. @*Methods@#From >2,000 urine samples, a total of 128 urine samples containing bacterial counts of ≥2 × 10 4 CFU/mL with a uniform bacterial shape were initially included based on flow cytometry (Sysmex UF-1000i, Japan) and Gram staining, respectively. A total of 103 samples showing the presence of Enterobacteriaceae were finally selected in this study. The urine samples were directly inoculated on Mueller-Hinton agar, which was used in the current EUCAST rapid direct AST on blood samples. The size of the growth inhibition zones around antimicrobial disks was measured using a digital scanner (BIOMIC vision analyzer, Giles scientific, USA) and further confirmed by visualization with naked eyes after incubation for 4, 6, and 8 hours. The AST interpretations were compared to those of the conventional VITEK 2 AST system (bioMérieux, France) and the discrepancies between both tests were confirmed with the E-test. @*Results@#The antibiotics, namely ampicillin, cefazolin, aztreonam, ceftazidime, cefotaxime, cefoxitin, cefepime, gentamicin, ciprofloxacin, and cotrimoxazole showed excellent correlations with modified-EUCAST rapid direct test and conventional ASTs with >0.75 weighted kappa values. The categorical agreement of the rapid direct AST was 1,442 (93.3%), with 76 (4.9%) minor error, 9 (0.6%) major error and 18 (1.2%) very major error, implicating the reliability of this method for clinical application. @*Conclusion@#Performing the modified-EUCAST rapid direct AST on urine samples can predict reliable AST results within 8 hours. The rapid direct AST can help the physicians to initiate adequate antimicrobial treatment for urinary tract infections.

Determination of Colistin Resistance by Simple Disk Diffusion Test Using Modified Mueller-Hinton Agar

BACKGROUND: Colistin has become a last-resort antibiotic for the management of multidrug-resistant gram-negative bacteria. The disk diffusion test is cheap and easy to perform but may be unreliable for colistin susceptibility testing due to poor diffusion of the large colistin molecule. An improved agar diffusion test would increase the reliability of colistin susceptibility testing. This study aimed to modify Muller-Hinton agar (MHA) to improve colistin diffusion in agar.METHODS: MHA was modified by reducing the agar concentration from 100% to 30% and supplementing with protamine. We tested 60 gram-negative clinical isolates of Pseudomonas aeruginosa (N=27) and Acinetobacter calcoaceticus-baumannii complex (N=33). Disk diffusion test results were interpreted based on minimum inhibitory concentrations determined by broth microdilution.RESULTS: The modified MHA yielded the best performance metrics, including 94.7% sensitivity, 100% specificity, and an area under the curve of 0.995 (95% confidence interval, 0.982–1.000), P<0.001, at a cut-off point of 13 mm.CONCLUSIONS: A reduction of the agar concentration from 100% to 30% and the addition of protamine improved colistin diffusion in agar and allowed routine colistin susceptibility testing in a clinical microbiology laboratory, but should be handled with caution.

The First Case of Ochrobactrum pseudogrignonense Bacteremia in Korea

No abstract available.

Isolation of Non-Hydrogen Sulfide-Producing Salmonella enterica Serovar Infantis from a Clinical Sample: the First Case in Korea

No abstract available.

Application of 16S rRNA Gene-Targeted Next-Generation Sequencing for Bacterial Pathogen Detection in Continuous Ambulatory Peritoneal Dialysis Peritonitis / 대한임상미생물학회지

BACKGROUND: 16S rRNA gene-targeted next-generation sequencing (NGS) can detect microorganisms in a comprehensive reference database. To date, NGS has been successfully applied to samples such as urine, blood, and synovial fluid. However, there is no data for continuous ambulatory peritoneal dialysis (CAPD) fluid. The purpose of this study was to evaluate the clinical usefulness of microbiome analysis of CAPD fluids for the diagnosis of CAPD peritonitis.METHODS: We included 21 patients with high suspicion of CAPD peritonitis. Routine CAPD fluid culture was performed using a pellet of 50 mL CAPD fluid onto the chocolate and blood agar for two days, and thioglycollate broth for one week. 16S rRNA gene-targeted NGS of pellets, stored at −70℃ was performed with MiSeq (Illumina, USA).RESULTS: Many colonized or pathogenic bacteria were detected from CAPD fluids using NGS and the microbiomes were composed of 1 to 29 genera with a cut-off 1.0. Compared to the culture results, NGS detected the same pathogens in 6 of 18 valid results (three samples failed with low read count). Additionally, using NGS, anaerobes such as Bacteroides spp. and Prevotella spp. were detected in six patients. In two of five samples in which no bacterial growth was detected, possible pathogens were detected by NGS.CONCLUSION: To our knowledge, this is the first report about the application of 16S rRNA gene-targeted NGS for diagnosis of CAPD peritonitis. Etiology of culture-negative CAPD peritonitis can be better defined in NGS. Furthermore, it also helped the detection of anaerobic bacteria.

