Background Serratia marcescens is a gram-negative bacterium that is widespread in the environment. S. marcescens bacteremia can be fatal during pregnancy and cause persistent chorioamnionitis. This study reports an outbreak of Serratia marcescens bloodstream infection (BSI) among high-risk pregnant women in an obstetric ward. The purpose of this study is to report our experience with the usefulness of the ATP test in hospital environmental management and to confirm that bloodstream infections of patients with the same strain were correlated by WGS testing. Methods This retrospective study collected the data of inpatients with S. marcescens bacteremia in obstetric ward for high-risk pregnant women from August 22, 2021, to October 14, 2021. We performed: an adenosine triphosphate (ATP) bioluminescence test in the environment with a high-contact area; environmental culture; on-site monitoring and staff education; and whole-genome sequencing (WGS) to evaluate genetic relationships among S. marcescens isolates. Results S. marcescens BSI occurred in four consecutive patients. None of the patients had central venous catheters. An ATP bioluminescence test revealed that high-contact areas and areas for injection preparation were not clean (≥ 1000 relative light units). However, S. marcescens was not identified in the environmental cultures, likely due to intensive environmental cleaning and discarding of potentially contaminated specimens before the culture test. On-site monitoring and education were conducted for 1 month. There were no further reports of BSI until 6 months after the last patient was discharged. WGS performed on three isolates from three patients indicated that the isolated S. marcescens was likely from the same strain. Conclusions We controlled an S. marcescens outbreak by improving environmental cleaning as well as education of and behavior changes in healthcare workers. Using the ATP bioluminescence test can provide feedback on environmental cleaning and education. WGS played a role in determining the spread of BSI caused by the same strain.

BACKGROUND:We aimed to describe the clinical and microbiological characteristics of enterococcal bacteremia, as well as the effect of Enterococcus resistance against vancomycin on clinical outcomes in Korean children. METHODS:We retrospectively reviewed the medical records of children diagnosed with enterococci isolated from blood cultures at Pusan National University Children's Hospital between December 2009 and November 2021. RESULTS:In total, 64 patients were enrolled in the study. The median age was 0 years (range 0-15), and 43 (67.2%) patients were male. Enterococcus faecalis (50%) was the most commonly identified bacterial strain. Significant underlying diseases were present in 60 patients (93.8%), and the source of bacteremia was identified in 36 patients (56.3%). Among these, intravascular device was the most common identifiable source. Fifty-six (87.5%) patients had previously received broad-spectrum antibiotics and 54 (84.4%) patients were nosocomial in origin. Twenty-nine (45.3%) strains were resistant to ampicillin, and 16 (25%) strains were resistant to vancomycin. All patients with vancomycin-resistant enterococci (VRE) had underlying disease (P = 0.199), and focus of bacteremia was significantly more frequent in VRE patients (P = 0.014). Of all the patients, after appropriate antibiotic treatment, five (7.8%) patients had recurrent enterococcal bacteremia, and seven (10.9%) patients were diagnosed with bacteremia, defined as other pathogens from blood culture. The 30-day mortality rate was 7.8%. CONCLUSION:Enterococcal bacteremia in children is usually nosocomial and occurs in children with serious underlying diseases. Because the number of enrolled patients and mortality were small in our study, it is difficult to identify whether the factor that determines prognosis in patients with enterococcal bacteremia is VRE or an underlying disease. Further studies with a large number of patients in a specific group are needed.

