Objectives: In May 2025, clusters of salmonellosis were identified in 7 cities in the Republic of Korea, all associated with consumption of identical bakery products. This investigation aimed to characterize the outbreak, identify potential contributing factors, and inform strategies for preventing similar multi-facility foodborne outbreaks. Methods: A case series study was conducted among individuals who consumed Manufacturer H’s Product I and Product II on May 15–16, 2025 at 7 facilities (n = 1,235). Clinical specimens from symptomatic individuals, retained food samples, and environmental samples were collected and tested. Food-exposure histories were assessed, and active case finding was implemented across all supplied facilities. Traceback investigations were conducted at the manufacturer, distributor, and egg farms. Human and food isolates underwent pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS). Results: A total of 323 cases met the outbreak case definition (attack rate, 26.2%), of which 48 were laboratory-confirmed. Salmonella Enteritidis was isolated from both clinical specimens and retained bakery products. PFGE patterns were indistinguishable between human and food isolates, and WGS demonstrated high genetic relatedness. These findings confirmed a common-source outbreak linked to the implicated bakery products. Conclusion This outbreak underscores the value of integrating epidemiological investigation, active case finding, and molecular typing to identify common food vehicles in outbreaks involving widely distributed manufactured foods. Coordinated collaboration between public health and food safety authorities is essential for the effective detection, response, and prevention of multi-facility foodborne outbreaks.

Background: Community acquired lower respiratory tract infection (LRTI) is a leading cause for hospitalization in children and important cause for antibiotic prescription. We aimed to describe the aetiology of LRTI in children and analyse factors associated with bacterial or viral infection. Methods: Patients aged < 19 years with a diagnosis of LRTI were identified from the Observational Medical Outcomes Partnership Common Data Model Database of Seoul National University Bundang Hospital from January 2005–July 2019, and their clinical characteristics were obtained from the electronic medical records and retrospectively reviewed. Results: Among 5,924 cases of LRTI, 74.2% were pneumonia and 25.8% were bronchiolitis/ bronchitis. Patients’ median age was 1.8 (interquartile range, 3.1) years and 79.9% were < 5 years old. Pathogens were identified in 37.8%; 69.1% were viral and 30.9% were bacterial/ Mycoplasma pneumoniae. Respiratory syncytial virus was most common (70.9%) among viruses and M. pneumoniae (94.6%) was most common among bacteria. Viral LRTI was associated with winter, age < 2 years, rhinorrhoea, dyspnoea, lymphocytosis, thrombocytosis, wheezing, stridor, chest retraction, and infiltration on imaging. Bacteria/ M. pneumoniae LRTI was associated with summer, age ≥ 2 years, fever, decreased breathing sounds, leucocytosis, neutrophilia, C-reactive protein elevation, and positive imaging findings (consolidation, opacity, haziness, or pleural effusion). Conclusion In children with LRTI, various factors associated with viral or bacterial/ M. pneumoniae infections were identified, which may serve as guidance for antibiotic prescription.

Background: Community acquired lower respiratory tract infection (LRTI) is a leading cause for hospitalization in children and important cause for antibiotic prescription. We aimed to describe the aetiology of LRTI in children and analyse factors associated with bacterial or viral infection. Methods: Patients aged < 19 years with a diagnosis of LRTI were identified from the Observational Medical Outcomes Partnership Common Data Model Database of Seoul National University Bundang Hospital from January 2005–July 2019, and their clinical characteristics were obtained from the electronic medical records and retrospectively reviewed. Results: Among 5,924 cases of LRTI, 74.2% were pneumonia and 25.8% were bronchiolitis/ bronchitis. Patients’ median age was 1.8 (interquartile range, 3.1) years and 79.9% were < 5 years old. Pathogens were identified in 37.8%; 69.1% were viral and 30.9% were bacterial/ Mycoplasma pneumoniae. Respiratory syncytial virus was most common (70.9%) among viruses and M. pneumoniae (94.6%) was most common among bacteria. Viral LRTI was associated with winter, age < 2 years, rhinorrhoea, dyspnoea, lymphocytosis, thrombocytosis, wheezing, stridor, chest retraction, and infiltration on imaging. Bacteria/ M. pneumoniae LRTI was associated with summer, age ≥ 2 years, fever, decreased breathing sounds, leucocytosis, neutrophilia, C-reactive protein elevation, and positive imaging findings (consolidation, opacity, haziness, or pleural effusion). Conclusion In children with LRTI, various factors associated with viral or bacterial/ M. pneumoniae infections were identified, which may serve as guidance for antibiotic prescription.

