Background: The epidemiology of pathogenic bacteria varies according to the socioeconomic status and antimicrobial resistance status. However, longitudinal epidemiological studies to evaluate the changes in species distribution and antimicrobial susceptibility of pathogenic bacteria nationwide are lacking. We retrospectively investigated the nationwide trends in species distribution and antimicrobial susceptibility of pathogenic bacteria over the last 20 years in Korea. Methods: From 1997 to 2016, annual cumulative antimicrobial susceptibility and species distribution data were collected from 12 university hospitals in five provinces and four metropolitan cities in South Korea. Results: The prevalence of Staphylococcus aureus was the highest (13.1%) until 2012 but decreased to 10.3% in 2016, consistent with the decrease in oxacillin resistance from 76.1% in 2008 to 62.5% in 2016. While the cefotaxime resistance of Escherichia coli increased from 9.0% in 1997 to 34.2% in 2016, E. coli became the most common species since 2013, accounting for 14.5% of all isolates in 2016. Pseudomonas aeruginosa and Acinetobacter baumannii rose to third and fifth places in 2008 and 2010, respectively, while imipenem resistance increased from 13.9% to 30.8% and 0.7% to 73.5% during the study period, respectively.Streptococcus agalactiae became the most common pathogenic streptococcal species in 2016, as the prevalence of Streptococcus pneumoniae decreased since 2010. During the same period, pneumococcal penicillin susceptibility decreased to 79.0%, and levofloxacin susceptibility of S. agalactiae decreased to 77.1% in 2016. Conclusion The epidemiology of pathogenic bacteria has changed significantly over the past 20 years according to trends in antimicrobial resistance in Korea. Efforts to confine antimicrobial resistance would change the epidemiology of pathogenic bacteria and, consequently, the diagnosis and treatment of infectious diseases.

Objective: To compare the outcomes of digital breast tomosynthesis (DBT) screening combined with ultrasound (US) with those of digital mammography (DM) combined with US in women with dense breasts. Materials and Methods: A retrospective database search identified consecutive asymptomatic women with dense breasts who underwent breast cancer screening with DBT or DM and whole-breast US simultaneously between June 2016 and July 2019. Women who underwent DBT + US (DBT cohort) and DM + US (DM cohort) were matched using 1:2 ratio according to mammographic density, age, menopausal status, hormone replacement therapy, and a family history of breast cancer. The cancer detection rate (CDR) per 1000 screening examinations, abnormal interpretation rate (AIR), sensitivity, and specificity were compared. Results: A total of 863 women in the DBT cohort were matched with 1726 women in the DM cohort (median age, 53 years; interquartile range, 40–78 years) and 26 breast cancers (9 in the DBT cohort and 17 in the DM cohort) were identified. The DBT and DM cohorts showed comparable CDR (10.4 [9 of 863; 95% confidence interval {CI}: 4.8–19.7] vs. 9.8 [17 of 1726;95% CI: 5.7–15.7] per 1000 examinations, respectively; P = 0.889). DBT cohort showed a higher AIR than the DM cohort (31.6% [273 of 863; 95% CI: 28.5%–34.9%] vs. 22.4% [387 of 1726; 95% CI: 20.5%–24.5%]; P < 0.001). The sensitivity for both cohorts was 100%. In women with negative findings on DBT or DM, supplemental US yielded similar CDRs in both DBT and DM cohorts (4.0 vs. 3.3 per 1000 examinations, respectively; P = 0.803) and higher AIR in the DBT cohort (24.8% [188 of 758; 95% CI: 21.8%–28.0%] vs. 16.9% [257 of 1516; 95% CI: 15.1%–18.9%; P < 0.001). Conclusion DBT screening combined with US showed comparable CDR but lower specificity than DM screening combined with US in women with dense breasts.