Objective. MacConkey agar (MAC) is commonly used as a primary medium for conventional bacterial identification in clinical microbiology laboratories. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has revolutionized microbial identification and is considered a reliable identification tool. While conventional identification methods rely on colony characteristics, MALDI-TOF MS requires a pure isolate on a solid medium. Methods. This study investigated whether MAC can be omitted as a routine inoculation medium for urine, lower respiratory tract (LRT), and positive blood culture samples. The study included 462 clinical samples. Among these, 221 were urine samples, 141 were positive blood cultures, and the remaining 100 were LRT samples. The samples were inoculated on blood agar (BA) and MAC for the control group and on BA only for the experimental group, followed by incubation and identification with MALDI-TOF MS. Results. The BA only group showed the same microbial identification using MALDI-TOF MS as the control BA and MAC groups for blood and LRT specimens. For urine samples, 99.1% (219/221) of the samples produced the same identification results for the two groups. The cause of discrepant results for two urine specimens was due to Proteus species overgrowth on BA, which hindered non-Proteus spp. identification for the BA-only group. Conclusion. Our results may indicate that omitting MAC has little or no impact on the recovery of organisms present in culture. However, due to possible Proteus spp. overgrowth, caution should be exercised in the decision to omit MAC from the primary inoculating medium, which necessitates further studies in other centers with a larger sample size.

Background: We aimed to determine the impact of the coronavirus disease 2019 (COVID-19) pandemic on central nervous system (CNS) infections by comparing FilmArray Meningitis/Encephalitis (ME) panel (BioFire Diagnostics, USA) data before and during the pandemic, and the clinical significance of detecting human herpesvirus 6 (HHV-6) in ME panel.Methods: The positive rate and distribution of ME panel results were compared at a tertiary care hospital during pre-pandemic (P1: January 17, 2018 to August 31, 2018) and pandemic (P2: April 9, 2021 to December 21, 2021) periods.Clinical evaluations were performed in patients positive for HHV-6, and HHV-6 quantitative PCR (qPCR) was performed only on patients with samples available.Results: The total positive rate of the ME panel markedly decreased from 28.9% (125/432) in P1 to 7.3% (15/205) in P2 (P <0.05).The positive rates of enterovirus and human parechovirus also decreased significantly, from 15.3% to 0.0%, and from 5.3% to 0.0%, respectively (P <0.05).The most common pathogens identified were enterovirus (52.8%) in P1 and HHV-6 (46.7%) in P2.The detection of HHV-6 in the ME panel was clinically inconsistent with HHV-6 CNS infection in most cases.Only one patient, transplant recipient of hematopoietic stem cell, was positive for qPCR on cerebrospinal fluid and blood, likely to have HHV-6 CNS infection.Conclusions: The positive rates of the ME panel decreased during the COVID-19 pandemic, likely due to nonpharmaceutical interventions implemented worldwide.The detection of HHV-6 in the ME panel should be interpreted with caution, and additional qPCR can be helpful.

Acquired fluconazole resistance (FR) in bloodstream infection (BSI) isolates of Candida albicans is rare. We investigated the FR mechanisms and clinical features of 14 fluconazole non-susceptible (FNS; FR and fluconazole-susceptible dose-dependent) BSI isolates of C. albicans recovered from Korean multicenter surveillance studies during 2006- 2021. Mutations causing amino acid substitutions (AASs) in the drug-target gene ERG11 and the FR-associated transcription factor genes TAC1, MRR1, and UPC2 of the 14 FNS isolates were compared with those of 12 fluconazole-susceptible isolates. Of the 14 FNS isolates, eight and seven had Erg11p (K143R, F145L, or G464S) and Tac1p (T225A, R673L, A736T, or A736V) AASs, respectively, which were previously described in FR isolates. Novel Erg11p, Tac1p, and Mrr1p AASs were observed in two, four, and one FNS isolates, respectively. Combined Erg11p and Tac1p AASs were observed in seven FNS isolates. None of the FR-associated Upc2p AASs were detected. Of the 14 patients, only one had previous azole exposure, and the 30-day mortality rate was 57.1% (8/14). Our data show that Erg11p and Tac1p AASs are likely to contribute to FR in C. albicans BSI isolates in Korea and that most FNS C. albicans BSIs develop without azole exposure.

