Verification of the Performance of the Panbio COVID-19 Ag Rapid Test Device for Implementation in the Clinical Laboratory / 이화의대지

Objectives@#The Panbio COVID-19 Ag Rapid Test Device (Panbio COVID-19 Ag, Abbott Rapid Diagnostics) is a lateral flow immunochromatographic assay targeting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein in nasopharyngeal specimens for the diagnosis of coronavirus disease 2019 (COVID-19). This study aimed to verify the performance of the Panbio COVID-19 Ag for implementation in clinical laboratories. @*Methods@#Sixty nasopharyngeal swab specimens (30 positive and 30 negative) dipped in transport medium, and COVID-19 was confirmed using real-time RT-PCR using Allplex SARS-CoV-2 assay (Seegene), were tested using the Panbio COVID-19 Ag. Reproducibility was evaluated using positive and negative control materials. Sensitivity and specificity were calculated based on the results of realtime RT-PCR as the standard test method. @*Results@#Reproducibility was confirmed by the consistent results of repeated tests of the quality control materials. The overall sensitivity and specificity of Panbio COVID-19 Ag were 50.0% and 100.0%, respectively. Panbio COVID-19 Ag demonstrated high sensitivity (88.2%) in analyzing the detection limit cycle threshold (Ct) value of 26.67 provided by the manufacturer as a positive criterion, and the sensitivity was 100.0% for the positive criterion of Ct values <25, although it was less sensitive for Ct ≥ 25. @*Conclusion@#Considering the high sensitivity for positive samples with Ct values <25 and the rapid turnaround of results, Panbio COVID-19 Ag can be used in clinical laboratories to diagnose COVID-19 in limited settings.

Immunogenicity of SARS-CoV-2 Vaccine in Kidney Transplant Recipients:A Cross-Sectional Study in Korea

Eighty-five Korean kidney transplant recipients who received three doses of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine were tested with anti-receptor binding domain (RBD) antibody and neutralizing antibody. High anti-RBD antibody (≥ 100 U/mL) and neutralizing antibody responses (≥ 30%) were detected in 51/85 (60.0%) patients.When we divided the patients with the time from transplantation to vaccination (< 1, 1–2.4, 2.5–4.9, and ≥ 5-year), anti-RBD antibody titers were 3.2 U/mL, 27.8 U/mL, 370.2 U/mL, and 5,094.2 U/mL (P < 0.001) and anti-neutralizing antibody levels were 2.2%, 11.6%, 45.6%, and 93.0% (P < 0.001), respectively. Multivariate analysis revealed increased antibody responses when the time from transplantation to vaccination was five years or longer (odds ratio, 12.0; confidence interval, 2.7–52.8). Korean kidney transplant recipients had suboptimal antibody responses after the third dose of SARS-CoV-2 vaccine. A shorter time from transplantation to vaccination was a risk factor for a low antibody response.

Nationwide Survey for Current Status of Laboratory Diagnosis of Clostridioides difficile Infection in Korea

Background@#The interest in Clostridioides difficile infection (CDI) has increased, and the choice of assays became wider since the first national survey in Korea on CDI diagnosis in 2015. We conducted a survey of the domestic CDI assays with more varied questions to understand the current situation in Korea. @*Methods@#In April 2018, about 50 questions on the current status of CDI assays and details on implementation and perceptions were written, and a survey questionnaire was administered to laboratory medicine specialists in 200 institutions. @*Results@#One-hundred and fifty institutions responded to the questionnaire, of which 90 (60.0%) including one commercial laboratory, performed CDI assays. The toxin AB enzyme immunoassay (toxin AB EIA), nucleic acid amplification test (NAAT), and C. difficile culture, glutamate dehydrogenase assay, alone or in combination with other assays, were used in 75 (84.3%), 52 (58.4%), 35 (36.0%), and 23 (25.8%), respectively, and 65 (73.0%) institutions performed a combination of two or more assays. The sensitivity of toxin AB EIA was more negatively perceived, and that on specificity was more positively perceived. The perception of sensitivity and specificity of NAAT was mostly positive. Perception on the algorithm test projected it as useful but in need of countermeasures. Sixty-three (73.3%) institutions responded that they performed surveillance on CDI. @*Conclusion@#This study provides useful evidence on the current status of CDI laboratory diagnosis in Korea as well as on items that require improvement and is thought to aid in standardizing and improving the CDI laboratory diagnosis in Korea.