OBJECTIVES: We estimated the population prevalence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including unreported infections, through a Korea Seroprevalence Study of Monitoring of SARS-CoV-2 Antibody Retention and Transmission (K-SEROSMART) in 258 communities throughout Korea. METHODS: In August 2022, a survey was conducted among 10,000 household members aged 5 years and older, in households selected through two stage probability random sampling. During face-to-face household interviews, participants self-reported their health status, COVID-19 diagnosis and vaccination history, and general characteristics. Subsequently, participants visited a community health center or medical clinic for blood sampling. Blood samples were analyzed for the presence of antibodies to spike proteins (anti-S) and antibodies to nucleocapsid proteins (anti-N) SARS-CoV-2 proteins using an electrochemiluminescence immunoassay. To estimate the population prevalence, the PROC SURVEYMEANS statistical procedure was employed, with weighting to reflect demographic data from July 2022. RESULTS: In total, 9,945 individuals from 5,041 households were surveyed across 258 communities, representing all basic local governments in Korea. The overall population-adjusted prevalence rates of anti-S and anti-N were 97.6% and 57.1%, respectively. Since the Korea Disease Control and Prevention Agency has reported a cumulative incidence of confirmed cases of 37.8% through July 31, 2022, the proportion of unreported infections among all COVID-19 infection was suggested to be 33.9%. CONCLUSIONS The K-SEROSMART represents the first nationwide, community-based seroepidemiologic survey of COVID-19, confirming that most individuals possess antibodies to SARS-CoV-2 and that a significant number of unreported cases existed. Furthermore, this study lays the foundation for a surveillance system to continuously monitor transmission at the community level and the response to COVID-19.

Background/Aims: Besifovir dipivoxil maleate (BSV), an acyclic nucleotide phosphonate, shows potent antiviral activity against hepatitis B virus. Our previous 48-week trial revealed that BSV has comparable antiviral efficacy to tenofovir disoproxil fumarate (TDF) and better safety profiles in terms of improved renal and bone safety. This extension study evaluated the prolonged efficacy and safety of BSV in treatment-naive chronic hepatitis B patients. Methods: Patients continued to participate in an open-label BSV study after an initial 48-week double-blind comparison of BSV and TDF treatment. The antiviral efficacy and drug safety was evaluated up to 192 weeks in two groups: patients continuing BSV treatment (BSV-BSV) and patients switching from TDF to BSV after 48 weeks (TDF-BSV). Results: Among 197 patients receiving randomized treatments, 170 (86%) entered the open-label phase and 152 (77%) entered the 192-week extension study. Virological response rates over 192 weeks were 92.50% and 93.06% in the BSV-BSV and TDF-BSV groups, respectively (P=0.90). Hepatitis B envelop antigen seroconversion and alanine aminotransferase normalization rates were similar between the groups (P=0.75 and P=0.36, respectively). There were no drug-resistant mutations to BSV. Bone mineral density and renal function were well preserved in the BSV-BSV group, whereas these initially worsened then recovered after switching therapy in the TDF-BSV group. Conclusions BSV maintained potent antiviral efficacy after 192 weeks and showed no evidence of drug resistance. BSV was safe, well tolerated, and effective in patients who switched from TDF to BSV. Trial Registration Number: NCT01937806 (date: 10 Sep 2013).

Background/Aims: The clinical significance of partial virological response (PVR) in patients undergoing antiviral therapy is not well known. This study investigated whether PVR after 2 years of entecavir (ETV) therapy is associated with hepatocellular carcinoma (HCC) development in cirrhotic patients. Methods: A total of 472 naïve patients with hepatitis B virus (HBV)-associated cirrhosis who were treated with ETV for at least 2 years were retrospectively enrolled. Clinical characteristics, laboratory data, PVR, and noninvasive fibrosis markers (aspartate aminotransferase to platelet ratio and FIB-4 index) at 2 years after ETV commencement were analyzed for HCC risk. Results: After excluding those who developed HCC within 2 years of ETV therapy, 359 patients (mean age, 51±10 years; male 64.3%) were examined. During a median follow-up of 82 months, 80 patients developed HCC. In the univariate analysis, older age (hazard ratio [HR], 1.056; p<0.001), PVR (HR, 2.536; p=0.002), higher aspartate aminotransferase (HR, 1.018; p=0.005), lower albumin level (HR, 0.463; p<0.001), lower platelet count (HR, 0.993; p=0.01), and higher FIB-4 index (HR, 1.141; p<0.001) at 2 years after ETV commencement were risk factors for HCC. In the multivariate analysis, older age (HR, 1.046; 95% confidence interval [CI], 1.022 to 1.072; p<0.001), PVR (HR, 2.358; 95% CI, 1.310 to 4.245; p=0.004), and higher FIB-4 index (HR, 1.103; 95% CI, 1.035 to 1.177; p=0.003) were independent risk factors. Conclusions PVR and higher FIB-4 index after 2 years of ETV therapy were independent risk factors for HCC. Therefore, efforts to accomplish a complete virological response and reduce the FIB-4 index should be made.

