Lactobacillus rhamnosus Sepsis in a Preterm Infant Following Probiotic Administration: Challenges in Diagnosis

Probiotic administration has become common practice in neonatal intensive care units (NICUs) to prevent necrotizing enterocolitis (NEC) and promote gut health in preterm infants. While probiotics are generally considered safe, rare cases of probiotic-related sepsis have been reported. We present a case of Lactobacillus rhamnosus sepsis in a preterm infant, highlighting the challenges involved in its diagnosis. The infant developed symptoms of sepsis on the 13th day of probiotic treatment. Laboratory analyses, including MALDI-TOF, BioFire BCID2 panel, and whole-genome sequencing (WGS), helped confirm the diagnosis and the presence of Lactobacillus rhamnosus. In this case, accurately identifying the Lactobacillus rhamnosus strain proved challenging, as initial analyses using the Vitek 2 system yielded incorrect identifications. This highlights the limitations of automated systems in distinguishing closely related species, reinforcing the need for advanced molecular techniques to achieve precise strain identification and confirm a probiotic-related infection. Given these diagnostic complexities, it is crucial for clinicians to maintain a high index of suspicion for probiotic-related infections in cases of unexplained sepsis, as this awareness can prompt further diagnostic investigations to ensure accurate pathogen identification. The infant responded to ampicillin therapy, showing clinical improvement within 10 days and was discharged in good health at 67 days of life. This case underscores the importance of advanced molecular diagnostic methods to confirm probiotic-related infections and highlights the need for caution in administering probiotics to vulnerable populations, such as preterm infants. Clinicians must maintain a high index of suspicion for probiotic-associated sepsis in unexplained cases of infection and tailor antibiotic therapy based on susceptibility profiles. These findings emphasize the need for rigorous monitoring, appropriate probiotic strain selection, and optimized safety protocols in NICUs to mitigate potential risks.