Sang-Ho Choi

Background: The epidemiology of pneumococcal pneumonia can be influenced by vaccine implementation, serotype replacement, and viral circulation. We aimed to investigate 15-year trends in the epidemiological and clinical characteristics of severe pneumococcal pneumonia patients requiring intensive care unit (ICU) admission.Methods: We analyzed data from a prospective cohort of adult patients with severe pneumonia admitted to the 28-bed medical ICU of a 2,700-bed tertiary hospital in South Korea between 2010 and 2024. Temporal changes in incidence, resistance to antimicrobial agents, frequency of coinfections, and mortality were evaluated across three 5-year periods.Results: Among 2,511 ICU patients with severe pneumonia, 140 (5.6%) had pneumococcal infections. The proportion of pneumococcal cases decreased from 9.9% in 2010–2014 to 4.2% in 2015–2019, and further to 2.2% in 2020–2024 (p<0.001 for trend). Conversely, ceftriaxone non-susceptibility rates rose sharply from 4.8% to 16.7% and 45.5% across the same periods (p<0.001). Coinfections were frequent and increased significantly, largely due to respiratory viruses, with rates of 48.9%, 61.8%, and 77.8%, respectively (p=0.02). Influenza was the predominant co-pathogen during 2015–2019, whereas severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was most frequent in 2020–2024. The 90-day mortality rates remained stable over time (29.5%, 38.2%, and 27.8%, p=0.64).Conclusion: In this single-center ICU cohort, the proportion of severe pneumococcal pneumonia cases decreased over the 15-year period, whereas ceftriaxone non-susceptibility and viral coinfections became more frequent. These trends should be interpreted cautiously given the lack of serotype and individual vaccination data and incomplete susceptibility results. Continued surveillance of pneumococcal disease, antimicrobial resistance, and respiratory coinfections is warranted.

Background: Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are common among critically ill patients, leading to increased morbidity and mortality rates. Conventional culture-based diagnostics require 48–72 hours, which delays pathogen identification and prolongs the use of broad-spectrum antibiotics. Multiplex polymerase chain reaction (mPCR) enables the rapid detection of pathogens and resistance genes, but its effects on real-world antibiotic decision-making remain unclear.Methods: This retrospective study included patients in the intensive care unit who were diagnosed with HAP or VAP at a tertiary medical center between July 2023 and June 2024. All patients underwent both mPCR and respiratory culture. The primary outcome was the time to the first antibiotic modification based on mPCR or respiratory culture. The secondary outcome was the rate of antibiotic de-escalation from carbapenem or teicoplanin/vancomycin based on mPCR findings.Results: In total, 75 patients were included (median age, 68 years; 61.3% male). mPCR identified bacterial pathogens in 45.3% cases, with a median turnaround time of 281 minutes. The median time to antibiotic modification was 5.8 hours for mPCR versus 122.32 hours for culture (P<0.01). Despite negative mPCR results for gram-negative bacilli, carbapenem therapy was discontinued in only 1 of 24 cases (4.2%). Among 39 patients with negative results for Staphylococcus aureus, vancomycin or teicoplanin was discontinued in only 3 cases (7.7%).Conclusions: mPCR provided faster pathogen identification and earlier antibiotic modifications than conventional respiratory culture. However, antibiotic discontinuation remained uncommon despite negative mPCR results, highlighting challenges in real-world antimicrobial stewardship.

Methicillin-resistant Staphylococcus aureus (MRSA) remains a major cause of bloodstream infection worldwide. In Korea, sequence type (ST) 72 has predominated, whereas ST8, including the USA300 lineage, has recently emerged. Comparative data on these genotypes in MRSA bacteremia (MRSAB) are limited. We conducted a retrospective cohort study of adult patients with MRSAB admitted to a 2700-bed tertiary care hospital in Republic of Korea between July 2008 and December 2020. Clinical features and outcomes of patients with ST8 MRSA were compared with those of patients with ST72 MRSA. Among 1975 cases of S. aureus bacteremia, 998 (50.5%) were due to MRSA, including 327 (32.7%) ST72 and 23 (2.3%) ST8 isolates. Demographics and comorbidities were similar, though pneumonia appeared more frequent in ST8 cases without statistical significance. ST8 isolates exhibited greater resistance to ciprofloxacin and erythromycin and more frequent vancomycin E-test MICs ≥1 mg/L, while broth microdilution MICs were comparable. spa type distribution differed, with t324 predominating in ST72 and t008 in ST8. Management practices, persistent bacteremia, recurrence, and 30- and 90-day mortality did not differ significantly. In multivariable analysis, liver cirrhosis and Charlson comorbidity index >4, but not MRSA genotype, independently predicted 30-day mortality. These findings highlight the importance of continued surveillance of emerging ST8 clones.