Background/Aims: Besifovir dipivoxil maleate (BSV), an acyclic nucleotide phosphonate, shows potent antiviral activity against hepatitis B virus. Our previous 48-week trial revealed that BSV has comparable antiviral efficacy to tenofovir disoproxil fumarate (TDF) and better safety profiles in terms of improved renal and bone safety. This extension study evaluated the prolonged efficacy and safety of BSV in treatment-naive chronic hepatitis B patients. Methods: Patients continued to participate in an open-label BSV study after an initial 48-week double-blind comparison of BSV and TDF treatment. The antiviral efficacy and drug safety was evaluated up to 192 weeks in two groups: patients continuing BSV treatment (BSV-BSV) and patients switching from TDF to BSV after 48 weeks (TDF-BSV). Results: Among 197 patients receiving randomized treatments, 170 (86%) entered the open-label phase and 152 (77%) entered the 192-week extension study. Virological response rates over 192 weeks were 92.50% and 93.06% in the BSV-BSV and TDF-BSV groups, respectively (P=0.90). Hepatitis B envelop antigen seroconversion and alanine aminotransferase normalization rates were similar between the groups (P=0.75 and P=0.36, respectively). There were no drug-resistant mutations to BSV. Bone mineral density and renal function were well preserved in the BSV-BSV group, whereas these initially worsened then recovered after switching therapy in the TDF-BSV group. Conclusions BSV maintained potent antiviral efficacy after 192 weeks and showed no evidence of drug resistance. BSV was safe, well tolerated, and effective in patients who switched from TDF to BSV. Trial Registration Number: NCT01937806 (date: 10 Sep 2013).

Background/Aims: The clinical significance of partial virological response (PVR) in patients undergoing antiviral therapy is not well known. This study investigated whether PVR after 2 years of entecavir (ETV) therapy is associated with hepatocellular carcinoma (HCC) development in cirrhotic patients. Methods: A total of 472 naïve patients with hepatitis B virus (HBV)-associated cirrhosis who were treated with ETV for at least 2 years were retrospectively enrolled. Clinical characteristics, laboratory data, PVR, and noninvasive fibrosis markers (aspartate aminotransferase to platelet ratio and FIB-4 index) at 2 years after ETV commencement were analyzed for HCC risk. Results: After excluding those who developed HCC within 2 years of ETV therapy, 359 patients (mean age, 51±10 years; male 64.3%) were examined. During a median follow-up of 82 months, 80 patients developed HCC. In the univariate analysis, older age (hazard ratio [HR], 1.056; p<0.001), PVR (HR, 2.536; p=0.002), higher aspartate aminotransferase (HR, 1.018; p=0.005), lower albumin level (HR, 0.463; p<0.001), lower platelet count (HR, 0.993; p=0.01), and higher FIB-4 index (HR, 1.141; p<0.001) at 2 years after ETV commencement were risk factors for HCC. In the multivariate analysis, older age (HR, 1.046; 95% confidence interval [CI], 1.022 to 1.072; p<0.001), PVR (HR, 2.358; 95% CI, 1.310 to 4.245; p=0.004), and higher FIB-4 index (HR, 1.103; 95% CI, 1.035 to 1.177; p=0.003) were independent risk factors. Conclusions PVR and higher FIB-4 index after 2 years of ETV therapy were independent risk factors for HCC. Therefore, efforts to accomplish a complete virological response and reduce the FIB-4 index should be made.

