The gut microbiota is a reservoir of antibiotic resistance genes (ARGs) known as the intestinal resistome which is establishedfrom the beginning of life. However, this process, affected by many factors, remains mostly unknown. The aim of this work wasto analyse the burden of ARGs in the microbiota of neonates according to the type of feeding (breast milk or mixed feeding). Acohort of neonates recruited at the Hospital Universitario Central de Asturias (HUCA), consisting of 47 born at term (≥37 weeksof gestation) by vaginal delivery, was studied. 32 were exclusively breast-fed and 15 were mixed fed. Fecal samples werecollected at 2, 10, 30 and 90 days of life. After DNA extraction, the concentration of the most common ARGs at the neonatalresistome was determined by qPCR: bla SHV, bla TEM, mec A, tet O, tet M, cml A1 and aac(6′)-Ie-aph(2″) . We observed that infantsexclusively breastfed generally carried lower levels of ARGs. Out of the seven genes studied, four showed significant differencesaccording to the type of feeding at different time points. Our results show that the type of feeding during the first months oflife has an important effect on the levels of ARGs in the infant gut microbiota. Breastmilk may be playing a protective role.However, further studies are needed to assess the impact of perinatal factors on the intestinal resistome. The ultimate goal isthe development of nutritional intervention strategies for the reduction of this ARGs burden.

Resumen del trabajo presentado en el Agriculture and Health Summit - Cultivating gut health at the crossroads of food and medicine, celebrado de forma virtual del 11 al 13 de octubre de 2021