Comparative Analysis of Clinical Outcomes Using Propensity Score Matching: Coronavirus Disease 2019 vs. Seasonal Influenza in Korea.

BACKGROUND: The advent of the omicron variant and the formulation of diverse therapeutic strategies marked a new epoch in the realm of coronavirus disease 2019 (COVID-19). Studies have compared the clinical outcomes between COVID-19 and seasonal influenza, but such studies were conducted during the early stages of the pandemic when effective treatment strategies had not yet been developed, which limits the generalizability of the findings. Therefore, an updated evaluation of the comparative analysis of clinical outcomes between COVID-19 and seasonal influenza is requisite. METHODS: This study used data from the severe acute respiratory infection surveillance system of South Korea. We extracted data for influenza patients who were infected between 2018 and 2019 and COVID-19 patients who were infected in 2021 (pre-omicron period) and 2022 (omicron period). Comparisons of outcomes were conducted among the pre-omicron, omicron, and influenza cohorts utilizing propensity score matching. The adjusted covariates in the propensity score matching included age, sex, smoking, and comorbidities. RESULTS: The study incorporated 1,227 patients in the pre-omicron cohort, 1,948 patients in the omicron cohort, and 920 patients in the influenza cohort. Following propensity score matching, 491 patients were included in each respective group. Clinical presentations exhibited similarities between the pre-omicron and omicron cohorts; however, COVID-19 patients demonstrated a higher prevalence of dyspnea and pulmonary infiltrates compared to their influenza counterparts. Both COVID-19 groups exhibited higher in-hospital mortality and longer hospital length of stay than the influenza group. The omicron group showed no significant improvement in clinical outcomes compared to the pre-omicron group. CONCLUSION: The omicron group did not demonstrate better clinical outcomes than the pre-omicron group, and exhibited significant disease severity compared to the influenza group. Considering the likely persistence of COVID-19 infections, it is imperative to sustain comprehensive studies and ongoing policy support for the virus to enhance the prognosis for individuals affected by COVID-19.

Impact of Nonpharmacological Interventions on Severe Acute Respiratory Infections in Children: From the National Surveillance Database.

BACKGROUND: Nonpharmacological interventions (NPIs) reduce the incidence of respiratory infections. After NPIs imposed during the coronavirus disease 2019 pandemic ceased, respiratory infections gradually increased worldwide. However, few studies have been conducted on severe respiratory infections requiring hospitalization in pediatric patients. This study compares epidemiological changes in severe respiratory infections during pre-NPI, NPI, and post-NPI periods in order to evaluate the effect of that NPI on severe respiratory infections in children. METHODS: We retrospectively studied data collected at 13 Korean sentinel sites from January 2018 to October 2022 that were lodged in the national Severe Acute Respiratory Infections (SARIs) surveillance database. RESULTS: A total of 9,631 pediatric patients were admitted with SARIs during the pre-NPI period, 579 during the NPI period, and 1,580 during the post-NPI period. During the NPI period, the number of pediatric patients hospitalized with severe respiratory infections decreased dramatically, thus from 72.1 per 1,000 to 6.6 per 1,000. However, after NPIs ceased, the number increased to 22.8 per 1,000. During the post-NPI period, the positive test rate increased to the level noted before the pandemic. CONCLUSION: Strict NPIs including school and daycare center closures effectively reduced severe respiratory infections requiring hospitalization of children. However, childcare was severely compromised. To prepare for future respiratory infections, there is a need to develop a social consensus on NPIs that are appropriate for children.

Characteristics of recent HIV infection among individuals newly diagnosed as HIV-positive in South Korea (2008-2015).