Background and Objectives: This study aimed to evaluate the performance of a new chemiluminescent immunoassay-based tuberculosis (TB) interferon-gamma release assay (IGRA), AdvanSureI3 TB-IGRA (LG Chem Ltd., Seoul, Republic of Korea), for detecting latent tuberculosis infection in comparison with T-SPOT.TB (Oxford Immunotec, Oxford, UK). Materials and Methods: Between June 2021 and December 2021, 125 non-duplicate blood specimens were collected from adult volunteers; each subject received both tests concurrently. Total agreement and Cohen’s kappa coefficient (κ) were used to calculate concordance. The Jonckheere–Terpstra test was used to examine the correlation between interferon-gamma (IFN-γ) levels in AdvanSureI3 TB-IGRA and spot counts in T-SPOT.TB. Results: The IGRA findings of the two assays revealed 90.8% (95% confidence interval [CI] = 84.2–94.8) total agreement with κ of 0.740 (95% CI = 0.595–0.885), showing substantial agreement between the two tests. Additionally, the amount of IFN-γ in AdvanSureI3 TB-IGRA increased with the spot counts in T-SPOT.TB (p < 0.001). Conclusions: Our research revealed that the results of the AdvanSureI3 TB-IGRA were comparable to those of T-SPOT.TB.

Background There is a global increase in isolation of nontuberculous mycobacteria (NTM). The aim of the study was to analyze longitudinal trends of NTM identification and pattern of antimicrobial susceptibility testing. Methods NTM recovery rates, distribution of NTM species identification, and antimicrobial susceptibility pattern of NTM at Pusan National University Yangsan Hospital between January 2016 and December 2020 were retrospectively analyzed. Results A total of 52,456 specimens from 21,264 patients were submitted for mycobacterial culture, of which 2,521 from 1,410 patients were NTM positive over five years (January 2016 to December 2020). NTM isolation showed an increasing trend from 2016 to 2020 (p<0.001, test for trend) mainly caused by Mycobacterium avium complex. The vast majority of M. avium complex were susceptible to key agents clarithromycin and amikacin. For Mycobacterium kansasii, resistance to rifampin and clarithromycin is rare. Amikacin was the most effective drug against Mycobacterium abscessus subspecies abscessus and Mycobacterium subspecies massiliense. Most of M. subspecies massiliense were susceptible to clarithromycin, while the majority of M. abscessus subspecies abscessus were resistant to clarithromycin (p<0.001). Conclusion There was an increasing trend of NTM isolation in our hospital. Resistance to key drugs was uncommon for most NTM species except for M. abscessus subspecies abscessus against clarithromycin.

Tuberculosis (TB) is one of the leading cause of infection-related deaths worldwide. Conventional diagnostic methods for TB require infectious samples and are time-consuming. In this study, we aimed to develop an aptamer-based qPCR (Apta-qPCR) assay to diagnose TB safely and rapidly. The assay uses a single-stranded DNA aptamer with affinity for a TB biomarker, ESAT6, and molecular beacon capable of hybridizing to the aptamer. Apta-qPCR enables aptamer-mediated detection of ESAT6 via qPCR, wherein the aptamer serves as both a target recognition agent and template for quantification. This diagnostic method achieved a desirable detection limit of 2.03 nM in buffer and 2.56 nM in serum-spiked conditions with high reproducibility and reliability. In addition, the diagnostic performance was verified in a clinical application using human serum samples from normal controls and patients with active TB. The assay showed 50.0% sensitivity, 91.7% specificity, and 78.1% accuracy, similar to sputum smear microscopy, which is currently the most used method for TB diagnosis. Importantly, this assay has an advantage over smear microscopy in that it reduces the risk of infection by avoiding the use of sputum-containing infectious pathogens.

Seong-Eun Ryu, M.D., Hyun-Ji Lee, M.D., Ji-Hyun Shin, M.D., Kyung-Hwa Shin, M.D., Dong-Won Yoo, M.D., Hyung-Hoi Kim, M.D., Chulhun L. Chang, M.D.. KJBT 2022;33:171-7. https://doi.org/10.17945/kjbt.2022.33.3.171

Automated flow cytometry‐based urine analyzer is increasingly being used to identify and enumerate cells and particles in urine specimens. It measures electrical conductivity which could be transformed to osmolality. Using this machine, all urine specimens could be screened for osmolality without requiring a separate dedicated device. We evaluated the performance of the new instrument, the UF‐5000 (Sysmex Corporation), in the measurement of urine osmolality.

