Information regarding mothers and infants obtained from questionnaires answered by the infants' parents.

MIP: Mother Infant Pair.
aFor MA samples we report whether antibiotics were given during childbirth and the specific antibiotic given. In the case of C-sections, we report administration of amoxicillin, which is the standard practice in Spanish hospitals. None of the mothers had taken antibiotics before childbirth for at least three months.
bOftalmowell is a combination of gramicidin, neomycin and polymyxin B.