Background: Community acquired lower respiratory tract infection (LRTI) is a leading cause for hospitalization in children and important cause for antibiotic prescription. We aimed to describe the aetiology of LRTI in children and analyse factors associated with bacterial or viral infection. Methods: Patients aged < 19 years with a diagnosis of LRTI were identified from the Observational Medical Outcomes Partnership Common Data Model Database of Seoul National University Bundang Hospital from January 2005–July 2019, and their clinical characteristics were obtained from the electronic medical records and retrospectively reviewed. Results: Among 5,924 cases of LRTI, 74.2% were pneumonia and 25.8% were bronchiolitis/ bronchitis. Patients’ median age was 1.8 (interquartile range, 3.1) years and 79.9% were < 5 years old. Pathogens were identified in 37.8%; 69.1% were viral and 30.9% were bacterial/ Mycoplasma pneumoniae. Respiratory syncytial virus was most common (70.9%) among viruses and M. pneumoniae (94.6%) was most common among bacteria. Viral LRTI was associated with winter, age < 2 years, rhinorrhoea, dyspnoea, lymphocytosis, thrombocytosis, wheezing, stridor, chest retraction, and infiltration on imaging. Bacteria/ M. pneumoniae LRTI was associated with summer, age ≥ 2 years, fever, decreased breathing sounds, leucocytosis, neutrophilia, C-reactive protein elevation, and positive imaging findings (consolidation, opacity, haziness, or pleural effusion). Conclusion In children with LRTI, various factors associated with viral or bacterial/ M. pneumoniae infections were identified, which may serve as guidance for antibiotic prescription.

Background: Community acquired lower respiratory tract infection (LRTI) is a leading cause for hospitalization in children and important cause for antibiotic prescription. We aimed to describe the aetiology of LRTI in children and analyse factors associated with bacterial or viral infection. Methods: Patients aged < 19 years with a diagnosis of LRTI were identified from the Observational Medical Outcomes Partnership Common Data Model Database of Seoul National University Bundang Hospital from January 2005–July 2019, and their clinical characteristics were obtained from the electronic medical records and retrospectively reviewed. Results: Among 5,924 cases of LRTI, 74.2% were pneumonia and 25.8% were bronchiolitis/ bronchitis. Patients’ median age was 1.8 (interquartile range, 3.1) years and 79.9% were < 5 years old. Pathogens were identified in 37.8%; 69.1% were viral and 30.9% were bacterial/ Mycoplasma pneumoniae. Respiratory syncytial virus was most common (70.9%) among viruses and M. pneumoniae (94.6%) was most common among bacteria. Viral LRTI was associated with winter, age < 2 years, rhinorrhoea, dyspnoea, lymphocytosis, thrombocytosis, wheezing, stridor, chest retraction, and infiltration on imaging. Bacteria/ M. pneumoniae LRTI was associated with summer, age ≥ 2 years, fever, decreased breathing sounds, leucocytosis, neutrophilia, C-reactive protein elevation, and positive imaging findings (consolidation, opacity, haziness, or pleural effusion). Conclusion In children with LRTI, various factors associated with viral or bacterial/ M. pneumoniae infections were identified, which may serve as guidance for antibiotic prescription.