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  • MDPI AG  (6)
  • Kim, Sung-Han  (6)
  • 1
    Online Resource
    Online Resource
    Dynamics of Viral Shedding and Symptoms in Patients with Asymptomatic or Mild COVID-19
    MDPI AG ; 2021
    In:  Viruses Vol. 13, No. 11 ( 2021-10-22), p. 2133-
    Details
    In: Viruses, MDPI AG, Vol. 13, No. 11 ( 2021-10-22), p. 2133-
    Abstract: We conducted a prospective cohort study at a community facility designated for the isolation of individuals with asymptomatic or mild COVID-19 between 10 January and 22 February 2021 to investigate the relationship of viral shedding with symptom changes of COVID-19. In total, 89 COVID-19 adult patients (12 asymptomatic, 16 presymptomatic, 61 symptomatic) were enrolled. Symptom scores, the genomic RNA and subgenomic RNA of SARS-CoV-2 from saliva samples with a cell culture were measured. Asymptomatic COVID-19 patients had a similar viral load to symptomatic patients during the early course of the disease, but exhibited a rapid decrease in viral load with the loss of infectivity. Subgenomic RNA and viable virus by cell culture in asymptomatic patients were detected only until 3 days after diagnosis, and the positivity of the subgenomic RNA and cell culture in symptomatic patients gradually decreased in both from 40% in the early disease course to 13% at 10 days and 4% at 8 days after the symptom onset, respectively. In conclusion, symptomatic patients have a high infectivity with high symptom scores during the early disease course and gradually lose infectivity depending on the symptom. Conversely, asymptomatic patients exhibit a rapid decrease in viral load with the loss of infectivity, despite a similar viral load during the early disease course.
    Type of Medium: Online Resource
    ISSN: 1999-4915
    URL: Article
    DOI: 10.3390/v13112133
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2516098-9
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  • 2
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    In Vitro Activities of Ceftazidime–Avibactam and Aztreonam–Avibactam at Different Inoculum Sizes of Extended-Spectrum β-Lactam-Resistant Enterobacterales Blood Isolates
    MDPI AG ; 2021
    In:  Antibiotics Vol. 10, No. 12 ( 2021-12-05), p. 1492-
    Details
    In: Antibiotics, MDPI AG, Vol. 10, No. 12 ( 2021-12-05), p. 1492-
    Abstract: β-lactam–avibactam combinations have been proposed as carbapenem-sparing therapies, but little data exist on their in vitro activities in infections with high bacterial inocula. We investigated the in vitro efficacies and the inoculum effects of ceftazidime–avibactam and aztreonam–avibactam against extended-spectrum β-lactam-resistant Enterobacterales blood isolates. A total of 228 non-repetitive extended-spectrum β-lactam-resistant Escherichia coli and Klebsiella pneumoniae blood isolates were prospectively collected in a tertiary center. In vitro susceptibilities to ceftazidime, aztreonam, meropenem, ceftazidime–avibactam, and aztreonam–avibactam were evaluated by broth microdilution method using standard and high inocula. An inoculum effect was defined as an eightfold or greater increase in MIC when tested with the high inoculum. Of the 228 isolates, 99% were susceptible to ceftazidime–avibactam and 99% had low aztreonam–avibactam MICs (≤8 mg/L). Ceftazidime–avibactam and aztreonam–avibactam exhibited good in vitro activities; MIC50/MIC90 values were 0.5/2 mg/L, 0.125/0.5 mg/L, and ≤0.03/0.25 mg/L, respectively, and aztreonam–avibactam was more active than ceftazidime–avibactam. The frequencies of the inoculum effect with ceftazidime–avibactam and aztreonam–avibactam were lower than with meropenem (14% vs. 38%, p 〈 0.001 and 30% vs. 38%, p = 0.03, respectively). The β-lactam-avibactam combinations could be useful as carbapenem-sparing strategies, and aztreonam–avibactam has the better in vitro activity but is more subject to the inoculum effect than ceftazidime–avibactam.
