Original Article2021-07-01 Clinical Microbiology
So Hyun Yu 
, B.S., Jeong Hyun Lee , B.S., Min-Chul Kim , M.D., Ph.D., Seong-Ho Choi , M.D., Ph.D., Jin-Won Chung , M.D., Ph.D., and Mi-Kyung Lee , M.D., Ph.D.
Abstract : Background: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains were first detected in hospitals in Korea between the late 2000s and early 2010s. However, there is limited information regarding the prevalence of CA-MRSA strains among hospital isolates and their phenotypic changes over the last decade. We investigated the prevalence trend of CA-MRSA strains isolated from different clinical specimens and their phenotypic changes between September 2009 and September 2019. Methods: CA-MRSA strains were phenotypically identified by confirming their resistance to penicillin (PCN) and oxacillin (OXA) and evaluating their susceptibility to trimethoprim-sulfamethoxazole, rifampin, fusidic acid, tetracycline, and at least one of the following four antimicrobials: clindamycin (CLI), erythromycin (ERY), ciprofloxacin (CIP), and gentamicin (GEN). A CA-MRSA strain that exhibited resistance to ERY, CLI, CIP, or GEN was classified as having resistance pattern I, II, III, or IV, respectively, regardless of its resistance to other antimicrobial agents. Results: Of the 8,278 MRSA isolates identified in specimens obtained two days after admission, 1,385 (16.73%) were CA-MRSA strains. The prevalence of CA-MRSA strains increased from 12.2% to 26.6% (3.21% per period, P=0.05). Resistance type analysis revealed an increasing trend in the prevalence of PCN/OXA-resistant (1.84%; P=0.049) and PCN/OXA/ERY/CLI/CIP-resistant (0.98%; P=0.04) CA-MRSA strains and in resistance pattern III strains (2.08%; P=0.004). Conclusions: The prevalence of CA-MRSA strains in Korea has increased significantly over the last decade, and CA-MRSA strains have gained phenotypic diversity beyond PCN/OXA-resistance, including antimicrobial resistance to non-β-lactams, especially CIP.
Letter to the Editor2021-07-01 Clinical Microbiology
Dongke Chen , M.A., Han Wang , M.D., Xianlei Lu , M.A., Yao Cui , M.A., Xiaohan Ma , M.A., Jing Lou , M.M. and Haijian Zhou , M.M.
Original Article2023-01-01 Clinical Microbiology
Gyu Ri Kim , Ph.D., Eun-Young Kim , Ph.D., Si Hyun Kim , Ph.D., Hae Kyung Lee , M.D., Jaehyeon Lee , M.D., Jong Hee Shin , M.D., Young Ree Kim , M.D., Sae Am Song , M.D., Joseph Jeong , M.D., Young Uh , M.D., Yu Kyung Kim , M.D., Dongeun Yong , M.D., Hyun Soo Kim , M.D., Sunjoo Kim , M.D., Young Ah Kim , M.D., Kyeong Seob Shin , M.D., Seok Hoon Jeong , M.D., Namhee Ryoo , M.D., and Jeong Hwan Shin , M.D.
Abstract : Background: Streptococcus pneumoniae is a serious pathogen causing various infections in humans. We evaluated the serotype distribution and antimicrobial resistance of S. pneumoniae causing invasive pneumococcal disease (IPD) after introduction of pneumococcal conjugate vaccine (PCV)13 in Korea and investigated the epidemiological characteristics of multidrug-resistant (MDR) isolates. Methods: S. pneumoniae isolates causing IPD were collected from 16 hospitals in Korea between 2017 and 2019. Serotyping was performed using modified sequential multiplex PCR and the Quellung reaction. Antimicrobial susceptibility tests were performed using the broth microdilution method. Multilocus sequence typing was performed on MDR isolates for epidemiological investigations. Results: Among the 411 S. pneumoniae isolates analyzed, the most prevalent serotype was 3 (12.2%), followed by 10A (9.5%), 34 (7.3%), 19A (6.8%), 23A (6.3%), 22F (6.1%), 35B (5.8%), 11A (5.1%), and others (40.9%). The coverage rates of PCV7, PCV10, PCV13, and pneumococcal polysaccharide vaccine (PPSV)23 were 7.8%, 7.8%, 28.7%, and 59.4%, respectively. Resistance rates to penicillin, ceftriaxone, erythromycin, and levofloxacin were 13.1%, 9.2%, 80.3%, and 4.1%, respectively. MDR isolates accounted for 23.4% of all isolates. Serotypes 23A, 11A, 19A, and 15B accounted for the highest proportions of total isolates at 18.8%, 16.7%, 14.6%, and 8.3%, respectively. Sequence type (ST)166 (43.8%) and ST320 (12.5%) were common among MDR isolates. Conclusions: Non-PCV13 serotypes are increasing among invasive S. pneumoniae strains causing IPD. Differences in antimicrobial resistance were found according to the specific serotype. Continuous monitoring of serotypes and antimicrobial resistance is necessary for the appropriate management of S. pneumoniae infections.