Background/Aims: To prevent the perinatal transmission of hepatitis B virus (HBV) from mother to child, administration of an antiviral agent during pregnancy has been attempted in women who are either hepatitis B e antigen positive or have a high viral load. In this systematic review and meta-analysis with randomized controlled trials, we analyzed the efficacy and safety of tenofovir disoproxil fumarate (TDF) in preventing the perinatal transmission of HBV in pregnant women who have high HBV DNA titers. Methods: Multiple comprehensive databases (PubMed, EMBASE, and Cochrane databases) were searched for studies evaluating the efficacy of TDF for the prevention of perinatal transmission of HBV. Results: Two studies (one open label study and one double blind study) were included and analyzed. Intention-to-treat analysis (527 pregnancies) showed that the preventive effect of TDF was not significant (odds ratio [OR], 0.53; 95% confidence interval[CI], 0.13 to 2.17; p = 0.38, I2 = 81%). However, the per-protocol analysis showed that TDF significantly reduced perinatal transmission (OR, 0.10; 95% CI, 0.01 to 0.77; p = 0.03, I2 = 0%). There was no significant difference between the TDF group and the control group with respect to maternal and fetal safety outcomes. Conclusions In pregnant women who have high HBV DNA titers, TDF can reduce the perinatal transmission from mother to child without significant adverse events.

Purpose: This study compared the clinical and radiographic results of two proximal femoral nail antirotation II (PFNA-II) angled by 125° and 130° in patients with intertrochanteric fractures. Materials and Methods: From March in 2015 to September in 2016, 65 patients who underwent a closed reduction and internal fixation with PFNA-II for a femoral intertrochanteric fracture were evaluated retrospectively. The minimum follow-up period was two years. Of those, 30 and 35 patients underwent 125° angled PFNA-II and 130° angled PFNA-II, respectively. The clinical performance was evaluated using the Harris hip score, WOMAC (Western Ontario and McMaster Universities Osteoarthrtis Index), and UCLA (University of California Los Angeles) score. Radiographic analyses were performed using standardized anteroposterior and lateral radiographs to assess the implant position and quality of reduction. The blade length, distance between the blade tip and the tip of the greater trochanter, and distance between the blade tip and the most lateral protrusion point of the greater trochanter in the two groups were measured and compared. Results: The clinical results, including the Harris hip score, WOMAC, and UCLA, were similar in the two groups at the last follow-up postoperatively. In the radiography evaluation, the implant position, quality of reduction, and the blade length were similar in the two groups. The distances between the blade tip and the tip of the greater trochanter were 52.60±3.53 mm and 58.07±5.54 mm in the 125° angled PFNA-II and 130° angled PFNA-II groups, respectively. The distance between the blade tip and the most lateral protrusion point of greater trochanter were 16.48±2.54 mm and 21.19±4.43 mm in the 125° angled PFNA-II and 130° angled PFNA-II groups, respectively. The differences were significant (p=0.031, p=0.012). Conclusion The operation with the 125° angled PFNA-II showed a more superior and lateral position of the blade than that with the 130° angled PFNA-II. Nevertheless, lateral thigh pain can occur when the blade is positioned superolaterally.

Background: s/Aims: Rebleeding of gastric varices (GVs) after endoscopic variceal obturation (EVO) can be fatal. This study was performed to evaluate the usefulness of computed tomography (CT) for the prediction of rebleeding after EVO GV bleeding. Methods: Patients who were treated with EVO for GV bleeding and underwent CT before and after EVO were included. CT images of the portal phase showing pretreatment GVs and feeding vessels, and nonenhanced images showing posttreatment cyanoacrylate impaction were reviewed. Results: Fifty-three patients were included. Their mean age was 60.6±11.6 years, and 40 patients (75.5%) were men. Alcoholic liver disease was the most frequent underlying liver disease (45.3%). Complete impaction of cyanoacrylate in GVs and feeding vessels were achieved in 40 (75.5%) and 24 (45.3%) of patients, respectively. During the follow-up, GV rebleeding occurred in nine patients, and the cumulative incidences of GV rebleeding at 3, 6, and 12 months were 11.8%, 18.9%, and 18.9%, respectively. The GV rebleeding rate did not differ significantly according to the complete cyanoacrylate impaction in the GV, while it differed significantly according to complete cyanoacrylate impaction in the feeding vessels. The cumulative incidences of GV rebleeding at 3, 6, and 12 months were 22.3%, 35.2%, and 35.2%, respectively, in patients with incomplete impaction in feeding vessels, and there was no rebleeding during the follow-up period in patients with complete impaction in the feeding vessels (p=0.002). Conclusions Abdominal CT is useful in the evaluation of the treatment response after EVO for GV bleeding. Incomplete cyanoacrylate impaction in feeding vessels is a risk factor for GV rebleeding.