Antimicrobial stewardship programs (ASPs) can lower antibiotic use, decrease medical expenses, prevent the emergence of resistant bacteria, and enhance treatment for infectious diseases. This study summarizes the stepwise implementation and effects of ASPs in a single university-affiliated tertiary care hospital in Korea; it also presents future directions and challenges in resource-limited settings. At the study hospital, the core elements of the ASP such as leadership commitment, accountability, and operating system were established in 2000, then strengthened by the formation of the Antimicrobial Stewardship (AMS) Team in 2018. The actions of ASPs entail key components including a computerized restrictive antibiotic prescription system, prospective audit, post-prescription review through quantitative and qualitative intervention, and pharmacy-based interventions to optimize antibiotic usage. The AMS Team regularly tracked antibiotic use, the effects of interventions, and the resistance patterns of pathogens in the hospital. The reporting system was enhanced and standardized by participation in the Korea National Antimicrobial Use Analysis System, and educational efforts are ongoing. Stepwise implementation of the ASP and the efforts of the AMS Team have led to a substantial reduction in the overall consumption of antibiotics, particularly regarding injectables, and optimization of antibiotic use. Our experience highlights the importance of leadership, accountability, institution-specific interventions, and the AMS Team.

Invasive fungal infections (IFIs) are common causes of mortality and morbidity in patients with hematologic diseases. Delayed initiation of antifungal treatment is related to mortality. Aspergillus sp. is the leading cause of IFI followed by Candida sp. Diagnosis is often challenging owing to variable conditions related to underlying diseases. Clinical suspect and prompt management is important. Imaging, biopsy, and non-culture-based tests must be considered together. New diagnostic procedures have been improved, including antigen-based assays and molecular detection of fungal DNA. Among hematologic diseases, patients with acute myeloid leukemia, myelodysplastic syndrome, recipients of hematopoietic stem cell transplantation are at high risk for IFIs. Antifungal prophylaxis is recommended for these high-risk patients. There are continuous attempts to achieve ideal management of IFIs. Scoring system for quality control has been developed with important recommendations of current guidelines. Higher adherence to guidelines is related to decreased mortality in IFIs.

Objective: To report the clinical and radiological characteristics of patients with underlying B-cell lymphoma and coronavirus disease 2019 (COVID-19) showing migratory airspace opacities on serial chest computed tomography (CT) with persistent COVID-19 symptoms. Materials and Methods: From January 2020 to June 2022, of the 56 patients with underlying hematologic malignancy who had undergone chest CT more than once at our hospital after acquiring COVID-19, seven adult patients (5 female; age range, 37–71 years; median age, 45 years) who showed migratory airspace opacities on chest CT were selected for the analysis of clinical and CT features. Results: All patients had been diagnosed with B-cell lymphoma (three diffuse large B-cell lymphoma and four follicular lymphoma) and had received B-cell depleting chemotherapy, including rituximab, within three months prior to COVID-19 diagnosis. The patients underwent a median of 3 CT scans during the follow-up period (median 124 days). All patients showed multifocal patchy peripheral ground glass opacities (GGOs) with basal predominance in the baseline CTs. In all patients, followup CTs demonstrated clearing of previous airspace opacities with the development of new peripheral and peribronchial GGO and consolidation in different locations. Throughout the follow-up period, all patients demonstrated prolonged COVID-19 symptoms accompanied by positive polymerase chain reaction results from nasopharyngeal swabs, with cycle threshold values of less than 25. Conclusion COVID-19 patients with B-cell lymphoma who had received B-cell depleting therapy and are experiencing prolonged SARS-CoV-2 infection and persistent symptoms may demonstrate migratory airspace opacities on serial CT, which could be interpreted as ongoing COVID-19 pneumonia.

BACKGROUND: Recently, Citrobacter freundii bacteremia outbreak in a neonatal intensive care unit has attracted public attention in Korea. However, Citrobacter bacteremia is uncommon and usually occurs in patients with underlying diseases such as malignancy and hepatobiliary diseases. Increase in resistance and emerging of multidrug resistance among Citrobacter species have gradually been reported. The aim of this study was to investigate the clinical characteristics and outcome of C. freundii and non-freundii bacteremia and antimicrobial susceptibility trends. MATERIALS AND METHODS: We reviewed the medical records of patients with Citrobacter bacteremia at St. Mary's Hospital, from 2007 to 2017. RESULTS: A total of 43 patients with a median age of 72 (24-93) years was identified and 90.7% of them had comorbidities. Twenty-nine (67.4%) patients had C. freundii bacteremia while 14 had non-freundii bacteremia (six of C. braakii, five of C. koseri, two of C. amalonaticus and one of C. youngae). A total of 26 (51.2%) patients had community-acquired infection and intra-abdominal infection including hepatobiliary tract was the most common portal of entry (24/43, 55.8%). Moreover, hepatobiliary tract was the leading primary site of nosocomial infection (9/17, 52.9%). Polymicrobial bacteremia was observed in 21 (48.8%) patients. The percentages of Citrobacter species susceptible to ampicillin, amikacin, aztreonam, cefazolin, cefoxitin, cefotaxime, cefepime, piperacillin-tazobactam, ciprofloxacin, and imipenem were 9.5%, 97.6%, 73.8%, 9.5%, 14.3%, 71.4%, 92.9%, 83.3%, 83.3% and 100%, respectively. The resistance rate did not increase during the study period. Of 39 patients treated with antibiotics, 36 (92.3%) received appropriate empirical antibiotics. Overall mortality was 18.6%. High Charlson comorbidity index and Pitt bacteremia score were significant risk factors for death in univariate analysis and showed trends in the multivariate analysis. No significant difference in clinical features and antimicrobial susceptibility rate was observed between C. freundii and non-freundii bacteremia. CONCLUSION Citrobacter bacteremia was predominant in the elderly with comorbidities, while no pediatric case was observed. Hepatobiliary tract is the leading primary focus of bacteremia both in community-acquired and nosocomial infection. The rate of susceptibility to antibiotics has not changed in the last 11 years.

