Background: Specific probiotics prevent necrotizing enterocolitis (NEC). A mixture of lactobacilli and bifidobacteria (Infloran) was highly effective in Asian very-low-birth-weight (VLBW) infants. We analyzed the effect of Infloran on NEC, NEC severity, and the influence of enteral feedings (breast milk vs. formula) on NEC prevention in a cohort of European VLBW infants. Methods: Infloran was implemented for routine use at our department. VLBW infants receiving probiotics were prospectively followed (2010)(2011)(2012) and compared with historic controls (2008)(2009). Data on NEC, neonatal morbidity, feeding tolerance, and descriptive parameters on NEC cases were analyzed. results: Infloran had no statistically significant impact on NEC (controls: 24/233 (10.3%); probiotics: 16/230 (7%); P = 0.2). However, NEC was significantly reduced in infants of the probiotics group who were fed any breast milk (20/179 (11.2%) vs. 10/183 (5.5%); P = 0.027), whereas it was ineffective in infants exclusively fed formula (4/54 (7.4%) vs. 6/44 (13.6%); P = 0.345). Occurrence of severe NEC (IIIb), time until full feeds, and gastric residuals were similar. conclusion: Infloran was of lower efficacy in a European VLBW cohort and showed a reduction of NEC only in infants fed breast milk. Future studies should investigate the influence of feeding formula or breast milk on the effect of probiotics.n ecrotizing enterocolitis (NEC) is an important cause of mortality and morbidity in premature infants (1). Although its pathogenesis is incompletely understood, a relation to an immature intestinal barrier, aberrant bacterial colonization, and enteral feedings is well established (2). Due to the seriousness of the disease, preventive strategies like the use of human milk and standardized feeding protocols (3-5) are of highest interest.Probiotics are microorganisms that confer a health benefit after ingestion (6). They are generally regarded as safe, and only single cases of sepsis were described in patients with major comorbidities (7). In preterm infants, probiotics may act beneficially by improving the intestinal barrier (8) and promoting a healthy gut microflora (9). Furthermore, they exert antiinflammatory effects on the gut epithelium (10) and improve local and systemic immune responses (11) that may strengthen a preterm infant's still immature immune defense. In the recent past, a preventive effect against NEC was assumed (12), and a variety of probiotic preparations were studied in randomized trials. Meta-analyses of these trials reported on a reduction of NEC in very-low-birth-weight (VLBW) infants by 65% (13,14), and the use of probiotics in clinical routine was recommended. Based on these suggestions, we decided to introduce probiotics for NEC prophylaxis as standard of care at our department. The probiotic preparation Infloran (Laboratorio Farmaceutico, Mede, Italia) consists of a mixture of Lactobacillus acidophilus and Bifidobacterium infantis and was chosen as its use was suggested by European experts (14) and it was available ...