Laboratory Diagnostic Methods for Clostridioides difficile Infection: the First Systematic Review and Meta-analysis in Korea

Background@#Various methods are used for the diagnosis of Clostridioides difficile infection (CDI). We systematically analyzed and investigated the performance of current laboratory diagnostic methods for CDI. @*Methods@#We performed systematic review and meta-analysis of studies in PubMed, Web of Science, Cochrane Library, and KoreaMed. The following methods were evaluated: glutamate dehydrogenase (GDH) enzyme immunoassays (GDH EIAs), toxin A and B detection by enzyme immunoassays (toxin AB EIAs), and nucleic acid amplification tests (NAATs) for C. difficile toxin genes. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each method were calculated. @*Results@#Based on 39 studies, the pooled sensitivities/specificities were 92.7%/94.6%, 57.9%/97.0%, and 90.0%/95.8% for GDH EIAs, toxin AB EIAs, and NAATs, respectively, compared with those of toxigenic culture. The pooled sensitivities of automated EIAs were significantly higher than those of non-automated EIAs for both GDH and toxins A and B.The pooled sensitivity of Xpert C. difficile was significantly higher than those of other NAATs. PPVs increased as CDI prevalence increased, and NPVs were excellent when CDI prevalence was low; at CDI prevalence of 5%, PPV = 37%–65% and NPV = 97%–100%;at CDI prevalence of 50%, PPV = 92%–97% and NPV = 65%–98%. @*Conclusions@#Toxin AB EIAs still show unsatisfactory sensitivity, whereas GDH EIAs and NAATs show relatively high sensitivity. However, toxin AB EIAs are the most specific tests. This study may provide useful information for CDI diagnosis.

Evaluation of the AdvanSure TB/NTM Plus Real-Time PCR Assay for the Simultaneous Detection of Mycobacterium tuberculosis and Nontuberculous Mycobacteria from Clinical Specimens / 대한임상미생물학회지

Background@#The AdvanSure TB/NTM plus real-time PCR (AdvanSure plus PCR; LG Chem., Korea) assay has been developed to increase the diagnostic sensitivity of nontuberculous mycobacteria (NTM) compared with the currently used the AdvanSure TB/NTM real-time PCR (AdvanSure PCR;LG Chem., Korea) assay. In this study, we aimed to evaluate the performance of the AdvanSure plus PCR comparing the results with mycobacterial culture and the AdvanSure PCR. @*Methods@#Patients (n=199) with suspected NTM or Mycobacterium tuberculosis complex (MTC) were tested using AdvanSure plus PCR, AdvanSure PCR, acid-fast bacilli staining, and mycobacteria culture. Additionally, 200 DNA samples (n=100, MTC and n=100, NTM) were obtained from positive MTC or NTM cultures for evaluation using the AdvanSure plus PCR assay. @*Results@#The two real-time PCR systems showed a 94.0% (n=187/199) concordance rate (Kappa=0.94). Based on culture results, the sensitivity and specificity for the detection of MTC were 100% (45/45) and 83.8% (129/154) using AdvanSure plus PCR, and 100.0% (45/45) and 99.3% (153/154) using AdvanSure PCR, respectively. The sensitivity and specificity for NTM detection were 68.0% (n=17/25) and 90.2% (n=157/174), respectively, with AdvanSure plus PCR, and 64.0% (n=16/25) and 95.4% (n=166/174), respectively, using AdvanSure PCR. With culturepositive samples, AdvanSure plus PCR tested positive for 100% of both the MTC and NTM specimens. Seven (out of 200) culture-positive samples tested positive for both MTC and NTM using the AdvanSure plus PCR. @*Conclusion@#AdvanSure plus PCR had increased sensitivity but decreased specificity compared with AdvanSure PCR for the detection of NTM. The AdvanSure plus PCR assay can be used for the simultaneous detection of MTC and NTM in direct specimen and culture.