Evaluation of the Analytical Performance of Atellica CH 930 Automated Chemistry Analyzer

BACKGROUND: Recently, a new automated chemistry analyzer, Atellica CH930 (Siemens, Germany), was introduced. It automatically measures internal quality control (QC) materials according to a pre-determined schedule. For this purpose, the instrument has space for storage of QC materials. We evaluated the analytical performance of chemistry items by using the Atellica system. METHODS: The precision of 29 items was evaluated with three levels of QC materials with two storage methods. We stored the QC materials in the dedicated storage space in the instrument during the precision evaluation period. In addition, we aliquoted and stored the materials in the refrigerator, and then loaded the material in a timely manner. Linearity, carry-over, and agreement with current methods were also evaluated. RESULTS: The within-laboratory coefficient of variation (CV) of most items, except for total CO2 (tCO2), was within 5.0% in both QC storage methods without significant differences in CV between storage methods. The CV of tCO2 was 5.2%, 5.8%, and 5.1% at three different levels when the QC materials were stored in a dedicated space in the instrument. The linearity was acceptable, showing <5% nonlinearity. Although good agreement was observed for most items, some items, such as calcium, total bilirubin, aspartate transaminase, and chloride, showed unequivalent results. CONCLUSIONS: Atellica CH930 showed acceptable precision, linearity, and agreement in routine chemistry items. The automatic QC function using the storage device has no problem with stability or precision. It can reduce the manual process, allowing technicians to focus on reviewing the QC results and reporting reliable results.

Comparison of Multiplex Real-Time Polymerase Chain Reaction Assays for Detection of Respiratory Viruses in Nasopharyngeal Specimens / 대한임상미생물학회지

BACKGROUND: Respiratory tract infections are major public health threats, and the identification of their causative microbes helps clinicians to initiate timely and appropriate antimicrobial therapy and prevent the secondary spread of infection. The main goal of this study was to compare two multiplex real-time polymerase chain reaction (PCR) assays used to detect respiratory viral pathogens in nasopharyngeal swab specimens. METHODS: Between September and October 2017, a total of 84 nasopharyngeal specimens were obtained consecutively from patients in a tertiary hospital using a flocked swab with 3 mL universal transport medium (COPAN Diagnostics, USA). A total of 64 positive and 20 negative sample results from the LG AdvanSure RV real-time RT-PCR kit (LG Life Sciences, Korea) were further retested using a new AdvanSure RV-plus a real-time RT-PCR kit to compare their performance. RESULTS: Statistical analysis of positive and negative agreement between the two different kits was conducted between the newly introduced AdvanSure RV-plus real-time RT-PCR kit and the AdvanSure RV real-time RT-PCR. The overall agreement was 96.4%, with positive agreement of 98.4% and negative agreement of 90%. The evaluated sensitivity and specificity of AdvanSure RV-plus real-time RT-PCR were 96.9% and 94.7%, respectively, with a kappa value of 0.9 (P<0.001). CONCLUSION: The performances of LG AdvanSure RV real-time RT-PCR and the new AdvanSure RV-plus real-time RT-PCR kit showed strong overall agreement. AdvanSure RV-plus real-time RT-PCR had a better detection rate and could detect coronavirus 229E and enterovirus, especially with a high detection rate in coinfection. AdvanSure RV-plus real-time RT-PCR can be considered a useful tool for respiratory virus diagnosis in clinical laboratories.

