The study was performed by two groups. And these groups were constituted from the newborn preterm infants who are received probiotics (Lactobacillus reuteri) and no probiotics.

Lactobacillus reuteri (biogai AB, Sweden) was given to probiotic group, same way to all newborn newborn preterm infants, directly oral feeding and without any along with a mixture, admission following the in nicu, as a daily dose 1x108 cfu / day (1x5 drops / day) during hospitalization

The gut which is sterile in newborn preterm infants begins to colonize with birth. Factors such as developmental immaturity of the immune system, encountering with the flora of neonatal intensive care unit, exposure to diagnostic and therapeutic interventional procedures, use of antibiotics, delay of enteral feeding may poorly affect the development of natural and mucosal immunity of intestine in newborns preterm during postnatal period. Exposure to these factors, newborn preterm infants' life threatens especially to change the development of the normal intestinal flora and intestinal immunity. Many randomized controlled studies reported that probiotics reduce intestinal inflammatory process and to prevent colonization with pathogenic microorganisms of the intestines . In this study, we investigated the effect use of probiotic on colonization of resistant microorganisms in newborn preterm infants receiving antibiotics.

In the culture, all possible resistant microorganisms such as methicillin-resistant Staphylococci aureus, Enterococcus, Klebsiella spp, Escherichia coli, Pseudomonas aeruginosa, Enterobacter, Acinetobacter, Serratia, Candida species were investigated.