Authors: Arboleya S, Gueimonde M (Instituto de Productos Lácteos de Asturias, Villaviciosa, Asturias, Spain)
In 1928 Alexander Fleming discovered penicillin  and the ‘antibiotic revolution’ came about. Infections by bacteria could finally be battled and won, and millions of lives were saved. Ninety years later antibiotics are one of the most prescribed drugs in neonatal and pediatric populations during the first years of life . However, in the last decade another paradigm shift changed our vision of bacteria, we have understood the importance for our health of the millions of bacteria living with us (microbiota), in the so-called ‘microbiota revolution’ .
The gastro-intestinal tract is the most populated niche in the body and the microorganisms living there are known as ‘gut microbiota’. The colonization and establishment of the gut microbiota early in life is a critical event in the developmental programming of early and late health and disease, providing the essential stimulus for an adequate development of gut, immune or nervous systems. However, this process can be hampered by several perinatal factors, among them antibiotics .
It is known that antibiotics can disrupt irreversibly the correct gut microbiota maturation when they are administered to neonates or to mothers during pregnancy. However, the effect of the intrapartum antimicrobial prophylaxis (IAP) on the neonate gut microbiota development has been less studied . The IAP has been effective since the 70´s in the reduction of invasive disease by group B Streptococcus (GBS) in the first week of life. In the absence of a licensed GBS vaccine, IAP continues to be the keystone of early-onset GBS disease prevention. Nowadays, it is recommended for GBS prophylaxis (GBS mother colonization demonstrated by bacterial culture) and pre-labor rupture of membranes, prematurity or intrapartum fever ; it is also recommended in all caesareans with the objective to avoid surgical infections .