Author contributions MGDB, PCD and RK conceived and designed the study. MGDB, JFRC, HSP, JH, RR, OLB, MJB, LCP, AN, HC collected the samples and metadata. AB acquired LC-MS data. LIM led LC-MS data analysis. CC led taxonomy and metadata analysis. QZ led DNA data and multi-omics analysis. JJM performed qPCR. SJS, ME, HC, AN, AB, JJM provided additional contributions to data analysis. LIM

BackgroundNewborns 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.ResultsTo test this hypothesis, we sampled 11 sites in four 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, >1000 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 the 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).ConclusionsWe conclude that the dust from ORs, collected right after a C-section procedure, contains deposits of human skin bacteria. The OR microbiota is the first environment for C-section newborns, and OR microbes might be seeding the microbiome in these babies. Further studies are required to identify how this OR microbiome exposure contributes to the seeding of the neonatal microbiome. 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 the vaginal microbiome during labor and birth.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-015-0126-1) contains supplementary material, which is available to authorized users.

Home microbes track space-use and reflect a decreasing exposure to environmental microbes due to urbanization.

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