Prevalence and risk factors of concurrent bacteremia in children under 5 years of age hospitalized with viral lower respiratory tract infections.

Publication date: Jul 10, 2025

We aimed to investigate the prevalence and risk factors of concurrent bacteremia in otherwise healthy children under 5 years of age hospitalized with PCR-confirmed viral lower respiratory tract infections (VLRTIs), and to assess the impact of the COVID-19 pandemic on its prevalence and etiology. This retrospective study included children (≤ 5 years) hospitalized with PCR-confirmed VLRTIs between January 2018 and December 2024. Based on microbiology results obtained within 24 h of admission, we assessed the presence of concurrent, community-acquired bacteremia. Risk factors for bacteremia were evaluated using multivariate logistic regression. Among 1845 patients, concurrent bacteremia was identified in 36 (1. 9%) patients with influenza- and respiratory syncytial virus (RSV)-associated LRTIs. Age ≤ 6 months [adjusted odds ratio (aOR) 14. 6, 95% confidence interval (CI) 5. 7-37. 5], C-reactive protein (CRP) ≥ 4 mg/dL (aOR 3. 9, 95% CI 1. 5-9. 8), fever (≥ 39 ^0C) (aOR 4. 8, 95% CI 1. 3-18. 0), and the need for advanced respiratory support (aOR 8. 3, 95% CI 3. 0-23. 2) were independently associated with an increased risk of bacteremia. In the post-pandemic period, a significant shift in pathogen distribution was observed, with gram-negative bacteria, particularly Klebsiella spp. , emerging as the predominant cause of bacteremia. Although rare, concurrent bacteremia was associated with high fever, elevated CRP levels, the need for advanced respiratory support, and an age of ≤ 6 months in children hospitalized with RSV and influenza associated LRTIs. Notably, gram-negative bacteria, particularly Klebsiella spp. , emerged as predominant pathogens in the post-pandemic period, suggesting a potential shift in the epidemiology of bacteremia associated with VLRTIs.

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