Performance of Xpert Carba-R Assay for Identification of Carbapenemase Gene in the Clinical Microbiology Laboratory / 이화의대지

Objectives@#The Xpert Carba-R Assay is a diagnostic test designed for the rapid detectionand differentiation of the blaKPC, blaNDM, blaVIM, blaOXA-48, and blaIMP-1 genes. We verifiedthe performance of Xpert Carba-R Assay for identification of carbapenemase genein the clinical microbiology laboratory. @*Methods@#The analytical limit of detection was determined with two suspensions ofcarbapenemase-producing Enterobacteriaceae (CPE) isolates (KPC and NDM). A totalof 52 specimens were evaluated: 21 bacterial isolates from clinical specimens, 21 rectalswabs, and 10 contrived stool specimens. @*Results@#In bacterial isolates, concordant results between the Xpert Carba-R Assayand PCR were found in 20 of 21; 8 KPC, 8 NDM, 1 IMP, and 2 multiple carbapenamasegenes (KPC/NDM, NDM/OXA) were detected both by Xpert Carba-R Assay and PCR.In one GES-positive isolate, Xpert Carba-R Assay showed a negative result as expected.One VIM-positive isolate tested negative by Xpert Carba-R Assay. Complete concordancewas seen in rectal swab specimens: 4 specimens with KPC and 17 specimenswith negative results both by Xpert Carba-R Assay and surveillance culture. Among the10 contrived stool specimens, Xpert Carba-R Assay detected carbapenemase genes in9 specimens as expected according to the CPE strains spiked into the contrived stool; 2KPC, 4 NDM, 1 IMP, and 2 multiple carabapenamase genes (NDM/KPC, NDM/OXA).One VIM-positive specimen tested negative by Xpert Carba-R Assay. @*Conclusion@#In conclusion, the Xpert Carba-R Assay can be used to identify carbapenemasegene in bacterial isolates cultured from clinical specimens and detect CPE carrierusing rectal swab in clinical laboratories.

Application of Six Sigma Metrics to Improve Quality Control for Point-of-care Glucose Testing / 이화의대지

Objectives@#Six sigma is a quality management system for the assessment of precisionand accuracy. We aim to apply the six sigma rule to quality control (QC) of point-of-care(POC) glucose meters in a tertiary hospital. @*Methods@#Thirty POC glucose meters installed at Ewha Womans University MokdongHospital were monitored between January 2013 and March 2014. The QC data fromthe POC glucose meters at low and high levels were collected. The monthly mean, standarddeviation, bias, coefficient of variation, and mean sigma metrics were calculated.The correlation between accuracy and precision was assessed based on the percentagebias and coefficient of variation. Comprehensive instructions on the QC and maintenanceof the devices were provided in the departments with poor sigma scores. Afollow-up assessment was performed after the intervention. @*Results@#The mean sigma values for the low and high controls were 3.29 and 3.71, respectively.At the low and high controls, 36.6% and 10% of the glucose meters showeda sigma value <3. The causes of low sigma values included the use of expired controlmaterials, prolonged air exposure of the sample strip, lack of user training, and errors indevice maintenance. On follow-up monitoring for 3 months following QC intervention,23.3% (low control) and 6.6% (high control) of the glucose meters scored a sigma value<3, indicating improved QC. @*Conclusion@#Sigma metrics-based QC can successfully improve accuracy and precisionof POC glucose meters in an objective and quantitative manner and can be usedfor follow up after QC intervention.

Effects of Pre-analytical Variables on Cell-free DNA Extraction for Liquid Biopsy

BACKGROUND: Extraction of cell-free DNA (cfDNA) is a key step for determining the quality of cfDNA-related molecular diagnostics. We evaluated the effect of sample containers and sample storage conditions on cfDNA extraction. METHODS: The cfDNA extraction using the MagMAX Cell-Free DNA Isolation Kit from five healthy controls and five lung cancer patients was evaluated according to the type of sample container and storage conditions: K2-EDTA container, <1, 6, 24, and 48 hr storage at 4℃ after immediate plasma separation; and Cell-Free DNA BCT container, <1, 3, 7, and 14 days stored at room temperature. Mutation analysis of EGFR exons 18–21 was performed. To assess the effect of a delay in centrifugation, EDTA whole blood samples from five healthy individuals were stored at 4℃ for 6, 12, and 24 hr before plasma separation. RESULTS: There was no significant difference in the amount and nucleic acid size of cfDNA in both controls and patients with cancer when EDTA plasma was stored at 4℃ up to 48 hr. The amount and size of cfDNA in the BCT container were not different up to 7 days; however, the 14-day sample showed an increase in cfDNA concentration due to genomic DNA contamination. EGFR mutations were detected on EDTA containers up to 48 hr and with BCT containers up to 14 days. When EDTA whole blood was stored at 4℃ and plasma separation was delayed, the cfDNA concentration increased from 24 hr. CONCLUSIONS: The cfDNA extraction was affected by the sample containers and storage conditions.

