Fig. 4

Principal component analysis of morning and afternoon nasopharyngeal swab samples based on their bacterial composition. Morning samples were collected in the households, afternoon samples were collected after an 8 h exposure to the workplace environment. The dots represent the samples color-coded according to the participants’ workplaces – maternity hospital (NEO/N; n = 8), pediatric hospital (ENT/E; n = 6), and the research center (RCX/R; n = 8). Paired samples from the same participant are connected with a grey line. One nasopharyngeal sample (E6) collected in the afternoon was excluded from the analysis due to the low DNA conent in the sample