Background: The high prevalence of suspected early-onset neonatal sepsis among preterm infants leads to immediate antibiotic administration upon admission. Notably, most blood cultures for suspected early-onset neonatal sepsis do not yield a causative pathogen. This study aimed to assess polymerase chain reaction (PCR) targeting the variable region V4 of the 16S ribosomal gene (16S rDNA) and Sanger sequencing for bacterial identification in preterm infants with suspected early-onset neonatal sepsis. Methods: Therefore, this prospective study was conducted. Preterm infants with suspected early-onset neonatal sepsis were included in this study. The three groups were formed based on the risk of infection and clinical sepsis. Blood samples were collected upon admission to the neonatal unit for culture and molecular analysis. PCR amplification and subsequent Sanger sequencing of the V4 region of the 16S rDNA were performed. Results: Twenty-eight patients were included in this study. Blood cultures were negative in 100% of the patients. Amplification and sequencing of the V4 region identified bacterial genera in 19 patients across distinct groups. The predominant taxonomically identified genus was Pseudomonas. Conclusions: Amplifying the 16S rDNA variable region through PCR and subsequent Sanger sequencing in preterm neonates with suspected early-onset neonatal sepsis can enhance the identification of microbial species that cause infection, especially in negative cultures.

Introducción. El coronavirus del SARS-CoV-2 ha sido una de las pandemias más significativas de la era moderna. Es un coronavirus con alta tasa de mutación, lo que genera variantes con cambios en la proteína espícula (spike), que dificulta su contención. La vigilancia genómica es crucial para adaptar estrategias de salud pública y vacunación, especialmente en los países de ingresos bajos y medios, donde el impacto ha sido considerable.Objetivo. Identificar variantes virales y sus presentaciones clínicas en una cohorte prospectiva de pacientes hospitalizados con infección por SARS-CoV-2 entre octubre de 2021 y febrero de 2023.Materiales y métodos. Se recopilaron datos demográficos, historial médico, estado de vacunación y progresión clínica. Se hizo secuenciación del genoma viral en muestras de hisopados nasales confirmadas con la prueba de reacción en cadena de la polimerasa en tiempo real con transcripción inversa para clasificar las cepas y detectar variantes.Resultados. De 63 muestras positivas para SARS-CoV-2, la variante predominante fue ómicron (84 %), seguida de la delta (14 %). La variante delta presentó la mayor proporción de enfermedad grave (100 % casos críticos) comparada con ómicron (30 % casos críticos). Se identificaron mutaciones en la proteína espícula en cuatro categorías (A-D), junto con mutaciones específicas del gen S.Conclusión. Los patrones de mutación observados coinciden con los reportes globales, con mayor seriedad clínica en la variante delta. Se identificaron mutaciones en la proteína espiga que confieren propiedades distintivas al virus. Estos hallazgos resaltan la necesidad de la vigilancia genómica continua para comprender la dinámica de la infección y orientar las estrategias de salud pública.

Background: Despite hybrid and vaccine-induced immunity, SARS-CoV-2 continues to cause disease. The characterization of humoral and cellular immune responses is essential for guiding prevention strategies and booster dose policies; Methods: A prospective cohort study was conducted with 131 hospitalized patients with confirmed COVID-19 in the Aburrá Metropolitan Valley, Colombia. Clinical and immunological data were evaluated on days 1–3, days 5–7, days 8–12, and 4–5 months after diagnosis. Humoral immunity was assessed by enzyme-linked immunosorbent assay (ELISA), chemiluminescent microparticle immunoassay (CMIA), and neutralization testing, and cellular immunity by CD4⁺/CD8 T-cell responses. Results: vaccinated patients had higher baseline levels of IgG and neutralizing antibody positivity than unvaccinated patients (ELISA 89.1% vs. 60.0%; CMIA 86.4% vs. 50.0%; neutralizing antibodies 88.2% vs. 65.0%), but cases of severe disease occurred in both groups. Adults aged ≥65 years had higher antibody positivity, but severe disease persisted. Mortality at 28 days was 7.6%, mainly among critically ill patients with comorbidities. Antibodies persisted at 4–5 months but were lower in those with severe acute disease. Those who received the booster dose showed stronger CD4⁺/CD8⁺ activation (notably against the Omicron variant) than unvaccinated/partially vaccinated patients. Conclusions: Vaccination improved humoral and cellular responses, but severe breakthrough infections still occurred, particularly in high-risk patients.