Background: Enzyme immunoassays (EIAs), which detect glutamate dehydrogenase (GDH) and toxin A/B, are widely used to screen for Clostridioides difficile infection (CDI); however, their sensitivity is lower than that of molecular assays. This study aimed to evaluate the performance of two EIAs, C. Diff Quik Chek Complete (QCC) and RIDASCREEN (RIDA), and investigate the cycle threshold (Ct) values from two real-time polymerase chain reaction (PCR) assays (Allplex GI–Bacteria(I) and Xpert C. difficile) in EIA-discordant samples. Methods: A total of 180 clinical stool samples were tested using QCC, RIDA, and Allplex GI– Bacteria(I) PCR assays. The Xpert C. difficile assay was used to analyze discordant results. Results: QCC and RIDA showed high sensitivities for GDH detection, 100.0% and 94.4%, respectively. QCC was significantly more sensitive than RIDA for toxin detection (51.4% vs. 28.6%, p = 0.007). In 25 EIA-discordant, Xpert positive samples, the Ct values of the toxin B gene ranged from 31.5 to 44.8 (mean, 38.1) for Allplex PCR and from 23.7 to 36.3 (mean, 30.4) for Xpert PCR. The Ct values of the two PCR assays were not significantly correlated (r = 0.201, p = 0.324). Conclusion QCC is a suitable initial immunological test for diagnosing CDI. The lack of correlation in the Ct values between the two real-time PCR assays suggests that assay-specific validation is necessary for cutoff level interpretation.

Background: The accurate laboratory-based detection of respiratory viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is essential for effective patient management and infection control in the post–coronavirus disease 2019 era. In this study, the performance of the PowerChek Respiratory Virus Panels 1–4 assay (Kogene Biotech) in detecting non-SARS-CoV-2 respiratory viruses and SARS-CoV-2 was compared with those of two established commercial assays. Methods: Residual clinical respiratory specimens collected between December 2023 and February 2024 were retested using the PowerChek assay. Of the 129 specimens retested, 80 had tested positive for 14 non-SARS-CoV-2 respiratory virus targets in the Allplex Respiratory Panels 1–3 assay (Seegene) and 49 had been tested using the Alinity m SARS-CoV-2 assay (Abbott; 20 positive and 29 negative for SARS-CoV-2). Agreement, Cohen’s kappa, and discordant results were assessed. Results: For the 14 non-SARS-CoV-2 respiratory virus targets, the virus-specific overall percent agreement (OPA) ranged from 95.0% to 100%, the positive percent agreement (PPA) ranged from 66.7% to 100%, and the negative percent agreement (NPA) ranged from 96.0% to 100%, with kappa values of 0.64–1.00. Lower agreements were observed for human coronavirus OC43 and influenza A virus. For SARS-CoV-2 detection, the OPA was 98.0% (PPA, 95.0%; NPA, 100%; kappa, 0.96). Conclusion The detection performance of the PowerChek assay was comparable to those of the established assays for most respiratory virus targets, with lower agreement observed for some targets. These features support its practical utility for the routine multiplex molecular detection of respiratory viruses, including SARS-CoV-2.

Background: Pathogenic Escherichia coli (PEC) is a leading cause of acute diarrhea worldwide. With increasing antibiotic use, antimicrobial resistance in PEC has become a significant public health concern. In this study, we investigated the distribution and antimicrobial susceptibility patterns of PEC isolated from patients with acute diarrhea in the Busan and Gyeongnam regions of South Korea. Methods: In this retrospective cross-sectional laboratory-based study, 272 PCR-positive residual stool or rectal swab specimens collected between October 2023 and June 2024 were screened; after exclusion of 80 specimens without recoverable or confirmable isolates, 192 pathogenic E. coli isolates were included for pathotype identification and antimicrobial susceptibility testing. Pathotypes were identified using multiplex real-time polymerase chain reaction, and antimicrobial susceptibility was tested against 18 agents using the VITEK II system. Results: Enteroaggregative E. coli (EAEC) was the most prevalent pathotype (44.8%), followed by enteropathogenic E. coli (34.9%). High resistance rates were observed for ampicillin (77.1%), cefazolin (55.2%), and amoxicillin/clavulanic acid (44.3%). EAEC demonstrated the highest multidrug resistance (MDR) rate (34.9%). Pediatric patients (< 18 years) exhibited significantly higher resistance rates and MDR frequencies compared with adults, particularly against β-lactam antibiotics. Conclusion EAEC was identified as the predominant and most resistant pathotype in this region. The elevated resistance levels in children and the prevalence of MDR EAEC underscore the need for continuous local surveillance and appropriate antibiotic stewardship.