A Case Report of Transfusion-associated Circulatory Overload

Transfusion-associated circulatory overload (TACO) is recently becoming more important than transfusion-related acute lung injury (TRALI) in terms of the number of patients with definite diagnosis as well as its prognosis. In order to diagnose TACO, it is helpful to recognize early the symptoms suspicious of transfusion reaction through electronic medical record system and computer network, and this will be of help for obtaining samples for brain natriuretic peptide (BNP) measurement before and after the onset of transfusion reaction. We report a case in which a transfusion reaction was diagnosed as TACO. A 62-year-old woman was admitted to the emergency room due to bleeding tendency. Two fresh frozen plasma units and one unit of leukocyte-reduced red blood cells were transfused. Blood pressure increased during transfusion, and the chest X-ray showed findings suggestive of newly developed pulmonary edema. N-terminal prohormone of BNP (NT-proBNP) test was carried out using the specimens in refrigerated storage. Compared with the NT-proBNP level measured 12 hours before the transfusion, that measured 6 hours after the transfusion was markedly increased (>48 fold of pre-transfusion level). As a result, this case was diagnosed with TACO.

Evaluation of the Level of Minimum Hemoglobin Trigger for Red Blood Cell Transfusion according to Clinical Departments / 대한수혈학회지

BACKGROUND: Red blood cell (RBC) transfusion is one of the major treatments for correcting anemia, but its use should be carefully considered because of adverse transfusion reactions and inappropriate usage. Therefore, individual health care facilities have self evaluated their use of transfusion in an attempt to decrease unnecessary procedures. In this study, we evaluated the differences in the minimum hemoglobin (Hb) trigger for RBC transfusion among clinical departments in Severance Hospital. METHODS: We analyzed the electronic medical records of RBC transfusion episodes that were conducted at a Hb level above 8 g/dL from July 2014 to September 2015. We classified these data by clinical department, and considered the overall medical conditions of the patients. The minimum Hb trigger level in this study was defined as the lowest Hb level within 24 hours prior to RBC transfusion. RESULTS: A total of 4,953 RBC transfusion episodes that were conducted at Hb levels above 8 g/dL were analyzed over that period. In general, the minimum Hb trigger level was higher in the operation group than the hemorrhage group. When compared among clinical departments, the department of orthopedic surgery, neurosurgery, rehabilitation medicine, and anesthesiology showed high levels of minimum Hb trigger equal to or greater than 10 g/dL. CONCLUSION: The minimum Hb trigger level differed among clinical departments, with the operation group showing a much higher level of minimum Hb trigger. We hope that these data will be practically applied to establish plans and strategies for managing the appropriateness of RBC transfusions in Korea. In addition, continuous evaluation and transfusion education for clinical departments should be performed.

A Case of Panagglutination on Antibody Identification in a Multiple Myeloma Patient Receiving Daratumumab / 대한수혈학회지

Herein, we report a patient showing panagglutination in the unexpected antibody identification test after the administration of daratumumab. The patient was a 66-year-old woman who had undergone multiple cycles of chemotherapy and autologous peripheral blood stem cell transplantation for treating multiple myeloma; however, despite treatment, she had relapsed. Therefore, daratumumab, on clinical trials in Korea, started to be administered. After administration of daratumumab, the result of antibody screening test was positive, on the contrary to the result prior to the administration. Moreover, all positive reactions were shown in the antibody identification to the panel cells. After destroying CD38 antigens on the surface of RBCs using DTT, negative results were obtained. Daratumumab—a novel therapeutic human CD38 monoclonal antibody that can be used as targeted immunotherapy—is an FDA-approved drug for treating multiple myeloma. Because CD38 is expressed not only on myeloma cells, but also on red blood cells (RBCs), the use of daratumumab might lead to RBC agglutinations, and thereby resulting in false-positive results on the pre-transfusion tests. Therefore, caution is needed in case of a patient receiving daratumumab. Furthermore, additional test using DTT is required, especially when panagglutination was shown in the antibody identification test, as in this case.

Therapeutic RBC Exchange in a Patient with Severe Plasmodium Falciparum Infection / 대한수혈학회지

With increasing travel to tropical area, the number of patients with imported malaria in this country is increasing. RBC exchange transfusion has proposed as a adjunct therapy for very severe falciparum malaria to reduce the parasite load rapidly. We report a patient with severe Plasmodium falciparum infection with 26% of erythrocyte parasitized, treated with RBC exchange transfusion in addition to conventional chemotherapy. The exchange of 1200 mL of red blood cells was carried out with 7 packed red cells using automatic cell separator. This patients recovered from his disease despite respiratory distress syndrome and acute renal failure. We conclude that RBC exchange is a useful adjunct to conventional chemotherapy and should be considered in patients with severe and complicated falciparum malaria.