Laboratory Diagnosis of Clostridium difficile Infection in Korea: The First National Survey

In May 2015, we conducted a voluntary online survey on laboratory diagnostic assays for Clostridium difficile infection (CDI) across clinical microbiology laboratories in Korea. Responses were obtained from 66 laboratories, including 61 hospitals and five commercial laboratories. Among them, nine laboratories reported having not conducted CDI assays. The toxin AB enzyme immunoassay (toxin AB EIA), nucleic acid amplification test (NAAT), and C. difficile culture, alone or in combination with other assays, were used in 51 (89.5%), 37 (64.9%), and 37 (64.9%) of the remaining 57 laboratories, respectively, and 23 (40.4%) of the laboratories performed all three assays. Only one laboratory used the glutamate dehydrogenase assay. Nine laboratories used the toxin AB EIA as a stand-alone assay. The median (range) of examined specimens in one month for the toxin AB EIA, NAAT, and C. difficile culture was 160 (50–2,060), 70 (7–720), and 130 (9–750), respectively. These findings serve as valuable basic data regarding the current status of laboratory diagnosis of CDI in Korea, offering guidance for improved implementation.

Comparison of PANA RealTyper HPV Kit with AdvanSure HPV GenoBlot Assay for Human Papillomavirus Genotyping / 대한임상미생물학회지

BACKGROUND: The PANA RealTyper HPV kit (PANAGENE, Korea; PANA RealTyper) was developed to genotype human papillomavirus (HPV) and was based on multiplex real-time PCR amplification and melting curve analysis. In this study, we compared PANA RealTyper to the AdvanSure HPV GenoBlot assay (LG Life Sciences, Korea; AdvanSure assay) and attempted to evaluate the performance of PANA RealTyper. METHODS: A total of 60 cervical specimens were collected from women undergoing routine cervical cancer screening. The AdvanSure assay and PANA RealTyper kit identified the same 20 high-risk genotypes. However, the AdvanSure assay identified 15 low-risk genotypes, while the PANA RealTyper kit identified only 2 but detected 18 low-risk genotypes. RESULTS: Among the total 60 specimens, 54 high-risk genotypes (40 specimens) and 20 low-risk genotypes (18 specimens) were detected. The agreement rates of the assays ranged from 94.4 to 100% for high-risk genotypes. Among 9 genotypes that were positive in the PANA RealTyper kit but negative in the AdvanSure assay, 7 were confirmed as true positive (HPV genotypes 16 (n=1), 39 (n=1), 52 (n=1), 58 (n=2), 68 (n=2)). Among 4 genotypes that were negative in the PANA RealTyper kit but positive in the AdvanSure assay, 3 were confirmed as HPV genotype 59. Among the 19 low-risk genotypes positive in the AdvanSure assay, there were 2 cases of HPV 6 and 1 case of HPV 11. In comparison, only 1 positive case of HPV 6 was determined by the PANA RealTyper kit. CONCLUSION: The PANA RealTyper kit was comparable with the AdvanSure assay. The PANA RealTyper kit would be useful and suitable for HPV genotyping in the clinical laboratory.