Most HIV-positive individuals diagnosed in Korea are infected through sexual contact, with the time of HIV infection therefore often being unknown. The aim of this study was to investigate the characteristics of diagnosed patients near the time of HIV seroconversion to establish useful HIV intervention strategies. Cross-sectional study. Newly diagnosed HIV cases based on the national HIV surveillance system in South Korea, 2008-2015. To distinguish recent from long-standing HIV infection among 5898 nationwide HIV-positive specimens, limiting antigen avidity assays (Sedia HIV-1 LAg-Avidity EIA, cut-off = 1.5) were performed. Data on CD4+ T cell count at HIV diagnosis and death from AIDS within one year after first HIV diagnosis were used to distinguish recent HIV infections. Acute HIV infection is characterized by detectable HIV RNA or HIV p24 antigen levels, along with a negative or indeterminate antibody western blot result, but with the subject subsequently testing positive after a predetermined period. We analyzed the characteristics of recent and acute HIV infections by sex, age, nationality, HIV testing site, region, and reason for HIV testing. Recent and acute HIV infections were described as the proportion of recent and acute HIV infections among newly-diagnosed cases in a given year. Recent and acute HIV infections over the 8-year study period were 20.5% (1210/5898) and 9.5% (562/5898), respectively. Both infections were generally higher in the following groups: males, younger age, Koreans, individuals who were tested due to disease, residents of smaller city or rural area, and individuals diagnosed in recent calendar years. Acute infections were significantly higher among individuals tested in hospitals and due to suspected HIV infection. The recent and acute HIV infection in younger age groups (< 30 years) has been increasing in a given year. There was an increase in the proportion of young individuals with recent HIV infection, and we identified risk groups more at risk of HIV infection recently in Korea. Therefore, our results could prove useful for the development and assessment of national HIV prevention strategies in Korea and provide valuable data for further HIV research.

Author Correction: Characteristics of Adolescents and Young adults with HIV in the Republic of Korea from 2010 through 2015.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Characteristics of Adolescents and Young adults with HIV in the Republic of Korea from 2010 through 2015.

Although the number of newly diagnosed cases of HIV is decreasing worldwide, those in Korea have been steadily on the rise, especially among adolescents (ages 10-19 years) and young adults (ages 20-29 years). To identify the characteristics in the new diagnosis among these age groups, we analyzed HIV testing sizes and HIV prevalence under the national HIV surveillance system in Korea in the last six years. We collected data of HIV tests conducted at Blood Banks (BB), Public Health Centers (PHCs), and Military Manpower Administration (MMA) nationwide every year from 2010 to 2015, except for anonymous tests. HIV prevalence, calculated as the number of new HIV-diagnosed cases per 10,000 test-takers per year, was analyzed according to sex, age, institution, and reason for HIV testing. Data were analyzed using logistic regression. In the three testing institutes, there were new cases of HIV with 50% and 95% of cases diagnosed in young adults and adolescents, respectively. The total size of HIV tests at the three sites was approximately 3.5 million tests per year; 80% of these were conducted in BBs, 10% in PHCs, and 10% in MMA. HIV prevalence, according to age, increased across all age groups for the six years, especially prevalent in young adults doubled during that period (1.01 per 10,000 test-takers in 2010, 2.45 in 2015). HIV prevalence among the "suspected" young male adults who visited PHCs for tests, was highest during the six years, increasing 6.5 times in the last two years (315.79 per 10,000 test-takers in 2014, 335.55 in 2015) compared to before 2014. We identified the characteristics of growing HIV infection in Korea as the increase of HIV prevalence among the suspected of young male adults at PHCs. Further, we propose that HIV prevalence in MMA can be used as an essential index for national HIV surveillance of adolescent boys in Korea.

Tuberculosis prevention and care in Korea: Evolution of policy and practice.