Background: Patients with hematologic diseases are at high risk of bloodstream infections (BSIs). This study aimed to analyze clinical features and distributions of microorganisms in patients with hematologic diseases presenting at a tertiary care university-affiliated hospital in Korea. Materials and Methods: We retrospectively reviewed all BSI episodes recorded in patient medical records at two hematologic wards of the Catholic Hematology Hospital from January to December 2020. Our aim was to analyze demographic and clinical characteristics relevant to BSIs. We also described the antimicrobial resistance patterns of the major pathogens identified in this study, and evaluated risk factors for extended-spectrum beta-lactamase (ESBL) production in Enterobacteriaceae isolates and for vancomycin resistance in enterococcal isolates. Results: A total of 380 BSI episodes were identified in 334 patients over the course of 1 year (monomicrobial BSI episodes, 86.1%; polymicrobial BSI episodes, 13.9%). Gram-negative bacteria accounted for 242 isolates (54.8%). The most frequently isolated Gram-negative bacteria isolates were Escherichia coli (107 [24.2%]) followed by Klebsiella spp. (72 [16.3%]), Pseudomonas spp. (21 [4.8%]), and Enterobacter spp. (12 [2.7%]). The most commonly identified Gram-positive bacteria were Enterococcus spp. (72 [16.3%]) followed by viridans streptococci (54 [12.2%]), coagulase-negative staphylococci (CoNS) (24 [5.4%]), and Corynebacterium spp. (22 [5.0%]). ESBL-producing Enterobacteriaceae accounted for 25.1% of the total distribution. Among 54 Enterococcus faecium isolates, 100.0% were resistant to ampicillin and 55.6% showed resistance to vancomycin, while 100.0% (n = 12) of Enterococcus faecalis isolates were susceptible to ampicillin and vancomycin, respectively. Use of ciprofloxacin prophylaxis (odds ratio: 5.20; 95% confidence interval: 1.11 - 24.34; P = 0.04) was an independent risk factor for ESBL production in Enterobacteriaceae BSIs. Conclusion Compared with the results of a previous study conducted at the same institution, our findings demonstrated that Gram-negative bacteria remained dominant pathogens in BSIs occurring in patients with hematologic diseases. Our findings also demonstrated a comparatively decreased prevalence of ESBL-producing Enterobacteriaceae in the evaluated BSIs. However, the prevalence of enterococcal BSIs had not decreased, and the proportion of vfancomycin-resistant Enterococcus isolates from E. faecium BSIs had increased. In addition, we found that ciprofloxacin prophylaxis was statistically significantly associated with ESBL production in Enterobacteriaceae BSIs. We conclude that, in order to avoid critical complications and to reduce the burden of antimicrobial-resistant organisms in patients with hematologic diseases, it is necessary to conduct periodic examinations evaluating changes in BSI epidemiology within a single medical center.

Identifying inappropriately prescribed antibiotics for infectious diseases by monitoring the quality of antibiotics use is essential for effective implementation of antibiotic stewardship. Qualitative assessment of the use of antibiotics has been conducted in some countries, including Korea, since the 2000s. The qualitative assessment generally involves an assessment of each component of the antibiotics prescription process, based on specific criteria. However, there is no standardized assessment method or cycle, and infectious diseases or antibiotics included in the assessments vary from country-to-country.According to the results reported in the United States, Europe, Australia, and Korea so far, approximately 20 - 55% of all antibiotics prescriptions are inappropriate. In this review, we describe the current progress in the quality assessment of the use of antibiotics on a global scale. Further, we highlight the future directions to improve antibiotic stewardship activities and the quality assessment of the use of antibiotics in Korea.

Background/Aims: The risk factors and clinical impacts of coronavirus disease 2019 (COVID-19)-associated pulmonary aspergillosis (CAPA) remain controversial, and no data have been reported in Korea. This study aimed to investigate the epidemiology and importance of CAPA diagnostic efforts and to identify the predictors of CAPA and the impacts on clinical outcomes. Methods: Between January 2020 and May 2021, data of severely to critically ill COVID-19 patients were extracted from seven hospitals of the Catholic Medical Center through a clinical data warehouse. Corticosteroid use was subcategorized into total cumulative dose, early 7-day dose, mean daily dose, and duration of use. Results: A total of 2,427 patients were screened, and 218 patients were included. CAPA was diagnosed in 4.6% (10/218) of all hospitalized and 11.2% (10/89) of intensive care unit patients. Total cumulative dose (over 1,000 mg as methylprednisolone) and daily high-dose corticosteroid use (over 60 mg/day) were independent predictors but not early 7-day high-dose corticosteroid use (over 420 mg/week) (odds ratio [OR], 1.731; 95% confidence interval [CI], 0.350 to 8.571) nor prolonged use (OR, 2.794; 95% CI, 0.635 to 13.928). In-hospital overall mortality was 11.9% (26 of 218). CAPA itself did not affect the outcome; rather, daily high-dose steroid use significantly increased the 30-day mortality (hazard ratio, 5.645; 95% CI, 1.225 to 26.091). Conclusions CAPA was not uncommon, especially in critically ill patients. Daily high-dose corticosteroid use was the predictor of CAPA and associated with high mortality rates. High-dose corticosteroids use after early inflammatory phase should be avoided, and active surveillance methods for CAPA are essential for those high-risk patients.