Antibiotics-Associated Hemorrhagic Colitis Caused by Klebsiella oxytoca: Two Case Reports / 대한소아소화기영양학회지

Nowadays, Klebsiella oxytoca is described as a causative organism for antibiotic-associated hemorrhagic colitis (AAHC). Here we report two cases of pediatric AAHC, from which K. oxytoca was cultured after starting amoxicillin-clavulanate or amoxicillin treatment. The patients developed severe abdominal pain and a large amount of bloody diarrhea. K. oxytoca was obtained in intestinal fluid culture of a boy through the colonoscopy. On the other hand, colonic tissue culture and intestinal fluid culture were negative of the other patient. K. oxytoca was detected in stool culture when he was admitted. These cases showed characteristic endoscopic findings of segmental hemorrhagic colitis, and both boys recovered spontaneously within 2–3 days after they stopped taking the antibiotics. Therefore, in children who develop relatively large amount of bloody diarrhea after antibiotic treatment, we should consider AAHC caused by K. oxytoca.

Comparative Evaluation of Multiplex Real-Time PCR Assays for Six Pathogens of Sexually Transmitted Infections / 대한임상미생물학회지

BACKGROUND: The multiplex real-time PCR assay is a sensitive test for simultaneous detection of various pathogens of sexually transmitted infections (STIs). We evaluated the performance of two multiplex real-time PCR assays for six STI pathogens. METHODS: DNA samples after being used to conduct PCR for STI pathogens were stored below −70℃. Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), Mycoplasma genitalium (MG), Mycoplasma hominis (MH), Ureaplasma urealyticum (UU), and Trichomonas vaginalis (TV) were detected by multiplex real-time PCR with GeneFinder STD I (CT/NG/UU)/II (MG/MH/TV) Multiplex Real-time PCR Kits (Infopia, Korea; GeneFinder assay) and Real-Q CT&NG/MH&TV/MG&UU Kits (BioSewoom, Korea; Real-Q assay). Discrepant results were resolved by another multiplex real-time assay, Anyplex II STI-7 Detection (Seegene, Korea). Any two positive results for the assays were considered true positive. RESULTS: Among 81 samples, the GeneFinder assay detected 63 pathogens from 45 cases (16 CT, 2 NG, 6 MG, 20 MH, 18 UU, and 1 TV) and Real-Q assay detected 66 pathogens from 47 cases (16 CT, 2 NG, 8 MG, 20 MH, 19 UU, and 1 TV). For the results of positive cases and negative cases, the overall concordance rate between the two multiplex real-time assays was 93.8% (Kappa=0.87). For each pathogen, the agreement rates of the two assays ranged from 97.5 to 100% (Kappa>0.8). CONCLUSION: There was no significant difference between the results of GeneFinder assay and Real-Q assay. Both multiplex real-time PCR assays can be useful methods for the detection of STI pathogens in clinical laboratories.

Effects of Blood Volume Monitoring on the Rate of Positive Blood Cultures from the Emergency Room / 대한임상미생물학회지

BACKGROUND: Blood cultures are essential in diagnosing and treating sepsis. There are several factors that affect the diagnostic yield of blood cultures such as the number of blood sampling episodes, the incubation period, the type and volume of culture media, and the amount of blood drawn. This study aimed to elucidate whether monitoring the volume of blood drawn with an educational intervention could affect the diagnostic quality of blood cultures. METHODS: We implemented quality monitoring for the blood volume drawn during blood culture testing for adults in an emergency room. We instructed the nurses in the emergency room to draw the optimal amount of blood and to reduce the number of blood culture sets from three to two. We analyzed and compared the amount of blood drawn, the rate of positive blood cultures, the contamination rate, and time to positivity (TTP) between 908 patients pre-intervention and 921 patients post-intervention. RESULTS: The amount of blood drawn increased from 0.7±0.3 mL per bottle (pre-intervention) to 6.5±1.7 mL per bottle (post-intervention) (P<0.0001). The rate of positive blood culture post-intervention (12.14%) was higher than that pre-intervention (6.65%) (P<0.0001). The contamination rate post-intervention (1.82%) was also significantly greater than that pre-intervention (0.60%) (P<0.0001). Except for anaerobes, there was no significant difference in the distribution of microorganisms between the pre- and post-intervention periods. The TTP for anaerobe bottles post-intervention was significantly shorter than that of pre-intervention (16.1±16.3 versus 18.6±18.3 h). CONCLUSION: This study suggests that continuing education about adequate blood volume and aseptic techniques is needed to increase the rate of positive blood cultures and reduce the contamination rate of blood cultures.