Diabetes mellitus predisposes individuals to a broad spectrum of infections. People with diabetes face a 1.5- to 4-fold increased risk of both common and severe infections, and infections remain the leading cause of morbidity and mortality. Chronic hyperglycemia impairs neutrophil chemotaxis, oxidative burst, and complement activation, while vascular insufficiency and neuropathy compromise tissue perfusion and barrier integrity. These defects, together with altered skin, mucosal, and gut microbiota, influence the marked susceptibility to urinary tract infections (especially renal abscess and emphysematous pyelonephritis), osteomyelitis, diabetic foot infections, pneumonia (including influenza), tuberculosis, skin and soft tissue infections, and lifethreatening syndromes such as emphysematous cholecystitis and rhino-orbital mucormycosis that are almost exclusive to people with diabetes. Outcomes from infections are worse in diabetes. Although the core therapeutic principles align with those for patients without diabetes, management should be individualized. Glycemic control should balance infection risk and hypoglycemia; antimicrobial dosing should account for renal function and drug interactions; and strict antimicrobial stewardship is required. If needed, prompt debridement and multidisciplinary intervention are necessary to mitigate complications and reduce mortality. Preventive care relies on comprehensive vaccination (influenza, pneumococcus, severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], hepatitis B, herpes zoster, and Tdap/Td) and regular foot surveillance with offloading to avert ulceration.

Background: Staphylococcus aureus bacteremia (SAB) is a significant cause of morbidity and mortality, with a high risk of metastatic infections. Understanding the timing and distribution of metastatic infections based on the primary infection focus is crucial for effective management. We aimed to identify patterns that could guide clinicians in prioritizing surveillance and interventions for patients at high risk of metastatic infection. Methods: This retrospective cohort study analyzed 1725 patients diagnosed with SAB. We assessed the incidence and distribution of metastatic infections within the cohort, stratifying the data by the timing postdiagnosis and the primary infection focus. Results: In the cohort of 1725 patients, 289 (16.7%) experienced a total of 439 metastatic infection events within the 90-day follow-up period. The majority of metastatic infections (approximately 85%) occurred within the first 7 days following diagnosis. The incidence of metastatic infections varied significantly with the primary focus of SAB, being highest in patients with endocarditis at 73.4%. The lung was the most frequent metastatic site (23.7%), followed by bones and joints (16.8%) and the central nervous system (12.3%). The distribution of metastatic sites significantly differed according to the primary infection focus. Conclusions: Our study findings provide essential insights into the risk and distribution of metastatic infections in patients with SAB, highlighting the critical role of the timing and primary infection focus. These findings enable healthcare professionals to adopt a more proactive and targeted approach to managing patients with SAB.

Objectives: Tuberculosis (TB) in immunocompromised patients presents a significant diagnostic challenge. These patients are sometimes empirically treated with quinolones before a definitive diagnosis is established. However, there are limited data on the impact of fluoroquinolone exposure on TB diagnosis and outcomes in these patients. Methods: We retrospectively analysed immunocompromised adults with missed TB diagnoses who did not receive anti-TB therapy before obtaining positive mycobacterial culture results, from January 2011 to December 2023. Patients were categorized according to their fluoroquinolone exposure. Propensity score matching, survival analysis, and competing risk analysis were performed to evaluate the association between fluoroquinolone exposure and its impact on diagnostic timelines and patient mortality. Results: Among 373 immunocompromised patients with missed diagnosis, 97 (26%) received empirical fluoroquinolone therapy before anti-TB therapy. These patients were propensity-score-matched 1:1 to 97 patients who did not receive fluoroquinolone therapy. Fluoroquinolone exposure before sampling did not significantly delay the time to microbiological diagnosis (median 21 days, IQR 17–29 versus 21 days, IQR 17.5–27, P = 0.75) or initiation of anti-TB therapy (median 27 days, IQR 21–34.75 versus 28 days, IQR 22–38, P = 0.76). Survival analysis showed that fluoroquinolone exposure was not significantly associated with 90-day all-cause mortality (P = 0.44), and competing risk analysis showed that fluoroquinolone exposure was not significantly associated with TB-related death (sub-distribution hazard ratio 1.53, 95% CI 0.26–9.03, P = 0.64). Conclusion: Fluoroquinolone exposure in immunocompromised patients with TB did not adversely affect diagnostic timelines or mortality outcomes.