Letter to the Editor2022-01-01 Diagnostic Immunology
Danilo Villalta , M.D., Anna Moratto , Ph.D., Valeria Salgarolo , Ph.D., Mirella Da Re , Ph.D., Roberto Giacomello , Ph.D., and Giacomo Malipiero , M.D.
Original Article2022-07-01 Diagnostic Immunology
Younhee Park , M.D., Ph.D., Juhye Roh , M.D., Ph.D., and Sinyoung Kim , M.D., Ph.D.
Abstract : Background: Accurate and consistent viral load (VL) quantitation of HIV type 1 (HIV-1), hepatitis B virus (HBV), and hepatitis C virus (HCV) is important for diagnosis and clinical monitoring. Assay results have to be concordant and compatible across laboratories. We evaluated the performance of three Aptima assays (Hologic, San Diego, CA, USA) and compared their VL values with corresponding cobas 6800 assay (Roche Diagnostics, Mannheim, Germany) results, using 840 clinical samples. Methods: The correlation between VL results obtained using the two assays was evaluated in terms of analytical sensitivity, precision/reproducibility, linearity, and cross-reactivity. Agreement rates were determined using kappa statistics. The overall agreement of VL values was examined using Passing–Bablok regression analysis. Results: All CVs were within 5%; the assays had good precision for detecting all three viruses. The linearity of quantitation assessed using three AccuSpan linearity panels (Seracare, Milford, MA, USA), was excellent for the Aptima assays. For HIV-1 and HCV, the results of both assays showed excellent agreement (κ=0.89 and 0.90, respectively) while for HBV, the results showed good agreement (κ=0.69). For analytical sensitivity, the VLs required for a 100% detection rate of HIV-1, HBV, and HCV were 20 copies/mL, 7.5 IU/mL, and 5.0 IU/mL, respectively. The results for HIV-1, HBV, and HCV obtained using both assays correlated strongly (R2=0.97, 0.93, and 0.95, respectively). Conclusions: The cobas 6800 and Aptima assays, with fully automated and high-throughput molecular platforms for HIV-1, HBV, and HCV VL measurements, show good analytical performance and a strong correlation between results. The study results suggest that the assays can be used interchangeably for long-term monitoring of chronic infections.
Original Article2022-07-01 Diagnostic Hematology
Minjeong Nam , M.D., Ph.D., Sumi Yoon , M.D., Mina Hur , M.D., Ph.D., Gun Hyuk Lee , M.D., Hanah Kim , M.D., Ph.D., Mikyoung Park , M.D., Ph.D., and Hyeong Nyeon Kim , M.D.
Abstract : Background: Digital morphology (DM) analyzers are increasingly being used for white blood cell (WBC) differentials. We assessed the laboratory efficiency of the Sysmex DI-60 system (DI-60; Sysmex, Kobe, Japan) in comparison with manual counting in leukopenic samples. Methods: In total, 40 peripheral blood smear samples were divided into normal, mild leukopenia, moderate leukopenia, and severe leukopenia groups based on WBC count. In each group, the risk and turnaround time (TAT) were compared between DI-60 and manual counting. Risk was determined by failure mode and effect analysis using the risk priority number (RPN) score, and TAT was recorded for the analytical phase. Results: Overall, DI-60 showed a five-fold lower risk (70 vs. 350 RPN) and longer TAT than manual counting. In severe leukopenic samples, DI-60 showed a shorter TAT/slide and a remarkably lower cell count/slide than manual counting. In all samples, the TAT/cell for DI-60 was substantially longer than that for manual counting (DI-60 vs. manual: total, 1.8 vs. 1.0 sec; normal, 1.5 vs. 0.7 sec; mild leukopenia, 1.9 vs. 0.9 sec; moderate leukopenia, 1.8 vs. 1.0 sec; severe leukopenia, 28.8 vs. 19.0 sec). Conclusions: This is the first comparative assessment of risk and TAT between DI-60 and manual counting in leukopenic samples. DI-60 decreases the laboratory risk and improves patient safety, but requires more time to count fewer cells, especially in severe leukopenic samples. DM analyzers should be applied selectively depending on the WBC count to optimize laboratory efficiency.