Background Multidrug-resistant Acinetobacter baumannii (MDRAB) is widespread among intensive care units worldwide, posing a threat to patients and the health system. We describe the successful management of a MDRAB outbreak by implementing an infection-control strategy in a pediatric intensive care unit (PICU). Methods This retrospective study investigated the patients admitted to the PICU in periods 1 (8 months) and 2 (7 months), from the index MDRAB case to intervention implementation, and from intervention implementation to cessation of MDRAB spread. An infection-control strategy was designed following six concepts: 1) cohort isolation of colonized patients, 2) enforcement of hand hygiene, 3) universal contact precautions, 4) environmental management, 5) periodic surveillance culture study, and 6) monitoring and feedback. Results Of the 427 patients, 29 were confirmed to have MDRAB colonization, of which 18 had MDRAB infections. Overall incidence per 1,000 patient days decreased from 7.8 (period 1) to 5.8 (period 2). The MDRAB outbreak was declared terminated after the 6-month follow-up following period 2. MDRAB was detected on the computer keyboard and in condensed water inside the ventilator circuits. The rate of hand hygiene performance was the lowest in the three months before and after index case admission and increased from 84% (period 1) to 95% (period 2). Patients with higher severity, indicated by a higher Pediatric Risk of Mortality III score, were more likely to develop colonization (P = 0.030), because they had invasive devices and required more contact with healthcare workers. MDRAB colonization contributed to an increase in the duration of mechanical ventilation and PICU stay (P < 0.001), but did not affect mortality (P = 0.273). Conclusion The MDRAB outbreak was successfully terminated by the implementation of a comprehensive infection-control strategy focused on the promotion of hand hygiene, universal contact precautions, and environmental management through multidisciplinary teamwork.

Objective: Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease. Identifying mutated causative genes can provide diagnostic and prognostic information. In this study, we describe the clinical application of a next generation sequencing (NGS)-based, targeted multi-gene panel test for the genetic diagnosis of patients with ADPKD. Methods: We applied genetic analysis on 26 unrelated known or suspected patients with ADPKD. A total of 10 genes related to cystic change of kidney were targeted. Detected variants were classified according to standard guidelines. Results: We identified 19 variants (detection rate: 73.1%), including PKD1 (n = 18) and PKD2 (n = 1). Of the 18 PKD1 variants, 8 were novel. Conclusion: Multigene panel test can be a comprehensive tool in a clinical setting for genetic diagnosis of ADPKD. It allows us to identify clinically significant novel variants and confirm the diagnosis, and these objectives are difficult to achieve using conventional diagnostic tools.

The electronic nose is a reliable practical sensor device that mimics olfactory organs. Although numerous studies have demonstrated excellence in detecting various target substances with the help of ideal models, biomimetic approaches still suffer in practical realization because of the inability to mimic the signal processing performed by olfactory neural systems. Herein, we propose an electronic nose based on the programable surface chemistry of M13 bacteriophage, inspired by the neural mechanism of the mammalian olfactory system. The neural pattern separation (NPS) was devised to apply the pattern separation that operates in the memory and learning process of the brain to the electronic nose. We demonstrate an electronic nose in a portable device form, distinguishing polycyclic aromatic compounds (harmful in living environment) in an atomic-level resolution (97.5% selectivity rate) for the first time. Our results provide practical methodology and inspiration for the second-generation electronic nose development toward the performance of detection dogs (K9).

There is a growing interest in electronic nose-based diagnostic systems that are fast and portable. However, existing technologies are suitable only for operation in the laboratory, making them difficult to apply in a rapid, non-face-to-face, and field-suitable manner. Here, we demonstrate a DNA-derived phage nose (D2pNose) as a portable respiratory disease diagnosis system requiring no pretreatment. D2pNose was produced based on phage colour films implanted with DNA sequences from mammalian olfactory receptor cells, and as a result, it possesses the comprehensive reactivity of these cells. The manipulated surface chemistry of the genetically engineered phages was verified through a correlation analysis between the calculated and the experimentally measured reactivity. Breaths from 31 healthy subjects and 31 lung cancer patients were collected and exposed to D2pNose without pretreatment. With the help of deep learning and neural pattern separation, D2pNose has achieved a diagnostic success rate of over 75% and a classification success rate of over 86% for lung cancer based on raw human breath. Based on these results, D2pNose can be expected to be directly applicable to other respiratory diseases.

