A Particularly Severe Diarrhea in Young Infants With Klebsiella spp. Cultured From the Stool: A Case Series

Background: Klebsiella spp. are frequently found as commensals of the gastrointestinal tract in infants, and their presence in stool cultures is often dismissed as colonization. However, their role in causing severe diarrhea in previously healthy infants remains unclear. Methods: We retrospectively analyzed 4 cases of previously healthy term infants under 3 months of age hospitalized between 2016 and 2024 with unusually severe diarrhea. All had Klebsiella spp. isolated in stool cultures as the sole pathogen. Clinical and laboratory features were evaluated. Additional hospital records from 2020 to 2024 were reviewed to identify other infants with Klebsiella spp. in stool. Results: All 4 infants presented with profound watery diarrhea, lethargy and poor general condition, requiring intensive fluid resuscitation. Stool cultures revealed monoculture or abundant growth of Klebsiella pneumoniae (n = 3) or Klebsiella oxytoca (n = 1). No viral or bacterial co-pathogens were identified. All patients had elevated inflammatory markers and methemoglobinemia. Symptoms improved following antibiotic therapy, and hospital stays ranged from 11 to 24 days. Conclusions: This case series highlights a potentially underrecognized role of Klebsiella spp. in severe infantile gastroenteritis. In young infants with unusually severe diarrhea and no other identifiable cause, Klebsiella may be pathogenic. These findings support the need for further investigation into its clinical significance and management strategies.