The first microbial environment of infants born by C-section: The operating room microbes

Background: Newborns delivered by C-section acquire human skin microbes just after birth, but the sources remain unknown. We hypothesized that the operating room (OR) environment contains human skin bacteria that could be seeding C-section born infants. Results: To test this hypothesis, we sampled 11 sites in 4 operating rooms from three hospitals in two cities. Following a C-section procedure, we swabbed OR floors, walls, ventilation grids, armrests, and lamps. We sequenced the V4 region of the 16S rRNA gene of 44 samples using Illumina MiSeq platform. Sequences were analyzed using the QIIME pipeline. Only 68% of the samples (30/44, >1,000 sequences per site) yielded sufficient DNA reads to be analyzed. The bacterial content of OR dust corresponded to human skin bacteria, with dominance of Staphylococcus and Corynebacterium. Diversity of bacteria was highest in the ventilation grids and walls, but was also present on top of the surgery lamps. Beta diversity analyses showed OR dust bacterial content clustering first by city and then by hospital (t-test using unweighted UniFrac distances, p<0.05). Conclusions: We conclude that dust from C-section ORs contains deposits of human skin bacteria. As the first bacteria-rich environment encountered by infants born by C-section, this built environment might be seeding the millions of C-section born infants that are void of antenatal vaginal exposure. The results might be relevant to infant health, if the current increase in risk of immune and metabolic diseases in industrialized societies is related to lack of natural exposure to vaginal microbiome during labor and birth.