Original Article2022-05-01 Clinical Chemistry
Sunyoung Ahn , Ph.D., Hyun-Ki Kim , M.D., Woochang Lee , Ph.D., Sail Chun , Ph.D., and Won-Ki Min , Ph.D.
Abstract : Background: We established high-sensitivity cardiac troponin I (hsTnI) 99th percentile upper reference limits (URLs) for the Centaur XPT High-Sensitivity Troponin I assay (Centaur hsTnI; Siemens, Erlangen, Germany) and Atellica IM High-Sensitivity Troponin I assay (Atellica hsTnI; Siemens) and assessed the effect of outlier elimination. Methods: The reference population comprised 380 men and 387 women, satisfying the strict systematic reference population criteria. After reference population verification by the N-terminal pro-B-type natriuretic peptide (NT-proBNP) assay, 99th percentile URLs for Centaur hsTnI and Atellica hsTnI were calculated before and after outlier elimination. Results: The 99th percentile URL for Centaur hsTnI was 60.4 (men, 74.7; women, 57.5) ng/L and that for Atellica hsTnI was 59.6 (men, 75.2; women, 55.1) ng/L. After the elimination of 61 (8.0%) outlier samples in Centaur hsTnI and 58 (7.6%) in Atellica hsTnI, the 99th percentile URLs were 13.5 ng/L (men, 15.3 ng/L; women, 11.9 ng/L) and 13.4 ng/L (men, 15.5 ng/L; women, 12.9 ng/L), respectively, significantly lower than those before outlier elimination. The CVs at the 99th percentile URLs were 5.2% and 3.5%, respectively. The measurable fractions among the reference population were 91.5% and 93.4%, respectively. Performance evaluation of Atellica B-type natriuretic peptide (BNP), Atellica NT-proBNP, Centaur hsTnI, and Atellica hsTnI showed outstanding results. Conclusions: The Korean hsTnI 99th percentile URLs calculated in this study were significantly lower after outlier elimination than before. Centaur hsTnI and Atellica hsTnI meet the “Guideline acceptable” and “Level 3 (second generation, high sensitivity)” requirements, satisfying international standards.
Editorial2021-11-01
Young Jin Kim , M.D., Ph.D., Heungsup Sung , M.D., Ph.D., Chang-Seok Ki , M.D., Ph.D., and Mina Hur , M.D., Ph.D.
Editorial2022-03-01
Young Jin Kim , M.D., Ph.D., Soo-Youn Lee , M.D., Ph.D., and Mina Hur , M.D., Ph.D.
Brief Communication2021-09-01 Clinical Microbiology
Jun Ho Jeon , Ph.D., Chi-Hwan Choi , Ph.D., Jeong Hyun Kim , M.D., Junghee Hyun , M.S., Eun-Sun Choi , Ph.D., Sang-Yoon Choi , Ph.D., Yong-Woo Shin , Ph.D., Seong Wook Pyo , M.S., Dae-Won Kim , Ph.D., Byung Hak Kang , Ph.D., Young Joon Park , M.D., and Gi-eun Rhie , Ph.D.
Abstract : Botulism is a neuroparalytic disease caused by a neurotoxin produced by Clostridium botulinum. This study aimed to genetically characterize C. botulinum strain isolated from the first case of infant botulism in Korea reported on June 17, 2019. We isolated C. botulinum strain CB-27 from a stool sample of the patient and analyzed the toxin types and toxin gene cluster compositions of the strain using a mouse bioassay, real-time PCR, and genome sequencing. Toxin gene cluster analysis showed that strain CB-27 possesses a C. botulinum neurotoxin type A harboring an unexpressed B gene. Although the nucleotide and amino acid sequences of toxin genes as well as the toxin gene cluster arrangements in strain CB-27 were identical to those of the known strain CDC_69094, the total nucleotide sequences of the toxin gene clusters of CB-27 differed from those of CDC_69094 by 0.47%, indicating genetic diversity of toxin gene clusters of CB-27 among other previously reported C. botulinum strains. To our knowledge, this is the first description of a C. botulinum strain with two separate toxin gene clusters in Korea.
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