Tuberculosis (TB) in Korea remains a serious health problem with an estimated 77 per 100,000 incidence rate for 2016. This makes Korea as the only OECD country with high incidence of TB. The government has increased budgets and strengthened patient management policies since 2011. The management of latent tuberculosis was added to the response with strengthened and extensive contact investigations in the five-year tuberculosis control plan (2013-2017) and implementation was established in 2013. Due to these efforts Korea has achieved an average 5.2% reduction annually in tuberculosis incidence rate between 2011 and 2016. To further expedite the reduction of the TB burden the government has introduced additional measures including mandatory screening of latent tuberculosis infection for community workers in congregate settings including daycare centers for children, kindergarten, and teachers in schools and health care workers in clinics and hospitals to solve the problems identified through contact investigations in 2017. Providing high quality free diagnosis and treatment of active TB including for multidrug resistant TB combined with active contact investigations is the mainstay of the current programmatic response in Korea. However, the limitation of existing tools for LTBI pose challenge including absence of best mechanism for effective communication with professionals and the public, the need for at least 3 months of treatment and the risk of side effects. Developing effective tools will help to overcome these challenges.

Complete Genome Sequence of Klebsiella pneumoniae subsp. pneumoniae KP617, Coproducing OXA-232 and NDM-1 Carbapenemases, Isolated in South Korea.

The prevalence of Klebsiella pneumoniae coproducing carbapenemase metallo-ß-lactamase 1 (NDM-1) and OXA-48 has been increasing globally since 2013. The complete genome of KP617 was sequenced and assembled into a circular chromosome and two plasmids. This sequence provides the genetic background for understanding the evolution of carbapenemase genes in K. pneumoniae KP617.

Investigation of Biofilm Formation and its Association with the Molecular and Clinical Characteristics of Methicillin-resistant Staphylococcus aureus.

OBJECTIVES: To investigate the biofilm-forming related factors against MRSA bloodstream isolates and evaluates their clinical features and treatment outcomes by biofilm production. METHODS: We collected 126 consecutive methicillin-resistant Staphylococcus aureus (MRSA) causing blood stream infections (BSIs) at 10 tertiary hospitals from 2007 to 2009. We investigated biofilm-forming ability using a microtiter plate assay, and molecular characteristics including multilocus sequence typing, staphylococcal cassette chromosome mec and accessory gene regulator types. We compared the clinical characteristics and outcomes of patients infected with biofilm-forming and non-biofilm-forming MRSA isolates. RESULTS: Of the 126 samples, 86 (68.3%), including 5 strong level (OD570 ≥ 1.0) and 81 weak level (0.2 ≤ OD570 < 1.0), had biofilm-forming capacity. Detection of fibronectinbinding protein in biofilm-forming strains was significantly higher than biofilm non-forming ones (p = 0.001) and three enterotoxin genes (sec-seg-sei) islands had a high frequency regardless of biofilm production. However, biofilm-forming strains were more likely to be multidrug resistant (three or more non-ß-lactam antibiotics) than biofilm non-forming ones [79.2% vs. 59.2%, p = 0.015, odds ratio (OR) 2.629, 95% confidence interval (CI) 1.92-5.81]. Clinical features of patients with BSIs caused by biofilm-forming MRSA strains were more likely to be hospital onset [77.9% vs. 60.0%, p = 0.024, OR 2.434, 95% CI 1.11-5.33) and more frequently occurred in patients with use of invasive devices [85.7% vs. 61.2%, p = 0.002, OR 3.879, 95% CI 1.61-8.97]. The other clinical features were compared with the clinical outcomes of the two groups and were not significant (p > 0.05). CONCLUSION: Biofilm-forming MRSA strains showed higher frequency of fnbB gene than biofilm non-forming ones and more incidence rates on particular genotypes. And, their patient's features were not significantly different between two groups in this study, except for several clinical factors.

Comparison of genetic epidemiology of vancomycin-resistant Enterococcus faecium isolates from humans and poultry.