Background: Environmental contamination with multidrug-resistant organisms (MDROs), including carbapenem-resistant Acinetobacter baumannii (CRAB) and multidrug-resistant Pseudomonas aeruginosa (MRPA), remains a major challenge in healthcare facilities.Hypochlorous acid water (HOCl) has emerged as a promising disinfectant owing to its strong antimicrobial activity and favorable safety profile. This study aimed to evaluate the bactericidal efficacy of atomized HOCl against CRAB and MRPA in a hospital room. Methods: An atomization experiment was conducted in a two-bed room. CRAB and MRPA were prepared using drying and non-drying methods, respectively. HOCl (CLFine) at concentration of 40 and 300 ppm was atomized using ultrasonic humidifiers. Bacterial samples were collected at 0, 1, 3, and 5 h after atomization. Viable bacterial counts were determined by culture, and bactericidal efficacy was evaluated. Results: Atomized HOCl exhibited time- and concentration-dependent bactericidal effects against CRAB and MRPA. CRAB and MRPA reached their limits of detection at 3 and 5 h postatomization at 40 ppm, and at 1 and 3 h at 300 ppm, respectively. Conclusion Atomized HOCl effectively inactivated CRAB and MRPA in a hospital room within 3–5 h. These findings support the potential application of HOCl atomization as an adjunctive environmental disinfection strategy for controlling MDRO contamination in healthcare facilities.

Cutaneous dermatophyte infections, dermatophytosis, are common worldwide, affecting various age groups and body parts. Despite advancements in antifungal therapies, the prevalence of dermatophytosis continues to increase, posing significant challenges for diagnosis and treatment. This review provides an overview of the prevalence, clinical features, and diagnostic methods for dermatophytosis in Korea. A comprehensive review of domestic reports and research on dermatophytosis in Korea was conducted using data from KoreaMed.This study covers the various clinical presentations, age distributions, seasonal trends, and types of dermatophytes identified in different body areas. Dermatophytosis in Korea have shown changing patterns in terms of prevalence and causative species. Trichophyton rubrum remains the most common causative organism, with varying presentations depending on the site of infection, such as tinea pedis, tinea corporis, tinea capitis, tinea faciei, and onychomycosis. Diagnostic practices largely depend on the potassium hydroxide smear test, which has limited sensitivity, particularly for onychomycosis. Recent trends indicate an increase in the incidence of dermatophytosis among older adults, which may be linked to underlying health conditions and lifestyle changes. Dermatophytosis in Korea exhibit diverse clinical manifestations influenced by factors such as patient age, body site, and seasonal variation. Improved diagnostic methods are needed to enhance the accuracy and guide appropriate treatment, especially with the emergence of antifungal-resistant strains. This review aims to provide a better understanding of the current state of dermatophytosis in Korea and contribute to more effective management and prevention strategies.

Background: The coronavirus disease 2019 (COVID-19) pandemic has significantly impacted global infrastructure. We surveyed laboratories to analyze the changes in testing methods and procedures to improve future pandemic preparedness. Methods: This study surveyed laboratory physicians and technologists in South Korea and analyzed responses from 126 of 323 institutions. The survey was conducted in May 2023 using the proficiency test of the Korean Association of External Quality Assessment Service and examined the diagnostic procedures, personnel, equipment, and quality control. The survey comprised 15 questions covering respondent demographics, public-private proficiency projects, COVID-19 testing procedures, and laboratory status. Results: Of the 126 laboratories, 66.7% performed bacterial smear and culture, 65.9% had biosafety level 2 facilities, and 39.7% had separate nucleic acid extraction areas. Furthermore, 98.4% of the laboratories had biological safety cabinets, the median number of PCR machines was four units, and 77.8% had autoclaves. The median numbers of personnel managing and conducting tests were one and three, respectively. Additionally, 88.1% of the laboratories found the COVID-19 proficiency test helpful, with key benefits in terms of accuracy and skill improvement. COVID-19 tests were primarily used for symptomatic or contact person testing, pre-admission screening, and periodic proactive testing. Specialized testing laboratories conducted up to 50,000 tests daily, and tertiary hospitals conducted up to 1,500 tests.Emergency, pooled, and rapid antigen tests were widely used. Most respondents wanted future tests for respiratory viruses, bacteria, and viral diarrhea, indicating a willingness to participate. Conclusion Aggressive testing and collaboration between health agencies and laboratories are crucial for managing emerging diseases. Systematic preparations are essential to maintain and strengthen laboratory capabilities for future infectious disease outbreaks.

Background: The 16S rRNA-targeted next-generation sequencing (NGS) has been widely used as the primary tool for microbiome analysis. However, whether the sequenced microbial diversity absolutely represents the original sample composition remains unclear. This study aimed to evaluate whether 16S rRNA gene-targeted NGS accurately captures bacterial community composition. Methods: Mock communities were constructed using equal amounts of DNA from 18 bacterial strains in three formats: genomic DNA, recombinant plasmids, and polymerase chain reaction (PCR) templates. The V3V4 region of the 16S rRNA gene was amplified and sequenced using the Illumina MiSeq. Results: Data regression analysis revealed that the recombinant plasmid produced more accurate and precise correlation curve than that by the gDNA and PCR products, with a slope closest to 1 (1.0082) and the highest R² value (0.9975). Despite the same input amount of bacterial DNA, the NGS read distribution varied across all three mock communities. Using multiple regression analysis, we found that the guanine-cytosine (GC) content of the V3V4 region, 16S rRNA gene, size of gDNA, and copy number of 16S rRNA were significantly associated with the NGS output of each bacterial species. Conclusion This study demonstrated that recombinant plasmids are the preferred option for quality control and that NGS output is biased owing to certain bacterial characteristics, such as %GC content, gDNA size, and 16S rRNA gene copy number. Further research is required to develop a system that compensates for NGS process biases using mock communities.