    Type of Medium: Online Resource
    ISSN: 2079-6382
    URL: Article
    DOI: 10.3390/antibiotics10121492
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2681345-2
    SSG: 15,3
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  • 3
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    Kinetics of Glycoprotein-Specific Antibody Response in Patients with Severe Fever with Thrombocytopenia Syndrome
    MDPI AG ; 2022
    In:  Viruses Vol. 14, No. 2 ( 2022-01-27), p. 256-
    Details
    In: Viruses, MDPI AG, Vol. 14, No. 2 ( 2022-01-27), p. 256-
    Abstract: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tickborne disease in East Asia that is causing high mortality. The Gn glycoprotein of the SFTS virus (SFTSV) has been considered to be an essential target for virus neutralization. However, data on anti-Gn glycoprotein antibody kinetics are limited. Therefore, we investigated the kinetics of Gn-specific antibodies compared to those of nucleocapsid protein (NP)-specific antibodies. A multicenter prospective study was performed in South Korea from January 2018 to September 2021. Adult patients with SFTS were enrolled. Anti-Gn-specific IgM and IgG were measured using an enzyme-linked immunosorbent assay. A total of 111 samples from 34 patients with confirmed SFTS were analyzed. Anti-Gn-specific IgM was detected at days 5–9 and peaked at day 15–19 from symptom onset, whereas the anti-NP-specific IgM titers peaked at days 5–9. Median seroconversion times of both anti-Gn- and NP-specific IgG were 7.0 days. High anti-Gn-specific IgG titers were maintained until 35–39 months after symptom onset. Only one patient lost their anti-Gn-specific antibodies at 41 days after symptom onset. Our data suggested that the anti-Gn-specific IgM titer peaked later than anti-NP-specific IgM, and that anti-Gn-specific IgG remain for at least 3 years from symptom onset.
    Type of Medium: Online Resource
    ISSN: 1999-4915
    URL: Article
    DOI: 10.3390/v14020256
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2516098-9
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  • 4
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    Pitfall of Universal Pre-Admission Screening for SARS-CoV-2 in a Low Prevalence Country
    MDPI AG ; 2021
    In:  Viruses Vol. 13, No. 5 ( 2021-04-30), p. 804-
    Details
    In: Viruses, MDPI AG, Vol. 13, No. 5 ( 2021-04-30), p. 804-
    Abstract: It is unclear whether universal PCR screening for SARS-CoV-2 in asymptomatic individuals prior to admission is useful. From April to December 2020, the positive rate of universal pre-admission screening was 0.005% (4/76,521) in a tertiary care hospital in Korea. The positive rates were not different between the periods (period 1 (daily new patients of 〈 1 per million inhabitants) vs. period 2 (1–8.3 per million inhabitants) vs. period 3 (10.3 to 20 per million inhabitants); P = 0.45). Universal pre-admission screening for SARS-CoV-2 had a lower positive rate than that of symptom-based screening (0.005% vs. 0.049% (53/109,257), p 〈 0.001). In addition, seven patients with negative pre-admission test results had subsequent positive PCR during hospitalization, and four patients had secondary transmission. Universal pre-admission PCR screening may not be practical in settings of low prevalence of COVID-19, and negative PCR results at admission should not serve as a basis for underestimating the risk of nosocomial spread from asymptomatic patients.