This study was conducted to investigate the molecular characteristics and genetic relatedness of vancomycin-resistant Enterococcus faecium (VREF) isolates obtained from humans and poultry in Korea. A total of 147 VREF isolates from humans (71 clinical isolates) and poultry (76 isolates) in Korea were compared with respect to their antibiotic susceptibilities, organization of the Tn1546 transposon element, detection of virulence genes (esp and hyl), pulsed-field gel electrophoresis (PFGE) typing and multilocus sequence typing (MLST). All of the human and poultry isolates had the vanA gene and 11.3% (8/71) of the clinical isolates showed the VanB phenotype/vanA genotype. PCR mapping of the Tn1546 elements was different for isolates of the two groups: human isolates were classified into five transposon types, whereas all poultry isolates were identical to Tn1546 of E. faecium strain BM4147. The esp gene was detected in both human (93.0%, 66/71) and poultry (26.3%, 20/76) isolates, as was the hyl gene (human isolates: 80.3%, 57/71; poultry isolates: 26.3%, 20/76). Using MLST, the 71 human isolates could be divided into ten sequence types (STs) belonging to clonal complex (CC) 17 (except for one singleton). The 76 poultry isolates were categorized into 14 STs and 88.2% (67/76) of the poultry isolates belonged to CC26. PFGE typing of the human isolates demonstrated diverse PFGE profiles among the strains. However, the PFGE patterns of the poultry isolates were possibly related to the strains collected from individual farms. These data suggest that epidemic clonal groups of human and poultry VREFs in Korea have evolved through different evolutionary processes.

In vitro biofilm formation and bactericidal activities of methicillin-resistant Staphylococcus aureus clones prevalent in Korea.

The purpose of this study was to quantify the biofilm formations of various methicillin-resistant Staphylococcus aureus (MRSA) clones (ST1, ST5, ST72, ST89, ST239, and ST254) and to evaluate the in vitro activities of antibiotics. Of 86 MRSA isolates tested, 44 isolates (51.2 %) formed biofilms, including 8 strong biofilm producers (7 isolates of ST72 and 1 isolate of ST89). The planktonic MICs, minimal bactericidal concentrations, and minimum biofilm eradication concentrations (MBECs) of 6 antibiotics (clindamycin, gentamicin, linezolid, vancomycin, daptomycin, and tigecycline) were measured for 8 MRSA isolates. The planktonic isolates were susceptible to all agents, with daptomycin being the most effective, followed by gentamicin and vancomycin. However, clindamycin, linezolid, and tigecycline showed bacteriostatic activity against most of the isolates. The biofilms were resistant to high concentrations of most drugs. However, the MBEC values of daptomycin and tigecycline were lower overall than that of other antibiotics. Microscopy studies verified that daptomycin was the most effective drug used in adhesive biofilms, while gentamicin and tigecycline exhibited some bactericidal efficacy. Our results demonstrated that ST72 and ST89 form strong biofilms that may cause problems in hospital setting, and daptomycin, gentamicin, and tigecycline may be choice therapeutics against biofilm-mediated S. aureus infections.

Nationwide surveillance study of vancomycin intermediate Staphylococcus aureus strains in Korean hospitals from 2001 to 2006.

We investigated the prevalence and the molecular characteristics of vancomycin-intermediate Staphylococcus aureus (VISA) among methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from clinical samples at tertiary or general hospitals participating in a nationwide surveillance program for VISA and vancomycin-resistant Staphylococcus aureus (VRSA) in Korea during an 8-week period in each year from 2001 to 2006. Of 41,639 MRSAs isolated, 37,856 were screened and 169 grew on brain heart infusion agar supplemented with 4 microg/ml vancomycin. A vancomycin MIC of 4 microg/ml was confirmed for 33 VISA isolates of the 169 isolates. Eighteen of the 33 isolates were classified as hetero-VISA (hVISA) by the population analysis profile (PAP) method. All VISA isolates were susceptible to linezolid, tigecycline, and quinupristin-dalfopristin. Most VISA isolates (MIC 4 microg/ml) showed a PFGE C pattern with sec, seg, and sei enterotoxin genes, including ST5-SCCmec type II, or a PFGE A pattern with sea, including ST239-SCCmec type III.