Two Cases of Medical Device-Related Corynebacterium striatum Infection: A Meningitis and A Sepsis / 대한임상미생물학회지

Corynebacterium striatum is a commonly isolated contaminant in the clinical microbiology. However, it can be an opportunistic pathogen in immunocompromised and even immunocompetent hosts. The increasing prevalence of C. striatum infection has been associated with immunosuppression and prosthetic devices. We report a case of meningitis with cerebrospinal fluid drainage and a case of catheter-related bloodstream infection caused by C. striatum. The isolates were identified as nondiphtherial Corynebacterium species by VITEK 2 (bioMérieux, France) anaerobe and Corynebacterium card. The final identification by 16S rRNA gene sequencing analysis was C. striatum with 99.7% identity and 99.6% identity with C. striatum ATCC 6940, respectively. Both strains were sensitive to vancomycin and gentamicin, but multidrug-resistant to ciprofloxacin, penicillin, erythromycin and imipenem.

Diagnostic Utility of Serum Glycated Albumin for Diabetes Mellitus and Its Correlation With Hyperlipidemia

BACKGROUND: Glycated albumin (GA) is a better marker of short-term glycemic control than glycated hemoglobin (A1c). Dyslipidemia is the main cause of cardiovascular complications in diabetes mellitus (DM). Studies on the correlation of GA with lipid indices are sparse. We investigated the diagnostic utility of GA for DM and its relationship with serum lipid profiles compared with that of A1c. METHODS: The GA enzymatic method was used to determine the diagnostic utility of GA for DM by using samples from 163 normal subjects (group 1) and 102 patients newly diagnosed with type 2 DM (T2DM; group 2). To analyze the lipid profiles, 263 patients with T2DM receiving treatment (group 3) were recruited. RESULTS: GA correlated with A1c (r=0.934, P<0.0001). Linear regression analysis indicated that GA levels were about 2.48 folds those of A1c. In the ROC analysis for GA to diagnose DM, the areas under the curve (0.988, 95% confidence interval 0.972-1.004) was excellent. HDL levels were significantly lower in groups 2 and 3. In group 1, positive correlations were observed between A1c and triglyceride (TG), total cholesterol (TC), LDL, TG/HDL, TC/HDL, and LDL/HDL levels. A negative correlation was observed between HDL and A1c levels. In group 3, HDL levels (P=0.0124 and P=0.0141, respectively) were significantly higher and LDL levels tended to be lower, not statistically significant, in the well-controlled group categorized using the A1c and GA cut-off values. CONCLUSIONS: GA is a potential diagnostic tool for DM. Compared with A1c, GA seems less relevant to dyslipidemia.

Increasing Carbapenem-Resistant Gram-Negative Bacilli and Decreasing Metallo-beta-Lactamase Producers over Eight Years from Korea

The trends and types of carbapenemase-producing Gram-negative bacilli were analyzed from clinical specimens collected between 2005 and 2012 at a Korean teaching hospital. The proportions of carbapenem-resistant Acinetobacter spp. increased markedly to 66%. Metallo-beta-lactamase producers significantly decreased and the majority shifted from the bla(VIM-2) type to the bla(IMP-1) type.

Therapeutic Plasma Exchange for a Patient with Severe Cold Agglutinin Disease / 대한수혈학회지

Cold agglutinin disease is a kind of autoimmune hemolytic anemia, caused by cold agglutinin, serum autoantibodies activated at reduced body temperatures to produce red blood cell agglutination and hemolysis. In this paper we described a case of severe hemolytic anemia in a cold agglutinin disease patient treated with therapeutic plasma exchange. Therapeutic plasma exchanges were performed four times every other day. Over the same period, a total of 8 units of washed red blood cells were transfused. Then hemoglobin was increased from 4.0 g/dL to 7.8 g/dL. On the 12th hospital day hemoglobin level was decreased again to 4.2 g/dL and fludarabine chemotherapy was started on the 14th hospital day. The patient's symptoms were relieved and she was discharged on the 30th hospital day. As in this case, therapeutic plasma exchange could be considered as secondary therapy for temporary improvement of acute severe hemolytic anemia in cold agglutinin disease.