Background In Korea, there were issues regarding the use of immunoassays for anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies to detect infection. So, we compared antibody results of eight kinds of commercial immunoassays using clinical remnant specimens. Methods We compared the results of several immunoassay kits tested on 40 serum samples from 15 confirmed patients and 86 remnant serum samples from clinical laboratory. Eight kinds of IVD kits—four enzyme-linked immunosorbent assay, two lateral flow rapid immunochromatographic assays, and two chemiluminescent immunoassays with one RUO kit were tested. Results Among 40 serum samples from 15 coronavirus disease 2019 (COVID-19) patients, 35 yielded at least one positive result for detecting antibodies in the combined assessment. There were inconsistent results in 12 (28%) samples by single immunoassay. Forty samples collected in 2019 before the first COVID-19 Korean case showed negative results except for one equivocal result. Conclusion The discrepant results obtained with different immunoassay kits in this study show that serological assessment of SARS-CoV-2 by a single immunoassay requires caution not only in detecting infection but also in assessing immunologic status.

Multidrug-resistant strain of Acinetobacter baumannii (MDRAB) is an emerging pathogen in health care facilities, preventing MDRAB is a public health concern. We conducted this experiment on a clinical isolate of A. baumannii with two main goals: the role of the efflux pump system in the stress provision of carbapenem and the response to the transcription level of the efflux pump gene. A total of 34 strains of A. baumannii was isolated from the Yangsan Hospital of Pusan National University. First, when we compared and observed the expression of the efflux pump gene and antibacterial resistance to carbapenem, a strong correlation was observed between carbapenem resistance and overexpression of adeB ( P =0.0056). Second, a correlation between the efflux pump and concentration gradient and tolerance to carbapenem stress at the AdeABC efflux pump genes transcription level was confirmed. Our results revealed that the expression of the AdeABC efflux pump is an important resistance determinant in obtaining antibiotic resistance of the carbapenem group in A. baumannii .

Background: We retrospectively evaluated the pathogens in the cerebrospinal fluid (CSF) of pediatric meningitis/encephalitis (M/E) by FilmArray meningitis/encephalitis panel (FA-MEP), and the characteristics of children showing positive and negative FA MEP results. Method: FA-MEP along with conventional tests (bacterial/viral cultures, and polymerase chain reaction tests) was performed in children who presented symptoms of M/E. Clinical and laboratory data were reviewed to evaluate the characteristics of children with pathogens detected by FA-MEP. Results: The CSF specimens from 110 pediatric M/E patients were enrolled. Mean age of the patients was 5.9 5.2 years. Overall positive rate of FA-MEP was 46.4% (51/110). The pathogens detected in the patients were enterovirus (23/51, 45.1%), parechovirus (10/51, 19.6%), S. pneumoniae (7/51, 13.7%), human herpesvirus type 6 (6/51, 11.8%), S. agalactiae (3/51, 5.9%), herpes simplex virus type 2 (1/51, 2.0%), and E. coli (1/51, 2.0%). Aseptic meningitis (OR, 3.24, 95% CI, 1.18-12.73) and a duration of <2 days from onset of symptoms to CSF test (OR, 3.56, 95% CI, 0.1-0.91) significantly contributed to detection of pathogens by the FA-MEP. Among the 14 children who were administered empiric antibiotics before the CSF test, the detection rate was significantly higher in the FA-MEP than in the conventional test (28.6 vs. 0.0%, p = 0.031). Conclusions: FA-MEP had a higher detection rate in children with M/E compared with conventional tests, particularly aseptic meningitis, and in case of shorter duration of time-to-test. This test was more effective than the conventional test in pediatric M/E patients that had been administered empiric antibiotics. (C) 2020 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.