The use of probiotics in the neonatal population has contributed to a decrease in morbidity and mortality in this population through the reduction in the incidence of entities such as necrotizing enterocolitis, infections associated with health care and neonatal sepsis. Despite the multiple beneficial effects described due to the use of probiotics, this type of medication should be administered with caution in high-risk patients because reports of cases of neonatal sepsis by Lactobacillus rhamnosus, Saccharomyces boulardii and Bifidobacterium, among others, have been documented. We present an atypical case of neonatal sepsis due to Lactobacillus reuteri in an extreme preterm newborn in a highly complex institution in the city of Bogotá D. C., Colombia. The outcome in our case was fatal despite the established medical management.