The purpose of this study is to evaluate the incidence of necrotizing enterocolitis and its effect over the secreting immunoglobulin A in the feces with the use of probiotics of the strain Lactobacillus acidophilus boucardii vs. Multispecies in premature newborns weighting less than 1500 g.

Randomized controlled trial, in the Neonatal department of Highly Specialized Medical Unit (UMAE) of Hospital Pediatric - Gynecology No. 48 of Mexican Institute of Social Security (IMSS ) on Leon, Mexico, between 15th of December 2013 and 30th of October 2014, on premature newborns of less than 1500 g. They were two groups of patients:

Group A: was given Lacteol fort, which contains 1x10⁹(CFU) of Lactobacillus acidophilus strain boucardii every 24 hours during 3 weeks. Its presentation is a powder of 160 mg. It's manufactured by (Carnot ® laboratories), scientific products .

Group B: was given multispecies probiotic, which contains 1x10⁹ (CFU) of Lactobacillus acidophilus, rhamnosus, casei, plantarum, Bifidobacterium infantis, Streptococcus thermophilus , every 24 hours during 3 weeks. Its presentation is a powder with 1. (ITALMEX laboratories), scientific products .

All patients received trophic enteral stimulation for 5 days, then an increasing amount of 12-20 ml/kg of breast milk on a daily basis, according to the Clinical Practice Guidelines of feeding premature newborns of the investigators hospital.

The envelops containing the probiotic they were labeled with patient data and handled to the nurse in charge of the feeding so that it can be added preferably to the prescribed breast milk, and administered at12 o´clock every day with the feeding.

The diagnosis of Necrotizing Enterocolitis (NEC) was made by the attending physician using Bell criteria. Moreover the attending physician did the adjustments in the amount of breast milk consumed by the patient.

Gastric tolerance will be observed through: the presence of vomit, abdominal distention, presence of blood or bile juice on the gastric tube, and the pattern and characteristics of the feces using a daily record.Stool samples were taken between 9 am. and 21:00., before the first administration of probiotics and at the end of the third week of probiotic treatment. The samples were processed and frozen at -70'C. Quantifying secrete immunoglobulin A (IgA s) was made by immunodiagnostic assay K8870, Benshein, Germany ELISA.

was monitored the clinical evolution of Necrotizing Enterocolitis (NEC), medical or surgical treatment and the complications.

Inclusion Criteria:

• All of the premature newborns of 34 weeks of gestational age, and with a weight between 700 to 1500 g. that are admitted in the Neonatal Intensive Care Unit or the Neonatology Department that have no contraindication for oral intake in the first 7 days of life. Must not have been diagnosed of sepsis of early onset, prenatal asphyxia, patent ductus arterious with hemodynamic repercussion, major congenital malformations. In all cases the parents or legal guardian must sign the informed consent.

Exclusion Criteria:

• All preterm newborns younger than 34 weeks of gestational age that develop any disease different of (NEC) that require to stop the enteral feeding for more than seven days or whose parents or legal guardians revoke the informed consent form.

11 months

The quantification of the amount of breast milk administered was imprecise because in the Unit there is no Milk Bank, and the visits from the mothers are restricted, however we acknowledge the crucial role of breast milk in the prevention of (NEC).