Evaluation of the Performance of a New Chromatographic Assay BD Veritor System for Rapid Detection of Influenza A & B / 대한임상미생물학회지

BACKGROUND: For early diagnosis and treatment of influenza, rapid influenza diagnostic tests are commonly used. We evaluated the performance of the BD Veritor System for Rapid Detection of Flu A+B (BD Veritor System; BD Diagnostics, USA) compared to multiplex real-time RT-PCR. METHODS: A total of 3,213 nasal and nasopharyngeal swab specimens in transport media from patients with influenza-like symptoms were tested with the BD Veritor System from December 2013 to April 2014. The sensitivity and specificity of 127 specimens were determined simultaneously using multiplex real-time RT- PCR with the AdvanSure RV real-time PCR (AdvanSure PCR; LG Life Sciences, Korea). RESULTS: Influenza viruses were detected in 41.3% (1,327/3,213) of all specimens tested using the BD Veritor System. Of the 127 specimens, 27 influenza A and 17 influenza B viruses were identified by the AvanSure PCR. The sensitivity and specificity of the BD Veritor System relative to the AdvanSure PCR was 85.2% and 99.0% for influenza A, and 58.8% and 99.1% for influenza B. Of the 190 specimens that tested negative using the BD Veritor System, the AdvanSure PCR detected influenza A and influenza B in 19 and 13 specimens, respectively. The mean threshold cycle (Ct) values of the antigen positive specimens were lower than those of the antigen negative specimens. CONCLUSION: The BD Veritor System showed excellent specificity for both influenza types and good sensitivity for influenza A. However, the system was less sensitive for influenza B compared to multiplex real-time RT-PCR. For accurate diagnosis of false negative specimens, a molecular diagnostic test should be performed. The BD Veritor system could be a useful tool for screening and early diagnosis of influenza.

The sul1 Gene in Stenotrophomonas maltophilia With High-Level Resistance to Trimethoprim/Sulfamethoxazole

Emerging resistance to trimethoprim/sulfamethoxazole (SXT) poses a serious threat to the treatment of Stenotrophomonas maltophilia infections. We determined the prevalence and molecular characteristics of acquired SXT resistance in recent clinical S. maltophilia isolates obtained from Korea. A total of 252 clinical isolates of S. maltophilia were collected from 10 university hospitals in Korea between 2009 and 2010. Antimicrobial susceptibility was determined by using the CLSI agar dilution method. The sul1, sul2, and sul3 genes, integrons, insertion sequence common region (ISCR) elements, and dfrA genes were detected using PCR. The presence of the sul1 gene and integrons was confirmed through sequence analysis. Among the 32 SXT-resistant isolates, sul1 was detected in 23 isolates (72%), all of which demonstrated high-level resistance (> or =64 mg/L) to SXT. The sul1 gene (varying in size and structure) was linked to class 1 integrons in 15 of the 23 isolates (65%) harboring this gene. None of the SXT-susceptible isolates or the SXT-resistant isolates with a minimum inhibitory concentration of 4 and 8 mg/L were positive for sul1. Moreover, the sul2, sul3, and dfrA genes or the ISCR elements were not detected. The sul1 gene may play an important role in the high-level SXT resistance observed in S. maltophilia.

Clinical and Microbiological Characteristics of Six Staphylococcus pettenkoferi Isolates From Blood Samples

Coagulase-negative staphylococci (CoNS) are reported to be the leading cause of nosocomial bloodstream infections. Staphylococcus pettenkoferi is a novel member of CoNS that was first isolated from the human blood and bursitis wound in 2002. We have reported cases of 6 S. pettenkoferi strains isolated from blood specimens, including one pathogen and 5 contaminants and catheter colonizers. Brucker Biotyper (Brucker Daltonics, Bremen, Germany) and molecular typing with 16S rRNA gene sequencing confirmed the 6 isolates as S. pettenkoferi. The conventional phenotypic identification of these isolates is not reliable owing to their inconsistent biochemical characteristics. Five of the 6 isolates were found to be resistant to oxacillin, and all isolates showed susceptibility to vancomycin and linezolid. For accurate identification of this novel species, advanced methods by using Brucker Biotyper or molecular methods such as 16S rRNA gene sequencing are required.