    Type of Medium: Online Resource
    ISSN: 1999-4915
    URL: Article
    DOI: 10.3390/v13050804
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2516098-9
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  • 5
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    In Vitro Activities and Inoculum Effects of Ceftazidime-Avibactam and Aztreonam-Avibactam against Carbapenem-Resistant Enterobacterales Isolates from South Korea
    MDPI AG ; 2020
    In:  Antibiotics Vol. 9, No. 12 ( 2020-12-15), p. 912-
    Details
    In: Antibiotics, MDPI AG, Vol. 9, No. 12 ( 2020-12-15), p. 912-
    Abstract: Ceftazidime-avibactam (CAZ-AVI) and aztreonam-avibactam (AZT-AVI) are novel antibiotic combinations active against multidrug-resistant Gram-negative pathogens. This study aimed to evaluate their in vitro activities and inoculum effects in carbapenem-resistant Enterobacterales (CRE), including carbapenemase-producing (CP)-CRE and non-CP-CRE. A total of 81 independent clinical isolates of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae were collected. CAZ-AVI and AZT-AVI minimal inhibitory concentrations (MICs) were evaluated by broth microdilution using standard and high inocula. The inoculum effect was defined as an ≥8-fold increase in MIC with high inoculum. Phenotypic determination of β-lactam resistance mechanism and PCR for carbapenemase genes were performed. Of the 81 CRE isolates, 35 (43%) were CP-CRE. Overall, 73% of the isolates were susceptible to CAZ-AVI, and 95% had low AZT-AVI MICs (≤8 µg/mL). The MIC50/MIC90s of CAZ-AVI and AZT-AVI were 4/≥512 µg/mL and 0.5/4 µg/mL, respectively. CAZ-AVI was more active against non-CP-CRE than against CP-CRE (susceptibility 80% vs. 63%, p = 0.08; MIC50/MIC90, 2/16 μg/mL vs. 4/≥512 μg/mL), whereas AZT-AVI was more active against CP-CRE (MIC50/MIC90, 0.25/1 μg/mL vs. 0.5/8 μg/mL). All four isolates with high AZT-AVI MIC (≥16 μg/mL) were resistant to CAZ-AVI, but only 18% (4/22) of CAZ-AVI-resistant isolates had high AZT-AVI MIC. The rates of the inoculum effect for CAZ-AVI and AZT-AVI were 18% and 47%, respectively (p 〈 0.001). Interestingly, the frequency of the AZT-AVI inoculum effect was higher in K. pneumoniae than E. coli (64% vs. 8%, p 〈 0.001). AZT-AVI is more active against CRE than CAZ-AVI, even in CP-CRE and CAZ-AVI-resistant isolates. The presence of a substantial inoculum effect may contribute to clinical failure in high-inoculum infections treated with AZT-AVI.
    Type of Medium: Online Resource
    ISSN: 2079-6382
    URL: Article
    DOI: 10.3390/antibiotics9120912
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2681345-2
    SSG: 15,3
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  • 6
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    Molecular Characteristics and Prevalence of Rifampin Resistance in Staphylococcus aureus Isolates from Patients with Bacteremia in South Korea
    MDPI AG ; 2023
    In:  Antibiotics Vol. 12, No. 10 ( 2023-10-04), p. 1511-
    Details
    In: Antibiotics, MDPI AG, Vol. 12, No. 10 ( 2023-10-04), p. 1511-
    Abstract: Rifampin resistance (RIF-R) in Staphylococcus aureus (S. aureus) with rpoB mutations as one of its resistance mechanisms has raised concern about clinical treatment and infection prevention strategies. Data on the prevalence and molecular epidemiology of RIF-R S. aureus blood isolates in South Korea are scarce. We used broth microdilution to investigate RIF-R prevalence and analyzed the rpoB gene mutation in 1615 S. aureus blood isolates (772 methicillin-susceptible and 843 methicillin-resistant S. aureus (MRSA)) from patients with bacteremia, between 2008 and 2017. RIF-R prevalence and antimicrobial susceptibility were determined. Multilocus sequence typing was used to characterize the isolate’s molecular epidemiology; Staphylococcus protein A (spa), staphylococcal cassette chromosome mec (SCCmec), and rpoB gene mutations were detected by PCR. Among 52 RIF-R MRSA isolates out of 57 RIF-R S. aureus blood isolates (57/1615, 0.4%; 5 methicillin-susceptible and 52 MRSA), ST5 (44/52, 84.6%), SCCmec IIb (40/52, 76.9%), and spa t2460 (27/52, 51.9%) were predominant. rpoB gene mutations with amino acid substitutions showed that A477D (17/48, 35.4%) frequently conferred high-level RIF resistance (MIC 〉 128 mg/L), followed by H481Y (4/48, 8.3%). RIF-R S. aureus blood isolates in South Korea have unique molecular characteristics and are closely associated with rpoB gene mutations. RIF-R surveillance through S. aureus–blood isolate epidemiology could enable effective therapeutic management.
    Type of Medium: Online Resource
    ISSN: 2079-6382
    URL: Article
    DOI: 10.3390/antibiotics12101511
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2681345-2
    SSG: 15,3
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