Staphylococcus epidermidis in feedings and feces of preterm neonates

Staphylococcus epidermidis has emerged as the leading agent causing neonatal late-onset sepsis in preterm neonates; although the severity of the episodes caused by this species is often underestimated, it might exert relevant short- and long-term detrimental effects on neonatal outcomes. In this context, the objective of this study was to characterize a collection of S. epidermidis strains obtained from meconium and feces of preterm infants, and to assess the potential role of the enteral feeding tubes as potential reservoirs for this microorganism. A total of 26 preterm infants were enrolled in the study. Meconium and fecal samples were collected weekly during their first month of life (n = 92). Feeding samples were collected after their pass through the enteral feeding tubes (n = 84). S. epidermidis was present in the fecal samples of all the infants in, at least, one sampling time at concentrations ranging from 6.5 to 7.8 log(10) CFU/g. Initially, 344 isolates were obtained and pulsed-field gel electrophoresis (PFGE) profiling allowed the reduction of the collection to 101 strains. Among them, multilocus sequence typing (MLST) profiling showed the presence of 32 different sequence types (ST). Globally, most of the STs to hospital-adapted high-risk clones and belonged to clonal complexes (CC) associated to the hospital environment, such as CC2. The virulence gene most commonly detected among the strains was altE. High resistance rates to macrolides and aminoglycosides were detected and 64% of the strains harboured the mecA gene, which was codified in SCCmec types. Our results indicates the existence of a complex and genetically diverse S. epidermidis population in the NICU environment. A better knowledge of S. epidermidis strains may help to devise strategies to avoid their conversion from symbiont to pathobiont microorganisms in the NICUs.